Research I.
Into the Production and Analysis of Nitrous Oxide, and the Aëriform Fluids Related to It
Division I
Experiments and OBSERVATIONS on the composition of NITRIC ACID, and on its combinations with Water and Nitrous Gas.
I. Though since the commencement of Pneumatic Chemistry, no substance has been more the subject of experiment than Nitrous Acid; yet still the greatest uncertainty exists with regard to the quantities of the principles entering into its composition.
In comparing the experiments of the illustrious Cavendish on the synthesis of nitrous acid, with those of Lavoisier on the decomposition of nitre by charcoal, we find a much greater difference in the results than can be accounted for by supposing the acid formed, and that decomposed, of different degrees of oxygenation.
In the most accurate experiment of Cavendish, when the nitrous acid appeared to be in a state of deoxygenation, 1 of nitrogene combined with about 2,346 of oxygene.3 In an earlier experiment, when the acid was probably fully oxygenated, the nitrogene employed was to the oxygene nearly as 1 to 2,92.4
Lavoisier, from his experiments on the decomposition of nitre, and combination of nitrous gas and oxygene, concludes, that the perfectly oxygenated, or what he calls nitric acid, is composed of nearly 1 nitrogene, with 3,9 of oxygene; and the acid in the last state of deoxygenation, or nitrous acid, of about 3 oxygene with 1 nitrogene.5
Great as the difference is between the estimations of these philosophers, we find differences still greater in the accounts of the quantities of nitrous gas necessary to saturate a given quantity of oxygene, as laid down by very accurate experimentalists. On the one hand, Priestley found 1 of oxygene condensed by 2 of nitrous gas, and Lavoisier by 1⅞. On the other, Ingenhouz, Scherer, and De la Metherie, state the quantity necessary to be from 3 to 5.6 Humbolt, who has lately investigated Eudiometry with great ingenuity, considers the mean quantity of nitrous gas necessary to saturate 1 of oxygene, as about 2,55.7
II. To reconcile these different results is impossible, and the immediate connection of the subject with the production of nitrous oxide, as well as its general importance, obliged me to search for means of accurately determining the composition of nitrous acid in its different degrees of oxygenation.
The first desideratum was to ascertain the nature and composition of a fluid acid, which by being deprived of, or combined with nitrous gas, might become a standard of comparison for all other acids.
To obtain this acid I should have preferred the immediate combination of oxygene and nitrogene over water by the electric spark, had it been possible to obtain in this way by a common apparatus sufficient for extensive examination; but on carefully perusing the laborious experiments of Cavendish, I gave up all thoughts of attempting it.
My first experiments were made on the decomposition of nitre, formed from a known quantity of pale nitrous acid of known specific gravity, by phosphorus, tin, and charcoal: but in those processes, unascertainable quantities of nitrous acid, with excess of nitrous gas, always escaped undecompounded, and from the non-coincidence of results, where different quantities of combustible substances were employed, I had reasons for believing that water was generally decomposed.
Before these experiments were attempted, I had analized nitrous gas and nitrous oxide, in a manner to be particularly described hereafter; so that a knowledge of the quantities of nitrous gas and oxygene entering into the composition of any acid, enabled me to determine the proportions of nitrogene and oxygene it contained. In consequence of which I attempted to combine together oxygene and nitrous gas, in such a manner as to absorb the nitrous acid formed by water, in an apparatus by which the quantities of the gases employed, and the increase of weight of the water, might be ascertained; but this process likewise failed. It was impossible to procure the gases perfectly free from nitrogene, and during their combination, this nitrogene made to pass into a pneumatic apparatus communicating with a vessel containing the water carried over with it, much nitrous acid vapor, of different composition from the acid absorbed.
After many unsuccessful trials, Dr. Priestley’s experiments on nitrous vapor8 induced me to suppose that oxygene and nitrous gas, made to combine out of the contact of bodies having affinity for oxygene, would remain permanently aëriform, and on throwing them separately into an exhausted glass balloon, I found that this was actually the case; increase of temperature was produced, and orange colored nitrous acid gas formed, which after remaining for many days in the globe, at a temperature below 56°, did not in the slightest degree condense.
This fact afforded me the means not only of forming a standard acid, but likewise of ascertaining the specific gravity of nitrous acid in its aëriform state.
III. Previous to the experiment, for the purpose of correcting incidental errors, I was induced to ascertain the specific gravity of the gases employed, particularly as I was unacquainted with any process by which the weight of nitrous gas had been accurately determined. Mr. Kirwan’s estimation, which is generally adopted, being founded upon the comparison of the loss of weight of a solution of copper in dilute nitrous acid, with the quantity of gas produced.9
The instruments that I made use of for containing and measuring my gases, were two mercurial airholders graduated to the cubic inch of Everard, and furnished with stop-cocks.10
They were weighed in a glass globe, of the capacity of 108 cubic inches, which with the small glass stop-cock affixed to it, was equal, when filled with atmospheric air, to 1755 grains. The balance that I employed, when loaded with a pound, turned with less than one eighth of a grain.
Into a mercurial airholder, of the capacity of 200 cubic inches, 160 cubic inches of nitrous gas were thrown from a solution of mercury in nitrous acid.
70 measures of this were agitated for some minutes in a solution of sulphate of iron,11 till the diminution was complete. The nitrogene remaining hardly filled a measure; and if we suppose with Humbolt12 that a very small portion of it was absorbed with the nitrous gas, the whole quantity it contained may be estimated at 0,0142, or ¹/₇₀.
75 cubic inches received from the airholder into an exhausted balloon, increased it in weight 25,5 grains; thermometer being 56°, and barometer 30,9. And allowing for the small quantity of nitrogene in the gas, 100 cubic inches of it will weigh 34.3 grains.
One hundred and thirty cubic inches of oxygene were procured from oxide of manganese and sulphuric acid, by heat, and received in another mercurial airholder.
10 measures of it, mingled with 26 of the nitrous gas, gave, after the residuum was exposed to solution of sulphate of iron, rather more than one measure. Hence we may conclude that it contained about 0,1 nitrogene.
60 cubic inches of it weighed 20,75 grains; and accounting for the nitrogene contained in these, 100 grains of pure oxygene will weigh 35,09 grains.
Atmospherical air was decomposed by nitrous gas in excess; and the residuum washed with solution of sulphate of iron till the Nitrogene remained pure; 87 cubic inches of it weighed 26,5 grains, thermometer being 48°, barometer 30,1; 100 will consequently weigh 30,45.
90 cubic inches of the air of the laboratory not deprived of its carbonic acid, weighed 28,75 grains; thermometer 53, barometer 30: 100 cubic inches will consequently weigh 31,9.13 16 measures of this air, with 16 nitrous gas, of known composition, diminished to 19. Hence it contained about,26 oxygene.14
In comparing my results with those of Lavoisier and Kirwan, the estimation of the weights of nitrogene and oxygene is very little different, the corrections for temperature and pressure being made, from that of those celebrated philosophers. The first makes oxygene to weigh15 34,21, and nitrogene 30,064 per cent; and the last, oxygene 34,16 and nitrogene 30,5.
The specific gravity of nitrous gas, according to Kirwan, is to that of common air as 1194 to 1000. Hence it should weigh about 37 grains per cent. This difference from my estimation is not nearly so great as I expected to have found it.17
IV.18 The thermometer in the laboratory standing at 55°, and the barometer at 30,1, I now proceeded to my experiment. The oxygene that I employed was of the same composition as that which I had previously weighed. The nitrous gas contained,0166 nitrogene.
For the purpose of combining the gases, a glass balloon was procured, of the capacity of 148 cubic inches, with a glass stop-cock adapted to it, having its upper orifice tubulated and graduated for the purpose of containing and measuring a fluid. The whole weight of this globe and its appendages, when filled with common air, was 2066,5 grains.
It was partially exhausted by the air-pump, and lost in weight just 32 grains. From whence we may conclude that about 15 grains of air remained in it.
In this state of exhaustion it was immediately cemented to the stop-cock of the mercurial airholder, and the communication being made with great caution, 82 cubic inches of nitrous gas rushed into the globe, on the outside of which a slight increase of temperature was perceived, while the gases on the inside appeared of a deep orange.
Before the common temperature was restored, the communication was stopped, and the globe removed. The increase of weight was 29,25 grains; whence it appeared that 1,14 grains of common air, part of which had been contained in the stop-cocks, had entered with the nitrous gas.
Whilst it was cooling, from the accidental loosening of the stopper of the cock, 3 grains more of common air entered.19
The communication was now made between the globe and the mercurial airholder containing oxygene. 64 cubic inches were slowly pressed in, when the outside of the globe became warmer, and the color on the inside changed to a very dark orange. As it cooled, 6 cubic inches more slowly entered; but no new increase of temperature, or change of color took place.
The globe being now completely cold, was stopped, removed, and weighed; it had gained 24,5 grains, from whence it appears that 0,4 grains of common air contained in the stop-cocks, had entered with the oxygene.20
To absorb the nitrous acid gas, 41 grains of water were introduced by the tube of the stop-cock, which though closed as rapidly as possible, must have suffered nearly,5 grains of air to enter at the same time, as the increase of weight was 41,5 grains. The dark orange of the globe diminished rapidly; it became warm at the bottom, and moist on the sides. After a few minutes the color had almost wholly disappeared.
To ascertain the quantity of aëriform fluid absorbed, the globe was again attached to the mercurial air apparatus, containing 140 cubic inches of common air. When the communication was made, 51 cubic inches rushed in, and it gained in weight 16,5 grains.
A quantity of fluid equal to 54 grains was now taken out of the globe. On examination it proved to be slightly tinged with green, and occupied a space equal to that filled by 41,5 grains of water. Its specific gravity was consequently 1,301.
To ascertain if any unabsorbed aëriform nitrous acid remained in the globe, 13 grains of solution of ammonia were introduced in the same manner as the water, and after some minutes, when the white vapor had condensed, the communication was again made with the mercurial airholder containing common air. A minute quantity entered, which could not be estimated at more than three fourths of an inch, and the globe was increased in weight about 13,25 grains.21
Common air was now thrown into the globe till the residual gases of the experiment were judged to be displaced; it weighed 2106,5 grains, that is, 40 grains more than it had weighed when filled with common air before the experiment.22
And if from those 40 grains we take 13 for the solution of ammonia introduced, the remainder, 27, will be the quantity of solution of nitrous acid in water remaining in the globe, which added to 54, equals 81 grains, the whole quantity formed; but if from this be taken 41 grains, the quantity of water, the remainder 40 grains, will be the quantity of nitrous acid gas absorbed in the solution.
To find the absolute quantity of nitrous acid formed, we must find the specific gravity of that absorbed; but as during, and after its absorption, 17 grains of air, equal to 53,2 cubic inches entered, it evidently filled such a space. 53,2 cubic inches of it consequently weigh 40 grains, and 100 cubic inches 75,17 grains. Then,75 cubic inches weigh,56 grains, and this added to 40, makes 40,56 grains, equal to 53,95 cubic inches, the whole quantity of aëriform nitrous acid produced.
But the quantity of nitrous gas entering into this, allowing for the nitrogene it contained, is 27,6 grains, equal to about 80,5 cubic inches; and the oxygene is 40,56-27,6 = to 12,96 grains, or 36,9 cubic inches.
V. There could exist in this experiment no circumstance connected with inaccuracy, except the impossibility of very minutely determining the quantities of common air which entered with the gases from the stop-cocks. But if errors have arisen from this source, they must be very inconsiderable; as will appear from a calculation of the specific gravity of the nitrous acid gas, founded on the volume of the gases that entered the globe.
| The air that remained in the globe | ||
| after exhaustion was 15 grains = | 4723 | cub. in. |
| The nitrous gas introduced was | 82 | |
| Common air | 13 | |
| Oxygene | 70 | |
| Common air | 1 | |
| —— | ||
| Whole quantity of air thrown into the globe | 213 | |
| From which subtract its capacity | 148 | |
| —— | ||
| The remainder is | 65 | |
And this remainder taken from 80,5 nitrous gas + 36,9 oxygene, leaves 52,4 cubic inches, which is the space occupied by the nitrous acid gas, and which differs from 53,95 only by 1,55 cubic inches.
I ought to have observed, that before this conclusive experiment, two similar ones had been made. In comparing the results of one of them, performed with the assistance of my friend, Mr. Joseph Priestley, Dr. Priestley’s eldest son, and chiefly detailed by him in the journal, I find a coincidence greater than could be even well expected, where the processes are so complex. According to that experiment, 41,5 grains of nitrous acid gas fill a space equal to 53 cubic inches, and are composed of nearly 29 nitrous gas, and 12,5 oxygene.
We may then conclude, First, that 100 cubic inches of nitrous acid, such as exists in the24 aëriform state saturated with oxygene, at temperature 55°, and atmospheric pressure 30,1 weigh 75,17 grains.
Secondly, that 100 grains of it are composed of 68,06 nitrous gas, and 31,94 oxygene. Or assuming what will be hereafter proved, that 100 parts of nitrous gas consist of 55,95 oxygene, and 44,05 nitrogene, of 29,9 nitrogene, and 70,1 oxygene; or taking away decimals, of 30 of the one to 70 of the other.
Thirdly, that 100 grains of pale green solution of nitrous acid in water, of specific gravity 1,301, are composed of 50,62 water, and 49,38 acid of the above composition.
VI. Having thus ascertained the composition of a standard acid, my next object was to obtain it in a more condensed state, as it was otherwise impossible to saturate it to its full extent with nitrous gas. But this I could effect in no other way than by comparing mixtures of known quantities of water, and acids of different specific gravities and colors, with the acid of 1,301.
For the purpose of combining my acids with water, I made use of a cylinder about 8 inches long, and,3 inches in diameter, accurately graduated to grain measures, and furnished with a very tight stopper.
The concentrated acid was first slowly poured into it, and the water gradually added till the required specific gravity was produced;25 the cylinder being closed and agitated after each addition, so as to produce combination without any liberation of elastic fluid.
After making a number of experiments with acids of different colors in this advantageous way, I at length found that 90 grains of a deep yellow acid, of specific gravity 1,5, became, when mingled at 40° with 77,5 grains of water, of specific gravity 1,302, and of a light green tinge, as nearly as possible resembling that of the standard acid.
Supposing, then, that these acids contain nearly the same relative proportions of oxygene and nitrogene, 100 grains of the deep yellow acid of 1,5, are composed of 91,9 grains true nitrous acid,26 and 8,1 grains of water.
To ascertain the difference between the composition of this acid, and that of the pale, or nitric acid, of the same specific gravity, I inserted 150 grains of it into a small cylindrical mattrass of the capacity of,5 cubic inches, accurately graduated to grain measures, and connected by a curved tube with the water apparatus. After heat had been applied to the bottom of the mattrass for a few minutes, the color of the fluid gradually changed to a deep red, whilst the globules of gas formed at the bottom of the acid, were almost wholly absorbed in passing through it. In a short time deep red vapour began to fill the tube, and being condensed by the water in the apparatus, was converted into a bright green fluid, at the same time that minute globules of gas were given out. As the heat applied became more intense, a very singular phænomenon presented itself; the condensed vapor, increased in quantity, at length filled the curvature of the tube, and when expelled, formed itself into dark green spherules, which sunk to the bottom of the water, rested for a moment, and then resolved themselves into nitrous gas.27
When the acid was become completely pale, it was suffered to cool, and weighed. It had lost near 15 grains, and was of specific gravity 1,491. 2 cubic inches and quarter of nitrous gas only were collected.
From this experiment evidently no conclusions could be drawn, as the nitrous gas had carried over with it much nitrous acid (in the form of what Dr. Priestley calls nitrous vapor) and was partially dissolved with it in the water.28
To ascertain, then, the difference between the pale and yellow acids, I was obliged to make use of synthesis, compared with analysis, carried on in a different mode, by means of the following apparatus.
VII. To the stop-cock of the upper cylinder of the mercurial airholder, a capillary tube was adapted, bent so as to be capable of introduction into an orifice in the stopper of a graduated phial similar to that employed for mingling acids with water, and sufficiently long to reach the bottom. With another orifice in the stopper of the phial was connected a similar tube curved, for the purpose of containing a fluid, and of increased diameter at the extremity.29
50 cubic inches of pure nitrous gas30 were thrown into the mercurial apparatus. The graduated phial, containing 90 grains of nitric acid, of specific gravity 1,5, was placed on the top of the airholding cylinder, and made to communicate with it by means of the stop-cock and first tube. Into the second tube a small quantity of solution of potash was placed. When all the junctures were carefully cemented, by pressing on the airholder, the nitrous gas was slowly passed into the phial, and absorbed by the nitrous acid it contained; whilst the small quantities of nitrogene evolved, slowly drove forward the solution in the curved tube; from the height of which, as compared with that of the mercury in the conducing tube, the pressure on the air in the cylinder was known.
In proportion as the nitrous gas was absorbed, the phial became warm, and the acid changed color; it first became straw-colored, then pale yellow, and when about 7½ cubic inches had been combined with it, bright yellow. It had gained in weight nearly 3 grains, and was become of specific gravity 1,496.
This experiment afforded me an approximation to the real difference between nitric and yellow nitrous acid; and learning from it that nitric acid was diminished in specific gravity by combination with nitrous gas, I procured a pale acid of specific gravity 1,504.31 After this acid had been combined in the same manner as before, with about 8 cubic inches of nitrous gas,32 it became nearly of specific gravity 1,5, and had gained in weight about 3 grains.
Assuming the accuracy of this experiment as a foundation for calculation, I endeavoured in the same manner to ascertain the differences in the composition of the orange colored acids, and the acids containing still larger proportions of nitrous gas.
93 grains of the bright yellow acid of 1,5 became, when 6 cubic inches of gas had been passed through it, orange colored and fuming, whilst the undissolved gas increased in quantity so much as to render it impossible to confine it by the solution of potash. When 9 cubic inches had passed through, it became dark orange. It had gained in weight 2,75 grains, and was become of specific gravity 1,48 nearly. Hence it was evident that much nitrous gas had passed through it undissolved. 25 cubic inches more of nitrous gas were now slowly sent through it: it first became of a light olive, then of a dark olive, then of a muddy green, then of a bright green, and lastly of a blue green. After its assumption of this color, the gas appeared to pass through it unaltered, and large globules of fluid, of a darker green than the rest, remained at the bottom of the cylinder, and when agitated, did not combine with it. The increase of weight was only 1 grain, and the acid was of specific gravity 1,474 nearly.
In this experiment it was evident that the unabsorbed nitrous gas had carried over with it a considerable quantity of nitrous acid. I endeavoured to correct the errors resulting from this circumstance, by connecting the curved tube first with a small water apparatus, and afterwards with a mercurial apparatus; but when the water apparatus was used, the greater part of the unabsorbed gas was dissolved with the nitrous acid it held in solution, by the water; and when mercury was employed, the nitrous acid that came over was decomposed, and the quantity of nitrous gas evolved, in consequence increased.
As it was possible that a small deficiency of weight might arise from the red vapor given out during the processes of weighing and examining the acid in the last experiment, 35 cubic inches of nitrous gas were very slowly passed through 90 grains of pale nitrous acid, of specific gravity 1,5: it became of similar appearance to that just described, had gained in weight 6,75 grains, and was become of specific gravity 1,475.
These experiments did not afford approximations sufficiently accurate towards the composition of deoxygenated acids, containing more nitrous gas than the dark orange colored. To obtain them, a solution consisting of 94,25 grains of blue green, or perfectly nitrated acid, (if we may be allowed to employ the term), of specific gravity 1,475, was inserted into a graduated phial, and connected by a curved tube, with the mercurial airholder; in the conductor of which a small quantity of water was inserted to absorb the nitrous acid which might be carried over by the gas. Heat was slowly applied to the phial, and nitrous gas given out with great rapidity. When 4 cubic inches were collected, the acid became dark olive, when 9 dark red, when 13 bright orange, and when 18 pale. It had lost 31 grains, and when completely cool, was of specific gravity 1,502 nearly. The water in the apparatus was tinged of a light blue; from whence we may conclude that some of the nitrous gas was absorbed by it with the nitrous acid: but it will be hereafter proved that the orange colored acid is the most nitrated acid capable of combining undecompounded with water, and that the color it communicates to a large quantity of water, is light blue. If then we take 6,1 grains, the quantity of gas collected, from 31 the loss, the remainder is 24,9, which reasoning from the synthetical experiment, may be supposed to contain nearly 3 cubic inches of nitrous gas. Consequently, 94,25 grains of dark green acid, of specific gravity 1,475, are composed of nearly 21 cubic inches, or 7,2 grains of nitrous gas, and 87,05 grains of pale nitrous acid, of 1,504.
