Chapter III Raw Materials Used in Soap-Making
Fats and Oils—Waste Fats—Fatty Acids—Less-known Oils and Fats of Limited Use—Various New Fats and Oils Suggested for Soap-making—Rosin—Alkali (Caustic and Carbonated)—Water—Salt—Soap-stock.
Fats and Oils.—All animal and vegetable oils and fats intended for soap-making should be as free as possible from unsaponifiable matter, of a good colour and appearance, and in a sweet, fresh condition. The unsaponifiable matter naturally present as cholesterol, or phytosterol, ranges in the various oils and fats from 0.2 to 2.0 per cent. All oils and fats contain more or less free acidity; but excess of acidity, though it may be due to the decomposition of the glyceride, and does not always denote rancidity, is undesirable in soap-making material. Rancidity of fats and oils is entirely due to oxidation, in addition to free acid, aldehydes and ketones being formed, and it has been proposed to estimate rancidity by determining the amount of these latter produced. It is scarcely necessary to observe how very important it is that the sampling of fats and oils should be efficiently performed, so that the sample submitted to the chemist may be a fairly representative average of the parcel.
In the following short description of the materials used, we give, under each heading, figures for typical samples of the qualities most suitable for soap-making.
Tallows.—Most of the imported tallow comes from America, Australia and New Zealand. South American mutton tallow is usually of good quality; South American beef tallow is possessed of a deep yellow colour and rather strong odour, but makes a bright soap of a good body and texture. North American tallows are, as a general rule, much paler in colour than those of South America, but do not compare with them in consistence. Most of the Australasian tallows are of very uniform quality and much in demand.
Great Britain produces large quantities of tallow which comes into the market as town and country tallow, or home melt. Owing to the increasing demand for edible fat, much of the rough fat is carefully selected, rendered separately, and the product sold for margarine-making. Consequently the melted tallow for soap-making is of secondary importance to the tallow melter.
The following are typical samples of tallow:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | |
| Australian mutton | 285 | 0.85 | 45 |
| Australian mutton | 284.4 | 0.48 | 48.3 |
| Australian beef | 284.2 | 1.68 | 43.9 |
| Australian beef | 283.6 | 0.85 | 42.6 |
| Australian mixed | 285.1 | 3.52 | 44 |
| Australian mixed | 284.6 | 1.89 | 43.5 |
| South American mutton | 284.5 | 1.11 | 47 |
| South American mutton | 285 | 0.90 | 47.4 |
| South American beef | 284.7 | 0.81 | 45 |
| South American beef | 284 | 0.94 | 44 |
| North American mutton | 284.3 | 1.32 | 44 |
| North American mutton | 85 | 2.18 | 43.2 |
| North American beef, fine | 284.5 | 1.97 | 41.5 |
| North American beef, good | 283.8 | 4.30 | 42 |
| North American ordinary | 285.2 | 5.07 | 41.75 |
| North American prime city | 286 | 1.01 | 41.2 |
| Selected English mutton | 283.9 | 1.45 | 47 |
| Selected English beef | 284.2 | 2.40 | 44 |
| Home-rendered or country tallow | 284.6 | 5.1 | 43 |
| Town tallow | 285.3 | 7.4 | 42.5 |
Tallow should absorb from 39 to 44 per cent. iodine.
Lard.—Lard is largely imported into this country from the United States of America. The following is a typical sample of American hog’s fat offered for soap-making:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Refractive Index at 60° C. |
| 286 | 0.5 | 37.5 | 1.4542 |
Lard should absorb 59 to 63 per cent. iodine.
Cocoa-nut Oil.—The best known qualities are Cochin and Ceylon oils, which are prepared in Cochin (Malabar) or the Philippine Islands and Ceylon respectively.
The dried kernels of the cocoa-nut are exported to various ports in Europe, and the oil obtained comes on the market as Continental Coprah Oil, with the prefix of the particular country or port where it has been crushed, e.g., Belgian, French and Marseilles Coprah Oil. Coprah is also imported into England, and the oil expressed from it is termed English Pressed Coprah.
