C H E M I 
pable of affording a great quantity of thefe cryftals 5 for 
the Society of Medicine is in polfeffion of a gall-bladder 
entirely filled with this fiiline tranfparent concretion. 
Fourcroy, on examining thefe cryftallized biliary calculi, 
found them to be of an oily nature, 'fimilar to fpermaceti. 
Soap, the mixture of oil of turpentine and ether, &c. 
have been propofed to.diffolve the biliary calculi. It is 
an important obfervation, that they are only found in the 
gall-bladder of oxen after dry feafons and a fcarcity of 
fre'fh fodder; and that they difappear in the fpring and 
fummer, when thefe animals find abundance of green and 
fucculent vegetables. The butchers are well acquainted 
with this phenomenon ; they know that thefe itones are 
found in oxen from the month of November to the month 
of March, and not afterwards. This phenomenon fuf- 
ficiently fhows the power of the faponaceous juices of 
plants in diffolving the biliary calculi. Yet it is not to 
be thought, that medicines, however afiiive and volatile, 
can be introduced into the gall-bladder in fufficient 
quantity to dilfolve the biliary calculi, with the fame 
energy as in our experiments. The ceflation of fpafm, 
and confequently the dilatation of the biliary canal, is 
probably the true caufe of the good effedls of the ethereal 
mixtures that have been propoled by Durande, which we 
would recommend to be made up without oil of turpen¬ 
tine ; belides being very heating, it produces no uleful 
effedi but that of diminifliing the volatility of the ether; 
and it has been proved, that the yolks of eggs, and un¬ 
doubtedly many other fubftances, will ferve the fame pur- 
pofe as well, and without the fame inconveniences. 
Of FAT. 
Fat.varies according to the parts it occupies; it is fof- 
ter and more fluid about the heart, and large vefiels; if 
it becomes folid round the heart, it is a difeafe. 
In examining- the nature of Art, we fit all take that of 
quadrupeds, and chiefly that about the kidneys, called 
axunge, or fuet. Axunge, properly fo called, is a fblid 
mafs, enclofed in many veficles of a cellular texture; it 
fis leparated from foreign bodies for the purpole of ana- 
lyfis ; this is termed purification. To prepare it for phar¬ 
maceutical purpofes, or for inveltigating its chemical 
properties, it muft be cut in pieces, and the membranes 
and veflels feparated; it is afterwards to be waftied with 
much water, and meited in a new earthen veffel, with 
the addition of a fmall quantity of water; when this fluid 
is diflipated, and the ebullition ceafes, it mull be ltrained 
into a glazed earthen veffel, where it fixes, and becomes 
folid. 
The fat of any animal, expofed to a gentle heat, li¬ 
quefies, and congeals by cooling. If it be llrongly heat¬ 
ed, with contaft of air, it emits a fmoke of a penetrating 
fmel), which excites tears and coughing, and takes fire 
when fufticiently heated to be volatilized : the char¬ 
coal it affords is not abundant. If fat be diftiiled on a 
water bath, an infipid water, of a flight animal, finell, 
is obtained, which is neither acid nor alkaline, but which 
foon acquires a putrid fmell, and depofits filaments 
of a mucilaginous nature. This, phenomenon, which 
takes place with the water obtained by diftillation on 
the water-bath, from any animal fubftance, proves, 
that this fluid carries up with it a mucilaginous princi¬ 
ple, which is the caufe of its alteration. Fat, diftiiled in 
a retort, affords phlegm, at firit aqueous, and afterwards 
llrongly acid; an oil partly liquid, and partly concrete ; 
and a very fmall quantity of charcoal, exceedingly diffi¬ 
cult to incinerate, in which Crell found a fmali quantity 
of calcareous phofphat. Thefe products have an acid and 
penetrating fmell, as ftrong as that of the fulpliureous 
acid. The acid is of a peculiar nature, and has been 
carefully examined by Crell; but, as it is very difficult to 
obtain by dithllation, this celebrated chemiff has ufed a 
much more certain and expeditious procefs. The con¬ 
crete oil may be rectified, by repeated diltiilation, fo as 
to become very fluid, volatile, and penetrating ; in a word, 
to prefent all the characters of a true ellential or volatile 
S T R y. 363. 
oil. Twenty-eight ounces of human fat afforded Crell 
twenty ounces five drachms forty grains of fluid oil, 
three ounces three drachms and thirty grains of febacic 
acid, three ounces one drachm forty grains of a brilliant- 
charcoal, confiderably refembling plumbago, or carbure 
of iron, as Morveau remarks. Five drachms ten grains 
of matter were loft in this analyfis, which may be at¬ 
tributed to the water in vapour, and the elaftic fluids,- 
becaufe Crell did not ufethe pneumatical chemical appa¬ 
ratus. 
