325 
ACETOUS FERMENTATION. 
Chap. III. 
tous acid. Part of the extractive matter has also under 
gone the same change, and seems indeed to have been 
the substance that first began the absorption of oxygen. 
Part of it is deposited in the state of flakes ; part re 
mains in solution, and disposes the vinegar to decompo 
sition. Vinegar also contains a little tartar, and pro 
bably also citric acid. Malic acid is also found in new 
vinegar ; a proof that this part of the wine is the last 
to undergo the acetous fermentation. 
6. Acetous acid is formed in many other cases of the Acetous 
acid formed 
decomposition of vegetables besides the acetous fermen 
by other 
processes. 
tation. These have been pointed out with much in 
genuity by Vauquelin and Fourcroy. They may be re 
duced under three heads. First, When sugar, gum, 
tartar, wood, &c. are distilled in a retort, or even burnt 
in the open fire, acetous acid separates in combination 
with an empyreumatic oil which distinguishes its odour. 
Hence it was mistaken for other acids, and distinguished 
by the names of pyromucous, pyrolignous, pyrotartarous 
acids, till its real nature was ascertained by these dis 
Secondly, When concentrated 
tinguished chemists *. 
sulphuric acid is poured upon the same vegetable bodies, 
they are decomposed in a very different manner; be 
ing converted into water, charcoal, and acetous acid. 
Tbirdly, Acetous acid is evolved in considerable quan 
tity during the spontaneous decomposition of urine 
and some other animal substances. Thus it appears, 
that the component parts of acetous acid are extremely 
apt to combine together in these proportions which con 
stitute that important acid. 
* Ann. de Cbim. XXXV. 183. 
X( 3