870 
u n i 
If R I 
substance e; disengaged when urea is treated 
wirh barytes, lime, or even magnesia. Renee 
n io evident, that tins appearance must be as- 
cribed to the muriat of ammonia, with which 
u is constantly mixed. When pure solid po- 
tass is triturated with urea, heat is produced, 
a great quantity of ammonia is disengaged, 
tee mixture becomes brown, and a substance 
is deposited, having the appearance of an em- 
py i cumatic oil. One part of urea .and two 
<)t potass, dissolved in lour times its weight of 
water, when distilled, gives out a great quan- 
tity ot aimnoniacal water ; the residuum con- 
tains acetat and carbonat of potass. 
W hen muriat of soda is dissolved in a solu- 
tion of urea in water, it is obtained by evapo- 
lation, not in cubic crystals, its usual form, 
but in regular octahedrons. Muriat of am- 
monia, on the contrary, which crystallizes na- 
turally in octahedrons, is converted into cubes 
by dissolving and crystallizing it in the solu- 
tion of urea. 
UkENA, a genus of the monadelphia po- 
ly and; ia class ot plants, the corolla whereof 
consists ot live oblong, obtuse, connated pe- 
tals, broader than the apex, and narrower at 
the base ; the fruit is a round echinated cap- 
sule, vvitii five angles, consisting of live cells, 
and made up ot live valves; the seeds are so- 
litary, roundish, and compressed. There are 
eight species. 
L RE I E RS. See Anatom y. 
t 1 i\L ! LIRA. See Anatomy. 
I RIG AC ID. Uricorlithic acid was disco" 
Vered by Scheele in 1 77 6. It is the most conr 
inon constituent of urinary calculi, and exists 
also m human urine. That species of calculus 
v hich resembles wood in its colour and ap- 
pea ranee is composed entirely of this sub - 
stance. It was called at first lithic acid; but 
tins name, in consequence of tha remarks 
made by Dr. Pearson on its impropriety, has 
been laid aside, and that of uric acid substi- 
tuted in its place. 
_ U’ * c acid in this state has a brown colour ; 
it is hard, ancj crystallized in small scales. It 
nai neither taste nor smell, is insoluble in cold 
water, but soluble in 360 parts of boiling wa- 
ter. File solution reddens vegetable blues, 
especially the tincture of turnsol. A great 
part of the acid precipitates again as the water 
cools. . It combines readily with alkalies and 
eaiths , but the compound is decomposed by 
every other acid. Muriatic acid has no ac- 
tion on it, neither has sulphuric acid while 
co.J, but when assisted by heat it decomposes 
it entirely. 1 
When triturated with potass or soda, it 
forms a saponaceous paste, very • soluble in 
water when there is an excess of alkali but 
sparingly when theaikali is neutralized. The 
mat ol potass or of soda is nearly tasteless. 
^ ne last is found crystallized, constituting 
gouty Concretions. Ammonia does not dis- 
soive uric acid, but it combines with it, and 
lorms a salt not more soluble than the* pure 
acid, and resembling it in its external charac- 
ters. Neither does uric acid dissolve in lime- 
water; the alkaline carbonats have no action 
whatever on it. 
Nitric acid dissolves it readily ; the solu- 
tion is of a pink-colour, and has the property 
ef tm S l »g amm.il substances, the skin for in- 
stance, of the same colour. When this so- 
lution is boiled, a quantity of azotic gas, car- 
U It I 
bonic acid gas, and of prussic acid, is disen- 
gaged. W hen oxymuriatic acid gas is made 
to pass into water containing this acid sus- 
pended in it, the acid assumes a gelatinous 
appearance, then 1 dissolves; carbonic acid 
gas is emitted, and the solution yields by eva- 
poration muriat of ammonia, superoxaiat of 
ammonia, muriatic acid, and malic acid. 
When uric acid is distilled, about a fourth 
of the acid passes over a little altered, and is 
tuund in the receiver crystallized in plates ; a 
few drops of thick oil make their appearance ; 
-g-th oi the acid of concrete carbonat of ammo- 
nia, some prussiat ot ammonia, some water, 
and carbonic acid, pass over ; and there re- 
mains in the retort charcoal, amounting to 
about -gpg-th ol the weight ot the acid dis- 
tilled. 
I hese facts are sufficient to shew us that 
uric acid is composed of carbon, azote, hydro- 
gen, and oxygen ; and that the proportion of 
the two last ingredients is much smaller than 
of the other two. 
URINE. No animal substance has at- 
tracted more attention than this, both on ac- 
count of its supposed connection with various 
diseases, and on account of the singular pro- 
ducts obtained from it. In general, healthy 
in me is a transparent liquid of a light amber-co- 
iour, an aromatic smell, and a disagreeable bit- 
ter taste. Its specific gravity varies, accord- 
ing to Mr. Cruikshank, from 1.005 to 1.033. 
