83. The rose colour of carthamus, extracted by soda, and afterwards detached from the alkali by citric acid, affords the basis of the beautiful paint known by the name of rouge. The colouring matter 'being slowly dried in the shade, is finely ground with the purest tale, and in this state is applied to give to the cheeks the hue of health and beauty, by those females who are distrust ful of their native charms.
84. Archil, or orchall, is a colouring matter, obtained from several species of lichens. When it is -prepared for the purposes of dyeing, it is in the form of a paste, andof a led violet colour. The most valuable is extract ed from the lichen rocrella, Linn. which grows at Cape Vcrd, and the Canary Isles, on the rocks near the sea.
nil:chins has endeavoured to shcty, that this plant is the same that was used by the ancients, and held by them in such estimation, that the colour which it afforded was reckoned more beautiful, w when first dyed, el en than the Tyrian purple. It is mentioned by Pliny under the name of fucus marinus, and was used in his time as a ground fur that colour.
85. The knowledge of archil as a dye, was lost, however, in Europe, till ahem the beginning of the 14th century, when it was restored by a native of Florence, who had be come acquainted with its properties during his residence in the Levant. Ile communicated the information he had acquired to his fellow citizens, and fur a considera ble time the Florentines enjoyed the exclusive use of it as a dye, as they purchased all that could be pi ocured of it, among the islands of the Archipelago, and on the shores of the Mediterranean. Alter the discovery of the Canary Isles, the lichen, which yielded the archil, was found in great abundance on their coasts, and by this means the other nations of Europe were relieved from their dependence upon Italy for a supply of the commo dity. The plants which yield this colouring matter, have also been discovered in great abundance at the Cape Verd Isles; and as they had been allowed to at tain their full maturity, they were found to be richer in colouring matter than any which had been previously known.
86. Michell has given an account of the method of preparing archil, conformable to the practice of Flo rence. The plant was first reduced to a fine powder, and after being passed through a sieve, was moistened slightly with stale urine. The mixture was stirred once a day, and a certain portion of soda added each time, till it acquired a dove colour. It was then put into a wooden cask, and covered with a sufficient quantity of urine, lime water, or a solution of gypsum ; and in this state it was retained until wanted by the dyer. In the description given in Plictho, (a work which we men tioned under the history of dyeing,) sal ammoniac, sal gem, and saltpetre, are added in tne preparation; but Hcllot thinks, from experience, that lime and urine are the only ingredients necessary ; and that the mixture ought to be frequently stirred, adding, at the same time, fresh quantities of these. It is proper when the process
is completed, says Berthollet, to allow the volatile alkali which has formed, to evaporate, that the archil may have the violet smell of that which is well prepared. To pre serve it any length of time, however, it must be kept moistened with urine.
The best kind of archil is extracted from the rocella, or orchella ; but this colouring matter is obtained from several other species of lichens. The French have long employed for this purpose a kind of lichen called perelle, which commonly adheres to volcanic stones or produc tions. The plant in question has been generally repre sented to be the lichen /tarellus of Linnaeus; but this supposition is disproved by a memoir of M. Cocq, lately published in the 81st vol. of the dnnale8 de Chinde. He states, that in Auvergne, where the perelle is princi pally gathered, the true lichen parellus is called Ia ponundee, and is always rejected as unfit by the persons employed for this purpose. M. Cocq describes, in the same memoir, the process by which the perelle is pre pared at Clermont for the use of the dyer. It appears, that the perelle is macerated and fermented in wooden troughs, which are commonly about six feet in length, two or three in breadth, (contracting towards the bottom), and about two feet in depth. Each trough is furnished with a cover, which fits it exactly, and retains as much as possible of the volatile alkali of the human urine.* About 200 libs. of perelle and 240 libs. of urine are mixed together in each trough, and afterwards stirred every three hours, during two days and nights, taking off the cover only as often and as long as is necessary for the stirring. On the third day, 10 libs. of sifted and slacked lime must be added, and well mixed, together with a quarter of a pound of arsenic, and an equal weight of alum. The workmen must avoid the fumes of the arsenic as much as possible, for some hours after its ad mixture. The stirring is then to be repeated several times, once every quarter of an hour, and afterwards every half hour, till the fermentation is established ; when this is the case, the mixture need not be stirred more frequently than is necessary to prevent a crust from forming on the surface, which, by obstructing the fermenting process, would resist the complete evolution of the colour. After the fermentation has continued 48 hours, it commonly begins to diminish, and must be re newed by the addition of two libs. more of sifted lime, and the stirring continued once every hour until the fifth day, when the frequency of stirring may be gradually diminished. After the eighth clay, it is sufficient to stir the mixture every six hours, extending the process a fortnight, and even in some cases three weeks longer. The colouring matter thus prepared, is afterwards to be kept moist in close casks. It improves during the first year ; suffers little change during the second; the third, it begins to decline, and becomes inferior in quality after wards.