%go Mr. Hatchett’s additional Experiments 
destructible of all the varieties of catechu, and on this account 
I attempted, although without success, to promote the destruc- 
tion of the properties of the artificial substance, by adding gum 
arable in one case, and sugar in another, to different portions, 
previous to exposing it to the action of nitrie acid. I am ' 
however, convinced, that the presence of gum or mucilage 
in natural substances which contain tannin, renders this more 
speedily destructible by nitric acid, and I shall soon have occa- 
sion to notice some experiments which tend to prove, that the 
presence of gum or mucilage in certain bodies, also prevents 
or impedes more or less the formation of the artificial tanning 
substance. The cause of this difference I am inclined to sus- 
pect is, that in those bodies the gum or mucilage is not simply 
mixed, but is present in a state of chemical combination, by 
which, certain modifications produced by the action of nitric acid 
upon the elementary principles of the original substance become 
facilitated. 
§ III- 
A. When sulphuric acid was added to a solution of the artifi- 
cial tanning substance, the latter became turbid, and a copious 
brown precipitate subsided, which was soluble in boiling dis- 
tilled water, and then was capable of precipitating gelatine. 
B. The same effect was produced by muriatic acid ; so that 
in these particulars, the artificial tanning substance was found 
to resemble precisely the tannin of galls and of other natural 
substances.* 
C. Carbonate of potash, when added to a solution of the 
* Mr. Davy on the Constituent Parts of Astringent Vegetables. Phil. Trans. 1803V 
p. 240, 24 j. 
