CHEMISTRY. 
ii. Pyroligneous acid, extra&ed from wood by diftil- 
lation, of a pungent fetid fmell, not cryftallizable, de- 
compofable by a ftrong fire, volatile, forming peculiar 
lalts with earths, alkalis, and metallic oxyds, and having 
particular attractions for thefe bafes, but in other re- 
i'pefts we are as little acquainted with it as with the two 
preceding acids. 
u. Acetous acid, formed by the fermentation of wine, 
on which account it is called vinegar, of an agreeable 
fmell and tafte, volatile and liquid, decompofable by a 
ftrong fire, capable of being furcharged with oxygen 
when diftilled with metallic oxyds, and thus becoming 
acetic acid, or radical vinegar, which is more acrid and 
odorous than the acetous acid, inflammable, and mixed 
with alkohol. 
Acids of the fourth clafs , or avith ternary radicals .—Acids 
with ternary compound radicals, which were fpoken of 
above as formed in general of carbon, hydrogen,- and 
azot, united with oxygen, appertain more efpecially to 
animal fubftances. With thefe we are Hill lefs acquaint¬ 
ed than with the preceding acids : but recalling here to 
the reader’s mind, that they all furnifh ammoniac on be¬ 
ing decompofed by the a&ion of fire, and pruflic acid on 
a change in the proportion of their principles, we lhall 
remark that the pruflic acid feems to be to thefe acids in 
general what the oxalic is to vegetable acids, and add, 
that, on converting animal fubftances into oxalic acid 
by the agency of nitric acid, pruflic acid is conftantly 
formed during the operation, and evolved in the ftate of 
vapour. There are feven animal acids known, all of 
which appear to belong to this clafs of compounds, 
namely, the laftic, faccholadfic, febacic, lithic, formic, 
bombic, and pruflic, acids. In each let us leek for a few 
charadieriftic properties. 
r. Laftic acid, formed, with a little acetous acid, in 
milk fpontaneoufly foured, net cryftallizable, foluble in 
alcohol, affording on diftillation an acid analogous to 
the pyrotartarous, forming deliquefeent faits with earthy 
and alkaline bales, and decompoling alkaline acetits. 
2. Saccholadtic acid, precipitating as a white powder 
from oxalic acid formed by fugar of milk and nitric acid, 
little fapid, fcarcely at all foluble, decompofable by fire, 
when a fait refembling benzoin in fmell iublimes from 
it, and forming cryftallizable faits with alkalis. This is 
very little known. 
3. Sebacic acid, obtained from fat by the action of 
fire, feparated from it alfo by alkalis and lime with the 
afliftance of a ftrong heat, liquid, white, fmoking, very 
acrid in tafte and fmell, forming cryftallizable and fixed 
faits with earth and the alkalis, decompofing muriat of 
mercury, and decompofable by a ftrong heat. 
4. Lithic acid, exifting in human urine, forming the 
ftone in the bladder, dry, cryftallized in flat needles, al- 
moft infipid and infoluble, in part volatile, decompofable 
by a ftrong heat, affording ammoniacal carbonat and 
pruflic acid by the agency of fire, forming a beautiful red 
iolution with nitric acid, foluble in caultic alkalis, and 
precipitating of a gridelin or reddifli colour from the 
urine of perlons labouring under fever. 
5. Formic acid, obtained from ants by diftillation or 
expreffion with water, reddening blue flowers while in 
the living infeff, flying off in a very highly odorous va¬ 
pour, in fmell analogous to mufk, killing animals in this 
form of gas capable of being employed for the fame do- 
meftic purpofes as vinegar, decompofable by a ftrong 
fire, taking oxygen from oxygenated muriatic acid, fre¬ 
quently ftronger than fulphuric acid, and forming cryf¬ 
tallizable and not deliquefeent faits with earth and alkalis. 
6. Bombic acid, contained in a relervoir near the anus 
of the cryfalis of the filk-worm, extra&ed from this re- 
fervoir either by expreffion or by means of alcohol, min¬ 
gled with a brown oil and a gum while in the worm, li¬ 
quid, of an amber yellow colour, decompofable fponta¬ 
neoufly, and affording pruflic acid by means of diftilla¬ 
tion and nitric acid. In its combinations it is unknown. 
