CHEMISTRY. 
366 
of ammoniac, which is very fcanty in frefli urine, in- 
creafing much by its decompofition, and by the formation 
• of ammoniac. It affords phofphorus when the fufible fait 
of urine is heated with charcoal. 7. The uric, formerly 
called the lithic, acid. It cryftallizes by the cooling of 
the urine, and forms the red fand which is depofi'ced at 
the bottom of the veffels. It is molt abundant in fick 
people, and is readily diffolved by alkalis in their cauftic 
ftate. 8. The benzoic acid, which is molt abundant in 
infants, is eafily obtained from evaporated urine, by mix¬ 
ing it with one-tenth of concentrated fulphuric acid. 
9. The gelatin and albumen are very variable in their 
proportion in different kinds of urine. They appear hi 
the form of clouds in urine in which ammoniac is form¬ 
ed, in that of filaments in urine into which an alkali is 
poured, and in flakes in evaporated urine; they are pre¬ 
cipitated by tannin, which ferves to afcertain their pro¬ 
portion; and fpeedily produce putrefa&ion in the urine, 
which contains them in large quantity. They appear to 
be, by their increafe, the primary caufe of the formation 
of calculi, and to afford the gluten which holds the pra¬ 
dicles of the calculi together. The quantity of thefe f'ub- 
jftances in urine is in proportion to the flrength or weaknefs 
of the digeftive organs. 10. The peculiar urinary matter, 
which gives to urine its charaCreriftic properties. It is the 
jnoft abundant of the matters contained in urine, forming 
alone about nineteen-twentieths of thefe matters. This 
.urinary .matter was'confidered, but improperly, as a fa- 
ponaceous extrafil, by Rouelle the younger. It is to this 
matter that we are to attribute the almolt complete cryf- 
tallization of urine, which has been evaporated to the 
..confiftence of a fyrup, the folid and cryftalline form 
which it affumes in this ftate, by the addition of concen¬ 
trated nitric,-and the cryft'allization of the muriats of 
foda and ammoniac. 
If urine be diftilled over a naked fire, an ammoniacal 
liquid will be found in the receiver, and very little oil. 
By continuing the operation, there will be fublimed in 
the neck of the retort fome carbonat of ammoniac, then 
fome benzoic acid, and laftly muriat of ammoniac ; the 
uric acid is moftly decompofed. There remains in the 
.retort a faline coaly mafs, whence the falts may be ex¬ 
tracted by the means already pointed out. 
Acids have no aCtion upon frefli urine; but they quickly 
take away the fmell of putrefied urine, by combining with 
the ammoniac, which is the principal caufe of its odour. 
Fixed alkalis and lime dilengage much ammoniac from 
urine. Lime-water forms a precipitate which at firft is 
.foluble, while the phofphoric acid is not entirely fatu- 
rated with it. In this ftate, the urine ftill reddens the 
blue vegetable colours; the phofphoric acid is at liberty; 
calcareous pholpliat is formed. When the precipitate is 
no longer foluble, it is a proof that the phofphoric acid 
is faturated; then it no longer reddens blue colours. 
■Cauftic ammoniac alfo precipitates the calcareous phof¬ 
phat from urine, by neutralizing the free phofphoric 
acid. Fixed alkali the fame. 
Urine decompofes many metallic folutions. Lemery 
diftinguifhed by the name of the rofe-coloured precipitate, 
a magma of that colour, which is formed when the nitric 
folution of mercury is poured into urine. This precipi¬ 
tate is partly formed by the muriatic acid, and partly by 
the phofphoric acid contained in this fluid. Brongniard 
lias obferved, that this preparation l'ometimes takes fire 
by friCtion, and burns rapidly on hot coals; he attri¬ 
butes this effeCt to a fmall portion of phofphorus. By 
treating the precipitate with cauftic alkali, the two falts 
may be decompofed. 
