A Treatise on Calico Printing, Of Vegetable Substances.

A Treatise on Calico Printing, VOL. I-II
Printed for C. O'Brien, Bookseller, Islington, and fold by Bew, Paternoster-row: Richardson, Royal Exchange: Murray, Fleet-Street: And the Booksellers of Manchester, Glasgow, Dublin, &c.
From the analysis of vegetable substances, it is clear they contain phlegm, an acid, alight oil, much air, and a thick oil, but none of these principles can be obtained pure by mere distillation, as their separation is only began by this process, therefore others are adopted to compleat the analysis.

Some vegetables, by analization, prove that they contain the same principles as animal substances possess, and instead of yielding an acid, a volatile alkaline only is to be obtained; probably because the acid of the vegetable suffers such changes when it enters into the composition of animals, that is, it combines with some of their earth and oil, in.such a manner as to be changed into a volatile alkali.

In burning any vegetable substance in the open air, the analysis is more rapid and compleat, burning till all its oil is consumed, and a coal remains, and this continues wasting till all its phlogiston is dissipated, what then is left is its earth and fixed alkali, commonly called the ashes. Water, the natural solvent of salts, takes all of them up that are contained in the ashes, so that by lixiviating them, nothing at last is left but the pure earth.

All balsams, as well as turpentine, are oily aromatic matters, procured by different methods from those trees which produce them; these abound with essential oils separated from the vegetable in which they exist.

Resins are distinguished from natural balsams by containing less oil, and more acid, so that they are less disposed to be fluid, and are soluble only in spirits of wjne; they however differ from each other according to the quantity or quality 6f acid to which they owe their consistence: The saline character of Benjamin is evident from its being soluble. in water, but then it must be boiling; the salt produced from it will chrystallize and may be dissolved in spirits, of wine.

Gums differ from resins in being soluble in water, but (as before said) resins are not; resin being an essential oil grown thick, and have an aromatic odour, which gums have not: the small portion of oil which gums contain, being so tho roughly mixed with their acid, does not hinder their dissolving in water, and therefore they re semble honey, and other vegetable juices, in being originally fluid, and only grown hard by the evaporation of their moisture; the same as resins become solid by losing, in the same manner, their fluid parts: but in gum-resins, the two qualities, are so blended, that each will dissolve in its proper menstruum, leaving the other entire.

Sugar, manna, and all the saccharine juices of fruits and plants, are of the nature of honey, containing a phlegm, an acid, an oil, and a coal: but differ from resiirs in not being inflammable, or will not flame till nearly reduced to a coal: All these substances are deemed natural soaps, consisting of an oil rendered mislible with water by means of a saline substance, but differ from common or artificial soaps in heaving their saline part an acid, while that of the others is an alkali: Why they are sweet, thongh containing much acid, is from the acid being intimately sheathed or smoothed by the oil: Of soap it may further be said, that alkalies or acids combined, in a certain manner with oil, produce them; for oily and saline substances combined, follow the same rules as other combinations, by reciprocally combining the properties belonging to each other, and (according to the rules of affinities) soaps are decomposed by alkalies, and alkalies by acids.

The most expeditious mode of making a soap (being Dr.Lewis's improvement on Mr.Beaume's) is, by heating the alkali red hot, then throwing it into oil of turpentine, and stirring them well together; in time, a salt crystallizes both within it, and over its surface, but its nature is unknown.

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