ORCHIL.

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exhausting afterwards with boiling alcohol, the purple matter is obtained,when the alcoholic liquid is evaporated in the shape of crystals. This sub-stance has not been as yet chemically investigated. The price of this Frenchpurple was at first 200 francs (,£8) per kilo.; it has come down to 80 francs(£3 5s.), and is distinguished from ordinary orchil by not being reddened byvegetable acids.

The researches made by M. Gauthier de Claubry have proved that the pro-duftion of French purple is mainly due to that portion of the process (thestoving) and the keeping up thereby of a very uniform temperature. Thesame chemist also ascertained that when orchil is prepared at 6o° a produdt isobtained yielding more solid dyes than when manufactured at lower tempera-tures. Although the process of making orchil is known in its generalfeatures, every individual manufacturer keeps his own peculiar process andeverything relating thereto secret. The quantity of colourable matter of thelichens can vary from 24 to 12 per cent. In order to ascertain comparativelythe tinctorial value of the various samples equal weights thereof (100 grms.)are macerated for a short time—a few minutes—with milk of lime ; the liquidis placed on a stout cloth, filtered, squeezed, and precipitated by means ofhydrochloric acid ; the resulting white paste is placed on a small silk sieve,rapidly washed, well drained, and weighed. Dr. Stenhouse applies a standardsolution of bleaching-powder, which, on being added drop by drop to thecalcareous lichen extract, causes first the prodution of colouration, and assoon as that has attained its summit decolouration ensues ; by comparing thedegrees of solution of hypochlorite required for the prodution of thesephenomena in different solutions of lichens their goodness may be approxi-mately estimated.

Another process is to exhaust 100 grms. of lichens with water renderedalkaline; this liquid may be concentrated by evaporation to 100 grms., andthe colouration may be caused by the addition of 30 grms. of ammonia. Inother terms the orchil manufature is executed on the small scale; a dyeingprocess with unmordanted wool will give some idea of the quantity ofcolouring matter formed. The manufactured article, orchil, is tested by adyeing process with unmordanted wool; for a piece of that material 5 centims.long by 2 centims. wide from 0'5 to ro grm. of orchil and 300 grms. of waterare taken. These materials are put in a suitably sized glass vessel placed ina water-bath, and kept at a boil for half an hour. When it is desired to testthe orchil by printing, 100 grms. of gum water, 12 of sulphate of alumina,100 of orchil are mixed and printed by roller or block over a sufficiently largesurface of wool, which is afterwards steamed.

Applications of Orchil in Dyeing and Printing.

Orchil is never applied to cotton or calico, for although it might be fixedupon that fibre by means of animal mordants the colours thus obtained areneither sufficiently fast nor brilliant enough to be of any use. This remarkdoes not apply to French purple, which is brilliant as well as fast. In orderto print French purple on cotton the lime or alumina lake is dissolved in amixture of acetic acid and alcohol, next a solution of albumen is added.M. Kopp gives the following prescription, which may, of course, be varied tosome extent:—French purple, 25 grms.; acetic acid, 50 grms.; alcohol,