VIII. Comparing the different synthetical and analytical experiments, we may conclude with tolerable accuracy, that 92,75 grains of bright yellow, or standard acid of 1,5, are composed of 2,75 grains of nitrous gas, and 90 grains of nitric acid of 1,504; but 92,75 grains of standard acid contain 85,23 grains of nitrous acid, composed of about 27,23 of oxygene, and 58, nitrous gas: now from 58, take 2,75, and the remainder 55,25, is the quantity of nitrous gas contained in 90 grains of nitric acid of 1,504; consequently, 100 grains of it are composed of 8,45 water, and 91,55 true acid, containing 61,32 nitrous gas, and 30,23 oxygene; or 27,01 nitrogene, and 64,54 oxygene: and the nitrogene in nitric acid, is to the oxygene as 1 to 2,389.
IX. My ingenious friend, Mr. James Thomson, has communicated to me some observations relating to the composition of nitrous acid (that is, the orange colored acid), from which he draws a conclusion which is, in my opinion, countenanced by all the facts we are in possession of, namely, “that it ought not to be considered as a distinct and less oxygenated state of acid, but simply as nitric or pale acid, holding in solution, that is, loosely combined with, nitrous gas.”33
It is impossible to call any substance a simple acid that is incapable of entering undecompounded into combination with the alkalies, &c; but it will appear hereafter that the salts called in the new nomenclature nitrites, cannot be directly formed. If, indeed, it could be proved, that the heat produced by the combination of nitrous acid with salifiable bases, was the only cause of the partial decomposition of it, and that when this process was effected in such a way as to prevent increase of temperature, no nitrous gas was liberated, the common theory might have some foundation; but though dilute phlogisticated nitrous acid combines34 with alkaline solutions without decomposition, yet no excess of nitrous gas is found in the solid salt: it is either disengaged in proportion as the water is evaporated, or it absorbs oxygene from the atmosphere, and becomes nitric acid.
In proportion as the nitrous acids contain more nitrous gas, so in proportion do they more readily give it out. From the blue green acid it is liberated slowly at the temperature of 50°, and from the green likewise on agitation. The orange coloured and yellow acids do not require a heat above 200° to free them of their nitrous gas; and all the colored acids, when exposed to the atmosphere absorb oxygene, and become by degrees pale.
If the nitrous vapour, i. e. such as is disengaged during the denitration of the colored acids, was capable of combining with the alkalies, it might be supposed a distinct acid, and called nitrous acid; and the acids of different colors might be considered simply as compounds of this acid with nitric acid; but it appears to be nothing more than a solution of nitric acid in nitrous gas, incapable of condensation, undecompounded, and when decompounded and condensed, constituting the dark green acid, which is immiscible with water,35 and uncombinable with the alkalies.36
It seems therefore reasonable, till we are in possession of new lights on the subject, to consider, with Mr. Thomson, the deoxygenated or nitrous acids simply as solutions of nitrous gas composed of sulphuric acid, metallic oxides, and nitrous gas.37
Supposing the truth of these principles according to the logic of the French nomenclature, there is no acid to which the term nitrous acid ought to be applied; but as it has been used to signify the acids holding in solution nitrous gas, it is perhaps better still to apply it to those substances, than to invent for them new names. A nomenclature, accurately expressing their constituent parts, would be too complex, and like all other nomenclatures founded upon theory, liable to perpetual alterations. Their composition is known from their specific gravity and their colors; hence it is better to denote it by those physical properties: thus orange nitrous acid, of specific gravity 1,480, will signify a solution of nitrous gas in nitric acid, in which the nitric acid is to the nitrous gas, nearly as 87 to 5, and to the water as 11 to 1.
X. The estimation of the composition of the yellow and orange colored nitrous acids given in the following table, may be considered as tolerably accurate, being deduced from the synthetical experiments in the sixth section, compared with the analytical ones. But as in the synthetical experiment, when the acid became green, it was impossible to ascertain the quantity of nitrous gas that passed through it unabsorbed, and as in the analysis the quantity of nitrous gas dissolved by the water at different periods of the experiment could not be ascertained, the accounts of the composition of the green acids must be considered only as very imperfect approximations to truth.
TABLE I.
Containing Approximations to the quantities of NITRIC ACID, NITROUS GAS, and WATER in NITROUS ACIDS, of different colors and specific gravities.
| 100 Parts | Specific Gravity | Nitric Acid | Water | Nitrous gas | ||
|---|---|---|---|---|---|---|
| Sol. Nitric Acid | 1,504 | c | 91,55 | 8,45 | — — | |
| Yellow Nitrous38 | 1,502 | o | 90,5 | 8,3 | 1,2 | |
| Bright Yellow | o | 1,500 | n | 88,94 | 8,10 | 2,96 |
| Dark Orange | f | 1,480 | t | 86,84 | 7,6 | 5,56 |
| Light Olive‡ | 1,479 | a | 86,00 | 7,55 | 6,45 | |
| Dark Olive‡ | 1,478 | i | 85,4 | 7,5 | 7,1 | |
| Bright Green‡ | 1,476 | n | 84,8 | 7,44 | 7,76 | |
| Blue Green39 | 1,475 | 84,6 | 7,4 | 8,00 | ||
| ‡ = “FOOTNOTE [38]” | ||||||
TABLE II.
Binary Proportions of OXYGENE and NITROGENE in NITRIC and NITROUS ACIDS.40
| 100 Parts | Oxygene | Nitrogene | Nitrogene | Oxygene | ||
|---|---|---|---|---|---|---|
| Nitric Acid | c | 70,50 | 29,50 | 1 | 2,389 | |
| o | ||||||
| Bright yellow Nitrous | n | 70,10 | 29,90 | Proportions. | 1 | 2,344 |
| t | Nitrogene. | |||||
| Orange coloured | a | 69,63 | 30,37 | Unity. | 1 | 2,292 |
| i | ||||||
| Dark Green | n | 69,08 | 30,92 | 1 | 2,230 |
XI. I have before mentioned that dilute nitric acids are incapable of dissolving so much nitrous gas in proportion to their quantities of true acid, as concentrated ones. During their absorption of it, they go through similar changes of color; 330 grains of nitric acid, of specific gravity 1,36, after 50 cubic inches of gas had been passed through it, became blue green, and of specific gravity 1,351. It had gained in weight but 3 grains; and when the nitrous gas was driven from it by heat into a water apparatus, but 7 cubic inches were collected.41
From the diminution of specific gravity of nitric acid by combination with nitrous gas, and from the smaller attraction of nitric acid for nitrous gas, in proportion as it is diluted, it is probable that the nitrated acids, in their combinations with water, do not contract so much as42 nitric acids of the same specific gravities. The affinities resulting from the small attraction of nitrous gas for water, and its greater attraction for nitric acid, must be such as to lessen the affinity of nitric acid and water for each other.
Hence it would require an infinite number of experiments to ascertain the real quantities of acid, nitrous gas, and water, contained in the different diluted nitrous acids; and after these quantities were determined, they would probably have no important connection with the chemical arrangement. As yet, our instruments of experiment are not sufficiently exact to afford us the means of ascertaining the ratio in which the attraction of nitric acid43 for water diminishes in its progress towards saturation.
The estimations in the following table, of the real quantities of nitric acid in solutions of different specific gravities, were deduced from experiments made in the manner described in section VI, except that the phial employed was longer, narrower, and graduated to half grains. The temperature, at the time of combination, was from 40° to 46°.
TABLE III.
Of the Quantities of True NITRIC ACID in solutions of different SPECIFIC GRAVITIES.
| 100 Parts Acid of specific gravity | True Acid44 | Water | |
|---|---|---|---|
| 1,5040 | 91,55 | 8,45 | |
| 1,4475 | c | 80,39 | 19,61 |
| 1,4285 | o | 71,65 | 28,35 |
| 1,3906 | n | 62,96 | 37,04 |
| 1,3551 | t | 56,88 | 43,12 |
| 1,3186 | a | 52,03 | 47,97 |
| 1,3042 | i | 49,04 | 50,96 |
| 1,2831 | n | 46,03 | 53,97 |
| 1,2090 | 45,27 | 54,73 |
XII. The blue green spherules mentioned in section V. produced by the condensation of nitrous vapor, and by the combination of nitric acid with nitrous gas, may be considered as saturated solutions of nitrous gas in nitric acid. The combinations of nitric acid and nitrous gas containing a larger proportion of nitrous gas, are incapable of existing in the fluid state at common temperatures; and, as appears from the first experiment, an increase of volume takes place during their formation. They consequently ought to be looked upon as solutions of nitric acid in nitrous gas, identical with the nitrous vapor of Priestley.
From the researches of this great discoverer, we learn that nitrous vapor is decomposable, both by water and mercury. Hence it is almost impossible accurately to ascertain its composition. In one of his experiments,45 when more than 130 grains of strong nitrous acid were exposed for two days to nearly 247 cubic inches of nitrous gas, over water: about half of the acid was dissolved, and deposited with the gas in the water.46
XIII. In comparing the results of my fundamental experiment on the composition of nitrous acid, with those of Cavendish, the great coincidence between them gave me very high satisfaction, as affording additional proofs of accuracy. If the acid formed in the last experiment of this illustrious philosopher be supposed analogous to the light green acid formed in my first experiment, our estimations will be almost identical.
Lavoisier’s account of the composition of the nitric and nitrous acids, has been generally adopted. According to his estimation, these substances contain a much larger quantity of oxygene than I have assigned to them.
The fundamental experiments of this great philosopher were made at an early period of pneumatic chemistry,47 on the decomposition of nitre by charcoal; and he considered the nitrogene evolved, and the oxygene of the carbonic acid produced in this process, as the component parts of the nitric acid contained in the nitre.
I have before mentioned the liberation of nitrous acid, in the decomposition of nitre by combustible bodies; and I had reasons for suspecting that this circumstance was not the only source of inaccuracy.
That my suspicions were well founded, will appear from the following experiments:
EXPERIMENT a. I introduced into a strong glass tube, 3 inches long, and nearly,3 wide, a mixture of 10 grains of pulverised, well burnt charcoal, and 60 grains of nitre. It was fired by means of touch-paper, and the tube instantly plunged under a jar filled with dry mercury. A quantity of gas, clouded with dense white vapor was collected. When this vapor was precipitated, so that the surface of the mercury could be seen, it appeared white, as if acted on by nitrous acid. On introducing a little oxygene into the jar, copious red fumes appeared.
EXP. b. A similar mixture was fired48 under the jar, the top of the mercury being covered with a small quantity of red cabbage juice, rendered green by an alkali. This juice, examined when the vapor was precipitated, was become red, and on introducing to it a little carbonate of potash, a slight effervescence took place.
EXP. c. Five grains of charcoal, and 20 of nitre, were now fired in the same manner as before, the mercury being covered with a stratum of water. After the precipitation of the vapor on the introduction of oxygene, no red fumes were perceived.
EXP. d. 30 grains of nitre, 5 of charcoal, and five of silicious earth,49 were now mingled and fired. The gas received under mercury was composed of 18 carbonic acid, and nearly 12 nitrogene.50 A little muriatic acid was poured on the residuum in the tube; a slight effervescence took place.
EXP. e. The top of the mercury in the jar was now covered with a little diluted muriatic acid, and a small glass tube filled with a mixture of 3 grains of charcoal, and 20 nitre. After the deflagration, the tube itself with the residuum it contained, were thrown into the jar. The carbonic acid was quickly detached from them by the muriatic acid, and the whole quantity of gas generated in the process, obtained; it measured 15 cubic inches.
4 cubic inches of it exposed to solution of potash, diminished to 1⁴/₁₀; 7 of the remainder, with 8 of oxygene, gave only 12.
EXP. f. 60 grains of nitre, and 9 of charcoal were fired, the top of the mercury in the jar being covered with water. After the deflagration, the tube that had contained them was introduced, and the carbonic acid contained by the carbonate of potash, disengaged by muriatic acid. 30 measures of the gases evolved were exposed to caustic potash; 20 exactly were absorbed, the 10 remaining, with 10 of oxygene, diminished to 17.
EXP. g. A mixture of nitre and charcoal were deflagrated over a little water in the mercurial jar: after the precipitation of the vapor, the water was absorbed by filtrating paper. This filtrating paper, heated in a solution of potash, gave a faint smell of ammoniac.
EXP. h. Water impregnated with the vapor produced in the deflagration, was heated with quicklime, and presented separately to three persons accustomed to chemical odors. Two of them instantly recognised the ammoniacal smell, the other could not ascertain it. Paper reddened with cabbage juice was quickly turned green by the vapor.
These experiments are sufficient to shew that the decomposition of nitre by charcoal is a very complex process, and that the intense degree of heat produced may effect changes in the substances employed, which we are unable to estimate.
The products, instead of being simply carbonic acid, and nitrogene, are carbonic acid, nitrogene, nitrous acid, probably ammonia, and sometimes nitrous gas. The nitrous acid is disengaged from the base by the intense heat. Concerning the formation of the ammonia, it is useless to reason till we have obtained unequivocal testimonies of its existence; it may be produced either by the decomposition of the water contained in the nitre, by the combination of its oxygene with the charcoal, and of its nascent hydrogene with the nitrogene of the nitric acid; or from some unknown decomposition of the potash.
As neither Lavoisier nor Berthollet found nitrous gas produced in the decomposition of nitre by charcoal, when a water apparatus was employed; and as it was not uniformly evolved in my experiments, the most probable supposition is, that it arises from the decomposition of a portion of the free nitrous acid intensely heated, by the mercury.
In none of my experiments was the whole of the nitre and charcoal decomposed, some of it was uniformly thrown with the gases into the mercurial apparatus. The nitrogene evolved, as far as I could ascertain by the common tests, was mingled with no inflammable gas.
If we consider experiment f as accurate, with regard to the relative quantities of carbonic acid and nitrogene produced, they are to each other nearly as 20 to 8; that is, allowing 2 for the nitrous gas, and consequently, reasoning in the same manner as Lavoisier, concerning the composition of nitric acid, it should be composed of 1 nitrogene to 3,38 oxygene. But though the quantity of oxygene in this estimation is far short of that given in his, yet still it is too much. From whatever source the errors arise, whether from the evolution of phlogisticated nitrous acid, or the decomposition of water, or the production of nitrous gas, they all tend to increase the proportion of the carbonic acid to the nitrogene.
I am unacquainted with any experiment from which accurate opinions concerning the different relative proportions of oxygene and nitrogene in the nitric and nitrous acids could be deduced. Lavoisier’s calculation is founded on his fundamental experiment, and on the combination of nitrous gas and oxygene.
Dr. Priestley’s experiment mentioned in section 12, on the absorption of nitrous gas by nitrous acid, from which Kirwan51 deduces the composition of the differently colored nitrous acids, was made over water, by which, as is evident from a minute examination of the facts52, the greater portion of the nitrous gas employed was absorbed.
XIV. The opinions heretofore adopted respecting the quantities of real or true acid in solutions of nitrous acid of different specific gravities, have been founded on experiments made on the nitro-neutral salts, the most accurate of which are those of Kirwan, Bergman, and Wenzel. The great difference in the results of these celebrated men, proves the difficulty of the investigation, and the existence of sources of error.53 Kirwan deduces the composition of the solutions of nitrous acid in water, from an experiment on the formation of nitrated soda. In this experiment, 36,05 grains of soda were saturated by 145 grains of nitrous acid, of specific gravity 1,2754. By a test experiment, he found the quantity of salt formed to be 85,142 grains.54 Hence he concludes that 100 parts of nitrous acid, of specific gravity 1,5543, contain 73,54 of the strongest, or most concentrated acid.
Supposing his estimation perfectly true, 100 parts of the aëriform acid of 55° would be composed of 74,54 of his real acid, and 25,46 water. In examining, however, one of his later experiments,55 we shall find reasons for concluding, that the acid in nitrated soda cannot contain much less water than the aëriform acid. A solution of carbonated soda, containing 125 grains of real alkali, was saturated by 306,2 grains of nitrous acid, of specific gravity 1,416. The evaporation was carried on in a temperature not exceeding 120°, and the residuum exposed to a heat of 400° for six hours, at the end of which time it weighed 308 grains. Now according to my estimation, 306 grains of nitric acid, of 1,416, should contain 215 true acid; and we can hardly suppose, but that during the evaporation and consequent long exposure to heat, some of the nitrated soda was lost with the water.
Bergman estimates the quantity of water in this salt at 25, and the acid at 43 per cent; but his real acid was not so concentrated as Kirwan’s, consequently the nitric acid in nitrated soda should contain more water than my true acid.
Wenzel, from an experiment on the composition of nitrated soda, concludes that it contains 37,48 of alkali, and 62,52 of nitrous acid; and 1000 of this acid, from Kirwan’s calculation, contain 812,6 of his real acid; consequently, 100 parts of my aëriform acid should contain 93,28 of Wenzel’s acid, and 6,72 of water.
I saturated with potash 54 grains of solution of nitric acid, of specific gravity 1,301. Evaporated at about 212°, it produced 66 grains of nitre. This nitre exposed to a higher temperature, and kept in fusion for some time, was reduced to 60 grains.
Now from the table, 54 of 1,301, should contain 26,5 of true acid. But according to Kirwan’s estimation, 100 parts of dry nitre contain 4456 of his real acid, with 4 water; consequently 60 should contain 26,4.
Again, 90 grains of acid, of specific gravity 1,504, saturated with potash, and treated in the same manner, gave 173 grains of dry nitre. Consequently, 100 parts of it should contain 47,3 grains of true acid.
Now Lavoisier57 allows about 51 of dry acid to 100 grains of nitre, and Wenzel 52.
From Berthollet’s58 experiments, 100 grains of nitre, in their decomposition by heat, give out nearly 49 grains of gas.59
Hence it appears that the aëriform acid, that is, the true acid of my table, contains rather less water than the acid supposed to exist in nitre.
Division II
Experiments and OBSERVATIONS on the composition of AMMONIAC and on its combinations with WATER and NITRIC ACID.
I. Analysis of AMMONIAC or VOLATILE ALKALI.
The formation and decomposition of volatile alkali in many processes, was observed by Priestley, Scheele, Bergman, Kirwan, and Higgins; but to Berthollet we owe the discovery of its constituent parts, and their proportions to each other. These proportions this excellent philosopher deduced from an experiment on the decomposition of aëriform ammoniac by the electric spark:60 a process in which no apparent source of error exists.
Since, however, his estimations have been made, the proportions of oxygene and hydrogene in water have been more accurately determined. This circumstance, as well as the conviction of the impossibility of too minutely scrutinizing facts, fundamental to a great mass of reasoning, induced me to make the following experiments.
A porcelain tube was provided, open at both ends, and well glazed inside and outside, its diameter being about,5 inches. To one end of this, a glass tube was affixed, curved for the purpose of communicating with the water apparatus. With the other end a glass retort was accurately connected, containing a mixture of perfectly caustic slacked lime, and muriate of ammoniac.
The water in the apparatus for receiving the gases had been previously boiled, to expel the air it might contain, and during the experiment was yet warm.
When the tube had been reddened in a furnace adapted to the purpose, the flame of a spirit lamp was applied to the bottom of the retort. A great quantity of gas was collected in the water apparatus; of this the first portions were rejected, and the last transferred to the mercurial trough.
A small quantity examined, did not at all diminish with nitrous gas, and burnt with a lambent white flame, in contact with common air.
2¾ of this gas, equal to 110 grain measures, were fired with 2, equal to 80, of oxygene, in a detonating tube, by the electric spark. They were reduced to 2¼, or 90. On introducing to the remainder a solution of strontian, it became slightly clouded on the top, and an absorption of some grain measures took place.
It was evident, then, that in this experiment, charcoal61 had been somehow present in the tube; which being dissolved by the nascent hydrogene, had rendered it slightly carbonated, and in consequence made the results inconclusive.
A tube of thick green glass carefully made clean, was now employed, inclosed in the porcelain tube. Every other precaution was taken to prevent the existence of sources of error, and the experiment conducted as before.
140 grain measures of the gas produced, fired with 120 of oxygene, left, in two experiments, nearly 110. Solution of strontian placed in contact with the residuum, did not become clouded, and no absorption was perceived.
Now 150 measures of gas were destroyed, and if we take Lavoisier’s and Meusnier’s estimation of the composition of water, and suppose the weight of oxygene to be 35 grains, and that of hydrogene 2,6 the hundred cubic inches; the oxygene employed will be to the hydrogene as 243 to 576. Put x for the oxygene, and y for the hydrogene.
Then
x + y = 150
x: y:: 243: 576
| 243y | |
| x = | —— |
| 576 |
819y = 86400
y = 105 x = 45
And
140 - 105 = 35
Consequently, the nitrogene in ammoniac is to the hydrogene as 35: 105 in volume: and 13,3 grains of ammoniac are composed of 10,6 nitrogene, (supposing that 100 cubic inches weigh 30,45 grains) and 2,7 hydrogene.
