A Dictionary of Arts (supplement): Archil.

(A Dictionary of Arts, Manufactures, and Mines; containing A Clear Exposition of Their Principles and Practice)
Recent improvements in
Arts, Manufactures, and Mines:
Being A supplement to his Dictionary
by Andrew Ure, M. D.,

Illustrated with one hundred and ninety engravings.

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ARCHIL has been lately the object of numerous chemical researches, but hitherto, it must be owned, without producing any results useful to the dyer, so as to promote the solidity of this beautiful and now cheap dye. The new experiments of Schunk, performed in Liebig's laboratory, tend to show that the whole matter is still involved in much mystery. By the action of either on the Variolaria lactea (on of the archil lichens), in an apparatus of displacement, he obtained crystals, which he calls Isomorine. It is convertible into the orcine of Robiquet and Heeren by hot barytes water. When moistened with water of ammonia, and exposed to the air, it gradually assumes the archil tint. Liebig is of opinion, that this product, and some other analogous ones, vary according to the nature of the solvents and the temperature of the digestions, so that they probably are mere metamorphoses of the self-same one or two substances, pre-existing in the lichens. Since lecanorine is decomposed by boiling water into carbonic acid, and orcine, it may also undergo this change from the boiling alcohol employed in Schunk's researches.

When ammonia acts upon orcine, it gives it a dark blood-red color, and converts it into orceine, a new compound containing azote, but in a different state of combination from what it is in ammonia. This orceine is the true colouring matter of the archil or orseille; and, according to Robiquet, it is here in the state of an orceate of ammonia, requiring for its production the co-operation of air and water. In these circumstances  the orceine absorbs oxygen, and is transformed into orceate of ammonia, without any other product, even carbonic acid, being formed. Variolarine, erythrine, and pseudo-erythrine, three products obtained by Robiquet and Heeren; the first from Variolaria dealbata, the second and third from Parmelia roccella, and Lecanora tartarea, are interesting merely in a scientific point of view. The last two are transformed into red colouring matters by ammonia and air. "Latterly," says Liebig, "Kane has made these two substances objects of a particular investigation; but the researches of this chemist are far, as appears to me, from clearing up their history." I need not therefore, give any account of these researches, which occupy a large portion of a recent volume of the Philosophical Transactions.

Tournesole, or litmus, consists, according to Peretti, of a red colouring matter, redered blue by combination with ammonia.

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