"Fermentation is a spontaneous and intestine motion, which takes
place amongst the principles of organic substance deprived of life,
the maximum of which always tends to change the nature of bodies,
and gives rise to the formation of new productions."
Bouillon la Grange.--Manual of a Course of Chymistry.
Fermentation has long since been divided into spirituous, acid, and
It is only since the revival or new epoch of chymistry, that the learned
have been occupied in researches on fermentation. I was the first who
gave a new hint on this important part of natural philosophy, in 1785.
It was then held as certain, that the saccharine substance was the
principle of spirituous fermentation. A series of experiments enabled me
to demonstrate the contrary, for I obtained a well crystallized sugar by
the fermentation of a substance which produces none by any other means.
In September, 1785, I read a memoir to the Academy of Sciences, at
Paris. In that memoir I developed my theory. That learned body nominated
four commissioners, for the purpose of examining my operations, and
sanctioned my discovery by a report, in which it was acknowledged that
I had discovered a new truth, and ordered the insertion of my memoir in
the collection of those of the Foreign Associates. I attributed the
principle of the spirituous fermentation to the mucilaginous substance.
This has been since demonstrated, by attentively observing that it
always begins with a motion of acid fermentation, which is produced by
the mucilaginous substance. The European chymists have since reasoned
upon fermentation; each of them has produced a new system; none have
been able to bring it to a regular demonstration; and the learned Gay
Lussac has said, that fermentation is one of the most mysterious
operations of chymistry. Be that as it may, there are facts that are
ascertained: let us endeavor to investigate them, that we may derive
from them all the information which is necessary to us.
It is incontestable that spirits are produced by the saccharine
substance. Grains, however, supply it, although they are not sensibly
sweet. This has made me suspect that the fermentation is at first
saccharine, which produces the sweet substance that is necessary for the
formation of spirit. It is thus that, by a series of internal motions,
the fermentation causes the formation of the spirit to be preceded by a
slight production of acid; that it transforms the vinous liquor into
vinegar, which the same fermentation changes in time into an animal
substance, destroyed in its turn by the putrid fermentation. Such are
the progressive changes operated by this all-disorganizing phenomenon,
and the unerring march of nature to bring back all substances to their
The necessary conditions for the formation of vinous fermentation, are--
1st. The presence of the saccharine substance.
2dly. That of a vegeto-animal substance, commonly called ferment, and
soluble in water.
3dly. A certain quantity of water.
4thly. A temperature of 70 deg. to 75 deg..
5thly. A sufficient mass.
When these are obtained, in a short time the liquor becomes turbid; it
bubbles, from the disengaging of the carbonic acid gaz, and the heat
increases considerably. After some days, these impetuous motions
subside; the fermentation ceases by degrees; the liquor clears up; then
it emits a vinous smell and taste. As soon as it ferments no more, it
must be distilled. However, some distillers have asserted that a greater
quantity of spirit is obtained when the liquor has acquired a certain
degree of acidity. Others are of opinion that it must be distilled as
soon as it is calm. I am of this opinion, because the acid can only be
formed at the expense of a little of the spirit, which is one of the
principles of the acetous acid. Besides, the longer the liquor remains
in a mass, the more spirit is wasted by evaporation.