163 
7. Pruflic acid, faturating iron and colouring it in Pruf- 
fian blue, obtained at prefent by the diftillation of blood, 
or the action of nitric acid on albumen, gluten, animal 
fibre, See. and difengaged in proportion as oxalic acid is 
formed, remarkable for a noxious fetid-fmell, analogous 
to that of bitter almonds, very decompofable by a ftrong 
fire, and then affording ammoniac, fufceptible of the 
form of gas, taking metallic oxyds from a great number 
of other acids, capable of being artificially formed by the ■ 
union of hydrogen, carbon, azot, and oxygen, little acid 
in its tafte, and containing, as far as appears, very little 
oxygen. 
It follows, from what has been advanced in the pre¬ 
ceding feftions, that if acids be divided into two claffes, 
diftinguifhed by having fimple or compound radicals, 
they will be found to differ principally in this circum- 
ftance, that thofe with fimple radicals are not convertible 
into each other, becaufe the properties of one fimple ra¬ 
dical, fuiphur for example, vary much from thofe of an¬ 
other, fuch as pholphorus, whence it would be neceflary 
to begin with converting thefe radicals into each other, 
which is far beyond the power of art.' The acids of the 
other clafs, on the contrary, being formed in general of 
a bafe compofed of hydrogen, carbon, and azot, united 
with oxygen, appear to differ from each other only in the 
proportions of the two or three principles which enter 
into the compofition of their radicals, and of the oxygen 
united with thefe, have a tendency to undergo inceflant 
changes in their compofition, efpecially from variation 
of temperature, humidity, See. and fpontaneoufly pals in¬ 
to different ftates. Thus, from the mere efforts of vege¬ 
tation, plants contain different acids at different periods 
of their growth: and thus folutions of vegetable acids 
in water (hange, alter their nature, and ultimately yield 
a certain quantity of carbonic acid and water, as they 
arrive at the laft ltage of decompofition. 
If we attend to thefe fafts, it is ealy to perceive that 
there ftill remain to be dilcovered, not only the nature 
of feveral acids, with the compofition of which we are 
unacquainted, but alfo, perhaps, a conliderable number 
of new acids, in plants and animais. For among the 
productions of thefe organized beings, the principles of 
which we have only begun to- inveftigate, we are far 
from having exhaufted all the polfible combinations of 
carbon, hydrogen, azote, and oxygen, as the mod fuper- 
ficial calculation will demonftrate. To this order of in- 
veltigation and difeovery, we muft refer the examination 
of the acids indicated in cork, grey-peale, and leveral 
other vegetable matters, as well as thofe of the gaftric 
juice, the coagulum of the blood, cruoric acid, &c. It 
wall be perceived too, from the l'ucceeding leCtion, that 
moft burnt metals feem to enter into the clafs of acids, 
and comport themfelves as thefe faits, in a great number 
of combinations : fo that acids appear to be the moft 
numerous of all bodies, and perform the principal parts 
in the chemical alterations, which both fimple and com¬ 
pound fubftances are deftined inceflantly to undergo. 
From the foregoing confiderations we are naturally led 
to the artificial formation of fulphuric acid, by the com- - 
bullion of fuiphur in the great: the dilcharging of co¬ 
lour from white linens and Huffs, by means of the ful- 
phureous acid : the new art of bleaching, by means- of 
the oxygenated muriatic acid: the theory of the aqua 
regia of the ancient chemifts : the art of engraving on 
glafs, by the fluoric acid : one part of the theory of the 
formation of artificial nitre-pits : the exiftence and for¬ 
mation of the known native acids : the influence of acids 
in mineralization : the extraftion and purification of ve¬ 
getable acids and acidules: the fpontaneous formation, 
and deftrudtion of vegetable acids : their reciprocal con- 
verfion into each other, by vegetation, fermentation, Sec. 
THE UNION OF ACIDS WITH EARTHS AND ALKALIS. 
All acids unite with alkalis and the alkaline earths, 
without being decompofed. The combinations thus form¬ 
ed. 
