Memoir on Human Urine. 4? 
aod eryfiallifed carbonat of ammonia long before it is dry: 
the laft portions of water obtained effervefce ftronely with 
acids, and become of a rofe-colour, not much fufceptible of 
changing in the open air. It arifes from the carbonat of 
ammonia which the liquid product contains; and urine has 
a fingular difpofition to form this falt in great abundance 
and with great eafe, as is proved by all the means of analyfis 
applied to it. The native acid of the urine is then faturated ; 
flakes of animal matter are depofited, as well as earthy phof- 
phats and the uric acid. All thefe phenomena continue until 
the predominance of the carbonat of ammonia, which is 
formed, becomes very manifeft. They take place at a con- 
tinued temperature of 60°. 
VIII. We never faw, with any exaétnefs, but three fa&ts 
in’ regard to the putrefaction, or fpontaneous and feptic de- 
compofition of urine, viz. the horrible fetor by which it is 
accompanied ; the formation of a great quantity of ammo- 
nia which characterifes it; and the abundance as well as 
eafy extraction of the fufible falts or alkaline phofphat which 
follows. C. Hallé has given an exceeding good defcription 
of the fucceflive alterations which urine, left to itfelf, expe- 
tiences, but he has not followed them in regard to the nature 
of their materials; the objeét of his refearch was only to de- 
fcribe the effects in their appearances. Urine contained in 
a clofe veffel becomes of a darker colour; turns brown, and 
even black; emits a fetid, ammoniacal odour; depofits firft 
a light cloud, which is gradually changed into mucous 
flakes more or Jefs coloured. There are formed at its fur- 
face, or on the blackened cruft by which it is covered, and 
on the fides of the vefiel which contains it, cryftals in needles 
or in regular prifms, or filky tufts. Urine is then ammoni- 
acal inftead of being acid. Diftilled te a half, it gives a great 
deal of the fetid carbonat of ammonia: being carried ftilf 
farther, fo as to beeome fyrupy, it furnifhes acetite of am- 
monia: the thick part gives, by the addition of acids, a fharp 
and acetous odour. This refiduum of urine, when putrid and 
evaporated, does not, by the addition of the concentrated 
nitric acid, prefent thofe white concrete and abundant cryf- 
tals which arife in frefh urine evaporated to the fame degree, 
and 