Such is the prefent ftate of our knowledge refpeCting 
the chemical properties of urine. Much remains to be 
-done, before we may efteem ourfelves in pofieffion of all 
that analyfis is capable of difcovering with regard to this 
ifiuid. It is neceffary, for this purpofe, to examine the 
different depofitions obferved in urine, and well defcribed 
by Halle, the red or tranfparent faline concretions which 
are formed, and which Sclieele takes to be the lithic acid, 
fnould alfo be analyzed, and the abundant fediment which 
urine affords after fits of the gout, in fuch as are attacked 
by the ftone, &c. Berthollet lias obferved, that the urine 
of gouty perfons contains lei's acid than that of perfons in 
perfeCt health ; that, during the fit of the gout, this fluid is 
much lefs acid than ufual. He conjectures, that in gouty 
patients, the phofphoric acid is not evacuated by urine, 
as in healthy perfons ; that it wanders, as it were, and is 
carried into the articulations, where it excites irritation 
and pain. This excefs of acid in the urine appears, to 
hold the calcareous phofphat in folution. 
Calculus of the Bladder. —It is only fince the 
time of Bergman and Scheele that we have had precife 
notions of the nature of calculi. Scheele difcovered the 
lithic acid, now called uric acid. Bergman obtained one 
two-lnindredth part of lime from it, by precipitating its 
nitric acid with fulphuric acid, and calcining the refidue 
of the fame folution : this had efcaped the obfervation of 
Scheele. 
The combination of lime with phofphoric acid, con- 
ftitutes a kind of calculus, well known by its whitenefs, 
friability, infolubility in w'ater, flow' folution in acids, 
and the fulphat of lime w'hich it furnifhes with fulphuric 
acid. But the late experiments of Fourcroy and Vau- 
quelin, enabled them to difcover five other fubftances in 
the human calculus. 1. Ammoniacal urat, or a faturated 
combination of uric acid with ammoniac. This fubftance 
is foluble in pure fixed alkalis, with a difengagement of 
ammoniac. 
a. Ammoniaco-magnefian phofphat. This fait, which 
contains magnefia, (an earth not hitherto found in the 
human body,) prefents fome remarkable phenomena. It 
never of.itfelf forms a human calculus: it is mixed fome- 
times with calcareous phofphat, fometimes with uric acid, 
fometimes with both at once: but it always forms the 
outer cruft of the calculi ; its furface is uneven, it is 
white and lamellous in its fracture. It is not foluble in 
alkalis; they produce from it an ammoniacal fmell, and 
precipitate magnefia, while they feize on the phofphoric 
acid. Analyfis difcovers the magnefia and ammoniac 
united to the phofphoric acid; muriatic acid diffolves 
them. It is this ammoniaco-magnefian phofphat, which 
occafions the calculus to acquire fuch a vaft fize, as fome¬ 
times to render its extraction impofilble. Thefe calculi 
are of the fame nature as thofe found in the colon of a 
liorfe, lately analyzed by the fame chemifts. 
3. Oxalat of lime. The difcovery of this infoluble fait 
in the bladder, greatly furprifed Fourcroy and Vauque- 
lin. They are black, ponderous, hard, full of prickles or 
turbercles like a mulberry; and they have been in con- 
fequence called mulberry-Jlones. They fcroop under the 
faw, and their divided furfaces take a high polifti like 
agate. Thefe calculi are infoluble in pure alkalis; but 
alkaline carbonats decompofe them, and diffolve their 
acid. Lime, added to thefe folutions, precipitates a white 
fait, which at firft fight might be taken for phofphat of 
lime; but analyfis prefentiy fhevvs that it is the oxalat of 
lime revived. Another exclufive character of thele cal¬ 
culi, is the pure or quicklime which they leave in the 
crucible, when they have been ftrongly calcined, and which 
is afforded by no other calculus. Thefe are foluble in the 
muriatic and nitric acids, See. 
4.. Silex. In 150 calculi analyzed by Fourcroy and 
Vauquelin, this fubftance was met with but once. It was 
not alone; but, in a calculus compofed of four or five 
ftrata, it formed the third, of a yellow horny colour, and 
very hard under the faw. This having refilled all.the 
modes of analyfis ufed for'the other calculi, they at length 
melted it, having firft pulverized it in a filter crucible, 
with fome potafh; and, with the help of an acid, they 
precipitated, from the aqueous folution of thefe two fub¬ 
ftances, a tranfparent powder which rendered water ge¬ 
latinous, and which thefe chemifts difcovered to be filex. 
5. A particular animal fubftance, more or lefs abun¬ 
dant. 
