Wittstein found only 20 per cent. of an iron-greening catechol-phloroglucol tannin allied to tormentil tannin, in the root-bark, the only active part of root.
ANACARDIACEÆ.
Loxopteryngium Lorenzii. Span. Quebracho colorado. South America, especially Argentine Republic; the highest proportion of tannin occurring in the wood from Gran Chaco district. Wood contains on an average about 20 per cent. of a red, difficultly-soluble tannin, yielding “reds,” and containing catechol and phloroglucol. The tannin is not very soluble in water, and hence can only be used in weak liquors, but is very astringent, and gives a firm, reddish leather. The wood also contains a catechin[139] and a colouring matter, fustin, identical with that of “young fustic.” It is imported into England, and more largely to Havre and Hamburg, in logs, which are there chipped like logwood, and either used direct for tanning, or made into extract. A very cheap tan. With alum it gives a yellow colour. The extract usually dissolves to a fawn-coloured turbid solution. Many quebracho extracts are now made completely soluble by treatment with alkalies or sulphites (cp. [p. 338]).
[139] See P. Arata, Journ. Chem. Soc., 1878, A, p. 986; 1881, A, p. 1152; and Perkin and Gunnell, Trans. Chem. Soc., 1896, 1303.
“Quebracho” means “axebreaker,” and is consequently applied to a variety of hard woods. Its specific gravity is 1·27-1·38, and it therefore sinks in water.
Pistacia lentiscus, Ital. Pistacio, Fr. Lentisque. Sicily, Cyprus, Algeria. Small myrtle-like leaves contain from 12-19 per cent. of a catechol-tannin, and are very largely used in the adulteration of sumach. Leather tanned with sumach adulterated with this material darkens and reddens on exposure to light and air, and for this reason its use in many cases is decidedly injurious. In Cyprus and the East it is known as “Skens,” Ital. Schinia, Fr. Poudre de Lentisque, in England, often called Cyprus sumach. (Cp. [p. 272].)
P. orientalis, terebinthus, vera, etc., India, Mediterranean. Various aphis galls, 30-40 per cent. tannin. A sample of galls of Pistacia vera, “Gool-i-pista,” India, recently examined in the Author’s laboratory, contained 30 per cent. of a light-coloured tannin.
Schinus molle, “Molle,” Buenos Ayres. Leaves only used; said to contain 19 per cent. tannin.
S. Aroeira, Brazil. Said to contain 14 per cent. tannin.
Rhus coriaria, Sicilian sumach. Ital. Somacco. ([Fig. 53].) A shrubby bush, of which leaves and small twigs are used.