According to Berthollet, the weight of the nitrogene in ammoniac is to that of the hydrogene as 121 to 29.62 The difference between this estimation and mine is so small as to be almost unworthy of notice, and arises most probably from the slight difference between the accounts of Lavoisier and Monge, of the composition of water, and the different weights assigned to the gases employed.
We may then conclude, that 100 grains of ammoniac are composed of about 80 nitrogene, and 20 hydrogene.
The decomposition of ammoniac by heat, as well as by the electric spark, was first discovered by Priestley. In an experiment63 when aëriform ammoniac was sent through a heated tube from a caustic solution of ammoniac in water, this great discoverer observed that an inflammable gas was produced, though in no great quantity, and that a fluid blackened by matter, probably carbonaceous, likewise came over.
In my experiments the whole of the ammoniac appeared to be decomposed; the quantity of gas generated was immense, and not clouded, as is usually the case with gases generated at high temperatures. It is possible, that the larger quantity of water carried over in his experiment, by its strong attraction for ammoniac in the aëriform state, might have, in some measure, retarded the decomposition. It is however, more probable to suppose, that a fissure existed in the earthen tube he employed, through which a certain quantity of gas escaped, and coaly matter entered.
Priestley found that the metallic oxides when strongly heated, decomposed ammoniac, the metal being revivified and water and nitrogene produced.64 The estimations of the composition of ammoniac that may be deduced from his experiments on the oxide of lead, differ very little from those already detailed.
II. Specific gravity of Ammoniac.
From the great solubility of ammoniac in water, it is difficult to ascertain its specific gravity in the same manner as that of a gas combinable to no great extent with that fluid. It is impossible to prevent the existence of a small quantity of solution of ammoniac in the mercurial airholder,65 or apparatus containing the gas; and during the diminution of the pressure of the atmosphere on this solution,66 a certain quantity of gas is liberated from it, and hence a source of error.
To ascertain, then, the weight of ammoniac, I employed an apparatus similar to that used for the absorption of nitrous gas by nitric acid.
50 cubic inches of gas were collected in the mercurial airholder, from the decomposition of muriate of ammoniac by lime; thermometer being 58°, and barometer 29,6.
100 grains of diluted sulphuric acid were introduced into the small graduated cylinder, which after being carefully weighed, was made to communicate with the airholder, the curved tube containing a small quantity of water. The gas was slowly passed into the fluid, and the globules wholly absorbed before they reached the top; much increase of temperature being consequent. When the absorption was compleat, the phial was increased in weight exactly 9 grains.
This experiment was repeated three times. The difference of weight, which was probably connected with alterations of temperature and pressure, never amounted to more than one sixth of a grain.
We may then conclude, that at temperature 58°, and atmospheric pressure 29,6, 100 cubic inches of ammoniac weigh 18 grains.
According to Kirwan, 100 cubic inches of alkaline air67 weigh 18,16 grains; barometer 30°, thermometer 61. The difference between these estimations, the corrections for temperature and pressure being made, is trifling.
III. Of the quantities of true Ammoniac in Aqueous Ammoniacal Solutions, of different specific gravities.
To ascertain the quantities of ammoniac, such as exists in the aëriform state, saturated with moisture, in solutions of different specific gravities, I employed the apparatus for absorption so often mentioned. Thermometer being 52°, the mercurial airholder was filled with ammoniacal gas, and the graduated phial, containing 50 grains of pure water, connected with it. During the absorption of the gas, the phial became warm. When about 30 cubic inches had been passed through, it was suffered to cool, and weighed: it had gained 5,25 grains, and the fluid filled a space equal to that occupied by 5768 grains of water.
Consequently, 100 grains of solution of ammoniac in water of specific gravity,9684 contain 9,502 grains of ammoniac.
The apparatus being adjusted as before, 50 grains of pure water were now perfectly saturated with ammoniac. They gained in weight 17 grains, and when perfectly cool, filled a space equal to 74 of water. Consequently 100 grains of aqueous ammonial solution of specific gravity,9054 contain 25,37 grams of ammoniac.
The two solutions were mingled together; but no alteration of temperature took place. Consequently the resulting specific gravity might have been found by calculation.
On mingling a large quantity of caustic solution of ammoniac with ¼ of its weight of water, of exactly the same temperature, no alteration of it was perceptible by a sensible thermometer.—Hence the two experiments69 being assumed as data, the intermediate estimations in the following table, were found by calculation.
TABLE IV.
Of approximations to the quantities of AMMONIAC, such as exists in the aëriform state, saturated with water at 52°, in AQUEOUS AMMONIACAL SOLUTIONS of different specific gravities.
| 100 Specific Gravity. | Ammoniac. | Water. | |
|---|---|---|---|
| 9054 | 25,37 | 74,63 | |
| 9166 | 22,07 | 77,93 | |
| 9255 | 19,54 | 80,46 | |
| 9326 | c | 17,52 | 82,48 |
| 9385 | o | 15,88 | 84,12 |
| 9435 | n | 14,53 | 85,47 |
| 9476 | t | 13,46 | 86,54 |
| 9513 | a | 12,40 | 87,60 |
| 9545 | i | 11,56 | 88,44 |
| 9573 | n | 10,82 | 89,18 |
| 9597 | 10,17 | 89,83 | |
| 9619 | 9,60 | 90,40 | |
| 9684 | 9,50 | 90,50 | |
| 9639 | 9,09 | 90,91 | |
| 9713 | 7,17 | 92,83 |
As yet no mode has been discovered for obtaining gases in a state of absolute dryness; consequently we are ignorant of the different quantities of water they hold in solution at different temperatures. As far as we are acquainted with the combinations of ammoniac, there is no state in which it exists so free from moisture, as when aëriform, at low temperatures.
That no considerable source of error existed in the two experiments, is evident from the trifling difference between the estimations of the quantities of real ammoniac, in the solution of,9684, as found in the first experiment, and as given by calculation from the last.
The quantity of ammoniac in a solution of specific gravity not in the table, may be thus determined—find the difference between the two specific gravities nearest to it in the table; d, and the difference between their quantities of alkali, b; likewise the difference between the given specific gravity and that nearest to it, c.
then
d: b:: c: x and
| bc | |
| x = | —— |
| d |
Which, added to the quantity of the lower specific gravity, is the alkali sought.
The differences in specific gravity of the solutions of ammoniac at temperatures between 4O° and 65°70 are so trifling as to be hardly ascertainable, by our imperfect instruments, and consequently are unworthy of notice.
It is possible at very low temperatures to obtain ammoniacal solutions of less specific gravity than,9, but they are incapable of being kept for any length of time under the common pressure of the atmosphere.
IV. Combinations of Ammoniac with Nitric Acid,
Composition of Nitrate of Ammoniac, &c.
200 grains of ammoniacal solution, of specific gravity,9056, were saturated by 385,5 grains of nitric acid, of specific gravity 1,306. The combination was effected in a long phial, the nitrous acid added very slowly, and the phial closed after every addition, to prevent any evaporation in consequence of the great increase of temperature.71 The specific gravity of the solution, when reduced to the common temperature, was 1,15. Evaporated at a heat of 212°,72 it gave 254 grains of salt of fibrous crystalization. This salt was dissolved in 331 grains of water; the specific gravity of the solution was 1,148 nearly.
Hence it was evident that some of the salt had been lost during the evaporation.
To find the quantity lost, fibrous nitrate of ammoniac was dissolved in small quantities in the solution, the specific gravity of which was examined after every addition of 3 grains. When 16 grains had been added to it, it became of 1,15.
Consequently, the solution composed of 200 grains of ammoniacal, and of 385,5 of nitric acid solution, contained 262 grains of salt of fibrous crystalization, and of this salt 8 grains were lost during the evaporation.
But the alkali in 200 grains of ammoniacal solution of,9056 = 50,5 grains. And the true nitric acid in 385,5 grains of solution of 1,306 = 190 grains.
Then 262-240,5 = 21,5, the quantity of water.
And 262 grains of fibrous crystalized nitrate of ammoniac, contain 190 grains true acid, 50,5 ammoniac, and 21,5 water. And 100 parts contain 72,5 acid. 19,3 ammoniac, and 8,2 water.
In proportion as the temperature employed for the evaporation of nitro-ammoniacal solutions, is above or below 212°, so in proportion does the salt produced contain more or less water than the fibrous nitrate. But whatever may have been the temperature of evaporation, the acid and alkali appear always to be in the same proportions to each other.
Of the salts containing different quantities of water, two varieties must be particularly noticed. The prismatic nitrate of ammoniac, produced at the common temperatures of the atmosphere, and containing its full quantity of water of crystalisation; and the compact nitrate of ammoniac, either amorphous, or composed of delicately needled crystals, formed at 300°, and containing but little more water than exists in nitric acid and ammoniac.
To discover the composition of the prismatic nitrate of ammoniac, 200 grains of fibrous salt were dissolved in the smallest possible quantity of water, and evaporated in a temperature not exceeding 70°. The greater part of the salt was composed of perfectly formed tetrahædral prisms, terminated by tetrahædral pyramids. It had gained in weight about 8,5 grains.
Consequently 100 grains of prismatic nitrate of ammoniac may be supposed to contain 69,5 acid, 18,4 ammoniac, and 12,1 water.
To ascertain the composition of the compact nitrate of ammoniac, I exposed in a deep porcelain cup, 400 grains of the fibrous salt, in a temperature below 300°. It quickly became fluid, and slowly gave out its water without any ebullition, or liberation of gas. When it was become perfectly dry, it had lost 33 grains. I suspected, that in this experiment some of the salt had been carried off with the water; to determine this, I introduced into a small glass retort, 460 grains of fibrous salt; it was kept at a heat below 320°, in communication with a mercurial apparatus, in a regulated air-furnace, till it was perfectly dry: it had lost 23 grains. No gas, except the common air of the retort came over, and the fluid collected had but a faint taste of nitrate of ammoniac.
Though in this experiment I had removed all the fluid retained in the neck of the retort, still a few drops remained in the head, and on the sides, which I could not obtain. It was of importance to me to be accurately acquainted with the composition of the compact salt, and for that reason I compared these analytical experiments with a synthetical one.
I saturated 200 grains of solution of ammoniac, of,9056 with acid, ascertained the specific gravity of the solution, evaporated it at 212°, and fused and dried it at about 300°-260°. It gave 246 grains of salt, and a solution made of the same specific gravity as that evaporated, indicated a loss of 9 grains. Consequently, 255 grains of this salt contain 50,5 grains alkali, 100 grains acid, and 14,5 grains water.
We may then conclude, that 100 parts of compact nitrate of ammoniac contain 74,5 acid, 19,8 alkali, and 5,7 water.
V. Decomposition of Carbonate of Ammoniac by Nitric Acid.
In my first experiments on the production of nitrate of ammoniac, I endeavoured to ascertain its composition by decompounding carbonate of ammoniac by nitric acid; and in making for this purpose, the analysis of carbonate of ammoniac, I discovered that there existed many varieties of this salt, containing very different proportions of carbonic acid, alkali, and water; the carbonic acid and water being superabundant in it, in proportion as the temperature of its formation was low, and the alkali in proportion as it was high: and not only that a different salt was formed at every different temperature, but likewise that the difference in them was so great, that the carbonate of ammoniac formed at 300° contained more than 50 per cent alkali, whilst that produced at 60° contained only 20.73
I found 210 grains of carbonate of ammoniac, which from comparison with other salts previously analised, I suspected to contain about 20 or 21 per cent alkali, saturated by 200 grains of nitric acid of 1,504. But though the carbonate was dissolved in much water, still, from the smell of the carbonic acid generated, I suspect that a small portion of the nitric acid was dissolved, and carried off by it. The solution, evaporated at about 200°, and afterwards exposed to a temperature below 300°, gave 232 grains of compact salt. But reasoning from the quantity of acid in 200 grains of nitric acid of 1,504, it ought to have given 245. Consequently 13 were lost by evaporation; and this loss agrees with that in the other experiments.
VI. Decomposition of Sulphate of Ammoniac by Nitre.
As a cheap mode of obtaining nitrate of ammoniac, Dr. Beddoes proposed to decompose nitre by sulphate of ammoniac, which is a well known article of commerce. From synthesis of sulphate of ammoniac, compared with analysis made in August 1799,74 I concluded that 100 grains of prismatic salt were composed of about 18 grains ammoniac, 44 acid, and 38 water; and supposing 100 grains of nitre to contain 50 acid, 100 grains of sulphate of ammoniac will require for their decomposition 134 grains of nitre, and form 90,9 grains of compact nitrate of ammoniac.
To ascertain if the sulphate of potash and nitrate of ammoniac could be easily separated, I added to a heated saturated solution of sulphate of ammoniac, pulverised nitre, till the decomposition was complete. After this decomposition, the solution contained a slight excess of sulphuric acid, which was combined with lime, and the whole set to evaporate at a temperature below 250°. As soon as the sulphate of potash began to crystalise, the solution was suffered to cool, and then poured off from the crystalised salt, which appeared to contain no nitrate of ammoniac. After a second evaporation and crystalisation, almost the whole of the sulphate appeared to be deposited, and the solution of nitrate of ammoniac was obtained nearly pure: it was evaporated at 212°, and gave fibrous crystals.
VII. Non-existence of Ammoniacal Nitrites.
I attempted in different modes to combine nitrous acids with ammoniac, so as to form the salts which have been supposed to exist, and called nitrites of ammoniac; but without success.
I first decomposed a solution of carbonate of ammoniac by dilute olive colored acid; but in this process, though no heat was generated, yet all the nitrous gas appeared to be liberated with the carbonic acid.75 I then combined a small quantity of nitrous gas, with a solution of nitrate of ammoniac. But after evaporating this solution at 70°-80°, I could not detect the existence of nitrous gas in the solid salt; it was given out during the evaporation and crystalisation, and formed into nitrous acid by the oxygene of the atmosphere. I likewise heated nitrate of ammoniac to different degrees, and partially decomposed it, to ascertain if in any case the acid was phlogisticated by heat: but in no experiment could I detect the existence of nitrous acid in the heated salt, when it had been previously perfectly neutralised.
When nitrate of ammoniac, indeed, with excess of nitric acid, is exposed to heat, the superabundant nitric acid becomes phlogisticated, and is then liberated from the salt, which remains neutral.76
We may therefore conclude that nitrous gas has little or no affinity for solid nitrate of ammoniac, and that no substance exists to which the name nitrite of ammoniac can with propriety be applied.
VIII. Of the sources of error in Analysis.
To compare my synthesis of nitrate of ammoniac with analysis, I endeavoured to separate the ammoniac and nitric acid from each other, without decomposition. But in going through the analytical process, I soon discovered that it was impossible to make it accurate, without many collateral laborious experiments on the quantities of ammoniac soluble in water at different temperatures.
At a temperature above 212°, I decomposed, by caustic slacked lime, 50 grains of compact nitrate of ammoniac in a retort communicating with the mercurial airholder, the moisture in which had been previously saturated with ammoniac. 22 cubic inches of gas were collected at 38°, and from the loss of weight of the retort, it appeared that 13 grains of solution of ammoniac in water, had been deposited by the gas.
Now evidently, this solution must have contained much more alkali in proportion to its water than that of 55°, otherwise the quantity of ammoniac in 50 grains of salt would hardly equal 8 grains.77
IX. Of the loss of Solutions of Nitrate of Ammoniac
during evaporation.
The most concentrated solution of nitrate of ammoniac capable of existing at 60°, is of specific gravity 1,304, and contains 33 water, and 67 fibrous salt, per cent. When this solution is evaporated at temperatures between 60° and 100, the salt is increased in weight by the addition of water of crystalisation, and no portion of it is lost.
During the evaporation of solutions of specific gravity 1,146 and 1,15, at temperatures below 120°, I have never detected any loss of salt. When the temperature of evaporation is 212°, the loss is generally from 3 to 4 grains per cent; and when from 230° to the standard of their ebullition, from 4 to 6 grains.
In proportion as solutions are more diluted, their loss in evaporation at equal temperatures is greater.
Division III
Decomposition of NITRATE of AMMONIAC: preparation of RESPIRABLE NITROUS OXIDE; its ANALYSIS.
I. Of the heat required for the decomposition of
NITRATE of AMMONIAC.
The decomposition of nitrate of ammoniac has been supposed by Cornette78 to take place at temperatures below 212°, and its sublimation at 234°.
Kirwan, from the non-coincidence in the accounts of its composition, has imagined that it is partially decomposable, even by a heat of 80°.79
To ascertain the changes effected by increase of temperature in this salt, a glass retort was provided, tubulated for the purpose of introducing the bulb of a thermometer. After it had been made to communicate with the mercurial airholder, and placed in a furnace, the heat of which could be easily regulated, the thermometer was introduced, and the retort filled with the salt, and carefully luted; so that the appearances produced by different temperatures could be accurately observed, and the products evolved obtained.
From a number of experiments made in this manner on different salts, the following conclusions were drawn.
1st. Compact, or dry nitrate of ammoniac, undergoes little or no change at temperatures below 260°.
2dly. At temperatures between 275° and 300°, it slowly sublimes, without decomposition, or without becoming fluid.
3dly. At 320° it becomes fluid, decomposes, and still slowly sublimes; it neither assuming, or continuing in, the fluid state, without decomposition.
4thly. At temperatures between 340° and 480°, it decomposes rapidly.
5thly. The prismatic and fibrous nitrates of ammoniac become fluid at temperatures below 300°, and undergo ebullition at temperatures between 360° and 400°, without decomposition.
6thly. They are capable of being heated to 430° without decomposition, or sublimation, till a certain quantity of their water is evaporated.
7thly. At temperatures above 450° they undergo decomposition, without previously losing their water of crystalisation.
II. Decomposition of Nitrate of Ammoniac; production of
respirable Nitrous Oxide; its properties.
200 grains of compact nitrate of ammoniac were introduced into a glass retort, and decomposed slowly by the heat of a spirit lamp. The first portions of the gas that came over were rejected, and the last received in jars containing mercury. No luminous appearance was perceived in the retort during the process, and almost the whole of the salt was resolved into fluid and gas. The fluid had a faint acid taste, and contained some undecompounded nitrate. The gas collected exhibited the following properties.—
a. A candle burnt in it with a brilliant flame, and crackling noise. Before its extinction, the white inner flame became surrounded with an exterior blue one.
b. Phosphorus introduced into it in a state of inflammation, burnt with infinitely greater vividness than before.
c. Sulphur introduced into it when burning with a feeble blue flame, was instantly extinguished; but when in a state of active inflammation (that is, forming sulphuric acid) it burnt with a beautiful and vivid rose-colored flame.
d. Inflamed charcoal, deprived of hydrogene, introduced into it, burnt with much greater vividness than in the atmosphere.
e. To some fine twisted iron wire a small piece of cork was affixed: this was inflamed, and the whole introduced into a jar of the air. The iron burned with great vividness, and threw out bright sparks as in oxygene.
f. 30 measures of it exposed to water previously boiled, was rapidly absorbed; when the diminution was complete, rather more than a measure remained.
g. Pure water saturated with it, gave it out again on ebullition, and the gas thus produced retained all its former properties.
h. It was absorbed by red cabbage juice; but no alteration of color took place.
i. Its taste was distinctly sweet, and its odor slight, but agreeable.
j. It underwent no diminution when mingled with oxygene or nitrous gas.
Such were the obvious properties of the Nitrous Oxide, or the gas produced by the decomposition of nitrate of ammoniac in a temperature not exceeding 440°. Other properties of it will be hereafter demonstrated, and its affinities fully investigated.
III. Of the gas remaining after the absorption of
Nitrous Oxide by Water.
In exposing nitrous oxide at different times to rain or spring water, and water that had been lately boiled, I found that the gas remaining after the absorption was always least when boiled water was employed, though from the mode of production of the nitrous oxide, I had reason to believe that its composition was generally the same.
This circumstance induced me to suppose that some of the residuum might be gas previously contained in the water, and liberated from it in consequence of the stronger affinity of that fluid for nitrous oxide. But the greater part of it, I conjectured to consist of nitrogene produced in consequence of a complete decomposition of part of the acid, by the hydrogene. It was in endeavoring to ascertain the relative purity of nitrous oxide produced at different periods of the process of the decomposition of nitrate of ammoniac, that I discovered the true reason of the appearance of residual gas.
I decomposed some pure nitrate of ammoniac in a small glass retort; and after suffering the first portions to escape with the common air, I caught the remainder in three separate vessels standing in the same trough, filled with water that had been long boiled, and which at the time of the experiment was so warm that I could scarcely bear my hands in it. The different quantities collected gave the same intense brilliancy to the flame of a taper.