The following are typical examples from bulk:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Refractive Index at 25° C. | |
| Cochin oil | 215.5 | 1.5 | 23.5 | 1.4540 |
| Cochin oil | 214.3 | 2.6 | 22.1 | 1.4541 |
| Ceylon oil | 214.6 | 5.47 | 23 | 1.4535 |
| Ceylon oil | 216 | 3.95 | 22.75 | 1.4535 |
| Belgian coprah | 214.2 | 1.65 | 23 | 1.4541 |
| Belgian coprah | 215 | 2.60 | 22.1 | 1.4540 |
| French coprah | 214.2 | 6.55 | 23 | 1.4535 |
| French coprah | 214.8 | 7.42 | 22 | 1.4540 |
| Pressed coprah | 215.8 | 7.45 | 22.2 | 1.4542 |
| Pressed coprah | 216 | 9.41 | 22 | 1.4555 |
Cocoa-nut oil should absorb 8.9 to 9.3 per cent. iodine.
Palm-nut Oil.—The kernels of the palm-tree fruit are exported from the west coast of Africa to Europe, and this oil obtained from them. Typical samples of English and Hamburg oils tested:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Refractive Index at 25° C. |
| 225 | 4.4 | 24 | 1.4553 |
| 227 | 7.7 | 23.8 | 1.4553 |
Palm-nut oil should absorb 10 to 13 per cent. iodine.
Olive Oil.—The olive is extensively grown in Southern Europe and in portions of Asia and Africa bordering the Mediterranean Sea. The fruit of this tree yields the oil.
The free fatty acid content of olive oil varies very considerably. Very fine oils contain less than 1 per cent. acidity; commercial oils may be graded according to their free acidity, e.g., under 5 per cent., under 10 per cent., etc., and it entirely depends upon the desired price of the resultant soap as to what grade would be used. The following is a typical sample for use in the production of high-class toilet soap:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Refractive Index at 15° C. |
| 288 | 1.8 | 21 | 1.4704 |
Olive oil should absorb 80 to 83 per cent. iodine.
Olive-kernel oil, more correctly termed Sulphur olive oil.
The amount of free fatty acids is always high and ranges from 40-70 per cent., and, of course, its glycerol content is proportionately variable. The free acidity increases very rapidly, and is, doubtless, due to the decomposition of the neutral oil by the action of hydrolytic ferment.
A representative sample of a parcel tested:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Refractive Index at 20° C. |
| 298 | 40.96 | 1.4666 |
Palm oil is produced from the fruit of palm trees, which abound along the west coast of Africa. Lagos is the best quality, whilst Camaroons, Bonny, Old Calabar and New Calabar oils are in good request for bleaching purposes.
Analysis of typical samples of crude palm oil has given:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Water and Impurities, Per Cent. |
| 278 | 10.7 | 45 | 1.6 |
| 280 | 31.2 | 44.5 | 2.8 |
Palm oil should absorb 51 to 56 per cent. iodine.
In the lower qualities we have examples of the result of hydrolytic decomposition by enzymes, the free acidity often amounting to 70 per cent.
Cotton-seed Oil.—This oil is expressed from the seeds separated from the “wool” of the various kinds of cotton tree largely cultivated in America and Egypt.
In its crude state cotton-seed oil is a dark fluid containing mucilaginous and colouring matter, and is not applicable for soap-making. The following figures are representative of well-refined cotton-seed oils:—
| Specific Gravity at 15° C. | Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Refractive Index at 20° C. |
| 0.9229 | 290 | 0.24 | 33.6 | 1.4721 |
| 0.924 | 299 | 0.39 | 35 | 1.4719 |
Cotton-seed oil should absorb 104 to 110 per cent. iodine.
Cotton-seed Stearine.—The product obtained by pressing the deposit which separates on chilling refined cotton-seed oil.
A typical sample tested:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. |
| 285.1 | 0.05 | 38 |
Arachis Oil.—The earth-nut or ground-nut, from which arachis oil is obtained, is extensively cultivated in North America, India and Western Africa. Large quantities are exported to Marseilles where the oil is expressed. Arachis oil enters largely into the composition of Marseilles White Soaps.
Representative samples of commercial and refined oils tested:—
| Specific Gravity at 15° C. | Saponification Equivalent | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Refractive Index at 20° C. | |
| Commercial | 0.9184 | 298 | 2.6 | 28.6 | ... |
| Refined | 0.9205 | 285 | 0.22 | 24.0 | 1.4712 |
Arachis oil should absorb 90 to 98 per cent. iodine.