Fat expofed to a hot air, alters very quickly; the mild 
and fcarcely fenfible fmell is changed to'ftrong rancidity. 
This alteration appears to confift of a true fermentation, 
by which the acid is developed and difengaged. Rancid 
fat may be correfled by two methods: water alone is ca¬ 
pable of carrying off the acid it contains, as Poerner 
has obferved; but alcohol has the fame property, accord¬ 
ing to Machy. This proves, that a part of the rancid 
fat is put into a faponaceous ftate by its acid, and by 
that means rendered foluble in water, and in alcohol: 
either of thefe fluids may therefore be ufed with fuccefs. 
to deprive fat of its rancidity. When fat is waftied with? 
a great quantity of diftiiled water, the fluid diffolves a 
gelatinous matter, which may be exhibited by evapora¬ 
tion ; but the fat always retains a certain portion of this, 
matter, with which it is intimately combined, and on 
wdiich its property of fermenting depends. The aftion 
of water on this animal fubftance has not yet been fur¬ 
ther inquired into. 
Sulphur unites very readily with-fat, and forms a com¬ 
bination, which has not yet been accurately examined. 
In the combinations of fat with the oxyds of metals, it 
is obferved, that the latter affume readily the metallic- 
ftate w'hen heated: this phenomenon arifes from the hydro¬ 
gen gas, which is difengaged from the flit, and unites 
with the oxygen of the oxyds. Water is formed by the- 
fame means; and the charcoal of the fat is more at li¬ 
berty, or naked, the more the oxygen has been abforbed 
from it. 
The fame effedl arifes from palling oxygen gas into 
melted greafe ; it becomes yellow, and comes to refem- 
ble wax; whence it appears that hydrogen is difengaged, 
which forms water with the oxygen, and the coal is left 
naked. Fourcroy and Alyon have lately made fome ex¬ 
periments upon oxygenated fat, as thinking it might 
anfwerall the purpofes of what is called yellow ointment. 
The following is Fourcroy’s method of oxygenating 
fat. Melt purifie'd axunge in an earthen'pot ; then add 
two thirds of its weight of pure nitric acid'at 28 or 30 0 . 
Stir the mixture in a glafs mortar till it is completely 
cool. Melt the whole mafs in thirty times its weight of 
river or rain water ; let the water boil for half an hour, 
ftirring the fat into all the liquor with a porcelain fpatu- 
la. Let it cool; then feparate the fat from the water, and 
melt it alone with a gentle heat: then pour it into moulds 
of glafs, porcelain, or earth, 
Alyon’s procefs is this. Take fixteen parts of puri¬ 
fied fuet, or axunge, and one part of nitric acid, at 32 0 . 
Melt the fat over a flow fire, and then add the acid : ftir the 
mixture with a glafs tube, leaving it on the fire till bub-, 
bles are formed ; then take it oft’. The atlion continues, 
according to this author, till all the nitric acid is decom- 
pofed ; nothing but azotic gas is decoinpoled during the 
efferveicence, and the oxygen remains in the fat without 
making it acid ; this principle, by increafing its weight* 
only makes it of firmer confidence, grained, in fliort, 
oxygenated. As Alyon is fatisfied that the nitric acid, en¬ 
tirely decompofed, communicates nothing but oxy¬ 
gen to the fat, he does not wadi it afterwards. By this* 
method of oxygenating fat, it abforbs much more than 
by Fourcroy’s mode; for he only communicated to it 
about a thirtieth part of its weight, while Alyon’s oxyge~. 
natfd ointment contains nearly double. 
The yellow ointment of the {hops is prepared with three* 
parts of mercury, dilfolved in four parts of nitric acid. 
When the mercury is entirely dilfolved, melt thirty-two 
parts 