26 measures of each of them were separately inserted into 3 graduated cylinders, of nearly the same capacity, over the same boiled water. As the water cooled, the gas was absorbed by agitation. When the diminution was complete, the residuum in each cylinder filled, as nearly as possible, the same space; about two thirds of a measure.
To each of the residuums I added two measures of nitrous gas; they gave copious red vapor, and after the condensation filled a space rather less than two measures.
Hence the residual gas contained more oxygene than common air.
I now introduced 26 measures of gas from one of the vessels into a cylinder filled with unboiled spring water of the same kind.80 After the absorption was complete, near two measures remained. These added to two measures of nitrous air, diminished to 2,5 nearly.
These experiments induced me to believe that the residual gas was not produced in the decomposition of nitrate of ammoniac, but that it was wholly liberated from the water.
To ascertain this point with precision, I distilled a small quantity of the same kind of water, which had been near an hour in ebullition, into a graduated cylinder containing mercury. To this I introduced about one third of its bulk, i. e. 12 measures of nitrous oxide, which had been carefully generated in the mercurial apparatus. After the absorption, a small globule of gas only remained, which could hardly have equalled one fourth of a measure. On admitting to this globule a minute quantity of nitrous gas, an evident diminution took place.
Though this experiment proved that in proportion as the water was free from air, the residuum was less, and though there was no reason to suppose that the ebullition and distillation had freed the water from the whole of the air it had held in solution, still I considered a decisive experiment wanting to determine whether nitrous oxide was the only gas produced in the slow decomposition of nitrate of ammoniac, or whether a minute quantity of oxygene was not likewise evolved.
I received the middle part of the product of a decomposition of nitrate of ammoniac, under a cylinder filled with dry mercury, and introduced to it some strong solution of ammoniac. After the white cloud produced by the combination of the ammoniacal vapor with the nitric acid suspended in the nitrous oxide, had been completely precipitated, I introduced a small quantity of nitrous gas. No white vapor was produced.
Now if any gas combinable with nitrous gas had existed in the cylinder, the quantity of nitrous acid produced, however small, would have been rendered perceptible by the ammoniacal fumes; for when a minute globule of common air was admitted into the cylinder, white clouds were instantly perceptible.
It seems therefore reasonable to conclude,
1. That the residual gas of nitrous oxide, is air previously contained in the water, (which in no case can be perfectly freed from it by ebullition), and liberated by the stronger attraction of that fluid for nitrous oxide.
2. That nitrate of ammoniac, at temperatures below 440°, is decompounded into pure nitrous oxide, and fluid.
3. That in ascertaining the purity of nitrous oxide from its absorption by water, corrections ought to be made for the quantity of gas dispelled from the water. This quantity in common water distilled under mercury being about ¹/₅₀; in water simply boiled, and used when hot, about ¹/₃₆; and in common spring water, ¹/₁₂.
IV. Specific gravity of Nitrous Oxide.
To understand accurately the changes taking place during the decomposition of nitrate of ammoniac, we must be acquainted with the specific gravity and composition of nitrous oxide.
90 cubic inches of it, containing about ¹/₃₅ common air, introduced from the mercurial airholder into an exhausted globe, increased it in weight 44,75 grains; thermometer being 51°, and atmospheric pressure 30,7.
106 cubic inches, of similar composition, weighed in like manner, gave at the same temperature and pressure nearly 52,25 grains; and in another experiment, when the thermometer was 41°, 53 grains.
So that accounting for the small quantity of common air contained in the gases weighed, we may conclude, that 100 cubic inches of pure nitrous oxide weigh 50,1 grains at temperature 50°, and atmospheric pressure 30,7.
I was a little surprised at this great specific gravity, particularly as I had expected, from Dr. Priestley’s observations, to find it less heavy than atmospherical air. This philosopher supposed, from some appearances produced by the mixture of it with aëriform ammoniac, that it was even of less specific gravity than that gas.81
The nitrous oxide may be analised, either by charcoal or hydrogene; during the combustion of other bodies in it, small portions of nitrous acid are generally formed, as will be fully explained hereafter.
The gas that I employed was generated from compact nitrate of ammoniac, and was in its highest state of purity, as it left a residuum of ¹/₃₈ only, when absorbed by boiled water.
10 cubic inches of it were inserted into a jar graduated to,1 cubic inches, containing dry mercury. Through this mercury a piece of charcoal which had been deprived of its hydrogene by long exposure to heat, weighing about a grain, was introduced, while yet warm. No perceptible absorption of the gas took place.82
Thermometer being 46°, the focus of a lens was thrown on the charcoal, which instantly took fire, and burnt vividly for about a minute, the gas being increased in volume. After the vivid combustion had ceased, the focus was again thrown on the charcoal; it continued to burn for near ten minutes, when the process stopped.
The gas, when the original pressure and temperature were restored, filled a space equal to 12,5 cubic inches.
On introducing to it a small quantity of strong solution of ammoniac83, white vapor was instantly perceived, and after a short time the reduction was to about 10,1 cubic inches; so that apparently, 2,4 cubic inches of carbonic acid had been formed. The 10,1 cubic inches of gas remaining were exposed to water which had been long in ebullition, and which was introduced whilst boiling, under mercury. After the absorption of the nitrous oxide by the water, the gas remaining was equal to 5,3.
But on combining a cubic inch of pure nitrous oxide with some of the same water, which had been received under mercury in a separate vessel, nearly ¹/₂₂ remained. Consequently we may conclude, that 5,1 of a gas unabsorbable by water, was produced in the combustion.
This gas extinguished flame, gave no diminution with oxygene, and the slightest possible with nitrous gas. When an electric spark was passed through it, mingled with oxygene; no inflammation, or perceptible diminution took place.84 We may consequently conclude that it was nitrogene, mingled with a minute portion of common air, expelled from the water.
The charcoal was diminished in bulk to one half nearly, but the loss of weight could not be ascertained, as its pores were filled with mercury.
Now 5 cubic inches of nitrous oxide were absorbed by the water, consequently 5 were decompounded by the charcoal; and these produced 5,1 cubic inches of nitrogene; and by giving their oxygene to the charcoal, apparently 2,4 of carbonic acid.
But 5 cubic inches of nitrous oxide weigh 2,5 grains, and 5,1 cubic inches of nitrogene 1,55; then 2,5-1,55 =,95.
So that reasoning from the relative specific gravities of nitrogene and nitrous oxide, 2,5 grains of the last are composed of 1,55 nitrogene, and,95 oxygene.
But from many experiments made on the specific gravity of carbonic acid, in August, 1799, I concluded that 100 cubic inches of it weighed 47,5 grains, thermometer being 60,1°, and barometer 29,5. Consequently, making the necessary corrections, 2,4 cubic inches of it weigh 1,14 grains; and on Lavoisier’s and Guyton’s85 estimation of its composition, these 1,13 grains contain 8,2 of oxygene.
So that, drawing conclusions from the quantity of carbonic acid formed in this experiment, 2,5 grains of nitrous oxide will be composed of,82 oxygene, and 1,68 nitrogene.
The difference between these estimations is considerable, and yet not more than might have been expected, if we consider the probable sources of error in the experiment.
1. It is likely that variable minute quantities of hydrogene remain combined with charcoal, even after it has been long exposed to a red heat.
2. It is probable that the nitrogene and carbonic acid produced were capable of dissolving more water than that held in solution by the nitrous oxide; and if so, they were more condensed than if saturated with moisture, and hence the quantity of carbonic acid under-rated.
We may consequently suppose the estimation founded on the quantity of nitrogene evolved, most correct; and making a small allowance for the difference, conclude, that 100 grains of nitrous oxide are composed of about 37 oxygene, and 63 nitrogene; existing in a much more condensed state than when in their simple forms.
The tolerable accuracy of this statement will be hereafter demonstrated by a number of experiments on the combustion of different bodies in nitrous oxide, detailed in Research II.
VI. Minute examination of the decomposition of Nitrate of Ammoniac.
Into a retort weighing 413,75 grains, and of the capacity of 7,5 cubic inches, 100 grains of pulverised compact nitrate of ammoniac were introduced. To the neck of this retort was adapted a recipient, weighing 711 grains, tubulated for the purpose of communicating with the mercurial airholder, and of the capacity of 8,3 cubic inches.
Temperature being 50° and atmospheric pressure 30,6, the recipient was inserted into a vessel of cold water, and made to communicate with the airholder. The heat of a spirit lamp was then slowly applied to the retort: the salt quickly began to decompose, and to liquify. The temperature was so regulated, as to keep up an equable and slow decomposition.
During this decomposition, no luminous appearance was perceived in the retort; the gas that came into the airholder was very little clouded, and much water condensed in the receiver.
After the process was finished, the communication between the mercurial airholder and the recipient was preserved till the common temperature was restored to the retort.
The volume of the gas in the cylinder was 85,5 cubic inches. The absolute quantity of nitrous oxide in those 85,5 cubic inches, it was difficult to ascertain with great nicety, on account of the common air previously contained in the vessels.
45 measures of it, exposed to well boiled water, diminished by agitation to 8 measures. So that reasoning from the quantity of air, which should have been expelled from the water by the nitrous oxide, we may conclude that the 85,5 cubic inches were nearly pure.
The retort now weighed 419,25 grains, consequently 5,5 grains of salt remained in it. This salt was chiefly collected about the lower part of the neck, and contained rather more water than the compact nitrate, as in some places it was crystalised.
The recipient with the fluid it contained, weighed 759 grains. It had consequently gained in weight 48 grains.
Now the 85,5 cubic inches of nitrous oxide produced, weigh about 42,5 grains; and this added to 48 and 5,5, = 96 grains; so that about 4 grains of salt and fluid were lost, probably by being carried over and deposited by the gas.86
As much of the fluid as could be taken out of the recipient, weighed 46 grains, and held in solution much nitrate of ammoniac with superabundance of acid. This acid required for its saturation, 3⅛ of carbonate of ammoniac (containing, as well as I could guess), about 20 per cent alkali.
The whole solution evaporated, gave 18 grains of compact nitrate of ammoniac. But reasoning from the quantity of carbonate of ammoniac employed, the free nitric acid was equal to 2,75 grains, and this must have formed 3,56 grains of salt. Consequently the salt pre-existing in the solution was about 14,44 grains.
But besides the fluid taken out of the recipient, 2 grains remained in it: let us suppose this, and the 4 grains lost, to contain 2 of salt, and,6 of free acid.
Then the undecompounded
| salt is 5,5 + 14,4 + 2 = | 21,9 |
| The free acid 2,75 +,6 = | 3,35 |
| Gas | 42,5 |
| Water | 32,25 |
| 100 |
Now about 78,1 grains of salt were decompounded, and formed into 42,5 grains of gas, 3,35 grains acid, and 32,25 grains water.
But there is every reason to suppose, that in this process, when the hydrogene of the ammoniac combines with a portion of the oxygene of the nitric acid to form water, and the nitrogene enters into union with the nitrogene and remaining oxygene of the nitric acid, to form nitrous oxide; that water pre-existing in nitric acid and ammoniac, such as they existed in the aëriform state, is deposited with the water produced by the new arrangement, and not wholly combined with the nitrous oxide formed. Hence it is impossible to determine with great exactness, the quantity of water which was absolutely formed in this experiment.
78,1 grains of salt are composed of 15,4 alkali, 58 acid, and 4,7 water.
And reasoning from the different affinities of water for nitric acid, ammoniac, and nitrous oxide, it is probable that ammoniac, in its decomposition, divides its water in such a ratio, between the nitrogene furnished to the nitrous oxide, and the hydrogene entering into union with the oxygene of the nitric acid, as to enable us to assume, that the hydrogene requires for its saturation nearly the same quantity of oxygene as when in the aëriform state; or that it certainly cannot require less.
But 15,4 alkali contain 3,08 hydrogene, and 12,32 nitrogene;87 and 3,08 hydrogene require 17,4 of oxygene to form 20,48 of water.
Now 32,5 grains of water existed before the experiment; 4,7 grains of water were contained by the salt decomposed, and 32,5-4,7 = 27,8: and 27,8-20,48, the quantity generated, = 7,52, the quantity existing in the nitric acid.
But the nitric acid decomposed is 58ᵍ-3,35 = to 54,7; and 54,7-7,5 = 47,2, which entered into new combinations. These 47,2 consist of 33,2 oxygene, and 14, nitrogene. And 33,2-17,4, the quantity employed to form the water, = 15,8, which combined with 14,0, nitrogene of the nitric acid, and 12,32 of that of the ammoniac, to form 42,12 of nitrous oxide. And on this estimation, 100 parts of nitrous oxide would contain 37,6 oxygene, and 62,4 nitrogene; a computation much nearer the results of the analysis than could have been expected, particularly as so many unavoidable sources of error existed in the process.
The experiment that I have detailed is the most accurate of four, made on the same quantity of salt. The others were carried on at rather higher temperatures, in consequence of which, more water and salt were sublimed with the gas.
To Berthollet, we owe the discovery of the products evolved during the slow decomposition of nitrate of ammoniac; but as this philosopher in his examination of this process, chiefly designed to prove the existence of hydrogene in ammoniac, he did not ascertain the quantity of gas produced, or minutely examine its properties; from two of them, its absorption by water and its capability of supporting the vivid combustion of a taper, he inferred its identity with the dephlogisticated nitrous gas of Priestley, and concluded that it was nitrous gas with excess of pure air.88
VII. Of the heat produced during the decomposition
of nitrate of ammoniac.
To ascertain whether the temperature of nitrate of ammoniac was increased or diminished after it had been raised to the point essential to its decomposition, during the evolution of nitrous oxide and water; that is, in common language, whether heat was generated or absorbed in the process; I introduced a thermometer into about 1500 grains of fibrous nitrate of ammoniac, rendered liquid in a deep porcelain cup. During the whole of the evaporation, the temperature was about 380°, the fire being carefully regulated.
As soon as the decomposition took place, the thermometer began to rise; in less than a quarter of a minute it was 410°, in two minutes it was 460°.
The cup was removed from the fire; the decomposition still went on rapidly, and for about a minute the thermometer was stationary. It then gradually and slowly fell; in three minutes it was 440°, in five minutes 420°, in seven minutes 405° in nine minutes 360° and in thirteen minutes 307°, when the decomposition had nearly ceased, and the salt began to solidify.
From this experiment, it is evident that an increase of temperature is produced by the decomposition of nitrate of ammoniac: though the capacity of water and nitrous oxide for heat, supposing the truth of the common doctrine, and reasoning from analogy, must be considerably greater than that of the salt.
VIII. Of the decomposition of Nitrate of Ammoniac
at high temperatures, and production of
Nitrous gas, Nitrogene, Nitrous Acid, and Water.
At an early period of my investigation relating to the nitrous oxide, I discovered that when a heat above 600° was applied to nitrate of ammoniac, so that a vivid luminous appearance was produced in the retort, certain portions of nitrous gas, and nitrogene, were evolved with the nitrous oxide. But I was for some time ignorant of the precise nature of this decomposition, and doubtful with regard to the possibility of effecting it in such a manner as to prevent the production of nitrous oxide altogether.
I first attempted to decompose nitrate of ammoniac at high temperatures, by introducing it into a well coated green glass retort, having a wide neck, communicating with the pneumatic apparatus, and strongly heated in an air-furnace. But though in this process a detonation always took place, and much light was produced, yet still the greater portion of the gas generated was nitrous oxide; the nitrous gas and nitrogene never amounting to more than one third of the whole.
After breaking many retorts by explosions, without gaining any accurate results, I employed a porcelain tube, curved so as to be capable of introduction into the pneumatic apparatus, and closed at one end.
The closed end was heated red, nitrate of ammoniac introduced into it, and all the latter portions of gas produced in the explosion, received in the pneumatic apparatus, filled with warm water.
Three explosions were required to fill a jar of the capacity of 20 cubic inches. The gas produced in the first, when it came over, was transparent and dark orange, similar in its appearance to the nitrous acid gas produced in the first experiment; but it speedily became white and clouded, whilst a slight diminution of volume took place.
When the second portion was generated and mingled with the clouded gas, it again became transparent and yellow for a short time, and then assumed the same appearance as before.
The water in the trough, after this experiment, had an acid taste, and quickly reddened cabbage juice rendered green by an alkali.
6 cubic inches of the gas produced were exposed to boiled water, but little or no absorption took place. Hence, evidently, it contained no nitrous oxide.
They were then exposed to solution of sulphate of iron: the solution quickly became dark colored, and an absorption of 1,6 took place on agitation.89
The gas remaining instantly extinguished the taper, and was consequently nitrogene.
This experiment was repeated, with nearly the same results.
We may then conclude, that at high temperatures, nitrate of ammoniac is wholly resolved into water, nitrous acid, nitrous gas, and nitrogene; whilst a vivid luminous appearance is produced.
The transparency and orange color produced in the gas that had been clouded, by new portions of it, doubtless arose from the solution of the nitric acid and water forming the cloud, in the heated nitrous vapor produced, so as to constitute an aëriform triple compound; whilst the cloudiness and absorption subsequent were produced by the diminished temperature, which destroyed the ternary combination, and separated the nitrous acid and water from the nitrous gas.
From the rapidity with which the deflagration of nitrate of ammoniac proceeds, and from the immense quantity of light produced, it is reasonable to suppose that a very great increase of temperature takes place. The tube in which the decomposition has been effected, is always ignited after the process.
IX. Speculations on the decompositions of
Nitrate of Ammoniac.
All the phænomena of chemistry concur in proving, that the affinity of one body, A, for another, B, is not destroyed by its combination with a third, C, but only modified; either by condensation, or expansion, or by the attraction of C for B.
On this principle, the attraction of compound bodies for each other must be resolved into the reciprocal attractions of their constituents, and consequently the changes produced in them by variations of temperature explained, from the alterations produced in the attractions of those constituents.
Thus in nitrate of ammoniac, four affinities may be supposed to exist:
1. That of hydrogene for nitrogene, producing ammoniac.
2. That of oxygene for nitrous gas, producing nitric acid.
3. That of the hydrogene of ammoniac for the oxygene of nitric acid.
4. That of the nitrogene of ammoniac for the nitrous gas of nitric acid.
At temperatures below 300°, the salt, from the equilibrium between these affinities, preserves its existence.
Now when its temperature is raised to 400°, the attractions of hydrogene for nitrogene,90 and of nitrous gas for oxygene,91 are diminished; whilst the attraction of hydrogene for oxygene92 is increased; and perhaps that of nitrogene for nitrous gas.
Hence the former equilibrium of affinity is destroyed, and a new one produced.
The hydrogene of the ammoniac combines with the oxygene of the nitric acid to generate water; and the nitrogene of the ammoniac enters into combination with the nitrous gas to form nitrous oxide: and the water and nitrous oxide produced, most probably exist in binary combination in the aëriform state, at the temperature of the decomposition.
But when a heat above 800° is applied to nitrate of ammoniac, the attractions of nitrogene and hydrogene for each other, and of oxygene for nitrous gas,93 are still more diminished; whilst that of nitrogene for nitrous gas is destroyed, and that of hydrogene for oxygene increased to a great extent: likewise a new attraction takes place; that of nitrous gas for nitric acid, to form nitrous vapor.94 Hence a new arrangement of principles is rapidly produced; the nitrogene of ammoniac having no affinity for any of the single principles at this temperature, enters into no binary compound: the oxygene of the nitric acid forms water with the hydrogene, and the nitrous gas combines with the nitric acid to form nitrous vapor. All these substances most probably exist in combination at the temperature of their production; and at a lower temperature, assume the forms of nitrous acid, nitrous gas, nitrogene, and water.
I have avoided entering into any discussions concerning the light and heat produced in this process; because these phænomena cannot be reasoned upon as isolated facts, and their relation to general theory will be treated of hereafter.
X. On the preparation of Nitrous Oxide
for experiments on Respiration.
When compact nitrate of ammoniac is slowly decomposed, the nitrous oxide produced is almost immediately fit for respiration; but as one part of the salt begins to decompose before the other is rendered fluid, a considerable loss is produced by sublimation.
For the production of large quantities of nitrous oxide, fibrous nitrate of ammoniac should be employed. This salt undergoes no decomposition till the greater part of its water is evaporated, and in consequence at the commencement of that process, is uniformly heated.
The gas produced from fibrous nitrate, must be suffered to rest at least for an hour after its generation. At the end of this time it is generally fit for respiration. If examined before, it will be found to contain more or less of a white vapor, which has a disagreeable acidulous taste, and strongly irritates the fauces and lungs. This vapor, most probably, consists of acid nitrate of ammoniac and water, which were dissolved by the gas at the temperature of its production, and afterwards slowly precipitated.
