which possesses the characteristic Properties of Tannin. 12 <9 
In my experiments on lac, printed in the Phil. Trans, for 
1804,, p. 2 c 8, I have particularly endeavoured to shew, how 
powerfully the acetic acid acts upon resin, gluten, and some 
other substances ; so that it may justly be regarded, as a 
valuable agent in the chemical analysis of vegetable bodies. 
In this point of view, it is as a solvent to be the more highly 
appreciated, because it appears to dissolve the resins, &c. 
without affecting their respective qualities, and thus by proper 
precipitants, these substances may be separated from it pure 
and unaltered. 
I am induced therefore to consider acetic acid to be the true 
acid solvent of the resinous substances, as it dissolves them 
speedily, without producing any apparent subsequent change 
in their natural proper ies. 
Sulphuric acid also, almost immediately dissolves the resins, 
balsams, &c. and forms transparent brown or sometimes 
crimson solutions, the latter colour being most commonly 
characteristic of the balsams. 
These solutions, however, are different from those made in 
the acetic acid, by not being permanent, for from the moment 
when the solution is completed, progressive alterations appear 
to be produced in the body which is dissolved ; thus turpen- 
tine is almost immediately converted into resin, then into the 
third variety of the tanning substance, and lastly into coal. 
Without being under the necessity of adducing other ex- 
amples, we may therefore state sulphuric acid to be a solvent 
of the resinous substances, but which continues afterwards to 
act on their principles, so as to decompose them, coal being 
the ultimate product. 
Nitric ac.d, as I have shewn in the course of these Papers, 
MDCCCVI. $ 
