of Astringent Substances. 335 



aether, pouring off the solution, recovering the greater portion 

 of the aether by distillation, and leaving the remainder to spon- 

 taneous evaporation, crystals of gallic acid were deposited in 

 a few hours. The quantity of gallic acid in myrobalans is 

 pretty considerable. 



Besides tannin and gallic acid, myrobalans contains a good 

 deal of mucilage, and a brownish -yellow colouring matter, 

 which Dr. Bancroft states was employed in India in his time 

 as a yellow dye. Myrobalans have long been employed by 

 the calico-printers of India instead of galls, and from the large 

 quantity of astringent matter they contain, I think perhaps 

 they might be worth the attention of the tanners and calico- 

 printers of this country. A decoction of myrobalans makes 

 a very tolerable ink, which however, as we have already stated, 

 is rather deficient in lustre. 



Bistort, Polygonum Bistortus. — The root of this plant, 

 which is pretty common in Scotland, has a pale pink colour 

 internally, but when it is exposed to the air for some time it 

 becomes deep yellow. Its aqueous solution is yellowish at 

 first, but on standing it assumes a fine red colour, and the same 

 effect is immediately produced by boiling it with any of the 

 alkalies. With protosulphate of iron it gives a bluish-black 

 precipitate, a good deal resembling that of galls, but having a 

 bluish-purple shade. Gelatine produces a copious brownish 

 precipitate in a solution of bistort, which shows that the quan- 

 tity of astringent matter it contains is considerable. With 

 tartar-emetic it gives a brownish-white precipitate. When 

 extract of bistort is evaporated to dryness and distilled, it gives 

 distinct indications of pyrogallic acid. The pyrogallic acid 

 however, as in the case of myrobalans, was derived not from 

 the tannin in bistort, but from a quantity of gallic acid with 

 which it was mixed, for on precipitating the tannin by sul- 

 phuric acid, and distilling it alone, not a trace of pyrogallic 

 acid was obtained, and when boiled with sulphuric acid it was 

 not converted into gallic acid. 



The gallic acid it contains was easily obtained from bistort 

 by precisely the same process as that already described. Its 

 quantity, compared with that of the tannin in the root, was 

 very considerable. 



Besides tannin and gallic acid, bistort contains a brownish- 

 red colouring matter, and a quantity of mucilage. Bistort 

 may likewise be made to .furnish' a very tolerable ink, which 

 appears to stand very well. It has a bluish-purple shade, 

 owing to the reddish colouring matter of the root. 



The Cashew 'Nut. — The outer rind of the Cashew nut, the 

 fruit of the Anacardium longifolium, contains a considerable 



