354 C H E M 
be collefled in the receiver. The refidue, wafhed, and 
evaporated, furnifhes cryftals of fulphat of copper. 
Acetic acid, or radical vinegar, has fo ftrong and pe¬ 
netrating a fraell, that it is impoflible to fupport it for 
any length of time ; its caufticity is fuch, that it corrodes 
and burns the fkin, and it is extremely volatile and in¬ 
flammable. When heated with contact of air, the rapi¬ 
dity with which it burns is the greater the more highly it 
is rectified. This experiment has induced chemifts to 
believe, that vinegar is an acid combined with an alco¬ 
hol ; it may, perhaps, be confidered as a kind of natural 
ether. This notion is rendered probable by the penetrat¬ 
ing and agreeable i'mell emitted by the firil portions of 
this acid in diftillation. Acetic acid evaporates entirely 
when expofed to the air; it unites to water with much 
heat. This acid was formerly regarded as acetous acid 
with a greater quantity of oxygen ; but late experiments 
have fixed the ideas of chemills on this head. Peres was 
the firlt who aflerted that the acetic acid was not acetous 
acid with an excefs of oxygen : his experiments con¬ 
vinced him that the acetic acid was nothing but acetous 
acid much concentrated and deprived of the greater part 
of its carbon. 
About the fame time, Adet publifhed a very intereft- 
ing paper on the fame fubjedf, but drawing conclulions 
fomewhat different from thofe of Peres. He diddled acetit 
of copper with the hydrargyro-pneumatic apparatus : 
befidesthe ufual products, he colledted of gas. Then 
examining each of the products feparately and attentive¬ 
ly, he found that the brown mafs remaining in the retort 
was a mixture of carbon and brown oxyd of copper, con¬ 
taining eight parts of oxygen; which convinced him, 
that more than feventeen parts of oxygen has been taken 
from this oxyd, which ought to be found again in the 
liquid or gafeous produ&s. The elaflic fluids which he 
collected, were compofed of io’So5 parts of hydrogen 
gas, and 22-686 of carbonic acid, which laft was made 
up of 16-297 parts of oxygen, and 6-339 of carbon ; the 
oxygen, of which the green oxyd of copper was deprived, 
is therefore found, except ro+8, in the acid gas. This 
convinced the author, that the acetous acid had not taken 
up oxygen to convert itfelf into acetous acid. This ex¬ 
periment, and many others, made Adet conclude, i.That 
the acid of vinegar, as it does not abforb oxygen in its 
fuceeflive combinations with metallic oxyds, cannot fur- 
nifh two different acids. 2. That it exifts always in the 
higheft degree of oxygenation of which it is capable; 
confequently that it is always in the ftate of acetic acid. 
3. That there is no acetous acid, unlels under that de¬ 
nomination are included the tartareous, oxalic, and ma¬ 
lic, acids, which, by abforbing oxygen, pafs to the ftate 
of acetic acid. 4. That the only difference which exifts 
between the acetic acid extracted from the acetat of cop¬ 
per, and that drawn from vinegar, arifes from the fmaller 
quantity of water contained in the firft. 
Since Adet’s paper appeared, Chaptal has made other 
experiments, the refults of which come much nearer,to 
the opinion of Peres. He has demonllrated very clearly, 
that there is a difference between the acetous and acetic 
acids, and that this difference is not merely in the quan¬ 
tity of water they relpeftively contain, but that the acetic 
acid contains a fmaller proportion of carbon than the 
acetous. 
In order to bring Adet’s hypothefes to the tell of ex- 
fperlment, Chaptal reduced the acetic acid to the fame 
degree of fpecific gravity with the acetous acid, by add¬ 
ing to it a quantity of diftilled water. The-fmell and 
talte of the tw-o acids were ftill very different; and the 
aflion of the acetic acid on metallic oxyds was more 
peedy and more energetic than that of the acetous. 