It is found in less quantity when compact nitrate is employed, because more salt is sublimed in this process, which being rapidly precipitated, carries with it the acid and water.
Whatever salt is employed, the last portions of gas produced, generally contain less vapor, and may in consequence be respired sooner than the first.
The nitrate of ammoniac should never be decomposed in a metallic vessel,95 nor the gas produced suffered to come in contact with any metallic surface; for in this case the free nitric acid will be decomposed, and in consequence, a certain quantity of nitrous gas produced.
The apparatus that has been generally employed in the medical pneumatic institution, for the production of nitrous oxide, consists
1. Of a glass retort, of the capacity of two or three quarts, orificed at the top, and furnished with a ground stopper.
2. Of a glass tube, conical for the purpose of receiving the neck of the retort; about,4 inches wide in the narrowest part, 4 feet long, curved at the extremity, so as to be capable of introduction into an airholder, and inclosed by tin plate to preserve it from injury.
3. Of airholders of Mr. Watt’s invention, filled with water saturated with nitrous oxide.
4. Of a common air-furnace, provided with dampers for the regulation of the heat.
The retort, after the insertion of the salt, is connected with the tube, carefully luted, and exposed to the heat of the furnace, on a convenient stand. The temperature is never suffered to be above 500°. After the decomposition has proceeded for about a minute, so that the gas evolved from the tube enlarges the flame of a taper, the curved end is inserted into the airholder, and the nitrous oxide preserved.
The water thrown out of the airholders in consequence of the introduction of the gas, is preserved in a vessel adapted for the purpose, and employed to fill them again; for if common water was to be employed in every experiment, a great loss of gas would be produced from absorption.
A pound of fibrous nitrate of ammoniac, decomposed at a heat not above 500°, produces nearly 5 cubic feet of gas; whilst from a pound of compact nitrate of ammoniac, rarely more than 4,25 cubic feet can be collected.
For the production of nitrous oxide in quantities not exceeding 20 quarts, a mode still more simple than that I have just described may be employed. The salt may be decomposed by the heat of an argands lamp, or a common fire, in a tubulated glass retort, of 20 or 30 cubic inches in capacity, furnished with a long neck, curved at the extremity; and the gas received in small airholders.
Thus, if the pleasurable effects, or medical properties of the nitrous oxide, should ever make it an article of general request, it may be procured with much less time, labor, and expence,96 than most of the luxuries, or even necessaries, of life.
Division IV
Experiments and OBSERVATIONS on the COMPOSITION of NITROUS GAS, and on its ABSORPTION by different bodies.
In my account of the composition of nitric acid, in Division I. I gave an estimation of the quantities of oxygene and nitrogene combined in nitrous gas: I shall now detail the experiments on which that estimation is founded.
At an early period of my researches relating to nitrous oxide, from the observation of the phænomena taking place during the production of this substance, I had concluded, that the common opinion with regard to the composition of nitrous gas, was very distant from the truth. I had indeed analysed nitrous gas, by converting it into nitrous oxide, before I attempted to ascertain its composition by immediately separating the constituent principles from each other: and my first hopes of the possibility of effecting this, were derived from Dr. Priestley’s experiments on the combustion of pyrophorus in nitrous gas, and on the changes effected in it, by heated iron and charcoal.
This great philosopher found, that pyrophorus placed in contact with nitrous gas, burnt with great vividness, whilst the gas was diminished in volume to about one half, which generally consisted of nitrogene and nitrous oxide. He likewise found, iron heated by a lens in nitrous gas, increased in weight, whilst the gas was diminished about ½, and converted into nitrogene.97
He heated common charcoal, and charcoal of copper,98 in nitrous gas by a lens. When common charcoal was employed, the gas was neither increased or diminished in bulk, but wholly converted into nitrogene; when charcoal of copper was used, the volume was a little increased, and the gas remaining consisted of ⁵/₇ nitrogene, and ²/₇ carbonic acid.
In his experiments on the iron and pyrophyrus, the nitrous gas was evidently decomposed. From the great quantity of nitrogene produced in those on the charcoal, it seems likely that both the common charcoal,99 and the charcoal of copper employed contained atmospherical air, which being dispelled by the heat of the lens, was decomposed by the nitrous gas: indeed, till I made the following experiment, I suspected that the carbonic acid produced, when the charcoal of copper was employed, arose from a decomposition of the nitrous acid, formed in this way.
I introduced a piece of well-burnt charcoal, which could hardly have weighed the eighth of a grain, whilst red hot, under a cylinder filled with mercury, and admitted to it half a cubic inch of nitrous gas. A slight absorption took place.
The sun being very bright, I kept the charcoal in the focus of a small lens for near a quarter of an hour. At the end of this time the gas occupied a space nearly as before the experiment, and a very minute portion of the charcoal had been consumed. On introducing into the cylinder a small quantity of solution of strontian, a white precipitation was perceived, and the gas slowly diminished to about three tenths of a cubic inch. To these three tenths a little common air was admitted, when very slight red fumes were perceived.
This experiment convinced me, that the attraction of charcoal for the oxygene of nitrous gas, at high temperatures, was sufficiently strong to effect a slow decomposition of it.
To be more accurately acquainted with this decomposition, and to learn the quantities of carbonic acid and nitrogene produced from a known quantity of nitrous gas, I proceeded in the following manner.
II. Analysis of Nitrous Gas by Charcoal.
A quantity of nitrous gas was procured in a water apparatus, from the decomposition of nitrous acid by mercury. A portion of it was transferred to the mercurial trough. After the mercury and the jar had been dried by bibulous paper, 40 measures of this portion were agitated in a solution of sulphate of iron. The gas remaining after the absorption was complete, filled about a measure and half; so that the nitrous gas contained nearly ¹/₂₆ nitrogene.
Thermometer being 53°, a small piece of well-burnt charcoal, the weight of which could hardly have equalled a quarter of a grain, was introduced ignited, into a small cylinder filled with mercury, graduated to,10 grain measures; to this, 16 measures, equal to 160 grain m. of nitrous gas, were admitted. An absorption of about one measure and half took place. When the focus of a lens was thrown on the charcoal, a slight increase of the gas was produced, from the emission of that which had been absorbed.
After the process had been carried on for about a half an hour, the charcoal evidently began to fume, and to consume very slowly, though no alteration in the volume of the gas was observed.
The sun not constantly shining, the progress of the experiment was now and then stopped: but taking the whole time, the focus could not have been applied to it for less than four hours. When the process was finished, the gas was increased in bulk nearly three quarters of a measure.
A drop of water was introduced into the cylinder, by means of a small glass tube, on the supposition that the carbonic acid, and nitrogene, might be capable of holding in solution, more water than that contained in the nitrous gas decomposed; but no alteration of volume took place.
When 20 grain measures of solution of pale green100 sulphate of iron were introduced into the cylinder, they became rather yellower than before, but not dark at the edges, as is always the case when nitrous gas is present. On agitation, a diminution of nearly half a measure was produced, doubtless from the absorption of some of the carbonic acid by the solution.
A small quantity of caustic potash, much more than was sufficient to decompose the sulphate of iron, was now introduced. A rapid diminution took place, and the gas remaining filled about 8 measures. This gas was agitated for some time over water, but no absorption took place. Two measures of it were then transferred into a detonating cylinder with two measures of oxygene. The electric spark was puffed through them, but no diminution was produced. Hence it was nitrogene, mingled with no ascertainable quantity of hydrogene: consequently little or no water could have been decomposed in the process.
Now supposing, for the greater ease of calculation, each of the measures employed, cubic inches.
16 of nitrous gas—¹/₂₆ = 15,4 were decomposed, and these weigh, making the necessary corrections, 5,2; but 7,4 nitrogene were produced, and these weigh about 2,2. So that reasoning from the relative specific gravities of nitrous gas and nitrogene, 5,2 grains of nitrous gas will be composed of 3 oxygene, and 2,2 nitrogene.
But 8,7 of carbonic acid were produced, which weigh 4,1 grains, and consist of 2,9 oxygene, and 1,2 charcoal.101 Consequently, drawing conclusions from the quantity of carbonic acid formed, 5,2 grains of nitrous gas will consist of 2,9 oxygene, and 2,3 nitrogene.
The difference in these estimations is much less than could have been expected; and taking the mean proportions, it would be inferred from them, that 100 grains of nitrous gas, contain 56,5 oxygene, and 43,5 nitrogene.
I repeated this experiment with results not very different, except that the increase of volume was rather greater, and that more unabsorbable gas remained; which probably depended on the decomposition of a minute quantity of water, that had adhered to the charcoal in passing through the mercury.
As nitrous gas is decomposable into nitrous acid, and nitrogene, by the electric spark; it occurred to me, that a certain quantity of nitrous acid might have been possibly produced, in the experiments on the decomposition of nitrous gas, by the intensely ignited charcoal. To ascertain this circumstance, I introduced into 12 measures of nitrous gas, a small piece of charcoal which had been just reddened. The sun being very bright, the focus of the lens was kept on it for rather more than an hour and quarter. In the middle of the process it began to fume and to sparkle, as if in combustion. In three quarters of an hour, the gas was increased rather more than half a measure; but no alteration of volume took place afterwards.
The mercury was not white on the top as is usually the case when nitrous acid is produced. On introducing into the cylinder a little pale green sulphate of iron, and then adding prussiate of potash, a white precipitate only was produced. Now, if the minutest quantity of nitric acid had been formed, it would have been decomposed by the pale green oxide of iron, and hence, a visible quantity of prussian blue102 produced, as will be fully explained hereafter.
III. Analysis of Nitrous Gas by Pyrophorus.
I placed some newly made pyrophorus, about as much as would fill a quarter of a cubic inch, in a jar filled with dry mercury, and introduced to it, four cubic inches of nitrous gas, procured from mercury and nitric acid.
It instantly took fire and burnt with great vividness for some moments.
After the combustion had ceased, the gas was diminished about three quarters of a cubic inch. The remainder was not examined; for the diminution appeared to go on for some time, after; in an half hour, when it was compleat, it was to 2 cubic inches. A taper, introduced into these, burnt with an enlarged flame, blue at the edges; from whence it appeared, that they were composed of nitrogene and nitrous oxide.
I now introduced about half a cubic inch of pyrophorus to two cubic inches of nitrous gas; the combustion took place, and the gas was rapidly diminished to one half; and on suffering it to remain five minutes to one third nearly; which extinguished flame.
Suspecting that this great diminution was owing to the absorption of some of the nitrogene formed, by the charcoal of the pyrophorus, I carefully made a quantity of pyrophorus; employing more than two thirds of alumn, to one third of sugar.
To rather more than half of a cubic inch of this, two cubic inches of nitrous gas, which contained about ¹/₄₀ nitrogene, were admitted. After the combustion, the gas remaining, apparently filled a space equal to 1,2 cubic inches; but, as on account of the burnt pyrophyrus in the jar, it was impossible to ascertain the volume with nicety, it was carefully and wholly transferred into another jar. It filled a space equal to 1,15 cubic inches nearly.
When water was admitted to this gas no absorption took place. It underwent no diminution with nitrous gas, and a taper plunged into it was instantly extinguished. We may consequently conclude that it was nitrogene.
Now 2 cubic inches of nitrous gas weigh,686 grains, and 1,1 of nitrogene—,05, the quantity previously contained in the gas = to 1,05, 3,19. Hence,686 of nitrous gas would be composed of,367 oxygene, and,319 nitrogene; and 100 grains would contain 53,4 oxygene, and 46,6 nitrogene.
IV. Additional observations on the combustion of bodies in Nitrous Gas,
and on its Composition.
Though phosphorus may be fused, and even sublimed, in nitrous gas, without producing the slightest luminous appearance,103 yet when it is introduced into it in a state of active inflammation, it burns with almost as much vividness as in oxygene.104 Hence it is evident, that at the heat of ignition, phosphorus is capable of attracting the oxygene from the nitrogene of nitrous gas.
I attempted to analise nitrous gas, by introducing into a known quantity of it, confined by mercury, phosphorus, in a vessel containing a minute quantity of oxygene.105 The phosphorus was inflamed with an ignited iron wire, by which, at the moment of the combustion, the vessel containing it was raised from the mercury into the nitrous gas. But after making in this way, five of six unsuccessful experiments, I desisted. When the communication between the vessels was made before the oxygene was nearly combined with the phosphorus, nitrous acid was formed, which instantly destroyed the combustion; when, on the contrary, the phosphorus was suffered to consume almost the whole of the oxygene, it was not sufficiently ignited when introduced, to decompose the nitrous gas.
In one experiment, indeed, the phosphorus burnt for a moment in the nitrous gas; the diminution however was slight, and not more than ¼ of it was decomposed.
Sulphur, introduced in a state of vivid inflammation, into nitrous gas, was instantly extinguished.
I passed a strong electric shock through equal parts of hydrogene and nitrous gas, confined by mercury in a detonating tube; but no inflammation, or perceptible diminution, was produced.
19,2 grain measures of hydrogene were fired by the electric shock, with 10 of nitrous oxide, and 6 of nitrous gas; the diminution was to 17; and pale green sulphate of iron admitted to the residuum, was not discolored. Consequently the nitrous gas was decomposed by the hydrogene, and as will be hereafter more clearly understood, nearly as much nitrogene furnished by it, as would have been produced from half the quantity of nitrous oxide.
Suspecting that phosphorated hydrogene might inflame with nitrous gas, I passed the electric spark through 1 measure of phosphorated hydrogene, and 4 of nitrous gas; but no diminution was perceptible. I likewise passed the electric spark through 1 of nitrous gas, with 2 of phosphorated hydrogene, without inflammation.
Perhaps if I had tried many other different proportions of the gases, I should have at last discovered one, in which they would have inflamed; for, as will be seen hereafter, nitrous oxide cannot be decomposed by the compound combustible gases, except definite quantities are employed.
From Dr. Priestley’s experiments on iron and pyrophorus, and from the experiments I have detailed, on charcoal, phosphorus, and hydrogene, it appears that at certain temperatures, nitrous gas is decomposable by most of the combustible bodies: even the extinction of sulphur, when introduced into it in a state of inflammation, depends perhaps, on the smaller quantity of heat produced by the combustion of this body, than that of most others.
The analysis of nitrous gas by charcoal, as affording data for determining immediately the quantities of oxygene and nitrogene, ought to be considered as most accurate; and correcting it by mean calculations derived from the decomposition of nitrous gas by pyrophorus and hydrogene, and its conversion into nitrous oxide, a process to be described hereafter, we may conclude, that 100 grains of nitrous gas are composed of 55,95 oxygene, and 44,05 nitrogene; or taking away decimals, of 56 oxygene, and 44 nitrogene.
This estimation will agree very well with the mean proportions that would be given from Dr. Priestley’s experiments on the decomposition of nitrous gas by iron; but as he never ascertained the purity of his nitrous gas,106 and probably employed different kinds in different experiments, it is impossible to fix on any one, from which accurate conclusions can be drawn.
Lavoisier’s estimation of the quantities of oxygene and nitrogene entering into the composition of nitrous gas, has been generally adopted. He supposes 64 parts of nitrous gas to be composed of 43½ of oxygene, and 20½ of nitrogene.107
The difference between this account and mine is very great indeed; but I have already, in Division 1st, pointed out sources of error in the experiments of this great man, on the decomposition of nitre by charcoal; which experiments were fundamental, both to his accounts of the constitution of nitrous acid, and nitrous gas.
V. Of the absorption of Nitrous Gas by Water.
Amongst the properties of nitrous gas noticed by its great discoverer, is that of absorbability by water.
In exposing nitrous air to distilled water, Dr. Priestley found a diminution of the volume of gas, nearly equal to one tenth of the bulk of the water; and by boiling the water thus impregnated, he procured again a certain portion of the nitrous gas.
Humbolt, in his paper on eudiometry, mentions the diminution of nitrous gas by water. This diminution, he supposes to arise from the decomposition of a portion of the nitrous gas, by the water, and the consequent formation of nitrate of ammoniac.108
I confess, that even before the following experiments were made, I was but little inclined to adopt this opinion: the small diminution of nitrous gas by water, and the uniform limits of this diminution, rendered it extremely improbable.
a. To ascertain the quantity of nitrous gas absorbable by pure water, and the limits of absorption, I introduced into a glass retort about 5 ounces of water, which had been previously boiled for some hours. The neck of the retort was inverted in mercury, and the water made to boil. After a third of it had been distilled, so that no air could possibly remain in the retort, the remainder was driven over, and condensed in an inverted jar filled with mercury. To three cubic inches of this water,109 confined in a cylinder graduated to,05 cubic inches, 5 cubic inches of nitrous gas, containing nearly one thirtieth nitrogene, were introduced.
After agitation for near an hour, rather more than ⁴/₂₀ of a cubic inch appeared to be absorbed; but though the process was continued for near two hours longer, no further diminution took place.
The remaining gas was introduced into a tube graduated to,02 cubic inches. It measured ¹⁴/₅₀; hence ¹¹/₅₀ had been absorbed.
Consequently, 100 cubic inches of pure water are capable of absorbing 11,8 of nitrous gas. In the water thus impregnated with nitrous gas I could distinguish no peculiar taste;110 it did not at all alter the color of blue cabbage juice.
b. To determine if the absorption of nitrous gas was owing, to a decomposition of it by the water, as Humbolt has supposed, or to a simple solution; I procured some nitrous gas from nitrous acid and mercury, containing about one seventieth nitrogene.,5 cubic inches of it, mingled with,25, of oxygene, from sulphuric acid and manganese left a residuum of,03. 5 cubic inches more were introduced to 3 of water, procured in the same manner as in the last experiment, in the same cylinder. After the diminution was complete, the cylinder was transferred in a small vessel containing mercury, into a water bath, and nearly covered by the water.
As the bath was heated, small globules of gas were given out from the impregnated water, and when it began to boil, the production of gas was still more rapid. After an hour’s ebullition, the volume of heated gas was equal to 1,4 cubic inches nearly.
The cylinder was now taken out of the bath, and quickly rendered cool by being placed in a water apparatus. At the common temperature the gas occupied, as nearly as possible, the space of,5 cubic inches: these,5 mingled with,25 of oxygene, of the same kind as that employed before, left a residuum nearly equal to,03.
From this experiment, which was repeated with nearly the same results, it is evident,
1. That nitrous gas is not decomposable by pure water.
2. That the diminution of volume of nitrous gas placed in contact with water, is owing to a simple solution of it in that fluid.
3. That at the temperature of 212°, nitrous gas is incapable of remaining in combination with water.
Humbolt’s opinion relating to the decomposition of nitrous gas by water, is founded upon the disengagement of vapor from distilled water impregnated with nitrous gas, by means of lime, which became white in the proximity of the muriatic acid. But this is a very imperfect, and fallacious test, of the presence of ammoniac. I have this day, April 2, 1800, heated 4 cubic inches of distilled water, impregnated with nitrous gas, with caustic lime; the vapor certainly became a little whiter when held over a vessel containing muriatic acid; but the vapor of distilled water produced precisely the same appearance,111 which was owing, most likely, to the combination of the acid with the aqueous vapor. Indeed, when I added a particle of nitrate of ammoniac, which might have equalled one twentieth of a grain, to the lime and impregnated water, the increased whiteness of the vapor was but barely perceptible, though this quantity of nitrate of ammoniac is much more considerable than that which could have been formed, even supposing the nitrous gas decomposed.
VI. Of the absorption of Nitrous Gas by
Water of different kinds.
In agitating nitrous gas over spring water, the diminution rarely amounts to more than one thirtieth, the volume of water being taken as unity. I at first suspected that this great differcnce in the quantity of gas absorbed by spring water, and pure water, depended on carbonic acid contained in the last, diminishing the attraction of it for nitrous gas: but by long boiling a quantity of spring water confined by mercury, I obtained from it about one twentieth of its bulk of air, which gave nearly the same diminution with nitrous gas, as atmospheric air.
This fact induced me to refer the difference of diminution to the decomposition of the atmospheric air held in solution by the water, the oxygene of which I supposed to be converted into nitric acid, by the nitrous gas, whilst the nitrogene was liberated; and hence the increased residuum.
a. I exposed to pure water, that is, water procured by distillation under mercury, nitrous gas, containing a known quantity of nitrogene. After the absorption was complete, I found the same quantity of nitrogene in the residuum, as was contained in a volume of gas equal to the whole quantity employed.
b. Spring water boiled for some hours, and suffered to cool under mercury, absorbed a quantity of nitrous gas equal to one thirteenth of its bulk; which is not much less than that absorbed by pure water.
c. I exposed to spring water, 10 measures of nitrous gas; the composition of which had been accurately ascertained; the diminution was one twenty-eighth, the volume of water being taken as unity. On placing the residuum in contact with solution of sulphate of iron, the nitrogene remaining was nearly one twentieth more than had been contained by the gas before its exposure to water.
d. Distilled water was saturated with common air, by being agitated for some time in the atmosphere. Nitrous gas placed in contact with this water, underwent a diminution of ¹/₁₈; the volume of water being unity. The gas remaining after the absorption contained about one twenty-seventh nitrogene more than before.
e. Nitrous gas exposed to water combined with about one fourth of its volume of carbonic acid, diminished to ¹/₃₂112 nearly. The remainder contained little or no superabundant nitrogene.
