| lbs. | lbs. | ||||
| 6 | parts | of carbon, | @ | 12, | 72 |
| 12 | “ | hydrogen, | “ | 1, | 12 |
| 6 | “ | oxygen, | “ | 16, | 96 |
| 180 | |||||
And the formula for water means that 18 pounds contain:
| lbs. | lbs. | ||||
| 2 | parts | of hydrogen, | @ | 1, | 2 |
| 1 | part | “ oxygen, | “ | 16, | 16 |
| 18 | |||||
In fermentation, it is glucose which is immediately transformed, although cane sugar ferments also; but, before doing so, it becomes changed or inverted into glucose, and one molecule takes up a molecule of water, and produces two of glucose, thus:
| Cane Sugar. | Water. | Glucose. | ||
| C₁₂H₂₂O₁₁ | + | H₂O = | 2 C₆H₁₂O₆ | |
| 342 | + | 18 = | 2 × 180 = | 360. |
Or, in the production of alcohol, 100 lbs. of pure cane sugar are equal to 105.26 lbs. of pure grape sugar.
The general formula for alcohol is C₂H₆O, and for carbonic acid CO₂.
Alcohol by Weight and by Volume.—The quantity of alcohol contained in a given mixture of alcohol and water may be expressed as per cent. by weight, or per cent. by volume. The first method is usually used by chemists, and the second in commerce. If we have 100 lbs. of a mixture of alcohol and water of which 10 lbs. are alcohol and 90 lbs. water, it contains 10 per cent. of alcohol by weight. If, however, we have 100 gallons of a mixture in which there are 10 gallons of alcohol and 90 gallons of water, we say that it contains 10 per cent. by volume of alcohol. This will serve to illustrate the meaning of the terms per cent. by volume and by weight, although it is well known that, owing to shrinkage, 10 gallons of alcohol and 90 gallons of water do not produce quite 100 gallons of mixture.
Whenever merchants and wine makers use the term per cent. of alcohol, they mean per cent. by volume or measure; and whenever the expression is used in this work, it is used in that sense, unless otherwise expressed.
Fermentation—Its Products.—Per cent. Sugar to per cent. Alcohol.—In theory, glucose, during the process of fermentation, is entirely changed into alcohol and carbonic acid; the two substances produced containing the same elements as glucose, and no others. If there was no loss of sugar, or degeneration, as it is called, the reaction would be exactly expressed as follows: