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or alkaline lye : in the first case the alcoholic fluid is evaporated to dryness,and the remaining extra# taken up with ether, which dissolves the colouringmatter; or, in case an alkali has been used, the pigment is precipitated byhydrochloric acid, the sediment washed and dried, and next treated withether. The pigment obtained by the evaporation of the ethereal solution canbe further purified by re-solution in alcohol, precipitation by acetate of lead,and decomposition of the precipitate so obtained by sulphuretted hydrogen.The mixture of sulphide of lead and curcumin is dried and taken up withether, which, on evaporation, yields curcumin, as a translucent, amorphous,cinnamon-coloured mass, which when powdered appears yellow. It is solublein ether, alcohol, alkalies, and concentrated acids, the alkaline solutions beingof a red-brown colour.*

M. E. Schlumberger has been the first to investigate the modifying a#ion ofboracic acid upon curcumin. It is well known that turmeric paper becomesbrown under the joint influence of the boracic and any mineral acid, preferablythe hydrochloric. Ammonia turns this colour blue. When an alcoholicsolution of curcumin is boiled with boracic acid its colour turns orange, andupon the addition of water to the previously cooled solution a Vermillion-coloured powder is thrown down, being a compound of the pigment withboracic acid. This combination is broken up by the sufficiently prolongedattion of water; the boracic acid dissolves, and there remains a yellow resinousmatter which differs from curcumin, inasmuch as it does not yield a redcolouration with boracic and hydrochloric acids, and on being dissolved inalkalies gives a greenish-grey colouration. The boracic compound of curcu-min dissolves with a purplish-violet colour in alkalies, but this soon turns togrey. When hydrochloric acid is added to an alcoholic solution of biomo-curcumin, and the fluid boiled, it rapidly assumes a blood-red tint; on coolinga new body is thrown down, while the boracic acid remains in solution. Thesubstance so deposited is first washed with dilute alcohol, next with purewater, in order to eliminate all boracic acid ; the residue is dried, and nextdissolved in a boiling mixture of 2 parts of alcohol and 1 part of acetic acid.This fluid, being filtered while hot, deposits on cooling rosocyanin, while thepseudocurcumin remains in solution. By pseudocurcumin is understood theorganic resinoid substance resulting from the prolonged adtion of water uponborocurcumin, just above mentioned. The rosocyanin is first dried, and nexttreated with ether, in order to remove the last traces of yellow colouringmatter : thus purified, it is a crystalline substance, of a cantharides-like lustre,insoluble in water, ether, and benzol, but very soluble in alcohol, to which itimparts a most magnificent deep rose-red, quite comparable to fuchsin solu-tions. This fluid becomes permanently yellow on being boiled. Ammoniaturns the alcoholic solution of rosocyanin a splendid blue, but this colour-ation changes shortly into a dirty grey; acids turn the blue ammoniacalsolution red again ; lime- and baryta-water yield blue precipitates in the alco-holic solutions, which do not contain any boracic acid at all.

The relations existing between curcumin and rosocyanin (also called roseo-cyanin) and pseudocurcumin are unknown, neither was until July, 1870, the

* “Journal de Pharmacie,” vol, ii. (2). p.20. Lepage, “Journal des ConnaissancesMedicales et Pharmaceutiquesvol. xxvi., p. 315. “ Repertoire de Chimie Appliques,” vol. i.,

P- 304.

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