Maize Oil.—America (U.S.) produces very large quantities of maize oil.
Typical samples of crude and refined oil gave these figures:—
| Specific Gravity at 15° C. | Saponification Equivalent | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Refractive Index at 20° C. | |
| Crude | 0.9246 | 294 | 1.41 | 15 | ... |
| Refined | 0.9248 | 294.1 | 0.40 | 17.2 | 1.4766 |
Maize oil should absorb 120 to 128 per cent. iodine.
Sesame Oil.—Sesame oil is very largely pressed in Southern France from the seeds of the sesame plant which is cultivated in the Levant, India, Japan and Western Africa.
A fairly representative sample of French expressed oil tested:—
| Specific Gravity at 15° C. | Saponification Equivalent | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Refractive Index at 20° C. |
| 0.9227 | 295.2 | 1.84 | 22.8 | 1.4731 |
Sesame oil should absorb 108 to 110 per cent. iodine.
Linseed Oil.—Russia, India, and Argentine Republic are the principal countries which extensively grow the flax plant, from the seeds of which linseed oil is pressed. It is used to a limited extent in soft-soap making.
A good sample gave on analysis:—
| Specific Gravity at 15° C. | Saponification Equivalent | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Refractive Index at 15° C. |
| 0.935 | 292 | 1.2 | 20 | 1.4840 |
Linseed oil should absorb 170 to 180 per cent. iodine.
Hemp-seed oil is produced from the seeds of the hemp plant which grows in Russia. This oil is used in soft soap-making, more particularly on the Continent.
A typical sample gave the following figures:—
| Specific Gravity at 15° C. | Saponification Equivalent. | Titre, °C. | Iodine No. |
| 0.926 | 292.6 | 15.8 | 143 |
Sunflower oil is produced largely in Russia.
A specimen tested:—
| Specific Gravity at 15° C. | Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Iodine No. |
| 0.9259 | 290.7 | 0.81 | 17 | 126.2 |
Castor Oil.—The castor oil plant is really a native of India, but it is also cultivated in the United States (Illinois) and Egypt.
A typical commercial sample tested:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Iodine No. | Optical Rotation αD | Refractive Index at 25° C. |
| 310 | 1.5 | 2.8 | 84.1 | + 4° 50’ | 1.4787 |
Fish and Marine Animal Oils.—Various oils of this class have, until recently, entered largely into the composition of soft soaps, but a demand has now arisen for soft soaps made from vegetable oils.
We quote a few typical analyses of these oils:—
| Specific Gravity at 15° C. | Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Unsaponifiable Matter Per Cent. | |
| Pale seal oil | 0.9252 | 289 | 0.947 | 15.5 | 0.8 |
| Straw seal oil | 0.9231 | 288 | 4.77 | 15.8 | 1.2 |
| Brown seal oil | 0.9253 | 291 | 16.38 | 16.2 | 1.9 |
| Whale oil | 0.9163 | 297 | 1.49 | 16.1 | 1.8 |
| Dark whale oil | 0.9284 | 303 | 12.60 | 21.8 | 2.4 |
| Japan fish oil | 0.9336 | 296 | 4.79 | 26 | 0.67 |
| Japan fish oil | 0.9325 | 302 | 10.43 | 28 | 1.55 |
| Brown cod oil | 0.9260 | 313 | 14.91 | 21.8 | 1.9 |
| Pure herring oil | 0.9353 | 288 | 11.39 | 21.6 | 1.5 |
| Kipper oil | 0.9271 | 297 | 5.14 | 22.7 | 3.25 |
Waste Fats.—Under this classification may be included marrow fat, skin greases, bone fats, animal grease, melted stuff from hotel and restaurant refuse, and similar fatty products. The following is a fair typical selection:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | |
| Marrow fat | 283.3 | 3.6 | 38.7 |
| White skin grease | 287.2 | 4.3 | 36.4 |
| Pale skin grease | 286.3 | 9.87 | 35.7 |
| Pale bone fat | 289.7 | 8.8 | 40.7 |
| Brown bone fat | 289.1 | 11.0 | 41 |
| Brown bone fat | 292 | 20.5 | 40.2 |
| Animal grease | 289.4 | 38.1 | 40.4 |
| Melted stuff | 286.3 | 12.8 | 37.7 |
The materials in the above class require to be carefully examined for the presence of unsaponifiable matter, lime salts and other impurities.
