COTTON.

3i

be distinguished by their different degrees of solubility in alcohol—one beingeasily soluble in cold alcohol, the other soluble in boiling, but very littlesoluble in cold alcohol. As these substances possess very few characteristicproperties, and it is doubtful whether they are peculiar to cotton or not, the onewhich is most easily soluble in alcohol is called simply Colouring matter A, theother Colouring matter B. These bodies were separated from one another andfrom the fatty acid in the following manner:—The liquid having beenevaporated, left a brown, semi-solid, resinous mass, which was treated with asmall quantity of warm or boiling alcohol. This dissolved only a part of themass, the remainder being left undissolved as a brown powder, consisting forthe most part of the colouring matter B. The liquid having been filtered,the powder was treated with a large quantity of boiling alcohol, in whichit usually dissolved almost entirely. A small quantity, however, of a brownflocculent substance was generally left undissolved; and this substance,which consisted of impure pedtic acid, having been filtered off while the liquidwas hot, the latter, on cooling, deposited the greatest part of the colouringmatter as a brown powder, which only required to be filtered off, washed withalcohol, and dried. The dark brown alcoholic liquid, containing the moresoluble colouring matter A, as well as the fatty acid and a portion of thecolouring matter B, was now mixed with ammonia and chloride of barium,which gave an abundant greyish brown precipitate, consisting of all theorganic matter previously contained in the liquid in combination with baryta.This precipitate was filtered off, and then treated with boiling alcohol. Thelatter being filtered boiling hot, afforded, on cooling, a small quantity of abrownish crystalline deposit. This process was repeated as long as thefiltered liquid deposited anything, and until, therefore, the precipitate wasthoroughly deprived of everything soluble in alcohol. The crystalline matterdeposited from the alcoholic liquid consisted almost entirely of the barytasalt of the fatty acid. After being filtered off it was treated with warm dilutehydrochloric acid, by which it was decomposed, the fatty acid rising to thesurface as a light brown oil, which became solid on cooling. The latter, afterbeing well washed with hot water, was dissolved in warm alcohol, and thesolution, having been decolourised with animal charcoal and filtered, wasevaporated spontaneously, when it left a perfedtly white mass of crystallineneedles, consisting of the fatty acid in a state of purity.

The baryta-precipitate, after treatment with boiling alcohol, was decom-posed with warm dilute hydrochloric acid, which left undissolved a dark brown,semi-fused mass. This mass, after being kneaded in hot water and thoroughlyfreed from barium salt, was treated with boiling alcohol. The alcoholgenerally left some brown powder undissolved, consisting of colouring matter B;and an additional quantity was usually deposited from the alcohol on cooling.Having been filtered off, it was purified by dissolving it in a sufficient quantity ofboiling alcohol, as above described. The filtered liquid left, on evaporation,a daik brown resinous mass, which was reduced to a fine powder, and thenagitated in a flask with ether. The ether dissolved only a very small portionof the mass, but it served to remove a trace of fatty acid contained in it.The ether, on evaporation, left a brown fatty residue, which, after combinationwith baryta and treatment of the compound with boiling alcohol, as justdescribed, yielded a quantity of pure fatty acid. The portion left undissolved