of Urinary Concretions. 49. 
left a black mark, furrounded by a pink margin. A few 
drops of nitric acid being evaporated from this refidue, 
nothing but a ftill lefs black mark, and a few red {pots re- 
mained. 
Nitric acid being added a third time, nothing but a black 
mark, {till fmaller, remained; which entirely difappeared, 
on evaporating this acid from it a fourth time. 
I found that a few drops of this folution, fo diluted that 
they did not contain the 3,5, or even a much fmaller| part, 
of a grain of the -precipitate, on evaporation, left a pink 
ftain on glafs. > 
The whole of the reft of the folution was difiilled in a 
very low temperature, fo that a drop only fell about every 
half-minute, till a thick brownifh fediment remained, with 
ared margin. <A fimilar difllation was performed, with 
the diftilled liquor, a fecond time, when there remained a 
hittle whitifh thick matter. On a third diftillation, as before, 
with the diftilled liquor, towards the clofe white fumes arofe 5 
and about half a drachm of liquid, which now remained in 
the retort, being left to ftand, prfmatical cryftals, decuf- 
fating each other, were formed. They had a fharp talte,. 
but were fcarcely four; were very foluble in the mouth, 
and evaporated in white fumes, leaving a very flight black 
dtain. 
15. Twenty grains of the precipitate were ieroducatline 
‘a tube, 1 of am inch widein the bore, fealed by melting at 
one extremity; which extremity was coated, and the tube 
was fitly bent for retaining fublimate, and collecting gaz. 
The temperature, from the fire applied, was at firft very low, 
but was gradually increafed, fo as to make the coated part, 
containing the charge, red hot. At firft, the precipitate 
turned black, and a little water appeared. Secondly, gaz 
came over, which had the finell of empyreumatic /:qwor 
corn cervi. Thirdly, a brown fublimate appeared, and’ gaz 
as before, but alfo with pruffic acid gaz., Fourthly, black 
matter, 