Fatty Acids.—We have already described the various methods of liberating fatty acids by hydrolysis or saponification.
Under this heading should also be included stearines produced by submitting distilled fat to hydraulic pressure, the distillates from e from unsaponifiable matter, cocoa-nut oleine, a bye-product from the manufacture of edible cocoa-nut butter and consisting largely of free acids, and palm-nut oleine obtained in a similar manner from palm-nut oil.
These are all available for soap-making.
Less-known Oils and Fats of Limited Use
Shea Butter.—Shea butter is extracted from the kernels of the Bassia Parkii and exported from Africa and Eastern India. This fat is somewhat tough and sticky, and the amount of unsaponifiable matter present is sometimes considerable. Samples examined by us gave the following data:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Refractive Index at 60° C. |
| 313 | 8.2 | 53.2 | 1.4566 |
| 303 | 7.33 | 53 | 1.4558 |
| 1.4471 (F. Acids) |
Mowrah-seed Oil.—The mowrah-seed oil now offered for soap-making is derived from the seeds of Bassia longifolia and Bassia latifolia. It is largely exported from India to Belgium, France and England. The following are the results of some analyses made by us:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | Refractive Index at 60° C. |
| 291 | 10 | 43.4 | 1.4518 |
| 291.5 | 7.1 | 42.7 | ... |
| 291.2 | 9.9 | 43.8 | ... |
| 292 | 11.26 | 40.5 | ... |
Chinese vegetable tallow is the name given to the fat which is found coating the seeds of the “tallow tree” (Stillingia sebifera) which is indigenous to China and has been introduced to India where it flourishes. The following is a typical sample:—
| Saponification Equivalent | Acidity Per Cent. | Titre, °C. |
| 280.2 | 5.24 | 52.5 |
The seeds of the “tallow tree” yield an oil (stillingia oil) having drying properties.
Borneo Tallow.—The kernels of several species of Hopea (or Dipterocarpus), which flourish in the Malayan Archipelago, yield a fat known locally as Tangawang fat. This fat is moulded (by means of bamboo canes) into the form of rolls about 3 inches thick, and exported to Europe as Borneo Tallow.
A sample tested by one of us gave the following data:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. |
| 292 | 36 | 50.8 |
Kapok oil is produced from a tree which is extensively grown in the East and West Indies. The Dutch have placed it on the market and the figures given by Henriques (Chem. Zeit., 17, 1283) and Philippe (Monit. Scient., 1902, 730), although varying somewhat, show the oil to be similar to cotton-seed oil.
Various New Fats and Oils Suggested for Soap-making
Carapa or Andiroba oil, derived from the seeds of a tree (Carapa Guianensis) grown in West Indies and tropical America, has been suggested as suitable for soap-making. Deering (Imperial Institute Journ., 1898, 313) gives the following figures:—
| Saponification Equivalent. | Acidity Per Cent. | Melting Point of Fatty Acids, °C. |
| 287 | 12 | 89 |
Another observer (Rev. Chem. Ind., 13, 116) gives the setting point of the fatty acids as 56.4° C.
Candle-nut oil obtained from the seeds of a tree flourishing in India and also the South Sea Islands.
The following figures have been published:—
| Saponification Equivalent.1 | Titre, °C. | Iodine No. | Observers. | References. |
| 299-304.9 | 13 | 136.3-139.3 | De Negri | Chem. Centr., 1898, p. 493. |
| 291 | ... | 163.7 | Lewkowitsch | Chem. Revue, 1901, p. 156. |
| 296 | 12.5 | 152.8 | Kassler | Farben-Zeitung, 1903, p. 359. |
Curcas oil is produced in Portugal from the seeds of the “purging nut tree,” which is similar to the castor oil plant, and is cultivated in Cape Verde Islands and other Portuguese Colonies.
The following data have been observed:—
| Saponification Equivalent.2 | Titre, °C. | Iodine No. | Observers. | References. |
| 291.4 | 0.36 | 99.5 | Archbut | J. S. C. Ind., 1898, p. 1010. |
| 290.3 | 4.46 | 98.3 | Lewkowitsch | Chem. Revue, 1898, p. 211. |
| 283.1 | 0.68 | 107.9 | Klein | Zeits. angew. Chem., 1898, p. 1012. |
The titre is quoted by Lewkowitsch as 28.6° C.
