on the constituent Parts of astringent Vegetables. 255 
The nitrate, or acetite, of lead, in concentrated solution, when 
poured into the infusion, produced in it a dense light brown 
precipitate, which gave to the fluid a gelatinous appearance. 
After this effect, there was no free acid found in it ; and both 
the tannin and the extractive matter seemed to have been car- 
ried down, in union with a portion of the metallic salt. 
The solution of muriate of tin, acted upon the infusion of 
catechu in a manner similar to that in which it acts upon the 
infusion of galls. 
The least oxygenated sulphate of iron produced no change in 
the infusion. With the most oxygenated sulphate it gave a dense 
black precipitate, which, when diffused upon paper, appeared 
rather more inclined to olive than the precipitate from galls. 
The infusions were precipitated by the solution of albumen. 
The precipitates by gelatine had all a pale tint of red-brown, 
which became deeper when they were exposed to the air. The 
compound of gelatine and the tannin of the strongest infusions 
of catechu appeared, by estimation of the quantity of isinglass 
in the solutions used for their precipitation, to consist of about 
41 parts of tannin, and 59 of gelatine. 
Of two pieces of calf-skin which weighed, when dry, 132 
grains each, and which had been prepared for tanning, one was 
immersed in a large quantity of the infusion of catechu from 
Bengal, and the other in an equal portion of the infusion of 
that from Bombay. In less than a month they were found con- 
verted into leather. When freed from moisture, by long exposure 
in the sunshine, they were weighed. The first piece had gained 
about 34 grains; and the second piece 35^ grains. The leather 
was of a much deeper colour than that tanned with galls, 
