The purely spirituous part of liquors, which have undergone the vinous fermentation. It is the product of the saccharine principle formed by the successive processes of vinous fermentation and distillation; and all fermented liquors will afford it. Although brandy, rum, arrack, malt spirits, and the like, differ much in colour, taste, smell, and other properties, the spirituous part, or alcohol, is the same in each. The chief properties of alcohol are the following: It is a colourless transparent liquor, very movable and light, from which cause the bubbles formed by shaking it subside instantly. Its smell is poignant and agreeable, and its taste hot and pungent. It is so exceedingly volatile as to be converted into vapour by the heat of the hand; when exposed to the air, it evaporates at 10° above the freezing point, and leaves no residue except a little water, when not quite pure. It boils at about 165° Fahr., and it is generally supposed that it cannot be frozen, although Dr. Hutton asserts that he succeeded in freezing it; but as he kept his method a secret, no one has been able to repeat the process.
Alcohol, when heated in contact with air, if it be pure, burns with a light flame, without leaving any residue, and yielding by the combustion a vapour, which is found to be nothing but water, and the weight of which Lavoisier found to exceed by 1/7 part the weight of the alcohol consumed. Alcohol mixes with water in any proportion, giving out heat by the mixture; and a mutual penetration of the parts takes place, so that the bulk of the two liquors, when mixed, is less than when separate. So strong is the affinity between these two fluids, that water is capable of separating alcohol from many of the substances which may be united with it; and again alcohol decomposes most saline solutions, and precipitates the salts. The following substances are soluble in alcohol in different proportions: all the alkalies, when pure; several of the neutral earths and metallic salts; sulphur in vapour; phosphorus slightly; the essential oils; and the odorous part of vegetables, resins, and gum-resins, wax, spermaceti, biliary calculi, etc.
The following substances are insoluble in alcohol:
*H the alkaline carbonates; all the sulphates; some of the nitrates and muriates; metals; metallic oxides and metallic acids; all the pure earths; the fixed oils, unless when united to alkalies, or converted into drying oils by metallic oxides; muscular fibre; the coagulum of blood; and albumen. To ascertain the purity of alcohol, various methods have been devised. It has been thought that alcohol which burns readily and leaves no residue is very pure, but this test is fallacious, for the heat produced is sufficient to dry up part of the water. Another method is, to drop a small quantity of it on gunpowder, and set fire to the spirit, and if the spirit be pure, it will burn quietly on the powder, and the last portion of it will ignite the powder, but if the spirit be watery, the powder will not explode. This proof is, also, not to be depended upon; for if any considerable quantity of even the best alcohol be poured on a small quantity of powder, the water which it affords as it burns, moistens the powder and prevents it from kindling; and if it be only barely moistened, any spirit that will burn will inflame it.
The uses of alcohol are very numerous, and it is extensively employed in medicine and the arts. In combination with copal, resin, etc. it forms varnishes. From its antiseptic power it is well calculated to preserve anatomical preparations. Its gentle and steady heat, unaccompanied by smoke, renders it eligible for burning in lamps; and from the impossibility of freezing it in any known degree of cold, it is well adapted for indicating the lower degrees of temperature in the thermometer. Having thus briefly noticed the properties and uses of alcohol, we shall proceed to describe the process by which it is obtained, giving, at the same time, an account of several modifications of the apparatus employed, which have been recently invented, and embracing a description of the most improved French distilling apparatus. The substances from which alcohol is chiefly prepared, are the juice of the grape, molasses, grain, and the farina of potatoes; these substances containing a large portion of saccharine matter, which is the basis of the vinous fermentation. The mode of extracting this saccharine matter depends upon the nature of the substance operated upon; but a saccharine solution being obtained, the mode of converting it into alcohol is the same for them all.
The solution is first set to ferment, a certain quantity of yeast or other fermenting principle being in some cases added. During the fermentation particular attention must be paid to the temperature; if it exceed 77° Fahr, the fermentation will be too rapid; if below 60° Fahr, the fermentation will cease. The mean between these points is considered as the most favourable, and the fermentation must be continued until the liquor grows fine and pungent to the taste, but not so long as to permit the acetous fermentation to commence. When the fermentation is finished, the liquor, if it be the juice of the grape, is termed wine; but if the produce of other substances, it is termed wash. The wine or wash is put into a still (of which it should occupy about three-fourths,) and distilled with a gentle fire, as long as any spirit comes over, which is generally until about half the wash is consumed. The form of the common still is too well known to need any particular description; it generally consists of a large boiler, made of copper, and fixed in masonry over a fireplace. The boiler has a head of a globular form, to which is soldered a neck, which, forming a complete arch, curves downwards, and fits into what is called the worm.