CHAP. XIV.
_Of the Putrefactive Fermentation._
The phenomena of putrefaction are caused, like those of vinous
fermentation, by the operation of very complicated affinities. The
constituent elements of the bodies submitted to this process cease to
continue in equilibrium in the threefold combination, and form
themselves anew into binary combinations[27], or compounds, consisting
of two elements only; but these are entirely different from the results
produced by the vinous fermentation. Instead of one part of the hydrogen
remaining united with part of the water and charcoal to form alkohol, as
in the vinous fermentation, the whole of the hydrogen is dissipated,
during putrefaction, in the form of hydrogen gas, whilst, at the same
time, the oxygen and charcoal, uniting with caloric, escape in the form
of carbonic acid gas; so that, when the whole process is finished,
especially if the materials have been mixed with a sufficient quantity
of water, nothing remains but the earth of the vegetable mixed with a
small portion of charcoal and iron. Thus putrefaction is nothing more
than a complete analysis of vegetable substance, during which the whole
of the constituent elements is disengaged in form of gas, except the
earth, which remains in the state of mould[28].
Such is the result of putrefaction when the substances submitted to it
contain only oxygen, hydrogen, charcoal and a little earth. But this
case is rare, and these substances putrify imperfectly and with
difficulty, and require a considerable time to complete their
putrefaction. It is otherwise with substances containing azote, which
indeed exists in all animal matters, and even in a considerable number
of vegetable substances. This additional element is remarkably
favourable to putrefaction; and for this reason animal matter is mixed
with vegetable, when the putrefaction of these is wished to be hastened.
The whole art of forming composts and dunghills, for the purposes of
agriculture, consists in the proper application of this admixture.
The addition of azote to the materials of putrefaction not only
accelerates the process, that element likewise combines with part of
the hydrogen, and forms a new substance called _volatile alkali_ or
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