on the Composition of Urinary Concretions. ig 
ments hitherto made, rather “ afford indications of what re- 
mains to be done, than furnish demonstrations of the nature 
“ of animal concretions/’ It is also too obvious to need expla- 
nation, that more efficacious and innocent practice, in diseases 
from these concretions, can only be discovered by a further 
investigation of their properties. It is with this view, as well 
as for the sake of chemical philosophy, that I think it my duty 
to submit to the Society some of the observations I have 
made, in the course of inquiry on this subject. 
The observations which I shall now offer, are principally 
on a substance, which my experiments inform me is very ge- 
nerally a constituent of both urinary and arthritic concretions. 
It is a substance obtained by dissolving it out of these concre- 
tions, by lye of caustic fixed alkali, and precipitating it from the 
solution by acids. In this way, Scheele separated this matter ; 
but he did not consider its importance, nor of course at all inves- 
tigate its properties. He does not even seem to have been aware 
that it was a distinct constituent part of the urinary concretion ; 
for, when he relates the experiment of precipitating matter 
from the nitric solution of calculus by metallic salts, no dis- 
tinction is made between the precipitations in this experiment, 
and that m the former; yet we can now show, that in the one 
case the precipitate is a peculiar animal oxide, and in the 
other they are metallic phosphates. As Scheele obtained an 
acid sublimate, it has been imagined by some writers, that the 
precipitate by any acid (even by the carbonic) from the alkaline 
menstruum, was an acid ; the same as that obtained by subli- 
mation, and which, in the new system of chemistry, has been 
denominated lithic acid. The following experiments show that 
these substances are different species of matter. 
D 2 