Goa butter or Kokum butter is a solid fat obtained from the seeds of Garcinia indica, which flourishes in India and the East Indies. Crossley and Le Sueur (Journ. Soc. Chem. Industry, 1898, p. 993) during an investigation of Indian oils obtained these results:—
| Saponification Equivalent.3 | Acidity Per Cent. | Iodine No. |
| 300 | 7.1 | 34.2 |
Safflower oil is extracted from the seeds of the Carthamus tinctorius, which, although indigenous to India and the East Indies, is extensively cultivated in Southern Russia (Saratowa) and German East Africa. Its use has been suggested for soft-soap making. The following figures have been published:—
| Saponification Equivalent.4 | Titre, °C. | Iodine No. | Observers. | References. |
| Average of Twelve Samples | 295.5 | 141.29 | Crossley and Le Sueur | J. S. C. Ind., 1898, p. 992; J. S. C. Ind., 1900, p. 104. |
| 287.1 | 141.6 | Shukoff | Chem. Revue, 1901, p. 250. | |
| 289.2 | 130 | Tylaikow | Chem. Revue, 1902, p. 106. | |
| 293.7 | 142.2 | Fendler | Chem. Zeitung, 1904, p. 867. |
Maripa fat is obtained from the kernels of a palm tree flourishing in the West Indies, but, doubtless, the commercial fat is obtained from other trees of the same family. It resembles cocoa-nut oil and gives the following figures:—
| Saponification Equivalent.5 | Iodine No. | Melting Point of Fatty Acids, °C. | Observer. | Reference. |
| 217 | 9.49 | 25 | Bassière | J. S. C. Ind., 1903, p. 1137. |
Niam fat, obtained from the seeds of Lophira alata, which are found extensively in the Soudan. The fat, as prepared by natives, has been examined by Lewkowitsch, and more recently Edie has published the results of an analysis. The figures are as follows:—
| Saponification Equivalent.6 | Titre, °C. | Iodine No. | Observers. | References. |
| 295.1 | 78.12 | 42.5 | Lewkowitsch | J. S. C. Ind., 1907, p. 1266. |
| 287.7 | 75.3 | Edïe. | Quart. J. Inst. Comm. Research in Tropics. |
Cohune-nut oil is produced from the nuts of the cohune palm, which flourishes in British Honduras. This oil closely resembles cocoa-nut and palm-nut oils and is stated to saponify readily and yield a soap free from odour. The following figures, obtained in the Laboratory of the Imperial Institute, are recorded in the official Bulletin, 1903, p. 25:—
| Saponification Equivalent. | Iodine No. | Melting Point of Fatty Acids, °C. |
| 253.9-255.3 | 12.9-13.6 | 27-30 |
Mafoureira or Mafura tallow from the nuts of the mafoureira tree, which grows wild in Portuguese East Africa. The following figures are published:—
| Saponification Equivalent. | Iodine No. | References. | |
| Titre, °C. | |||
| 253.8 | 44-48 | 46.14 | De Negri and Fabris, Annal. del Lab. Chim. Delle Gabelle, 1891-2, p. 271. |
| Acidity (as Oleic Acid) Per Cent. | |||
| 232.8-233.7 | 21.26 | 47.8-55.8 | Bulletin Imp. Inst., 1903, p. 27. |
Pongam oil, obtained from the beans of the pongam tree, which flourishes in East India, has been suggested as available for the soap industry, but the unsaponifiable matter present would militate against its use. Lewkowitsch (Analyst, 1903, pp. 342-44) quotes these results:—
| Saponification Equivalent.7 | Iodine No. | Acidity, Per Cent. | Unsaponifiable, Per Cent. | |
| Oil extracted in laboratory | 315 | 94 | 3.05 | 9.22 |
| Indian specimen | 306 | 89.4 | 0.5 | 6.96 |
Margosa oil is obtained from the seeds of Melia azedarach, a tree which is found in most parts of India and Burma.
