on the Composition of Urinary Concretions. 29 
like other analogous oxides, it was acidifiable , and I suspected 
that I had really rendered it into the acid state, by the nitric 
acid; which, in the above experiments, ( e , 14.) had imparted 
oxygen to it, and thereby rendered it soluble, deliquescent, 
pungent, and volatile. This change also would account for 
the nitric solution not affording the precipitate. 
In order to obtain, for examination, an adequate quantity of 
this supposed acid, the following experiments were instituted, 
with the three acids [viz. the oxymuriatic, the nitro-muriatic, 
and the nitric,) which can acidify oxides analogous to the 
present one. 
Experiment 1. Twenty-five grains of the above animal oxide, 
(for so I will now venture to call it,) and three ounces of nitric 
acid, of the specific gravity of 1 ,25, were put into a retort, and 
the hydro-pneumatic apparatus was adjoined. 
At a very low temperature, a clear solution was made. First, 
soon after the solution began to boil, 23 ounces, by measure, 
of colourless gaz came over, which were succeeded (secondly,) 
by white fumes, filling the apparatus, and 23 ounces more of 
gaz. Thirdly, a white sublimate ascended, and there was a 
strong smell of prussic acid. The sublimate was very readily 
washed out, being very soluble, and tasted pungent or sharp, 
but not sour. Fourthly, the distillation being renewed, more 
white sublimate appeared, but only 3 ounces more of gaz came 
over; and then the retort only contained a dark-brown solid 
matter. 
The first portion of gaz, viz. 23 ounces, consisted of about 
equal bulks of carbonic acid and atmospherical air. The se- 
cond portion, viz. 23 ounces, was two-thirds of its bulk 
carbonic acid, and the rest nitrogen gaz. The third portion, 
