Experiment XXXVII
It may ſeem ſomewhat ſtrange, that if you take the Crimſon Solution of Cochineel, or the Juice of Black Cherries, and of ſome other Vegetables that afford the like Colour, (which becauſe many take but for a deep Red, we do with them ſometimes call it ſo) and let ſome of it fall upon a piece of Paper, a drop or two of an Acid Spirit, ſuch as Spirit of Salt, or Aqua-fortis, will immediately turn it into a fair Red. Whereas if you make an Infuſion of Brazil in fair Water, and drop a little Spirit of Salt or Aqua-fortis into it, that will deſtroy its Redneſs, and leave the Liquor of a Yellow, (ſometimes Pale) I might perhaps plauſibly enough ſay on this occaſion, that if we conſider the caſe a little more attentively, we may take notice, that the action of the Acid Spirit ſeems in both caſes, but to weaken the Colour of the Liquor on which it falls. And ſo though it deſtroy Redneſs in the Tincture of Brazil, as well as produce Red in the Tincture of Chochineel, its Operations may be Uniform enough, ſince as Crimſon ſeems to be little elſe than a very deep Red, with (perhaps) an Eye of Blew, ſo ſome kinds of Red ſeem (as I have lately noted) to be little elſe than heightned Yellow. And conſequently in ſuch Bodies, the Yellow ſeems to be but a diluted Red. And accordingly Alcalizate Solutions and Urinous Spirits, which ſeem diſpos’d to Deepen the Colours of the Juices and Liquors of moſt Vegetables, will not only reſtore the Solution of Cochineel and the Infuſion of Brazil to the Crimſon, whence the Spirit of Salt had chang’d them into a truer Red; but will alſo (as I lately told you) not only heighthen the Yellow Juice of Madder into Red, but advance the Red Infuſion of Brazil to a Crimſon. But I know not whether it will not be much ſafer to derive theſe Changes from vary’d Textures, than certain kinds of Bodies; and you will perhaps think it worth while, that I ſhould add on this occaſion, That it may deſerve ſome Speculation, why, notwithſtanding what we have been obſerving, though Blew and Purple ſeem to be deeper Colours than Red, and therefore the Juices of Plants of either of the two former Colours may (congruouſly enough to what has been juſt now noted) be turn’d Red by Spirit of Salt or Aqua-fortis, yet Blew Syrrup of Violets and ſome Purples ſhould both by Oyl of Tartar and Spirit of Urine be chang’d into Green, which ſeems to be not a deeper but a more diluted Colour than Blew, if not alſo than Purple.