246 On the Fermentation and 
My present object is neither to enter fully into the 
investigation of acetous acid nor of the cause of pu- 
trefaction; but I shall make a few remarks upon each. 
To produce vinegar (which is chiefly obtained 
from fermented liquor) the presence of an acid is 
necessary, such as the taréareous acidula; but it may 
be obtained by other vegetable acids, as well as from 
gums and amylaceous foecula dissolved in water. A 
heat of from seventy to ninety degrees of Fahrenheit’s 
thermometer, is also necessary to the production of 
vinegar; and fermented liquors will become acid 
under this temperature by the solution of the tartar 
only; yet a perfect vinegar cannot be formed in a 
close vessel. A free access of vital air is absolutely 
necessary to the production of acetous acid, but is 
highly injurious to the spirituous fermentation: add 
to this, that insipid mucilages or gums dissolved-in 
water become acid without having been discernibly 
spirituous. Why then should the making of vine- 
gar be called fermentation? 
The production of ammoniac, which is called 
the putrid fermentation, arises from the texture of 
the solids being destroyed, and the nature of the 
fluids being altered; and it is a well-known fact, 
that many vegetable and other substances never un- 
dergo any sensible vinous fermentation, or are form- 
ed into vinegar previously to putrefaction. In some 
of my experiments on the fermenting infusion of 
malt, I have observed a beginning putrefaction with~ 
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