Young Fustic(CHAPTER VII. Flavonol Group.)

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.

Cotinus coggygria

Young fustic consists of the wood of the stem and larger branches of the Rhus cotinus (Linn.), a small tree which is a native of Southern Europe, and the West India Islands. It is a hard compact yellow wood, and is usually imported in small bundles or faggots. Within the last few years young fustic has almost disappeared from the market, not only on account of the artificial colouring matters, but because the shades it yields lack permanence, and the percentage of colouring matter it contains is small. The leaves of the R. cotinus constitute Venetian sumach, a tanning material which is employed to some extent in Italy and Southern Europe.

Fisetin, C₁₅H₁₀O₆, the colouring matter of young fustic, was first isolated by Chevreul ("Leçons de Chimie appliquee a la Teinture," A. ii., 150), who gave it the name "Fustin". Bolley (Schweiz. polyt. Zeitschr., 1864, 9, 22) considered that it was identical with quercetin, but Koch (Ber., 5, 285) maintained that fisetin was probably an aldehyde of quercetinic acid.

Schmid (Ber., 1886, 19, 1734), who carried out an exhaustive examination of this dyewood, obtained fisetin in a pure condition and proved that it was not identical with quercetin. He found that in addition to the free colouring matter, young fustic contains a glucoside of fisetin combined with tannic acid to which he gave the name of fustin tannide.

To prepare fisetin, Schmid (loc. cit.), and later Herzig (Monatsh., 12, 178), employed "cotinin" (v. infra), a commercial preparation of young fustic which is no longer on the market. According to Perkin and Pate (Chem. Soc. Trans., 1895, 67, 648), fisetin is readily isolated from the dyewood as follows:

Young fustic is extracted with boiling water, and the extract treated with lead acetate solution. The lead compound of the colouring matter is collected, made into a thin paste with water, and in a fine stream run into boiling dilute sulphuric acid. After removal of lead sulphate the dark-coloured filtrate, on cooling, deposits a semicrystalline brownish mass, which is collected and purified by crystallisation from dilute alcohol.

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Fisetin is a strong colouring matter and gives shades which are almost identical with those produced by quercetin, rhamnetin, and myricetin. The colours given with wool mordanted with chromium, aluminium, and tin are, respectively, red-brown, brown-orange, and bright red-orange (Perkin and Hummel, Chem. Soc. Trans., 1896, 69, 1290).

The glucoside of fisetin, according to Schmid (loc. cit.), is prepared as follows: A boiling aqueous extract of young fustic is treated with lead acetate, the precipitate removed, the clear liquid freed from lead by means of sulphuretted hydrogen, and saturated with salt. The mixture is filtered, the filtrate extracted with ethyl acetate, and the extract evaporated. There is thus obtained a residue consisting of the crude fustin-tannide, which is purified by solution in water, precipitation with salt, and extraction with ethyl acetate.

Fustin tannide crystallises in long yellowish- white needles, which are easily soluble in water, alcohol, and ether. When heated it decomposes above 200°. If a solution of fustin tannide in hot acetic acid is treated with water, and allowed to stand for some time, colourless crystals of fustin are gradually deposited.

Fustin crystallises from water in yellowish-white needles, melting-point 218-219°, and when digested with boiling dilute sulphuric acid gives fisetin and a sugar, the nature of which has not been determined. The formula given to this glucoside C₅₈H₄₆O₂₃ by Schmid cannot be regarded as correct, in view of the fact that the true formula of fisetin is now known to be C₁₅H₁₀O₆.

Dyeing Properties of Young Fustic.

The colours derived from young fustic are all fugitive to light, hence this dyestuff has lost its importance. In silk dyeing it was formerly used for dyeing brown, the silk being mordanted with alum, and afterwards dyed with a decoction of young fustic, peachwood, and logwood. With the various metallic salts as mordants young fustic yields colours somewhat similar to those obtained from old fustic, the chromium colour is, however, much redder, being a reddish-brown, and the aluminium yellow is much duller; stannous chloride on the contrary gives an incomparably more brilliant orange, not unlike that obtainable from flavin or from Persian berries (Hummel).

Fisetin is present also as glucoside in the wood of the yellow cedar, Rhodosphacra rhodanthema, and in the wood of the Quebracho Colorado (loc. cit.).

The leaves of the R. cotinus contain myricetin.