From these observations it appears, that the different degrees of diminution of nitrous gas by different kinds of water, may depend upon various causes.
1. Less nitrous gas will be absorbed by water holding in solution earthy salts, than by pure water; and in this case the diminution of the attraction of water for nitrous gas will probably be in the ratio of the quantities of salt combined with it. a. b.
2. The apparent diminution of nitrous gas in water, holding in solution atmospheric air, will be less than in pure water, though the absolute diminution will be greater; for the same portion will be absorbed, whilst another portion is combined with the oxygene of the atmospheric air contained in the water; and from the disengagement of the nitrogene of this air, arises an increased residuum. c. d.
3. Probably in waters containing nitrogene, hydrogene, and other gases, absorbable only to a slight extent, the apparent diminution will be less, on account of the disengagement of those gases from the water, by the stronger affinity of nitrous gas for that fluid.
4. In water containing carbonic acid, and probably some other acid gases, the diminution will be small in proportion to the quantity of gas contained in the water: the affinity of this fluid for nitrous gas being diminished by its greater affinity for the substance combined with it. e.
The different diminution of nitrous gas when agitated in different kinds of water, has been long observed by experimenters on the constituent parts of the atmosphere, and various solutions have been given of the phænomenon; the most singular is that of Humbolt.113 He supposes that the apparent diminution of nitrous gas is less in spring water than distilled water, on account of the decomposition of the carbonate of lime contained in the spring water, by the nitrous acid formed from the contact of nitrous gas with the water; the carbonic acid disengaged from this decomposition increasing the residuum.
This opinion may be confuted without even reference to my observations. It is, indeed, altogether unworthy of a philosopher, generally acute and ingenious. He seems to have forgotten that carbonic acid is absorbable by water.
VII. Of the absorption of Nitrous Gas, by solution
of pale green Sulphate of Iron.
a. The discovery of the exact difference between the sulphates of iron, is owing to Proust.114 According to the ingenious researches of this chemist, there exist two varieties of sulphate of iron, the green and the red. The oxide in the green sulphate contains ²⁷/₁₀₀ oxygen. This salt, when pure, is insoluble in spirit of wine; its solution in water is of a pale green color; it is not altered by the gallic acid, and affords a white precipitate with alkaline prussiates.
The red sulphate of iron is soluble in alcohol and uncrystalizable; its oxide contains ⁴⁸/₁₀₀ oxygene. It forms a black precipitate with the gallic acid, and with the alkaline prussiates, a blue one.
The common sulphates of iron generally consist of combinations of these two varieties in different proportions.
The green sulphate may be converted into the red by oxygenated muriatic acid or nitric acid. The common sulphate may be converted into green sulphate, by agitation in contact with sulphurated hydrogene.
The green sulphate has a strong affinity for oxygene, it attracts it from the atmosphere, from oxygenated marine acid, and nitric acid. The alkalies precipitate from it a pale green oxide, which if exposed to the atmosphere, rapidly becomes yellow red.
The red sulphate of iron has no affinity for oxygene, and when decomposed by the alkalies, gives a red precipitate, which undergoes no alteration when exposed to the atmosphere.115
b. The absorption of nitrous gas by a solution of sulphate of iron, was long ago discovered by Priestley. During this absorption, he remarked a change of color in the solution, analogous to that produced by the mixture of it with nitric acid.
This chemical fact has been lately applied by Humbolt, to the discovery of the nitrogene generally mingled with nitrous gas.
Vauquelin and Humbolt have published a memoir, on the causes of the absorption116 of nitrous gas by solution of sulphate of iron. They saturated an ounce and half of sulphate of iron in solution, with 180 cubic inches of nitrous gas.
Thus impregnated it strongly reddened tincture of turnsoyle; when mingled with sulphuric acid, gave nitric acid vapor; and saturated with potash, ammoniacal vapor.
By analysis, it produced as much ammoniac as that contained in 4 grains of ammoniacal muriate, and a quantity of nitric acid equal to that existing in 17 grains of nitre. Hence they concluded, that the nitrous gas and a portion of the water of the solution, had mutually decomposed each other; the oxygene of the water combining with the oxygene and a portion of the nitrogene of nitrous gas to form nitric acid; and its hydrogene uniting with the remaining nitrogene, to generate ammoniac.
They have taken no notice of the nature of the sulphate of iron employed, which was most probably the common or mixed sulphate; nor of the attraction of the oxide of iron in this substance for oxygene.
c. Before I was acquainted with the observations of Proust, the common facts relating to the oxygenation of vitriol of iron induced me to suppose, that the attraction of this substance for oxygene was in some way connected with the process of absorption. The comparison of the experiments of Humbolt and Vauquelin, with the observations of Proust, enabled me to discover the true nature of the process.
I procured a solution of red sulphate of iron, by passing oxygenated muriatic acid through a solution of common sulphate of iron, till it gave only a red precipitate, when mingled with caustic potash. To nitrous gas confined by mercury, a small quantity of this solution was introduced. On agitation, its color altered to muddy green; but the absorption that took place was extremely trifling: in half an hour it did not amount to,2, the volume of the solution being unity, when it had nearly regained the yellow color.
I now obtained a solution of green sulphate of iron, by dissolving iron filings in diluted sulphuric acid. The solution was agitated in contact with sulphurated hydrogene, and afterwards boiled; when it gave a white precipitate with prussiate of potash.
A small quantity of this solution agitated in nitrous gas, quickly became of an olive brown, and the gas was diminished with great rapidity; in two minutes, a quantity equal to four times the volume of the solution, had been absorbed.
These facts convinced me that the solubility of nitrous gas in common sulphate of iron, chiefly depended upon the pale green sulphate contained by it; and that the attraction of one of the constituents of this substance, the green oxide of iron, for oxygene, was one of the causes of the phænomenon.
d. Green sulphate of iron rapidly decomposes nitric acid. It was consequently difficult to conceive how any affinities existing between nitrous gas, water, and green sulphate of iron, could produce the nitric acid found in the experiments of Vauquelin and Humbolt.
To ascertain if the presence of a great quantity of water destroyed the power of green sulphate of iron to decompose nitric acid, I introduced into a cubic inch of solution of green sulphate of iron, two drops of concentrated nitric acid.
The solution assumed a very light olive color; prussiate of potash mingled with a little of it, gave a dark green precipitate. Hence the nitric acid had been evidently decomposed. As no nitrous gas was given out, which is always the case when nitric acid is poured on crystalised sulphate of iron, I suspected that a compleat decomposition of the acid had taken place; but when the solution was heated, a few minute globules of gas were liberated, and it gradually became slightly clouded.
Having often remarked that no precipitation is ever produced during the conversion of green sulphate of iron into red, by oxygenated muriatic acid, or concentrated nitric acid, I could refer the cloudiness to no other cause than to the formation of ammoniac.
To ascertain if this substance had been produced, a quantity of slacked caustic lime was thrown into the solution. On the application of heat, the ammoniacal smell was distinctly perceptible, and the vapor held over orange nitrous acid, gave dense white fumes.
e. When I considered this fact of the decomposition of nitric acid and water by the solution of green sulphate of iron, and the change of color effected in it by the absorption of nitrous gas, exactly analogous to that produced by the decomposition of nitric acid; I was induced to believe that the nitric acid found in the analysis of Vauquelin and Humbolt, had been formed by the combination of some of the nitrous gas thrown into the solution with the oxygene of the atmosphere: and that the absorbability of nitrous gas, by solution of green sulphate of iron, was owing to a decomposition produced by the combination of its oxygene with the green oxide of iron, and of its nitrogene with the hydrogene disengaged from water, decompounded at the same time.
To ascertain this, I procured a quantity of nitrous gas: it was suffered to remain in contact with water for some hours after its production. Transferred to the mercurial apparatus, it gave no white vapor when placed in contact with solution of ammoniac; and consequently held no nitric acid in solution.
Into a graduated jar filled with mercury, a cubic inch of concentrated solution of pure green sulphate of iron was introduced, and 7 cubic inches of nitrous gas admitted to it. The solution immediately became dark olive at the edges, and on agitation this color was diffused through it. In 3 minutes, when near 5¾ cubic inches had been absorbed, the diminution ceased. The solution was now of a bright olive brown, and transparent at the edges. After it had rested for a quarter of an hour, no farther absorption was observed; the color was the same, and no precipitation could be perceived. A little of it was thrown into a small glass tube, under the mercury, and examined in the atmosphere. Its taste was rather more astringent than that of solution of green sulphate; it did not at all alter the color of red cabbage juice. When a little of it was poured on the mercury, it soon lost its color, its taste became acid, and it quickly reddened cabbage juice, even rendered green by an alkali.
To the solution remaining in the mercurial jar, a small quantity of prussiate of potash was introduced, to ascertain if any red sulphate of iron had been formed; but instead of the production of either a blue, or a white precipitate, the whole of the solution became opaque, and chocolate colored.
Surprised at this appearance, I was at first induced to suppose, that the ammoniac formed by the nitrogene of the nitrous gas and the hydrogene of the water, had been sufficient to precipitate from the sulphuric acid, the red oxide of iron produced, and that the color of the mixture was owing to this precipitation. To dissolve any uncombined oxide that might exist in the solution, I added a very minute quantity of diluted sulphuric acid; but little alteration of color was produced. Hence, evidently, no red oxide had been formed.
This unexpected result obliged me to theorise a second time, by supposing that nitrate of ammoniac had been produced, which by combining with the white prussiate of iron, generated a new combination. But on mingling together green sulphate of iron, prussiate of potash, and nitrate of ammoniac in the atmosphere, the mixture remained perfectly white.
To ascertain if any nitric acid existed, combined with any of the bases, in the impregnated solution, I introduced into it an equal bulk of diluted sulphuric acid: it became rather paler; but no green or blue tinge was produced.
That the prussic acid had not been decomposed, was evident from the bright green produced, when less than a grain of dilute nitric acid was admitted into the solution.
f. From these experiments it was evident, that no red sulphate of iron, or nitric acid, and consequently no ammoniac, had been produced after the absorption of nitrous gas by green sulphate of iron. And when I compared them with the observations of Priestley, who had expelled by heat a minute quantity of nitrous gas from an impregnated solution of common sulphate of iron, and who found common air phlogisticated by standing in contact with it, I began to suspect that nitrous gas was simply dissolved in the solution, without undergoing decomposition.
g. To determine more accurately the nature of the process, I introduced into a mercurial cylinder 410 grains of solution of green sulphate of iron, occupying a space nearly equal to a cubic inch and quarter; it was saturated with nitrous gas, by absorbing 8 cubic inches. This saturated solution exhibited the same appearance as the last; and after remaining near an hour untouched, had evidently deposited no oxide of iron, nor gained any acid properties.
Into a small mattrass filled with mercury, having a tight stopper with a curved tube adapted to it, the greater part of this solution was introduced; judging from the capacity of the mattrass, about 50 grains of it might have been lost. To prevent common air from coming in contact with the solution, the stopper was introduced into the mattrass under the mercury; the curved tube connected with a graduated cylinder filled with that substance; and the mattrass brought over the side of the mercurial trough. But in spite of these precautions a large globule of common air got into the top of the mattrass, from the curvature of the tube. When the heat of a spirit lamp was applied to the solution, it gave out gas with great rapidity, and gradually lost its color. When 5 cubic inches were collected it became perfectly pale green, whilst a yellow red precipitate was deposited on the bottom of the mattrass.
On pouring a little of the clear solution into prussiate of potash, it gave only white prussiate of iron.
But on introducing a particle of sulphuric acid into the solution, sufficient to dissolve some of the red precipitate, and then pouring a little of it into a solution of prussiate of potash, it gave a fine blue prussiate of iron.
Hence the red precipitate was evidently red yellow oxide of iron.
I now examined the gas, suspecting that it was nitrous oxide. On mingling a little of it with atmospheric air, it gave red vapor, and diminished. Solution of sulphate of iron introduced to the remainder, almost wholly absorbed it: the small residual globule of nitrogene could not equal one thirtieth of a cubic inch.
Consequently it was nitrous gas, nearly pure.
Caustic potash was now introduced into the solution, till all the oxide of iron was precipitated. The solution, when heated, gave a strong smell of ammoniac, and dense white fumes when held over muriatic acid. It was kept at the heat of ebullition till the evaporation had been nearly compleated. Sulphuric acid poured upon the residuum gave no yellow fumes, or nitric acid vapor in any way perceptible; even when heated and made to boil, there was no indication of the production of any vapor, except that of the sulphuric acid.
h. This experiment, compared with the others, seemed almost to prove, that nitrous gas combined with solution of pale green sulphate of iron, at the common temperature, without decomposition; and that when the impregnated solution was heated, the greater portion of gas was disengaged, whilst the remainder was decompounded by the green oxide of iron; which attracted at the same time oxygene from the water and the nitrous gas; whilst their other constituent principles, hydrogene and nitrogene, entered into union as ammoniac.
Whilst, however, I was reasoning upon this singular chemical change, as affording presumptive proofs in favor of the exertion of simple affinities by the constituent parts of compound substances, a doubt concerning the decomposition of the nitrous gas occurred to me. As near as I could guess at the quantity of nitrous gas contained by the impregnated solution, at least ¾ of it must have been expelled undecompounded.
More than a quarter of a cubic inch of common air had been present in the mattrass: the oxygene of this common air must have combined with the nitrous gas, to form nitric acid. Might not this nitric acid have been decomposed, and furnished oxygene to the red oxide of iron, and nitrogene to the small quantity of ammoniac found in the solution, as in d?
i. I now introduced to a solution of green sulphate confined by mercury, nitrous gas, perfectly free from nitric acid. When the solution was saturated, a portion of it was introduced into a small mattrass filled with dry mercury, in the mercurial trough. The curved tube was closed by a small cork at the top, and filled with nitrous gas; it was then adapted to the mattrass, which was raised from the trough, and the solution thus effectually preserved from the contact of the atmosphere.
When the heat of a spirit lamp was applied to the mattrass, it began to give out gas with great rapidity. After some time the solution lost its dark color, and became turbid. When the production of nitrous gas had ceased, it was suffered to cool. A copious red precipitate had fallen down; which, examined by the same tests as in the last experiment, proved to be red oxide of iron.
The solution treated with lime, as before, gave ammoniac; but with sulphuric acid, not the slightest indications of nitric acid.
k. Having thus procured full evidence of the decomposition of nitrous gas in the heated solution, in order to gain a more accurate acquaintance with the affinities exerted, I endeavoured to ascertain the quantity of nitrous gas decomposed by a given solution, under known circumstances.
Into a cylinder of the capacity of 20 cubic inches, inverted in mercury, 1150 grains of solution of green sulphate of iron, of specific gravity 1,4, were introduced. Nitrous gas was admitted to it, and after some time 21 cubic inches were absorbed.
The impregnated solution was thrown into a mattrass, in the same manner as in the last experiment, and the same precautions taken to preserve it from the contact of atmospheric air. A quantity was lost during the process of transferring, which, reasoning from the space occupied in the mattrass by the remaining portion, as determined by experiment afterwards, must have amounted nearly to 240 grains.
The curved tube from the mattrass was now made to communicate with the mercurial airholder. By the application of heat 12,5 cubic inches of nitrous gas were collected, after the common temperature had been restored to the mattrass; which was suffered to remain in communication with the conducting tube.
The solution was now pale green, that is, of its natural color, and a considerable quantity of red oxide of iron had been deposited.
Solid caustic potash was introduced into it, till all the green oxide of iron had been precipitated, and till the solution rendered green, red cabbage juice.
A tube was now accurately connected with the mattrass, bent, and introduced into a small quantity of diluted sulphuric acid. Nearly half of the fluid in it was slowly distilled into the sulphuric acid, by the heat of a spirit lamp. The impregnated acid evaporated at a heat above 212°, and gave a small quantity of crystalised salt, which barely amounted to two grains and quarter: it had every property of sulphate of ammoniac. Sulphuric acid in excess was poured on the residuum, and the whole distilled by a heat not exceeding 300°, into a small quantity of water. This water, after the process, tasted strongly of sulphuric acid; it had no peculiar odor. Tin thrown into it when heated, was not perceptibly oxydated; mingled with strontitic lime water, it gave a copious white precipitate, and after the precipitation became almost tasteless. Hence it evidently contained no nitric acid.
The 12,5 cubic inches of undecompounded gas that came over were examined; and accounting for the small quantity of common air previously contained in the airholder, must have been almost pure.
l. Now supposing 927 grains of the impregnated solution (including the weight of the nitrous gas), to have been operated upon, this must have contained about 16,7 cubic inches of nitrous gas. But 12,5 cubic inches escaped undecompounded: hence 4,2 were decomposed; and these weigh 1,44 grains, and are composed of,8 oxygene, and,64 nitrogene.117
Consequently, the nitrous gas must have furnished,8 of oxygene to the green oxide of iron.
But,64 of nitrogene require,15 of hydrogene to form,79 of ammoniac:118 consequently 1 of water was decompounded, and this furnished,85 of oxygene to the green oxide of iron.
The green oxide of iron contains ²⁷/₁₀₀ oxygene; the red ⁴⁸/₁₀₀. But the whole quantity of oxygene supplied from the water and nitrous gas is 0,8 + 0,85 = 1,65; and calculating on the difference of the composition of the red and green oxide of iron, 5,7 grains of red oxide must have been deposited, and consequently these would saturate as much acid as,79 grains of ammoniac, or 4,1 grains of green oxide of iron.119
And supposing the ammoniac in sulphate of ammoniac to be to the acid as 1 is to 3,120 3.2 grains of sulphate of ammoniac must have been formed, containing about 2,4 grains acid; and then 6,5 grains of green sulphate of iron must have been decomposed.
Hence we gain the following equation:
| 6,5 green s. | = 2,41 sul. acid + 4,1 gr. ox. iron. |
| + | |
| 1,44 nit. gas | =,64 nitrogene +,8 oxygene. |
| + | |
| 1 water | =,85 oxygene, +,15 hydrogene, |
| equal | |
| 3,2 sul. am. | = 2,41 s. acid +,64 nit. +,15 hyd. |
| + | |
| 5,7 r. ox. iron | = 4,1 gr. ox. iron + 1,6 oxyg. |
Though the estimation of the quantities in this equation must not be considered as strictly accurate, on account of the degree of uncertainty that remains concerning the exact numerical expression of the quantities of the constituents of water, ammoniac, and the other compound bodies employed; yet as founded on a simple quantity, that is, the nitrous gas decomposed, it cannot be very distant from the truth.
The sulphate of ammoniac given by experiment, is considerably less than that which was really produced; much of it was probably carried off during the evaporation of the superabundant acid.
The conclusions that may be drawn from this experiment, afford a striking instance of the importance of the application of the science of quantity to the chemical changes: for the data being one chemical fact, the decomposition of a given quantity of nitrous gas by known agents; the composition of nitrous gas, of water, ammoniac, the oxides of iron, and sulphate of ammoniac; we are able not only to determine the quantities of the simple constituents that have entered into new arrangements, but likewise the composition of two compound bodies, the green and red sulphates of iron.121
m. Though from the experiments in e it appeared that no decomposition of nitrous gas had been produced during or even after its absorption by solution of sulphate of iron at the common temperature; yet a suspicion that it might take place slowly, and that indications of it might be given by deposition, induced me to examine minutely two impregnated solutions, one of which had been at rest, confined by mercury, for 19 hours, and the other for 27. In neither of them could I discover any deposition, or alteration of color, which might denote a change.
Two cubic inches of oxygene were admitted to half a cubic inch of one of these solutions. The oxygene was slowly absorbed, and the solution gradually lost its color.
To ascertain if during the conversion of the nitrous gas held in solution by sulphate of iron, into nitric acid, by the oxygene of the atmosphere at the common temperature, any water was decomposed; I suffered an impregnated solution, weighing nearly two ounces, to remain in contact with the atmosphere at 57°-62°, till it was become perfectly pale. It then had a strong acid taste, effervesced with carbonate of potash, and gave a blue precipitate with prussiate of potash.—It was saturated with quicklime, and heated: slight indications of the presence of ammoniac were perceived.
As in this experiment the nitric acid had been most probably decomposed by the green oxide of iron, as in f, I sent oxygenated muriatic acid through an impregnated solution, till all the green oxide of iron was converted into red, and all the nitrous gas into nitric acid.
