Sugar must be mixed with about four times its weight of water, to render it susceptible of fermentation; and even then the equilibrium of its elements would remain undisturbed, without the assistance of some substance, to give a commencement to the fermentation. This is accomplished by means of a little yeast from beer; and, when the fermentation is once excited, it continues of itself until completed. I shall, in another place, give an account of the effects of yeast, and other ferments, upon fermentable substances. I have usually employed 10 libs. of yeast, in the state of paste, for each 100 libs. of sugar, with as much water as is four times the weight of the sugar. I shall give the results of my experiments exactly as they were obtained, preserving even the fractions produced by calculation.

Table I. Materials of Fermentation.

libs.oz.grosgrs.
Water 400000
Sugar 100000
Yeast in paste, 10 libs. composed of{ Water73644
{ Dry yeast212128
————————
Total510

Table II. Constituent Elements of the Materials of Fermentation.

libs.oz.grosgrs.
407 libs, 3 oz. 6 gros 44 grs. of water, composed of{Hydrogen611271.40
{ Oxygen3462344.60
{Hydrogen8000
100 libs. sugar, composed of{Oxygen64000
{Charcoal28000
{Hydrogen0459.30
2 libs. 12 oz. 1 gros 28 grs. of dry yeast, composed of{Oxygen110228.76
{ Charcoal012459
{ Azote0052.94
———————————
Total weight510000

Table III. Recapitulation of these Elements.

libs.oz.grosgrs.
Oxygen:
of the water340000}libs.oz.grosgrs.
of the water in the yeast62344.60}4111261.36
of the sugar64000}
of the dry yeast110228.76}
Hydrogen:
of the water60000}
of the water in the yeast11271.40}69608.70
of the sugar8000}
of the dry yeast0459.30}
Charcoal:
of the sugar28000}
of the yeast012459.00}2812459.00
Azote of the yeast---- }0052.94
———————————
In all510000

Having thus accurately determined the nature and quantity of the constituent elements of the materials submitted to fermentation, we have next to examine the products resulting from that process. For this purpose, I placed the above 510 libs. of fermentable liquor in a proper[26] apparatus, by means of which I could accurately determine the quantity and quality of gas disengaged during the fermentation, and could even weigh every one of the products separately, at any period of the process I judged proper. An hour or two after the substances are mixed together, especially if they are kept in a temperature of from 15° (65.75°) to 18° (72.5°) of the thermometer, the first marks of fermentation commence; the liquor turns thick and frothy, little globules of air are disengaged, which rise and burst at the surface; the quantity of these globules quickly increases, and there is a rapid and abundant production of very pure carbonic acid, accompanied with a scum, which is the yeast separating from the mixture. After some days, less or more according to the degree of heat, the intestine motion and disengagement of gas diminish; but these do not cease entirely, nor is the fermentation completed for a considerable time. During the process, 35 libs. 5 oz. 4 gros 19 grs. of dry carbonic acid are disengaged, which carry alongst with them 13 libs. 14 oz. 5 gros of water. There remains in the vessel 460 libs. 11 oz. 6 gros 53 grs. of vinous liquor, slightly acidulous. This is at first muddy, but clears of itself, and deposits a portion of yeast. When we separately analise all these substances, which is effected by very troublesome processes, we have the results as given in the following Tables. This process, with all the subordinate calculations and analyses, will be detailed at large in the Memoirs of the Academy.