Lewkowitsch (Analyst, 1903, pp. 342-344) gives these figures:—
| Saponification Equivalent.8 | Iodine No. | Titre, °C. |
| 284.9 | 69.6 | 42 |
Dika fat or Wild Mango oil is obtained from the seed kernels of various kinds of Irvingia by boiling with water. Lemarié (Bulletin Imp. Inst., 1903, p. 206) states that this fat is used in the place of cocoa-nut oil in the manufacture of soap. Lewkowitsch (Analyst, 1905, p. 395) examined a large sample of dika fat obtained from seeds of Irvingia bateri (South Nigeria) and gives the following data:—
| Saponification Equivalent.9 | Iodine No. | Titre, °C. | Unsaponifiable, Per Cent. |
| 229.4 | 5.2 | 34.8 | 0.73 |
Baobab-seed Oil.—Balland (Journ. Pharm. Chem., 1904, p. 529, abstracted in Journ. Soc. Chem. Ind., 1905, p. 34) states that the natives of Madagascar extract, by means of boiling water, from the seeds of the baobab tree, a whitish solid oil, free from rancidity, and possessed of an odour similar to Tunisian olive oil. He suggests that it may, with advantage, replace cocoa-nut oil in soap manufacture.
Persimmon-seed Oil.—Lane (J. S. C. Ind., 1905, p. 390) gives constants for this oil which he describes as semi-drying, of brownish yellow colour, and having taste and odour like pea-nut (arachis) oil. The following are taken from Lane’s figures:—
| Saponification Equivalent.10 | Iodine No. | Titre, °C. |
| 298.4 | 115.6 | 20.2 |
Wheat oil, extracted from the wheat germ by means of solvents, has been suggested as applicable for soap-making (H. Snyder, abstr. J. S. C. Ind., 1905, p. 1074). The following figures have been published:—
| Saponification Equivalent.11 | Acidity, Per Cent. | Iodine No. | Titre, °C. | Observers. | References. |
| 306 | 5.65 | 115.17 | 29.7 | De Negri. | Chem. Zeit., 1898(abstr. J. S. C., 1898, p. 1155). |
| 297 | 20 | 115.64 | ... | Frankforter & Harding | J. Amer. C. Soc., 1899, 758-769 (abstr. in J. S. C. I., 1899, p. 1030). |
Tangkallah fat, from the seeds of a tree growing in Java and the neighbouring islands, is suitable for soap-making. Schroeder (Arch. Pharm., 1905, 635-640, abstracted in J. S. C. Ind., 1906, p. 128) gives these values:—
| Saponification Equivalent.12 | Acidity, Per Cent. | Iodine No. | Unsaponifiable, Per Cent. |
| 209 | 1.67 | 2.28 | 1.44 |
It is a hard fat, nearly white, possessing neither taste nor characteristic odour and solidifying at about 27° C.
Oil of Inoy-kernel.—(Bulletin Imp. Inst., 1906, p. 201). The seeds of Poga oleosa from West Africa yield on extraction an oil which gives the figures quoted below, and is suggested as a soap-maker’s material:—
| Saponification Equivalent. | Iodine No. | Titre, °C. |
| 304 | 89.75 | 22 |
Rosin
Rosin is the residuum remaining after distillation of spirits of turpentine from the crude oleo-resin exuded by several species of the pine, which abound in America, particularly in North Carolina, and also flourish in France and Spain. The gigantic forests of the United States consist principally of the long-leaved pine, Pinus palustris (Australis), whilst the French and Spanish oleo-resin is chiefly obtained from Pinus pinaster, which is largely cultivated.
Rosin is a brittle, tasteless, transparent substance having a smooth shining fracture and melting at about 135° C. (275° F.). The American variety possesses a characteristic aromatic odour, which is lacking in those from France and Spain. It is graded by samples taken out of the top of every barrel, and cut into 7/8 of an inch cubes, which must be uniform in size—the shade of colour of the cube determines its grade and value.
The grades are as follows:—
W. W. (Water white.)
W. G. (Window glass.)
N. (Extra pale.)
M. (Pale.)
K. (Low pale.)
I. (Good No. 1.)
H. (No. 1.)
G. (Low No. 1.)
F. (Good No. 2.)
E. (No. 2.)
D. (Good strain.)
C. (Strain.)
B. (Common strain.)
A. (Common.)
Unsaponifiable matter is present in rosin in varying amounts.
