Dr. Pearfon’s Experiments on Calculi. 385 
conclufive to induce them to admit its non-acidity, and con- 
fider it as an oxyd? He infifts that Dr. Pearfon has not cor-. 
re@tly comprehended the labours either of the Swedith or 
French chemifts ; that he has improperly believed that they 
gave the name of lithic acid to the fublimate of the calculus 
obtained by fire, whereas they gave it, either to the entire 
calculus as it comes from the reins or the bladder, when 
wholly formed of that fubftance, or, to this matter obtained 
by cooling a folution of it in water, or by precipitating it 
from an alkaline folution by the acetous acid ; and that the 
pretended oxyd is really Scheele’s acid, at firft called the 
bezoardic, and ‘fince, in the new nomenclature, the lithic 
acid. 
Dr. Pearfon gives a larger proportion of infoluble matter 
than his predeceffors, ftating it at almoft jd of the mixed 
calenli which he- employed; but Fourcroy oppofes to this 
what Dr. Pearfon fays in another place, “ that he found 
fome calculi contain even 1°2ths of the foluble part ;”’ and 
remarks, that there is no reafon to doubt that the greater | 
part of human urinary concretions contain a much greater 
proportion of matter foluble in alkalies than that of which 
he has given the analyfis. The difengagement of ammonia 
obferved by Dr. Pearfon, which accompanies the folution of 
the calculus in pure foda, was alfo feen by Scheele, and ob- 
ferved and carefully deferibed by Fourcroy. 
The foapy and untuous feel, fays Fourcroy, of the fpon- 
taneous depofit formed in the alkaline folution of the caleu- 
lus’ manifefily arifes from the fuperabundance of alkali; we 
perceive here the feparation of our lithiat of potafh from its 
faturated folution; and I may remark, that this is what'I 
have pointed out in my refearches, by faying that the lithiat 
of potafh eafily feparates in cryftals from its concentrated and 
faturated folution. This foapy depofit of Dr, Pearfon is ne- 
verthelefs foluble in water, and precipitated by acids with- 
out being re-diffolved: this is a decompofition of the lithiat 
Vov. II. Ce of 