Acetic acid, for inltance, diflblved the oxyd of copper, 
precipitated from the fulphat by potafh, and formed with 
it beautiful cryftals on cooling. The acetous acid, with 
the lame oxyd, acquired merely a bluifh green colour, 
I S T R y. 
and a green and faline cruft was precipitated on the fide- 
of the veffel containing the liquor. Eleven parts of ace¬ 
tic acid, require for figuration 6-98 of pure potafh, while 
the fame quantity of acetous acid require only 5-73. 
When fulphuric acid was added to equal parts of ace¬ 
tic and acetous acids, of the fame degree of concentra¬ 
tion, a very confiderable degree of heat was produced. 
The mixture with the acetic acid appeared at firft of a 
pale yellow colour, while in the acetous no change was 
produced. The mixture with the acetous acid boiled 
fooner than the other ; and, after the evaporation of 
about one-third, it afl'umed the tinge of very deep co¬ 
loured wine. The mixture with the acetic acid was 
much paler. During.diftillation much fulphureous acid 
was diiengaged, and at the end of the operation the refl- 
dues had loft their colour, and confided merely of con¬ 
centrated fulphuric acid. The acetous acid appeared to 
Chaptal to be brought to the ftate of acetic, by its de¬ 
carbonization in the retort. One hundred parts of potafh 
were faturated with each of the two acids, and the falts 
which they formed fubjedted to diftillation in a retort. 
By this procefs, reiidues of a black colour were obtained. 
The acetat afforded feventeen parts of its weight of car¬ 
bon, and the acetit only thirteen. There is therefore 
more carbon in the acetous than in the acetic acid. Si¬ 
milar phenomena take place in the diftillation of the ace¬ 
tat of copper; the acetous acid is deprived of its fuper- 
abundant carbon; one part of this carbon combines 
with the oxygen of the copper, and forms the carbonic 
acid, which is difengaged, while the other remains in. 
combination with the oxyd itfelf. The acetous acid de¬ 
prived in this manner of its carbon, pafles over in the 
ftate of acetic acid. Metallic oxyds, and fome acids, 
feem to be the only fubftances capable of effecting this 
decompofition. From thefe, and other experiments, 
Chaptal concludes : i.That the difference between the 
acetous and acetic acids depends on the different pro¬ 
portions of carbon which they contain. 2. That the 
acid is in the ftate of acetous acid in metallic falts; and, 
3. That it pafles to the ftate of the acetic, only by being 
deprived of a portion of its carbon. An. de Cbem. tom. 
xxviii. p. 113.. 
The acetic acid, combined with earths, alkalis, and 
metals, forms different falts from thofe of the acetous 
acid ; they are called acetats of potstjb,foda, mercury, zink , 
&c. Laffone has fhewn, that the ammoniacal fait formed 
by radical vinegar, or the acetic acid, is very different 
from that formed by the common acetous acid, and called 
Spirit of Mhidererus. Although we do not poffefs a fuffi- 
cient knowledge of the properties of all the acetats, yet 
their form, tafte, folubility, &c. fufficiently (hew that they 
really differ from the acetits. The Marquis de Courtan- 
vaux, has fhewn, that it is only the laft portion of the 
acetic acid obtained by diftillation from cryftals of ver¬ 
digris which is inflammable ; and that it likewife has the 
property of being congealed by cold. This laft portion, 
when re&ified, cryftallized in the receiver in large plates 
and needles, and did not become fluid at a lefs heat than 
about fixty-two degrees of Fahrenheit. In this property, 
likewife, it refembles the oxygenated muriatic acid. 
The acetic acid is given to perfons to fmell to in faint¬ 
ing-fits. For more commodious ufe, very fmall cryftals 
of fulphat of potafh are put into a bottle, and fprinkled 
with acetic acid : this is improperly called volatile fait 
of vinegar. 
Acetic acid decompofes alcohol, and forms ether with 
the fame facility as the mineral acids. For this purpofe, 
acetic acid is poured on an equal quantity of alcohol in 
a retort. A confiderable degree of heat is excited The 
retort is then placed in a land-bath, with two receivers 
fitted on, the outer being plunged in cold water or pounded 
ice. The mixture being quickly brought to ebullition, 
a dephlegmatic alcohol pafles firft, afterwards the ether; 
and, laftly, an acid, which is ftrqnger as the diftillation 
advances; 
