ORCHIL.

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Used state is exposed to the aCtion of ammoniacal vapours this conversiontakes place, and equally so when an aqueous solution of orcine containingfrom 10 to 20 per cent is exposed to the adtion of these vapours : time is avery essential item in this process. According to M. Dumas, the formula oforceine is C 7 H 7 N 0 3 , and the formation of this substance from orcine maytherefore be elucidated by—

C 7 H 6 0 2 +N H 3 + 0 2 = C 7 H 7 N0 3 + H a 0.

Orcine. Orceine.

Dry orceine is a brown powder, somewhat soluble in water, to which itimparts a red colour. The neutral alkaline salts precipitate this solution.Orceine is insoluble in ether, but very readily soluble in alcohol, giving ascarlet solution ; alkalies and ammonia also dissolve it, yielding magnificentpurplish-violet solutions. Orchil as met with in commerce exhibits, undersimilar conditions, the same phenomenon; it is essentially orceine in combi-nation with ammonia (orcineate of ammonia), which yields, when dissolved inwater with various metallic salts, diversely coloured precipitates or lakes, butafter drying the colour of these bodies is very faint. Orcineate of ammoniais decolourised by reducing agents, as, for instance, by boiling along withwater and metallic zinc, or addition of sulphydrate of sulphide of ammonium,but the colour reappears on exposure to air. When an ammoniacal solutionof orceine is acidified with hydrochloric acid, and zinc added, the fluid isdecolourised. The addition of ammonia to this liquid causes the precipitationof a flocculent white matter, leucorceine, which, on exposure to air, becomesviolet and purplish. Chlorine converts orceine into a yellowish-brown matter,chlororceine. Orceine is, by itself, a red substance, which, under the influenceof alkalies, becomes violet, but acids restore the primitive red colour.

Dr. Kane has found, in the orchil of commerce, two other red matters,orceine and azoerythrine, and, moreover, a semi-fluid purplish substance,erythroleic acid. The azoerythrine, C n Hi 9 NO n , is insoluble in water, alcohol,and ether, but soluble in alkalies, to which it imparts a wine-red colour; ery-throleic acid, C! 8 H xi 0 4 , is soluble in alcohol, ether, and alkaline solutions, butinsoluble in water. These products have not been, however, sufficientlyinvestigated.

New Methods of Preparing Orchil.

The researches above mentioned, more especially those of Drs. Schunck,Stenhouse, and Rochleder, have led to great improvements in the manufacture .of orchil, especially in this respeCt—that the colourability of the lichens is nota property of these plants as a whole, but is due to some principles thereincontained, which are capable of being rendered soluble by suitable reagents,or may be set free by mechanical means. These colourable materials formonly a very small portion of the total weight of the lichens. The chemicaloperations are, moreover, rendered easier and more manageable if the largebulk of ligneous matter is removed.

We have already observed that Frezon utilises the slight adherence of thecrythrine and the lecanoric acid, which are chiefly on the surface of theplants, in order to isolate and detach these substances. This is effected asfollows:—The lichens, previously sorted and washed several times with coldwater, are ground up to a somewhat liquid paste. This paste is exhaustedb y washing several times with cold water; the liquids obtained are filtered