This solution saturated with potash, and heated, gave no ammoniacal smell.
From these experiments we may conclude,
1st. That solution of red sulphate of iron has little or no affinity for nitrous gas122; and that solution of common sulphate absorbs nitrous gas only in proportion as it contains green sulphate.
2dly. That solutions of green sulphate of iron dissolve nitrous gas in quantities proportionable to their concentration, without effecting any decomposition of it at common temperatures. And the solubility of nitrous gas in solution of green sulphate, may be supposed to depend on an equilibrium of affinity, produced by the following simple attractions:
1. That of green oxide of iron for the oxygene of nitrous gas and water.
2. That of the hydrogene of the water for the nitrogene of the nitrous gas.
3. That of the principles of the sulphuric acid, for nitrogene and hydrogene.
3dly. That at high temperatures, that is, from 200° to 300°, the equilibrium of affinity producing the binary combination between nitrous gas and solution of green sulphate of iron is destroyed; the attraction of the green oxide of iron for oxygene being increased; whilst probably that of nitrogene for hydrogene is diminished.
Hence the nitrous gas is either liberated,123 in consequence of the affinity between oxygene and hydrogene, and oxygene and nitrogene not following the same ratio of alteration on increased temperature; or decomposed, because at a certain temperature the green oxide exerts such affinities upon water and nitrous gas, as to attract oxygene from both of them to form red oxide; whilst the still existing affinity between the hydrogene of the one, and the nitrogene of the other, disposes them to combine to form ammoniac.
4thly. That the change of color produced by introducing nitric acid to solution of common sulphate of iron, exactly analogous to that occasioned in it by impregnation with nitrous gas, is owing to the decomposition of the acid, by the combination of its oxygene with the green oxide of iron, and of its nitrous gas with the solution.
5thly. That nitrous gas in combination with solution of green sulphate of iron, is capable of exerting a strong affinity upon free or loosely combined oxygene, and of uniting with it to form nitric acid.
n. The products obtained from a solution of sulphate of iron saturated with nitrous gas, by Vauquelin and Humbolt, and their consequent mistake with regard to the nature of the process of absorption,124 must have arisen from exposure of their impregnated solution to the atmosphere.
Indeed, from the acidity of it, on examination, from the small portion of ammoniac, and the large quantity of nitric acid obtained, it appears most probable that the whole of the nitrous gas employed was converted into nitric acid, by combining with atmospheric oxygene; for no nitric acid could have been obtained in the mode in which they operated, unless the green oxide of iron in the solution had been previously converted into red.
VIII. On the absorption of Nitrous Gas by
solution of green Muriate of Iron.
a. The analogy between the affinities of the constituents of the muriate and sulphate of iron, induced me to conjecture that they possessed similar powers of absorbing nitrous gas; and I soon found that this was actually the case; for on agitating half a cubic inch of solution of muriated iron, procured by dissolving iron filings in muriatic acid, in nitrous gas, the gas was absorbed with great rapidity, whilst the solution assumed a deep and bright brown tinge.
b. Proust,125 who as I have before mentioned, supposes the existence of two oxides of iron only, one containing ²⁷/₁₀₀ oxygene, the other ⁴⁸/₁₀₀, has assumed, that the muriatic acid, and most other acids as well as the sulphuric, are capable of combining with these oxides, and of forming with each of them a distinct salt. He has, however, detailed no experiments on the muriates of iron.
As these salts are still more distinct from each other in their properties than the sulphates, and as these properties are connected with the phænomenon of the absorption and decomposition of nitrous gas, I shall detail the observations I have been able to make upon them.
c. When iron filings have been dissolved in pure muriatic acid, and the solution preserved from the contact of air, it is of a pale green color, and gives a white precipitate with alkaline prussiates. The alkalies throw down from it a light green oxide of iron.
When evaporated, it gives crystals almost white, which are extremely soluble in water; but insoluble in alcohol.
The solution of green muriate of iron has a great affinity for oxygene, and attracts it from the atmosphere, from nitric acid, and probably from oxygenated muriatic acid.
When red oxide of iron is dissolved in muriatic acid, or when nitric acid is decomposed by solution of green muriate of iron; the red muriate of iron is produced. The solution of this salt is of a deep brown red, its odor is peculiar, and its taste, even in a very diluted state, highly astringent. It acts upon animal and vegetable matters in a manner somewhat analogous to the oxygenated muriatic acid, rendering them yellowish white, or yellow.126
Sulphuric acid poured upon it, produces a smell resembling that of oxygenated muriatic acid. Evaporated at a low temperature, it gives an uncrystalisable dark, orange colored salt, which is soluble in alcohol, and when decomposed by the alkalies, gives a red precipitate. With prussiate of potash it gives prussian blue.
The common muriate of iron consists of different proportions of these two salts. It may be converted into red muriate by concentrated nitric acid, or into green by sulphurated hydrogene.
d. To ascertain if solution of red muriate of iron was capable of absorbing nitrous gas, I introduced into a jar filled with mercury, a cubic inch of nitrous gas, and admitted to it nearly half a cubic inch of solution of red muriate of iron. No discoloration took place. By much agitation, however, an absorption of nearly,2 was produced, and the solution became of a muddy green. But this change of color, and probably the absorption, was in consequence of the oxydation of either the mercury, or some imperfect metals combined with it, by the oxygene of the red muriate. For I afterwards found, that precisely the same change of color was produced when a solution was agitated over mercury.
e. I introduced to a cubic inch of concentrated solution of green muriate of iron, 7 cubic inches of nitrous gas, free from nitric acid; the solution instantly became colored at the edges, and on agitation absorbed the gas with much greater rapidity than even sulphate of iron; in a minute, only a quarter of a cubic inch remained.
The solution appeared of a very dark brown, but evidently no precipitation had taken place in it, and the edges, when viewed against the light, were transparent and puce colored.
Five cubic inches more of nitrous gas were now dissolved in the solution. The intensity of the color increased, and after an hour no deposition had taken place. A little of it was then examined in the atmosphere; it had a much more astringent taste than the unimpregnated solution, and effected no change in red cabbage juice. When prussiate of potash was introduced into it, its color changed to olive brown. A few drops of the solution, that had accidentally fallen on the mercury, soon became colorless, and then effervesced with carbonate of potash, and tasted strongly acid.
The remainder of the impregnated solution, which must have nearly equalled,75 cubic inches, was introduced into a mattrass, having a stopper and curved tube, as in the experiments on the solution of sulphate of iron; great care being taken to preserve it from the contact of air.
The mattrass was heated by a spirit lamp, the curved tube being in communication with a mercurial cylinder. Near 8 cubic inches of nitrous gas were collected, when the solution became of a muddy yellow. It was suffered to cool, and examined. A small quantity of yellow precipitate covered the bottom of the mattrass; the fluid was pellucid, and light green. A little of it thrown on prussiate of potash, gave a white precipitate, colored by streaks of light blue. When the yellow precipitate was partly dissolved by sulphuric acid, a drop of the solution, mingled with prussiate of potash, gave a deep blue green.
Hence, evidently, the precipitate was red oxide of iron.
Caustic potash in excess was introduced into the remainder of the solution, and it was heated. It gave an evident smell of ammoniac, and dense white fumes, when held over strong phlogisticated nitrous acid.
When half of it was evaporated, sulphuric acid in excess was poured on the remainder; muriatic acid was liberated, not perceptibly combined with any nitric acid.
f. In an experiment that I made to ascertain the quantity of nitrous gas capable of combining with solution of green muriate of iron; I found that,75 cubic inches of saturated solution absorbed about 18 of nitrous gas, which is nearly double the quantity combinable with an equal portion of the strongest solution of sulphate of iron. A part of this impregnated solution, heated slowly, gave out more gas in proportion to the quantity it contained, than the last, and consequently produced less precipitate; so that I am inclined to suppose it probable, that at a certain temperature, all the dissolved nitrous gas may be dispelled from a solution.
From these experiments we may conclude,
1st. That the solution of green muriate of iron absorbs nitrous gas in consequence of nearly the same affinities as solution of green sulphate of iron; its capability of absorbing larger quantities depending most probably on its greater concentration (that is, on the greater solubility of the muriate of iron), and perhaps, in some measure, on a new combining affinity, that of muriatic acid for oxygene.
2dly. That at certain temperatures nitrous gas is either liberated from solution of green muriate, or decomposed, by the combination of its oxygene with green oxide of iron, and of its nitrogene with hydrogene, produced from water decompounded by the oxide at the same time.
IX. Absorption of Nitrous Gas by
Solution of Nitrate of Iron.
a. As well as two sulphates and two muriates of iron, there exist two nitrates.127 When concentrated nitric acid is made to act upon iron, nitrous gas is disengaged with great rapidity, and with great increase of temperature: the solution assumes a yellowish tinge, and as the process goes on, a yellow red oxide is precipitated.
Nitrate of iron made in this way, gives a bright blue mingled with prussiate of potash, and decomposed by the alkalies, a red precipitate. Its solution has little or no affinity for nitrous gas.
b. When very dilute nitric acid, that is, such as of specific gravity 1,16, is made to oxydate iron, without the assistance of heat, the solution gives out no gas for some time, and becomes dark olive brown: when neutralised it gives, decomposed by the alkalies, a light green precipitate; and mingled with prussiate of potash, pale green prussiate of iron.
It owes its color to the nitrous gas it holds in solution. By exposure to the atmosphere it becomes pale, the nitrous gas combined with it being converted into nitric acid.
It is then capable of absorbing nitrous gas, and consists of pale nitrate of iron, mingled with red nitrate.
I have not yet obtained a nitrate of iron giving only a white precipitate with prussiate of potash, that is, such as contains only oxide of iron at its minimum of oxydation; for when pure green oxide of iron is dissolved by very dilute nitric acid, a small quantity of the acid is generally decomposed, which is likewise the case in the decomposition of nitre by green sulphate of iron. The solutions of nitrate of iron, however, procured in both of these modes, absorb nitrous gas with rapidity, and by sulphurated hydrogene might probably be converted into pale nitrate.
As it is impossible to obtain concentrated solutions of pale nitrate of iron, chiefly containing green oxide, its powers of absorbing nitrous gas cannot be compared with the muriatic and sulphuric solutions, unless they are made of nearly the same specific gravity.
Nitrous gas is disengaged by heat from the impregnated solution of nitrate of iron, at the same time that much red oxide of iron is precipitated. Whether any nitrous gas is decomposed, I have not yet ascertained; for when unimpregnated pale nitrate of iron is heated, a part of the acid, and of the water of the solution, is decomposed by the green oxide of iron;128 and in consequence ammoniac, and red nitrate of iron formed, whilst red oxide is precipitated.
X. Absorption of Nitrous Gas by other
Metallic Solutions.
a. White prussiate of iron in contact with water absorbs nitrous gas to a great extent, and becomes dark chocolate.129
b. Concentrated solution of sulphate of tin, probably at its minimum of oxydation, absorbs one eighth of its bulk of nitrous gas, and becomes brown, without deposition.
c. Solution of sulphate of zinc absorbs about one tenth of its volume of nitrous gas, and becomes green.
d. Solution of muriate of zinc130 absorbs nearly the same quantity, and becomes orange brown.
e. These are all the metallic substances on which I have experimented. It is more than probable that there exist others possessing similar powers of absorbing nitrous gas.
Whenever the metals capable of decomposing water exist in solutions at their minimum of oxydation, the affinities exerted by them on nitrous gas and water, will be such as to produce combination. The powers of metallic solutions to combine with nitrous gas at common temperatures, as well as to decompose it at higher temperatures, will probably be in the ratio of the affinity of the metallic oxides they contain, for oxygene.
XI. The action of Sulphurated Hydrogene on solution of
Green Sulphate of Iron, impregnated with Nitrous Gas.
a. In an experiment on the absorption of nitrous gas by solution of green sulphate of iron, I introduced an unboiled solution of common sulphate, deprived of red oxide of iron by sulphurated hydrogene, into a jar filled with nitrous gas; the absorption took place as usual, and nearly six of gas entered into combination, the volume of the solution being unity. On applying heat to a part of this impregnated solution, the whole of the nitrous gas it contained (as nearly as I could guess), was expelled undecompounded, and no yellow precipitate produced. Prussiate of potash poured into it gave only white prussiate of iron; and when it was heated with lime, no ammoniacal smell was perceptible.
I could refer this phænomenon to no other cause than to the existence of a small quantity of sulphurated hydrogene in the solution. That this was the real cause I found from the following experiment.
b. One part of a solution of green sulphate of iron, formed by the agitation of common sulphate of iron in contact with sulphurated hydrogene, was boiled for some minutes to expel the small quantity of gas retained by it undecompounded. It had then no peculiar smell, and gave a white prussiate of iron with prussiate of potash; the other part had a faint odor of sulphurated hydrogene, and gave a dirty white precipitate with prussiate of potash. Nearly equal quantities of each were saturated with nitrous gas, and heated. The unboiled impregnated solution gave out all its nitrous gas undecompounded; whilst in the boiled solution it was partly decomposed, yellow precipitate and ammoniac being formed.
c. This singular phænomenon of the power of a minute quantity of sulphurated hydrogene, in preventing the decomposition of nitrous gas and water, by green oxide of iron, will most probably take place in other impregnated solutions. It seems to depend on the strong affinity of the hydrogene of sulphurated hydrogene for oxygene.
a. For separating nitrous gas from gases absorbable to no great extent by water; a well boiled solution of green muriate of iron should be employed. Nitrous gas agitated in this is rapidly absorbed, and it has no affinity for, or action on, nitrogene, hydrogene, or hydrocarbonate.
b. Nitrous gas carefully obtained from mercury and nitric acid, when received under mercury, or boiled water, and absorbed by solution of green muriate, or sulphate of iron, rarely leaves a residuum of ¹/₂₀₀ of its volume: preserved over common water, and absorbed, the remainder is generally from ¹/₄₀ to ¹/₉₀, from the nitrogene disengaged by the decomposition of the common air contained in the water.
c. The nitrous gas carefully obtained from the decomposition of nitric acid of 1,26, by copper, I have hardly ever found to contain more than from ¹/₃₀ to ¹/₅₀ nitrogene, when received through common water: when boiled water is employed, the residuum is nearly the same as that of nitrous gas obtained from mercury.
d. Consequently the gas from those two solutions may be used in common. It is more than probable, that the small quantities of nitrogene generally mingled with nitrous gas from copper and mercury, arise either from the common air of the vessels in which it was produced, or that of the water over which it was received. There is no reason for supposing that it is generated by a complete decomposition of a portion of the acid.131
e. Whenever nitrous oxide is mingled with nitrous gas and nitrogene, it must be separated by well boiled water; and after the corrections are made for the quantity of air disengaged from the water, the nitrous gas absorbed by the muriatic solution.
Division V
Experiments and OBSERVATIONS on the production of NITROUS OXIDE from NITROUS GAS and NITRIC ACID, in different modes.
a.
The opinions of Priestley132 and Kirwan,133 relating to the causes of the conversion of nitrous gas into nitrous oxide, were founded on the theory of phlogiston. The first of these philosophers obtained nitrous oxide by placing nitrous gas in contact with moistened iron filings, or the alkaline sulphures. The last by exposing it to sulphurated hydrogene.
The Dutch chemists,134 the latest experimentalists on nitrous oxide, have supposed that the production of this substance depends upon the simple abstraction of a portion of the oxygene of nitrous gas. They obtained nitrous oxide by exposing nitrous gas to muriate of tin, to copper in solution of ammoniac, and likewise by passing it over heated sulphur.
The diminution of volume sustained by nitrous gas during its conversion into nitrous oxide, has never been accurately ascertained; it has generally been supposed to be from two thirds to eight tenths.
b. Nitrous gas may be converted into nitrous oxide in two modes.
First, by the simple abstraction of a portion of its oxygene, by bodies possessing a strong affinity for that principle, such as alkaline sulphites, muriate of tin, and dry sulphures.
Second, by the combination of a body with a portion both of its oxygene and nitrogene, such as hydrogene, when either in a nascent form, or a peculiar state of combination.
c. Each of these modes will be distinctly treated of; and to prevent unnecessary repetitions, I shall give an account of the general manner in which the following experiments on the conversion of nitrous gas into nitrous oxide, have been conduced.
Nitrous gas, the purity of which has been accurately ascertained by solution of muriate of iron, is introduced into a graduated jar filled with dry mercury. If a fluid substance is designed for the conversion of the gas into nitrous oxide, it is heated, to expel any loosely combined air which might be liberated during the process; and then carefully introduced into the jar, by means of a small phial. After the process is finished, and the diminution accurately noted, the nitrous oxide formed is absorbed by pure water. If any nitrous gas remains, it is condensed by solution of muriate of iron; other residual gases are examined by the common tests. The quantity of nitrous oxide dissolved by the fluid is determined by a comparative experiment; and the corrections for temperature and pressure being guessed at, the conclusions drawn.
If a solid substance is used, rather more nitrous gas than that designed for the conversion, is introduced into the jar. The substance is brought in contact with the gas, by being carried under the mercury; and as a little common air generally adheres to it, a small portion of the nitrous gas is transferred into a graduated tube, after the insertion, and its purity ascertained. In other respects the process is conducted as mentioned above.
II. Of the conversion of Nitrous gas into Nitrous Oxide,
by Alkaline Sulphites.
The alkaline sulphites, particularly the sulphite of potash, convert nitrous gas into nitrous oxide, with much greater rapidity than any other bodies.
At temperature 46°, 16 cubic inches of nitrous gas were converted, in less than an hour, into 7,8 of nitrous oxide, by about 100 grains of pulverised sulphite of potash, containing its water of crystalisation. No sensible increase of temperature was produced during the process, no water was decomposed, and the quantity of nitrogene remaining after the experiment, was exactly equal to that previously contained in the nitrous gas.
The nitrous oxide produced from nitrous gas by sulphite of potash, has all the properties of that generated from the decomposition of nitrate of ammoniac. It gives, as will be seen hereafter, the same products by analysis. Phosphorus, the taper, sulphur, and charcoal, burn in it with vivid light. It is absorbable by water, and capable of expulsion from it unaltered, by heat.
Nitrous gas is converted into nitrous oxide by the alkaline sulphites with the same readiness, whether exposed to the light, or deprived of its influence.
The solid sulphites act upon nitrous gas much more readily than their concentrated solutions; they should however always be suffered to retain their water of crystalisation, or otherwise they attract moisture from the gas, and render it drier, and in consequence more condensed than it would otherwise be. In case perfectly dry sulphites are employed, the gas should be always saturated with moisture after the experiment, by introducing into the cylinder a drop of water.
The sulphites, after exposure to nitrous gas, are either found wholly, or partially, converted into sulphates. Consequently the conversion of nitrous gas into nitrous oxide by these bodies, simply depends on the abstraction of a portion of its oxygene; the nitrogene and remaining oxygene assuming a more condensed state of existence.
If we reason from the different specific gravities of nitrous oxide and nitrous gas, as compared with the diminution of volume of nitrous gas, during its conversion into nitrous oxide, 100 parts of nitrous gas, supposing the former estimation of the composition of nitrous oxide given in Division III, accurate, would consist of 54 oxygene, and 46 nitrogene; which is not far from the true estimation. Or assuming the composition of nitrous gas, as given in Division IV, it would appear from the diminution, that 100 parts of nitrous oxide consisted of 38 oxygene, and 62 nitrogene.
III. Conversion of Nitrous Gas into Nitrous Oxide,
by Muriate of Tin, and dry Sulphures.
a. Nitrous gas exposed to dry muriate of tin, is slowly converted into nitrous oxide: during this process the apparent diminution is to about one half; but if the products are nicely examined, and the necessary corrections made, the real diminution of nitrous gas by muriate of tin, will be the same as by the sulphites; that is, 100 parts of it will be converted into 48 of nitrous oxide.
During this conversion, no water is decomposed, and no nitrogene evolved. Solution of muriate of tin converts nitrous gas into nitrous oxide; but with much less rapidity than the solid salt.
b. Nitrous gas exposed to dry and perfectly well made sulphures, particularly such as are produced from crystalised alumn135 and charcoal not sufficiently inflammable to burn in the atmosphere, is converted into nitrous oxide by the simple abstraction of a portion of its oxygene, and consequently undergoes a diminution of ⁵²/₁₀₀.
It is probable, that all the bodies having strong affinity for oxygene will, at certain temperatures, convert nitrous gas into nitrous oxide. Priestley, and the Dutch chemists, effected the change by heated sulphur. Perhaps nitrous gas sent through a tube heated, but not ignited, with phosphorus, would be converted into nitrous oxide.