W hen it cools, the aromatic smell leaves it, 
and is succeeded by another, well known by 
the name of urinous smell. This smell is suc- 
ceeded in two or three days by another, which 
has a considerable resemblance to that of sour 
milk, rhis smell gradually disappears in its 
turn, and is succeeded by a fetid alkaline 
odour. 
Urine reddens paper stained with turnsole 
and with the juice of radishes, and therefore 
contains an acid. 
If a solution of ammonia is poured into 
fresh urine, a white powder precipitates, 
which has the properties ot phosphat of lime. 
I he presence ot this substance in urine was 
first discovered by Scheele. If lime-water is 
poured into urine, phosphat of lime precipi- 
tates in greater abundance than when ammo- 
nia is used ; consequently urine contains plios- 
Phoric acid. I hus we see that the phosphat 
or lime is kept dissolved in urine by an excess 
amffi or it is in the state ofsuper-phosphat. 
I Ins also was first discovered by Scheele. 
1 his substance is most abundant in the urine 
ot the sick. Berthollet has observed, that the 
urme of gouty people is less acid than that of 
people in perfect health. The average quan- 
tity of phosphat of lime in healthy urine is, 
as Cruikshank has ascertained, about i 
of the weight of the urine. 
If the phosphat of lime precipitated from 
urine is examined, a little magnesia will be 
found mixed with it. Fourcroy and Vauque- 
iin have ascertained that this is owing to a little 
phosphat of magnesia which urine contains, 
and which is decomposed bv the alkali or 
hme employed to precipitate the phosphat of 
lime. 
. Proust informs us that carbonic acid exists 
in urine, and that its separation occasions the 
froth which appears during the evaporation of 
urine. F ourcroy and Vauquelin, on the other 
hand, consider this acid as formed during the 
evaporation, by the decomposition of the 
urea. The observations of Proust confirm 
those which had been made by Priestley anc 
Percival. " J 
Proust has observed, that urine kept in new 
casks deposits small crystals which effloresce 
in the air and fail to powder. I hese crvstals 
possess the properties of carbonat of lime. 
Hence we must conclude that urine contains 
carbonat of lime; a very extraordinary fact, 
if we reflect that super-piiosphat oflime'is also 
present. 
When fresh urine cools, it often lets fall a* 
brick- coloured precipitate, which Scheele first 
ascertained to be crystals of uric acid. All 
urine contains this acid, even when no sensibh 
precipitate appears when it cools. For if a 
sufficient quantity of clear and fresh urine is 
evaporated to T -~ of its weight, a subtle pow- 
der precipitates to the bottom, and attaches 
itself in part very firmly to the vessel. 
I his part may be dissolved in pure alkali, 
anc! precipitated again by acetic acid. It ex- 
hibits all the properties of uric acid. The fact 
is, that the precipitate which usually falls 
when urine cools consists chiefly of phosphat 
of lime and uric acid. It may be dissolved in 
diluted nitric acid. If the solution is heated and 
evaporated to dryness, it assumes a fine rose- 
colour if uric acicl is present. 'I he proportion 
of uric acid varies considerably in urine. It 
crystallizes in small red prisms, partly on the 
surface, if urine is mixed with some nitric acid, 
and left exposed to the air. 
During intermittent fevers, arid especially* 
during diseases of the liver, a copious sedi- 
ment of a brick-red colour is deposited from 
urine. This sediment is the rosacic acid c f 
1 ioust.^ Scheele considered this sediment cisy 
uric acid mixed with some phosphat of lime; 
and the same opinion has been entertained bv 
other chemists : but Proust affirms that it con- 
sists chiefly of a different substance, to which 
he lias given the name of rosacic acid from its. 
colour, mixed with a certain proportion of 
uiic acid and phosphat of lime. T his rosacic 
acid, iie informs us, is distinguished from the 
uric by the facility with which it dissolves in* 
hot water, the violet precipitate which it oc- 
casions in muriat of gold, and by the little ten- 
dency which it has to crystallize. 
If tiesh mine is evaporated to the consist- 
ence of a syrup, and muriatic acid is then 
poured into it, a precipitate appears which 
possesses the properties of benzoic acid. 
Scheele first discovered the presence of ben- 
zoic acid in urine. He evaporated it to dry- 
ness, separated the saline part, and applied 
heat to the residuum. The benzoic acid was 
sublimed, and found crystallized in the re- 
ceiver. Considerable quantities of benzoic 
acid may thus be obtained from the urine of 
hoi ses and cows, where it is much more a- 
bundant than in human urine. In human 
urine it varies from to 0 f the 
whole. Proust affirms that the acid obtained 
by Scheele’s process isnot the benzoic, but an- 
other possessed of similar properties ; but dif- 
fering in this circumstance, that nitric acid 
decomposes it, whereas it only whitens benzoic 
acid. . , 
When an infusion of tan is dropt into urine, 
a white precipitate appears, having the pro- 
perties ofthe combination of tan and albumen 
or gelatine. _ Urine, therefore, contains albu- 
men or gelatine. These substances had been 
suspected to be in urine, but theix presence 
