404 



then neutralized with chalk, gave ahundant indications of grape- 

 sugar. Another portion of the solution from the decomposed lead- 

 precipitate, when digested with nitric acid, yielded only oxalic acid. 



When a decoction of willow-bark is boiled with dilute sulphuric 

 acid, the brown-coloured liquid becomes very red, and a flocculent 

 brownish-red precipitate falls which is nearly insoluble in water, but 

 dissolves pretty readily in hot spirit of wine and in alkaline leys. 

 The brownish-red precipitate, when dissolved in spirit of wine and 

 left to spontaneous evaporation, did not crystallize, but formed a dark 

 brownish resin. It consisted chiefly of impure saliratine, resulting 

 most probably from the decomposition of salicine in solution. When 

 it was digested with nitric acid it yielded a good deal of nitropicric 

 acid. Willow-bark, therefore, is a tolerably good source of this acid. 



Alder-bark (Alnus glutinosa). Alder-bark yields a dark red de- 

 coction with water. It was precipitated with acetate of lead, and the 

 lead-salt decomposed with sulphuretted hydrogen. It formed a dark 

 red solution, which on digestion with sulphuric acid yielded no sugar. 

 Catechu. It was the light-coloured cubical variety of catechu 

 that I employed. The tannin from this astringent substance, when 

 digested with dilute sulphuric acid, yielded no sugar, a result which 

 corresponds with Neubauer's experiments (Ann. der Chem. und 

 Pharm. vol. xcv. p. 103). 



Larch-bark (Pinus larix, Linn.). The bark of the larch is em- 

 ployed in Scotland to some extent in tanning, though the leather 

 made with it is inferior in quality. Larch-bark contains a good deal 

 of a peculiar tannin, which yields olive-green precipitates with salts 

 of iron. The aqueous solution of larch-bark is strongly acid to test- 

 paper, and has at first a pale yellow colour, which exposure to the air 

 renders brownish-red. Acetate of lead threw down a copious yellow 

 precipitate: this was decomposed by sulphuretted hydrogen and 

 boiled with dilute sulphuric acid, when the liquid assumed a fine 

 scarlet colour, like infusion of Brazil-wood. The altered tannin pre- 

 cipitated on cooling in beautiful red flocks, as it is but little soluble 

 in cold water. It is very soluble in alcohol, and its solution has a 

 rich scarlet colour, which is characteristic of this species of tannin. 

 Its alcoholic solution, when left to spontaneous evaporation, did not 

 yield crystals, but formed a dark resinous mass. The clear liquid 

 from which the red flocks were precipitated, when neutralized with 