IV. Decomposition of Nitrous Gas, by Sulphurated Hydrogene.
a. When nitrous gas and sulphurated hydrogene are mingled together, a decomposition of them slowly takes place. The gases are diminished, sulphur deposited, nitrous oxide formed, and signs of the production of ammoniac136 and water perceived.
In this process no sulphuric, or sulphureous acid is produced; consequently none of the sulphur is oxydated, and of course the changes depend upon the combination of the hydrogene of the sulphurated hydrogene, with different portions of the oxygene and nitrogene of the nitrous gas, to form water and ammoniac, the remaining oxygene and nitrogene assuming the form of nitrous oxide.
This singular exertion of attractions by a simple body, appears highly improbable a priori, nor did I admit it, till the formation of ammoniac, and the non-oxygenation of the sulphur, were made evident by many experiments.
In those experiments, the diminution of the nitrous gas was not uniformly the same. It varied from ¹¹/₂₀ to ¹⁴/₂₀. In the most accurate of them, 5 cubic inches of nitrous gas were converted into 2.2 of nitrous oxide. Consequently the quantity of ammoniac formed was,047 grains.
In experiments on the conversion of nitrous gas into nitrous oxide, by sulphurated hydrogene, the gases should be rendered as dry as possible. The presence of water considerably retards the decomposition.
b. The sulphures137 dissolved in water convert nitrous gas into nitrous oxide. This decomposition is not, however, produced by the simple abstraction of oxygene from the nitrous gas to form sulphuric acid. It depends as well on the decomposition of the sulphurated hydrogene dissolved in the solution, or liberated from it. In this process sulphur is deposited on the surface of the fluid, sulphuric acid is formed, and the diminution, making the necessary corrections, is nearly the same as when free sulphurated hydrogene is employed.
It is extremely probable that sulphurated hydrogene, in combination with the alkalies, as well as with water, is capable of being slowly decomposed by nitrous gas.
V. Decomposition of Nitrous Gas by Nascent Hydrogene.
a. When nitrous gas, is exposed to wetted iron filings, a diminution of its volume slowly takes place; and after a certain time, it is found converted into nitrous oxide.
In this process ammoniac138 is formed, and the iron partially oxydated.
The water in contact with the iron is decomposed by the combination of its oxygene with that substance, and of its hydrogene with a portion of the oxygene and nitrogene of the nitrous gas, to form water and ammoniac.
That the iron is not oxydated at the expence of the oxygene of the nitrous gas, appears very probable from the analogy between this process, and the mutual decomposition of nitrous gas and sulphurated hydrogene. Besides, dry iron filings effect no change whatever in nitrous gas, at common temperatures.
I have generally found about 12 of nitrous gas converted into 5 of nitrous oxide in this process; which is not very different from the diminution by sulphurated hydrogene. It takes place equally well in light and darkness; but more rapidly in warm weather than in cold.
b. Nitrous gas exposed to a large surface of zinc, in contact with water, is slowly converted into nitrous oxide; at the same time that ammoniac is generated, and white oxide of zinc formed. This process appears to depend, like the last, upon the decomposition of water by the affinities of part of the oxygene and nitrogene of nitrous gas, for its hydrogene, to form ammoniac and water; and by that of zinc for its oxygene. Zinc placed in contact with water, and confined by mercury,139 decomposes it at the common temperature. Zinc, when perfectly dry, does not in the slightest degree act upon nitrous gas.
I have not been able to determine exactly the diminution of volume of nitrous gas, during its conversion into nitrous oxide by zinc. In one experiment 20 measures of nitrous gas, containing about,03 nitrogene, were diminished to 9, after an exposure of eight days to wetted zinc; but from an accident, I was not able to ascertain the exact quantity of nitrous oxide formed.
c. It is probable that most of the imperfect metals will be found capable of oxydation, by the decomposition of water, when its hydrogene is attracted by the oxygene and nitrogene of nitrous gas. I have this day (April 14, 1800), examined two portions of nitrous gas, one of which had been exposed to copper filings, and the other to powder of tin, for twenty-three days.
The gas that had been exposed to copper was diminished nearly two fifths. The taper burnt in it with an enlarged flame, blue at the edges. Hence it evidently contained nitrous oxide.
The nitrous gas in contact with tin had undergone a diminution of one fourth only, and did not support flame.
VI. Miscellaneous Observations on the conversion
of Nitrous Gas into Nitrous Oxide.
a. Dr. Priestley found nitrous gas exposed to a mixture of iron filings and sulphur, with water, converted after a certain time, into nitrous oxide. Sulphurated hydrogene is always produced during the combination of iron and sulphur, when they are in contact with water; and by the hydrogene of this in the nascent state, the nitrous gas is most probably decomposed.
b. Green oxide of iron moistened with water, exposed to nitrous gas, slowly gains an orange tinge, whilst the gas is diminished. Most likely it is converted into nitrous oxide; but this I have not ascertained.
c. I exposed nitrous gas, to the following bodies over mercury for many days, without any diminution, or apparent change in its properties. Alcohol, saccharine matter, hydrocarbonate, sulphureous acid, and phosphorus.
d. Crystalised sulphate, and muriate of iron, absorb a small quantity of nitrous gas, and become dark colored on the outside; but after this absorption, (which probably depends on their water of crystalisation,) has taken place, no change is effected in the gas remaining.
e. The power of iron to decompose water being much increased by increase of temperature, nitrous gas is converted into nitrous oxide much more rapidly when placed in contact with a surface of heated iron, than when exposed to it at common temperatures. During the decomposition of nitrous gas in this way, ammoniac140 is formed.
f. The curious experiments of Rouppe,141 on the absorption of gases by charcoal, compared with the phænomena noticed in this Division, render it probable that hydrogene in a state of loose combination with charcoal, will be found to convert nitrous gas into nitrous oxide.
VII. Recapitulation of conclusions concerning the
conversion of Nitrous Gas into Nitrous Oxide.
a. Certain bodies having a strong affinity for oxygene, as the sulphites, dry sulphures, muriate of tin, &c. convert nitrous gas into nitrous oxide, by simply attracting a portion of its oxygene; whilst the remaining oxygene enters into combination with the nitrogene, and they assume a more condensed state of existence.
b. Nitrous gas is converted into nitrous oxide by hydrogene, in a peculiar state of existence, as in sulphurated hydrogene; and that by a series of very complex affinities. Both oxygene and nitrogene are attracted from the nitrous gas by the hydrogene, in such proportions as to form water and ammoniac, whilst the remaining oxygene and nitrogene142 assume the form of nitrous oxide.
c. Nitrous gas placed in contact with bodies, such as iron and zinc decomposing water, is converted into nitrous oxide, at the same time that ammoniac is formed. It is difficult to ascertain the exact rationale of this process. For either the nascent hydrogene produced by the decomposition of the water by the metallic substance may combine with portions of both the oxygene and nitrogene of the nitrous gas; and thus by forming water and ammoniac, convert it into nitrous oxide. Or the metallic substance may attract at the same time oxygene from the water and nitrous gas, whilst the nascent hydrogene of the water seizes upon a portion of the nitrogene of the nitrous gas to form ammoniac.
The degree of diminution, and the analogy between this process and the decomposition of nitrous gas by sulphurated hydrogene, render the first opinion most probable.
VIII. The production of Nitrous Oxide during the
oxydation of Tin, Zinc, and Iron, in Nitric Acid.
a. Dr. Priestley discovered, that during the solution of tin, zinc, and iron, in nitric acid, certain portions of nitrous oxide were produced, mingled with quantities of nitrous gas, and nitrogene, varying in proportion as the acid employed was more or less concentrated.
It has long been known that ammoniac is formed during the solution of tin, zinc, and iron, in diluted nitric acid. Consequently, in these processes water is decomposed.
I had designed to investigate minutely these phænomena, so as to ascertain the quantities of water and acid decompounded, and of the new products generated. But after going through some experiments on the oxydation of tin without gaining conclusive results, the labor, and sacrifice of time they demanded, obliged me to desist from pursuing the subject, till I had completed more important investigations.
I shall detail the few observations which have occurred to me, relating to the production of nitrous oxide from metallic solutions.
b. When tin is dissolved in concentrated nitric acid, such as of 1.4, nitrous oxide is produced, mingled with generally more than twice its bulk of nitrous gas. In this process but little free nitrogene is evolved, and the tin is chiefly precipitated in the form of a white powder. If the solution, after the generation of these products, is saturated with lime, and heated, the ammoniacal smell is distinct.
When nitric acid of specific gravity 1.24, is made to act upon tin; in the beginning of the process, nearly equal parts of nitrous gas and nitrous oxide are produced; as it advances, the proportion of nitrous oxide to the nitrous gas increases: the largest quantity of nitrous oxide that I have found in the gas procured from tin is ¾, the remainder being nitrous gas and nitrogene.
When tin is oxydated in an acid of less specific gravity than 1.09, the quantities of gas disengaged are very small, and consist of nitrogene, mingled with minute portions of nitrous oxide, and nitrous gas.
Whenever I have saturated solutions of tin in nitric acid of different specific gravities, with lime, and afterwards heated them, the ammoniacal smell has been uniformly perceptible, and generally most distinct when diluted acids have been employed.
c. When zinc is dissolved in nitric acid, whatever is its specific gravity, certain quantities of nitrous oxide are produced.
Nitric acids of greater specific gravity than 1.2, act upon zinc with great rapidity, and great increase of temperature. The gases disengaged from these solutions consist of nitrous gas, nitrous oxide, and nitrogene; the nitrous oxide rarely equals one third of the whole.
When nitric acid of 1,104 is made to dissolve zinc, the gas obtained in the middle of the process consists chiefly of nitrous oxide. From such a solution I obtained gas which gave a residuum of one sixth only when absorbed by water. The taper burnt in it with a brilliant flame, and sulphur with a vivid rose-colored light.
100 grains of granulated zinc, during their solution in 300 grains of nitric acid, of 1,43, diluted with 14 times its weight of water, produced 26 cubic inches of gas. Of this gas ⁷/₃₆ were nitrous, ¹⁷/₃₆36 nitrous oxide, and the remainder nitrogene. The solution saturated with lime and heated, gave a distinct smell of ammoniac.
d. During the solution of iron in concentrated nitric acid, the gas given out is chiefly nitrous; it is however generally mingled with minute quantities of nitrous oxide. When very dilute nitric acids are made to act upon iron, by the assistance of heat, nitrous oxide is produced in considerable quantities, mingled with nitrous gas and nitrogene; the proportions of which are smaller as the process advances.143 The fluid remaining after the oxydation and solution of iron in nitric acid, always contains ammoniac.
e. As during the solution of tin, zinc, and iron, in nitric acid, the quantity of acid is diminished in proportion as the process advances, it is reasonable to suppose that the relative quantities of the gases evolved are perpetually varying. In the beginning of a dissolution, the nitrous gas generally predominates, in the middle nitrous oxide, and at the end nitrogene.
f. During the generation of nitrous gas, nitrous oxide, and ammoniac, from the decomposition of solution of nitric acid in water, by tin, zinc, and iron, very complex attractions must exist between the constituents of the substances employed. The acid and the water are decomposed at the same time, and in proportions different as the solution is more concentrated, by the combination of their oxygene with the metallic body.
The nitrous gas is produced by the combination of the metal with ³²/₁₀₀ of the oxygene of the acid. The nitrous oxide is most probably generated by the decomposition of a portion of the nitrous gas disengaged, by the nascent hydrogene of the water decompounded; some of it may be possibly formed from a more complete decomposition of the acid.
The production of ammoniac may arise, probably from two causes; from the decomposition of the nitrous gas by the combination of the nascent hydrogene of the water, with portions of its oxygene and nitrogene at the same time; and from the union of hydrogene with nascent nitrogene liberated in consequence of a complete decomposition of part of the acid.
IX. Additional Observations on the production
of Nitrous Oxide.
a. When nitric acid is combined with muriatic acid, or sulphuric acid,144 the quantities of nitrous oxide produced from its decomposition by tin, zinc, and iron, are rather increased than diminished. The nitrous oxide obtained from these solutions is, however, never sufficiently pure for physiological experiments. It is always mingled with either nitrous gas, nitrogene, or hydrogene, and sometimes with all of them.
b. From the solutions of bismuth, nickel, lead, and copper, in diluted nitric acid, I have never obtained any perceptible quantity of nitrous oxide: the gas produced is nitrous, mingled with different portions of nitrogene. Antimony and mercury, during their solution in aqua regia, give out only nitrous gas.
Probably none of the metallic bodies, except those that decompose water at temperatures below ignition, will generate nitrous oxide from nitric acid. On cobalt and manganese I have never had an opportunity of experimenting: manganese will probably produce nitrous oxide.
c. During the solution of vegetable matters145 in nitric acid, by heat, very minute portions of nitrous oxide are sometimes produced, always however mingled with large quantities of nitrous gas, and carbonic acid.
When nitric acid is decompounded by ether, fixed oils, volatile oils, or alcohol, towards the end of the process small quantities of nitrous oxide are produced, and sometimes sufficiently pure to support the flame of the taper.146
d. When green oxide of iron is dissolved in nitric acid, nitrous oxide is produced, mingled with nitrogene and nitrous gas.
e. During the conversion of green sulphate, or green muriate of iron into red, by the decomposition of dilute nitric acid, nitrous oxide is formed, mingled with different proportions of nitrous gas and nitrogene.
f. When solution of green nitrate of iron is heated, a part of the acid is decomposed, red oxide is precipitated, red nitrate formed, and impure nitrous oxide evolved.
g. When iron is introduced into a solution of nitrate of copper, the copper is precipitated in its metallic state, whilst nitrous oxide, mingled with small portions of nitrogene, is produced.147
Both zinc and tin precipitate copper in its metallic form from solution in the nitric acid. During these precipitations, certain quantities of nitrous oxide are generated, mingled however with larger quantities of nitrogene than that produced from decomposition by iron. In all these processes ammoniac is formed, and water consequently decomposed.
The decomposition of water and nitric acid, during the precipitation of copper from solution of nitrate of copper, by tin, zinc, and iron, depends upon the strong affinity of those metals for oxygene, and their powers of combining with a larger quantity of it than copper.
X. Decomposition of Aqua Regia by Platina, and
evolution of a Gas analogous to Oxygenated
Muriatic Acid, and Nitrogene.
a. De la Metherie, in his essay on different airs, has asserted that the gas produced by the solution of platina in nitro-muriatic acid, is identical with the dephlogisticated nitrous gas of Priestly. He calls it nitrous gas with excess of pure air, and affirms that it diminishes, both with nitrous gas and common air.
b. I introduced into a vessel containing 30 grains of platina, 2050 grains of aqua regia, composed of equal parts, by weight, of concentrated nitric acid of 1,43, and muriatic acid of 1,16. At the common temperature, that is, 49°, no action between the acid and platina appeared to take place. On the application of the heat of a spirit lamp, the solution gradually became yellow red, and gas was given out with rapidity. Some of this gas received in a jar filled with warm water, appeared of a bright yellow color. On agitation, the greater part of it was absorbed by the water, and the remainder extinguished flame. When it was received over mercury, it acted upon it with great rapidity, and formed on the surface a white crust.
As the process of solution advanced, the color of the acid changed to dark red, at the same time that the production of gas was much increased; more than 40 cubic inches were soon collected in the water apparatus.
Different portions of the gas were examined, it exhibited the following properties:
1. Its color was orange red,148 and its smell exactly resembled that of oxygenated muriatic acid.
2. When agitated in boiled water, it was rapidly absorbed, leaving a residuum of rather more than one twelfth.
3. The taper burnt in it with increased brilliancy, the flame being long, and deep red at the edges.
4. Iron introduced into it ignited, burnt with a dull red light.
5. Green vegetables exposed to it were instantly rendered white.
6. It underwent no diminution, mingled with atmospheric air.
7. When mingled with nitrous gas, it gave dense red vapor, and rapid diminution.
c. From the exhibition of these properties, it was evident that the gas produced during the solution of platina in aqua regia, chiefly consisted of oxygenated muriatic acid, or of a gas highly analogous to it. It was, however, difficult to conceive how a body, by combining with a portion of the oxygene of nitro-muriatic acid, could produce from it oxygenated muriatic acid, apparently mingled with very small portions of any other gas.
d. To ascertain whether any permanent gas was produced during the ebullition of aqua regia, of the same composition as that used for the solution of the platina; I kept a large quantity of it boiling for some time, in communication with the water apparatus; the gas generated appeared to be wholly nitro-muriatic, and was absorbed as fast as produced, by the water.
e. To determine whether any nitrous oxide was mingled with the peculiar gas, as well as the nature and quantity of the unabsorbable gas, nitrous gas was gradually added to 21 cubic inches of the gas produced from a new solution, till the diminution was complete: the gas remaining equalled 2,3 cubic inches; it was unabsorbable by water, and extinguished flame.
In another experiment, when the last portions of gas from a solution were carefully received in water previously boiled, 12 cubic inches agitated in water left a residuum of 1.3; whilst the same quantity decomposed by nitrous gas, containing,02 nitrogene, left about 1.5.
Hence it appeared that the aëriform products of the solution consisted of the peculiar gas analogous to oxygenated muriatic acid, and of a small quantity of nitrogene.
f. Consequently a portion of the nitric acid of the aqua regia had been decomposed; but if it had given oxygene both to the platina and muriatic acid, the quantity of nitrogene evolved ought to have been much more considerable.
g. To ascertain if any water had been decomposed, and the nitrogene condensed in the solution by its hydrogene, to form ammoniac, I saturated a solution with lime, and heated it, but no ammoniacal smell was perceived.
h. To determine if any nitrogene had entered into chemical combination with muriatic acid and oxygene, so as to form an aëriform triple compound, analogous in its properties to oxygenated muriatic acid, I exposed some of the gas to mercury, expecting that this substance, by combining with its oxygene, would effect a complete decomposition; and this was actually the case: for the gas was at first rapidly diminished, and the mercury became oxydated; its volume, however, soon increased; and the residual gas appeared to be nitrous, mingled with much nitrogene. The exact proportions of each, from an accident, I could not determine.
This experiment was inconclusive, because the nitro-muriatic acid suspended in the peculiar gas, from which it can probably be never perfectly freed, acted in common with it upon the mercury, and produced nitrous gas: and this nitrous gas, at the moment of its production, formed nitrous acid by combining with the oxygene of the peculiar gas; and the nitrous acid generated149 was again decomposed by the mercury; and hence nitrous gas evolved, and possibly some nitrogene.
i. Peculiar circumstances prevented me at this time from completely investigating the subject. It remains doubtful whether the gas consists simply of highly oxygenated muriatic acid and nitrogene,150 produced by the decomposition of nitric acid from the coalescing affinities of platina and muriatic acid for oxygene; or whether it is composed of a peculiar gas, analogous to oxygenated muriatic acid, and nitrogene, generated from some unknown affinities.151
XI. On the action of the Electric Spark on a mixture
of Nitrogene and Nitrous Gas.
Thinking it possible that nitrous gas and nitrogene might be made to combine by the action of the electric spark, so as to form nitrous oxide, I introduced 20 grain measures of each of them into a small detonating tube, graduated to grains, standing over mercury, and containing a very small quantity of cabbage juice rendered green by an alkali. After electric sparks had been passed through the gases for an hour and half, they were diminished to about 32, and the cabbage juice was slightly reddened. On introducing about 10 measures of hydrogene, and passing the electric spark through the whole, no inflammation or diminution was perceptible. Hence the condensation most probably arose wholly from the formation of nitrous acid,152 by the more intimate union of the oxygene of nitrous gas with some of its nitrogene, as in the experiments of Priestley.
As the nascent nitrogene, in the decomposition of nitrate of ammoniac, combines with a portion of oxygene and nitrogene, to form nitrous oxide; it is probable that nitrous oxide may be produced during the passage of nitrous gas and ammoniac through a heated tube.
There are no reasons for supposing that nitrous oxide is formed in any of the processes of nature; and the nice equilibrium of affinity by which it is constituted, forbids us to hope for the power of composing it from its simple principles. We must be content to produce it, either directly or indirectly, from the decomposition of nitric acid. And as in the decomposition of nitrate of ammoniac, not only all the nitrogene of the nitric acid enters into the composition of the nitrous oxide produced, but likewise that of the ammoniac, this process is by far the cheapest, as well as the most expeditious. A mode of producing ammoniac at little expence, has been proposed by Mr. Watt. Condensed in the sulphuric acid, it can be easily made to combine with nitric acid, from the decomposition of nitre by double affinity. And thus, if the hopes which the experiments at the end of those researches induce us to indulge, do not prove fallacious, a substance which has been heretofore almost exclusively appropriated to the destruction of mankind, may become, in the hands of philosophy, a means of producing health and pleasurable sensation.