analysis of which is perhaps impossible, but made choice of sugar, which
is easily analysed, and the nature of which I have already explained.
This substance is a true vegetable oxyd, with two bases, composed of
hydrogen and carbon, brought to the state of an oxyd by means of a
certain proportion of oxygen; and these three elements are combined in
such a way that a very slight force is sufficient to destroy the
equilibrium of their connection."

After giving the details of his analysis of sugar and of the products of
fermentation, Lavoisier continues:--

"The effect of the vinous fermentation upon sugar is thus reduced to the
mere separation of its elements into two portions; one part is oxygenated
at the expense of the other, so as to form carbonic acid; while the other
part, being disoxygenated in favour of the latter, is converted into the
combustible substance called alkohol; therefore, if it were possible to
re-unite alkohol and carbonic acid together, we ought to form sugar."[1]

[Footnote 1: _Elements of Chemistry_. By M. Lavoisier. Translated by
Robert Kerr. Second Edition, 1793 (pp. 186-196).]

Thus Lavoisier thought he had demonstrated that the carbonic acid and the
alcohol which are produced by the process of fermentation, are equal in
weight to the sugar which disappears; but the application of the more
refined methods of modern chemistry to the investigation of the products
of fermentation by Pasteur, in 1860, proved that this is not exactly
true, and that there is a deficit of from 5 to 7 per cent of the sugar
which is not covered by the alcohol and carbonic acid evolved. The
greater part of this deficit is accounted for by the discovery of two
substances, glycerine and succinic acid, of the existence of which
Lavoisier was unaware, in the fermented liquid. But about 1-1/2 per cent.
still remains to be made good. According to Pasteur, it has been
appropriated by the yeast, but the fact that such appropriation takes
place cannot be said to be actually proved.

However this may be, there can be no doubt that the constituent elements
of fully 98 per cent. of the sugar which has vanished during fermentation
have simply undergone rearrangement; like the soldiers of a brigade, who
at the word of command divide themselves into the independent regiments
to which they belong. The brigade is sugar, the regiments are carbonic
acid, succinic acid, alcohol, and glycerine.

From the time of Fabroni, onwards, it h