Kermes(CHAPTER I. The Anthraquinone Group.)(Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Kermes is the most ancient dyestuff on record, for it was known in the time of Moses, and is mentioned in Scripture by its Hebrew name, "tola" or "tolaschani". According to Tychsen (Bancroft's "Philosophy of Permanent Colours," i, 394), "the scarlet or kermes dye was known in the East in the earliest ages before Moses, and was a discovery of Phoenicians in Palestine, but certainly not of the small wandering Hebrew tribes". Under the name "coccus" it is frequently referred to by the Greek and Latin writers.

Kermes is an insect found on the oak kermes (Quercus coccifera, Linn.), and when living the female insects, which are fixed to the twigs of the tree, resemble bluish berries, and are covered with a whitish powder. As soon as their eggs are on the point of hatching these insects should be collected, killed by exposure to the steam of vinegar, and dried, and the product has then the appearance of pale reddish-brown grains. According to Bancroft, it would require 10 or 12 lbs. of kermes to produce the effect of a single lb. of cochineal.

Kermesic acid, C₁₈H₁₂O₉, the colouring matter of kermes, was first isolated, in the crystalline condition, by Heisse (Arbeit, a. d. K. Gesundheitsamte, 1895, 513), and has since been examined by Dimroth (Ber., 1910, 43, 1387; and Annalen, 1913, 399, 43). To isolate the kermesic acid, the kermes is first extracted with ether to remove wax, and this has been examined by Dimroth and Sherndal (Annalen, 1913, 399, 43), and identified as ceryl cerotate, C₅₂H₁₀₄O₂. The residue is then allowed to stand overnight with an ethereal solution of hydrochloric acid, by which means the kermesic acid, which exists in kermes in the form of a salt, is liberated and made capable of removal by repeated extraction with ether. For the purification of the substance, it is converted into its sparingly soluble sodium salt, which allows of its separation from flavo-kermesic acid, a substance stated by Dimroth to be present in kermes dye to the extent of about 0.06 per cent. the sodium salt of this being soluble in hot 2N sodium acetate solution, whereas the disodium salt of kermesic acid is almost insoluble. The sodium salt when dissolved in boiling sodium hydroxide solution and treated, whilst boiling, with excess of hydrochloric acid, yields a crystalline precipitate of kermesic acid.

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Kermesic acid is thus closely related to carminic acid, which is also considered by Dimroth to be a derivative of anthraquinone.

Dyeing Properties.

According to Hellot (Bancroft, "Philosophy of Permanent Colours," i, 404), "the red draperies of the figures exhibited in the ancient Brussels and other Flemish tapestries were all dyed with kermes". "The fine red or crimson colour of these tapestries, which was originally called simply scarlet, took the name of Venetian scarlet, after the cochineal scarlet upon a tin base was discovered...."

For the production of this scarlet, the wool, previous to dyeing, was mordanted with alum and tartar; and, according to Bancroft, there is no evidence even in more recent years of the employment of a tin mordant in respect of this colouring matter, although the experiments he carried out indicated that by this latter method a scarlet could be produced "in every respect as beautiful and estimable as any which can be dyed with cochineal".