Below are a few typical figures taken from a large number of collated determinations:—
| Saponification Equivalent. | Total Acid No. | Free Acid No. | Iodine No. | |
| American W. W. | 330.5 | 169.7 | 119.1 | 126.9 |
| American N. | 312.3 | 179.6 | 161.4 | 137.8 |
| French | 320.5 | 175 | 168 | 120.7 |
| Spanish | 313.4 | 179 | 160 | 129.8 |
Alkali (Caustic and Carbonated)
The manufacture of alkali was at one time carried on in conjunction with soap-making, but of late years it has become more general for the soap manufacturer to buy his caustic soda or carbonated alkali from the alkali-maker.
Although there are some alkali-makers who invoice caustic soda and soda ash in terms of actual percentage of sodium oxide (Na2O), it is the trade custom to buy and sell on what is known as the English degree, which is about 1 per cent. higher than this.
The English degree is a survival of the time when the atomic weight of sodium was believed to be twenty-four instead of twenty-three, and, since the error on 76 per cent. Na2O due to this amounts to about 1 per cent., may be obtained by adding this figure to the sodium oxide really present.
Caustic soda (sodium hydrate) comes into commerce in a liquid form as 90° Tw. (and even as high as 106° Tw.), and other degrees of dilution, and also in a solid form in various grades as 60°, 70°, 76-77°, 77-78°. These degrees represent the percentage of sodium oxide (Na2O) present plus the 1 per cent. The highest grade, containing as it does more available caustic soda and less impurities, is much more advantageous in use.
Carbonate of soda or soda ash, 58°, also termed “light ash,” and “refined alkali”. This is a commercially pure sodium carbonate containing about 0.5 per cent. salt (NaCl). The 58° represents the English degrees and corresponds to 99 per cent. sodium carbonate (Na2CO3).
Soda ash, 48°, sometimes called “caustic soda ash,” often contains besides carbonate of soda, 4 per cent. caustic soda (sodium hydrate), and 10 per cent. salt (sodium chloride), together with water and impurities.
The 48 degrees refers to the amount of alkali present in terms of sodium oxide (Na2O), but expressed as English degrees.
Caustic potash (potassium hydrate) is offered as a liquid of 50-52° B. (98-103° Tw.) strength, and also in solid form as 75-80° and 88-92°. The degrees in the latter case refer to the percentage of potassium hydrate (KHO) actually present.
Carbonate of Potash.—The standard for refined carbonate of potash is 90-92 per cent. of actual potassium carbonate (K2CO3) present, although it can be obtained testing 95-98 per cent.
Other Materials
Water.—Water intended for use in soap-making should be as soft as possible. If the water supply is hard, it should be treated chemically; the softening agents may be lime and soda ash together, soda ash alone, or caustic soda. There are many excellent plants in vogue for water softening, which are based on similar principles and merely vary in mechanical arrangement. The advantages accruing from the softening of hard water intended for steam-raising are sufficiently established and need not be detailed here.
Salt (sodium chloride or common salt, NaCl) is a very important material to the soap-maker, and is obtainable in a very pure state.
Brine, or a saturated solution of salt, is very convenient in soap-making, and, if the salt used is pure, will contain 26.4 per cent. sodium chloride and have a density of 41.6° Tw. (24.8° B.).
The presence of sulphates alters the density, and of course the sodium chloride content.
Salt produced during the recovery of glycerine from the spent lyes often contains sulphates, and the density of the brine made from this salt ranges higher than 42° Tw. (25° B.).
Soapstock.—This substance is largely imported from America, where it is produced from the dark-coloured residue, termed mucilage, obtained from the refining of crude cotton-seed oil. Mucilage consists of cotton-seed oil soap, together with the colouring and resinous principles separated during the treatment of the crude oil. The colouring matter is removed by boiling the mucilage with water and graining well with salt; this treatment is repeated several times until the product is free from excess of colour, when it is converted into soap and a nigre settled out from it.
Soapstock is sold on a fatty acid basis; the colour is variable.
Footnotes
1 Calculated by us from saponification value.
2 Calculated by us from saponification value.
3 Calculated by us from saponification value.
4 Calculated by us from saponification value.
5 Calculated by us from saponification value.
6 Calculated by us from saponification value.
7 Calculated by us from saponification value.
8 Calculated by us from saponification value.
9 Calculated by us from saponification value.
10 Calculated by us from saponification value.
11 Calculated by us from saponification value.
12 Calculated by us from saponification value.