

EXPERIMENTS ON ASTRINGENT VEGETABLES. 275 



The aqueous folution of it, when mixed with folutions of— -with other 

 nitrate of alumine and of muriate of tin, became flightly turbid. 



To nitrate of lead, it gave a derffe light brown precipitate. 



It was not perceptibly a6ted upon by folution of gelatine J 

 but, when folution of fulphate of alumine was added to the 

 mixture of the two fluids, a confiderable quantity of folid mat- 

 ter, of a light brown colour, was immediately depofited. 



To the folution of oxygenated fulphate of iron, it communi- 

 cated a fine grafs-green tint ; and green precipitate was de- 

 pofited, which became black by expofure to the air. 



It was not precipitated by the mineral acids. 



Linen, by being boiled in the ftrongeft folution of the ex- Linen abftra&s 

 tractive matter, acquired a light red-brown tint. The liquor 1 " t,ngs * 

 became almoft colourlefs ; and, after this, produced very little 

 change in the folution of oxygenated fulphate of iron. 



Raw fkin, prepared for tanning by being immerfed in the ~ as does raw 

 ltrong folution, foon acquired the fame kind of tint as the linen. ^ Ii * 

 It united itfelf to a part of the extractive matter; but it was 

 not rendered by it infoluble in boiling water. 



The folid extractive matter, when expofed to heat, foftened, The folid extract 



and became darker in its colour, but did not enter intofufion. fofte " s ^ <* oe * 



' not rule by heat. 



At a temperature below that of ignition, it was decompounded. Deftruclive de- 

 The volatile produces of its decompofition were, carbonic acid, composition, 

 hydrocarbonate, and water holding in folution acetous acid and 

 a little unaltered extractive matter. There remained a light 

 and very porous charcoal. 



In confidering the manner in which the catechu is prepared, 

 it would be reafonable to conclude, that different fpecimens of 

 that fubftance muft differ in fome meafure in their composition, 

 even in their pure flates ; and, for the purpofes of commerce, 

 they are often adulterated to a confiderable extent, with fand 

 and earthy matter *. 



In attempting to eftimatethe compofition of the pureft cate- Component parts 

 chu, I felecled pieces from different fpecimens, with which I catec u * 

 was fupplied by theprefident, and reduced them together into 

 powder ; mixing, however, only thofe pieces which were from 

 catechu of the fame kind. 



* One fpecirnen that I examined, of the terra japonica of com- 

 merce, furnifhed, by incineration, -J. of fand and earthy matter $ and 

 another fpecirnen, nearly £. 



T 2 Two 



