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DYEING AND CALICO PRINTING.

with a nacreous reflection. Contact of air and sunlight tend to redden orcinegradually; bleaching-powder colours it first a deep violet, but which turnsgradually to a brown, and becomes finally yellow. Under the influence offixed alkalies orcine absorbs oxygen very rapidly, and assumes a red orbrown colour. Vapours of ammonia convert orcine into a deep brownsubstance, orceine ; bichromate of potassa, either with or without addition ofsulphuric acid, converts orcine into a brown substance, while the prolongedadtion of nitric acid, aided by heat, produces oxalic acid.

Orcine may be prepared by various processes. Robiquet obtained it byexhausting Variolaria with boiling alcohol : this liquid deposits, on cooling,crystals, which are first removed, after which the fluid is evaporated todryness. The dry residue, treated with boiling water, yields, on concentra-tion, crystals of orcine. Dr. Schunck boils lecanorate of baryta with waterfor a long time ; carbonate of baryta is precipitated, while orcine remains insolution, and is purified by repeated crystallisation. Dr. Stenhouse extractsthe lichens in milk of lime, boils and concentrates the liquid, precipitates thelime by carbonic acid, evaporates the liquid to dryness, and takes up theresidue with concentrated boiling alcohol. The crystals of orcine whichseparate from this liquid, on cooling, are re-dissolved in pure anhydrous ether.The best process for preparing orcine is that above described, as devised byM. de Luynes. Dr. Stenhouse has extracted from the Roccella tinctoria, ofthe Cape of Good Hope, a substance termed roccellinine, by the followingprocess :—The lichen is treated with a cold milk of lime, the liquor is filtered,and next precipitated by hydrochloric acid ; the ensuing pasty white precipi-tate is first washed with water, and next boiled with alcohol: this procedurecauses the formation of orsellate of ethyl, which is soluble in boiling water,while the unaltered roccellinine is not thereby dissolved, and maybe separated,

Roccellinine is soluble in ammonia and alkalies, but these solutions do notbecome coloured on exposure to air; it is almost insoluble in alcohol andether when cold, but the boiling alcoholic solution deposits, on cooling, silkyneedle-shaped crystals, which, according to Dr. Stenhouse, consist of

C18H16O7.

Parelline, or Parellic Acid, according to Dr. Schunck, accompanies lecanoricacid, In order to obtain the former acid, lichens are exhausted with boilingalcohol, and the liquid thus obtained boiled for some time, and next evaporatedto dryness. The residue is taken up in boiling water, to dissolve the orsellateof ethyl; the residue is treated with boiling alcohol, from which the parellicacid separates, on cooling, in the shape of fine crystalline needles, insolublein water, but soluble to some extent in cold alcohol and ether. This sub-stance, C g H60 4 , it appears, does not yield, when treated with ammonia andin contadt with air, any red or violet matters.

Colouring Matters of Orchil,

Although there is no doubt that in the dye known as orchil several differentpigments exist, only one of these, viz., orceine,—formed according to theresearches of MM. Robiquet and Dumas, at the expense of orcine,—has beenclosely investigated. This orceine requires for its formation two conditions:—the presence of atmospheric oxygen and that of ammonia, while a tem-perature of from 30° to 50° favours its generation. When orcine in a crystal-