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DYEING AND CALICO PRINTING.

lavia:—dealbata (Pyrenees), orcina (Auvergne), lecanora tartarea (Sweden):their exterior form is that of an irregular crust, exhibiting hardly any organisedtexture visible to the naked eye, which distinguishes them very readily frommarine lichens. The entire plant was operated upon in the manufacture oforchil from land lichens. The process, as carried on about a. d. 1812, wasdescribed by M. Cocq.

In order to judge of the goodness of the material, a small quantity is putinto a glass, and ammonia is poured over it. The good kinds become brown,but the useless, or at least inferior, qualities assume a yellow or green tint.The collected lichen is dried by being spread out in well-aired lofts.

For the preparation of the colour 100 kilos, of lichen are placed in a woodentrough, wider at the top than at the bottom, and the dimensions of which areas follows :—Length 2 metres by a width of 1 metre, and a depth varying atthe top from 0*06 to 0^07 metre and at the bottom 0*04 metre. This troughcan be tightly closed by a wooden cover. To the lichen are added 240 litresof human urine, and this mixture is stirred up every three hours during twodays and nights. There are added, on the third day, 5 kilos, of slaked andsifted lime, 125 grms. of powdered whire arsenic, the same quantity of rockalum; whereupon the mixture is very frequently stirred. Fermentation setsin ; forty-eight hours after another kilo, of lime is added, and the stirring isless frequently performed. The action is at end after the lapse of a month,when the product, which becomes better by keeping, is put into casks. Theactivity of the putrefied urine is due to the presence of carbonate of am-monia, formed by a well-known reaction from the urea. The lime is added inorder to set the ammonia free and bind the carbonic acid: the orchil thusobtained is capable of yielding divers colours, viz., by simple treatment withboiling water amaranth is produced, and the intensity of this colour is entirelymodified by the lapse of time the woven fabrics are left in the bath, so that atlast a brown may be obtained. One of the first improvements in this branchof industry is the substitution of ammonia for the mixture of urine, lime, andarsenic, by which means time is economised and the whole process betterregulated. The use of lime was, moreover, found to be rather injurious to theprocess.

The principal forms in which these colours are now found in commerce areorchil paste, orchil liquor, cudbear, and “ French purple.” The paste andliquor are distinguished as “red” and “blue,” according as they incline toeither of these colours. Cudbear, known on the Continent as persio, is a drypowder, and, from the mode of its preparation, is of a reddish cast. Themanufacture of these dyes will be described below.

Since the colouring matter of orchil is soluble in water, that liquid has beenemployed to extract it from the orchil weeds,—an operation similar to the pre-paration of dye-extraCts from the woods, with this difference, that the lattercontain the colours ready formed, while in the former it has to be developed.In this way single and double extracts of orchil, and orchil lakes, may beobtained.

The colourable material of the lichens is not uniformly distributed throughthe plant, but is chiefly deposited as a greyish powder on the surface, easilydetached by mechanical means. M. Frezon has turned this observation toaccount, by submitting the lichens to the joint action of friction and water