[CHAPTER VIII.]
FERMENTED DRINKS.
Properties of Alcohol.—When a saccharine solution is subjected to the influence of warmth and moisture, and exposed to the air, it rapidly undergoes a process of fermentation. The most favourable temperature is about 70° Fahr. The ferment or agent exciting the change in the sugar is derived from the atmosphere; it is a minute fungus (torula cerevisiæ), the spores of which are constantly floating in the air. When once fermentation has started, exposure in the air is no longer necessary; the process continues in closed vessels. The essential change occurring in the vinous fermentation is that grape sugar (C₆H12O₆,H₂O) becomes split up into alcohol (C₂H₅OH) and carbonic acid (CO₂). Thus—
| C₂H₆O |  | Two of alcohol | |
| C₂H₆O | |||
| C₆C₆H₁₂O₆ = | |||
| CO₂ | | Two of carbonic acid. | |
| CO₂ |
There are other fermentations allied to the vinous. Thus the Acetous fermentation results in the conversion of alcohol into vinegar, as in the souring of beer or wine. The Lactic fermentation leads to the conversion of milk-sugar into lactic acid, with consequent souring of the milk.
Alcohol, or more correctly ethylic alcohol, is a colourless liquid, having a pleasant vinous odour, and evaporating rapidly on exposure to air. It burns with a bluish sootless flame, and is a capital solvent for resins and other substances.
Rectified spirit is absolute alcohol mixed with 16 per cent. of water. Proof-spirit is a mixture of 42·7 per cent. by volume of absolute alcohol, and 57·3 per cent. of water. Thus the ratio of alcohol to proof-spirit being as 1: 1·76, the amount of alcohol in any liquid being given, the amount of proof-spirit can readily be calculated. The fermented drinks containing alcohol may be classed as (1) malt liquors, (2) wines, and (3) distilled spirits. The relative properties of these will be considered afterwards; in the next two sections will be considered the effects of diluted alcohol in whatever form it is taken.
Effects of Moderate Doses of Alcohol on the System.—In studying the physiological effects of alcohol, one has to guard against the fallacy that these are the same, only differing in degree, whatever the dose may be. The effects of large doses of alcohol are almost exactly the reverse of those produced by small doses. It will be necessary to define, therefore, what we mean by a moderate dose. By a moderate dose, we understand the amount of alcohol which can be taken without any alcohol being eliminated in the urine. Dr. Anstie found that 1½ ounces, that is three tablespoonsful, of absolute alcohol, taken in twenty-four hours, caused its appearance in the urine; and Dr. Parkes and Count Wollowicz obtained almost precisely the same result. Anything below some quantity between 1 and 1½ fluid ounces per day can be disposed of in the system, and is probably oxidised like ordinary foods.
The amount of alcohol, in the form of alcoholic beverages, corresponding to this maximum dose of absolute alcohol is approximately as follows:—
| One imperial pint | (20 fluid ounces) | of bottled beer | (5 per cent. of alcohol). |
| One tumblerful | (10 fluid ounces) | of claret, hock, and and other weaker wines | (10 „ ). |
| 2½ glasses | (5 fluid ounces) | of port, sherry, and other strong wines | (20 „ ). |
| One glass | (2 fluid ounces) | of brandy or whiskey | (50 „ ). |