930 NEUTRAL COLOURING MATTERS. 



solution of carbonate of soda, when its colour is said to be 

 raised. A very minute quantity of alkali gives an infusion of 

 Brazil wood a violet colour, so that it is a delicate test of 

 alkalinity. Alum and the acetate of alumina throw down from 

 it an abundant carmine precipitate, while the liquid retains the 

 same colour; these compounds form the basis of common red 

 ink. For some years past brazil-wood has been nearly super- 

 seded in this country by a wood imported from Africa, and 

 named camwood by dyers, which is richer and gives a finer 

 colour than any of the varieties of Brazil wood. It is also not 

 so much affected by alkalies, nor so liable to assume a violet 

 shade ; and the yellow colouring matter with which it is mixed 

 gives the red a more lively appearance (Dr. Thomson.) But 

 the colour of these and all other red woods has little permanence 

 and does not produce fast colours. 



BERBERIN. 



This is a crystalline substance of a fine yellow colour derived 

 by the MM. Buchner from the bark of barbery root, Berberis 

 vulgaris^ The root is exhausted by means of boiling water, 

 the decoction concentrated to the consistence of a soft extract, 

 and this digested repeatedly in alcohol of 0.844, so long as the 

 liquid acquires a bitter taste. These tinctures are filtered, a 

 considerable portion of alcohol distilled off, and the residue left 

 in an open vessel to crystallize in a cool place. It forms fine 

 prisms of a clear yellow colour, without odour, but having an 

 intensely bitter taste. It is not fusible without decomposition. 

 It is sparingly soluble in cold water, largely soluble in hot 

 water, soluble in alcohol, for.ms compounds with bases, and pre- 

 cipitates readily all metallic salts. Its composition is expressed 

 by C 33 H 18 NO 12 . Berberin answers very well as a dye stuff, 

 and gives a fixed yellow on cotton cloth without any mordant. 

 It forms also a powerful tonic. 



QUERC1TRIN. 



The yellow colouring matter of quercitron bark has lately 

 been examined by M. Bolley.f It was obtained from a decoc- 



* Journal de Pharmacie, t. 17, p. 40 and t. 21, pp 309, 408. 

 t Liebig's Annalen, xxxvii, 101. 



