256 Mr. Davy's Experiments and Observations 
and on the upper surface was red-brown. It was not acted on 
by hot or cold water ; and its apparent strength was the same 
as that of similar leather tanned in the usual manner. 
In examining the remainder of the infusions of catechu, in 
which skin had been converted into leather, I found in them 
much less extractive matter than I had reason to expect, from 
the comparative analysis of equal portions of the unaltered in- 
fusions made by solutions of gelatine. At first, I was inclined 
to suppose that the deficiency arose from the action of the 
atmosphere upon the extractive matter, by which a part of it 
was rendered insoluble. But, on considering that there had been 
very little precipitation in the process, I was led to adopt the 
supposition, that it had entered into union with the skin, at the 
same time with the tannin ; and this supposition was confirmed 
by new experiments. 
Both kinds of catechu are almost wholly soluble in large 
quantities of water ; and, to form a complete solution, about 
18 ounces of water, at 52 0 , are required to 100 grains of extract. 
The residuum seldom amounts to of the original weight of 
the catechu ; and, in most cases, it is found to consist chiefly of 
calcareous and aluminous earths, and of fine sand, which, by 
accident or design, had probably been mixed with the primitive 
infusion at the time of its evaporation. 
A considerable portion of both kinds of catechu is soluble in 
alcohol; but, after the action of alcohol upon it, a substance 
remains, of a gelatinous appearance and a light brown colour, 
which is soluble in' water, and is analogous in its properties 
to gum or mucilage. 
The peculiar extractive matter in the catechu, is much less 
