on the Composition of Urinary Concretions . 25 
emitted fumes copiously, which were scarcely those of sulphu- 
reous acid ; and, on evaporation, a black mark only was left. 
13. I first digested, and then boiled, in water, the preci- 
pitate with prussiate of iron ; but the filtrated liquor afforded 
no precipitation with sulphate of iron. 
14. Two drachms, by measure, of nitric acid, of the spe- 
cific gravity of 1,35, were poured upon 7 grains of the precipi- 
tate. A violent effervescence took place, which was soon suc- 
ceeded by a complete solution. 
A few drops of this solution, being evaporated on glass, 
left a black mark, surrounded by a pink margin. A few drops 
of nitric acid being evaporated from this residue, nothing but 
a still less black mark,, and a few red spots remained. 
Nitric acid being added a third time, nothing but a black 
mark, still smaller, remained ; which entirely disappeared, on 
evaporating this acid from it a fourth time. 
I found that a few drops of this solution, so diluted that they 
did not contain the ^oo* or even a much smaller part, of a grain 
of the precipitate, on evaporation, left a pink stain on glass. 
The whole of the rest of the solution was distilled in a 
very low temperature, so that a drop only fell about every half- 
minute, till a thick brownish sediment remained, with a red 
margin. A similar distillation was performed, with the distilled 
liquor, a second time, when there remained a little whitish thick 
matter. On a third distillation, as before, with the distilled 
liquor, towards the close white fumes arose, and about half a 
drachm of liquid, which now remained in the retort, being left 
to stand, prismatical crystals, decussating each other, were 
- formed. They had a sharp taste, but were scarcely sour; 
mdccxcviil E 
