Alcohol, in popular language, the intoxicating principle of fermented liquors. The word is of Arabic origin, and means "to paint," probably in reference to the use of this compound to dissolve pigments which are insoluble in water. Chemists understand by alcohol the hydrate of a hydrocarbon radical, and include a numerous class of bodies under this designation. Ordinary vinic alcohol is formed in the decomposition of glucose (grape sugar) by fermentation. One part of grape sugar, represented by the formula C6H12O6, is split up by a ferment into two parts of alcohol and two parts of carbonic acid: 2(C2116O)+2CO2. Hennel so long ago as 1828 (see "Philosophical Transactions") says: "By combining olefiant gas with sulphuric acid, we may form sulpho-vinic acid, from which we may obtain at pleasure, by varying the circumstances of decomposition, either alcohol or ether." This observation has since been confirmed by M. Berthelot, who has succeeded in making alcohol synthetically, by combining water with olefiant gas: C2H4+H2O = C2H6O. Alcohol for commercial purposes is obtained by distilling wine and other liquors that have undergone vinous fermentation; carbonate of soda is sometimes added to keep back acetic acid, and fusel oil is removed by charcoal.

The alcohol of the London Pharmacopœia contains about 82 per cent, of alcohol and 18 of water. Its specific gravity is required to be 0.838, water being 1.000. It is thus seen that the less water it contains, the less is its specific gravity; and this property is therefore a convenient test of its purity. In consequence, however, of condensation of the two fluids when mixed, this test cannot be applied except in connection with tables of reference prepared for this purpose. - To prepare absolute or anhydrous alcohol, some substance must be placed in it which shall retain the water. Fused carbonate of potash is such a substance. It absorbs the water, and the alcohol nearly anhydrous occupies the upper part of the vessel, whence it is distilled off nearly pure. Its specific gravity is now reduced to 0.815, and its percentage of water to about 5. Quicklime, well powdered, and thoroughly mixed and shaken with the alcohol, is sometimes used instead of the carbonate of potash; but chloride of calcium is said by some to be more effective than either. The salt is first fused to free it from water, and is then mixed with an equal weight of the spirit in a well stoppered bottle. When the solution is effected, it is poured into a retort or still, and distilled at a moderate heat.

The product of the first half is absolute alcohol. Its specific gravity at a temperature of 60° is 0.794. - Rectified spirit may be deprived of a portion of water merely by being left in a bladder, or in a wide-mouthed bottle tied over with bladder, and kept at a temperature of 105° to 120°. By the principle of exosmose, the water evaporates in part through the membrane. Alcohol has thus been brought from sp. gr. 0.867 to 0.817. Pure alcohol is a colorless fluid, of an agreeable odor and strong pungent taste. It has a great affinity for water, absorbing it from the atmosphere, and increasing in specific gravity with the amount it receives. Mixed with water, heat is at first evolved, showing that a chemical union has taken place; another evidence of which is the condensation and diminution of bulk, and a less specific gravity. The greatest heat and condensation result from a mixture of 52.3 per cent, of alcohol an 47.7 of water, the volume after condensation being equal to 96.35. The specific gravity, therefore, of such mixtures can only be determined by experiment. - Diluted with water, alcohol acts as a stimulant, exciting particularly the nervous and vascular systems. In large doses it produces intoxication, and when taken pure acts as a narcotic poison, producing death.

It is very inflammable, burning with a pale bluish flame without smoke. The products of its combustion are carbonic acid and water. Absolute alcohol boils at 173° F. The specific gravity of its vapor is 1.0133. Under the exhausted receiver of an air pump it boils at common temperatures. No degree of cold ever yet obtain-d has effected its congelation. Faraday exposed it to a temperature of 166° F. below zero, which caused it to thicken considerably. It is thus well suited for thermometers for measuring low temperatures. - Alcohol is employed in medicine as a solvent in the preparation of tinctures. It is also a solvent of resins, gums, etc. With the former it makes varnishes; with essential oil, perfumed spirits. The ethers are preparations of it in combination with an acid. It is used with spirits of turpentine to make camphene and the various other illuminating fluids of this class. It is used to preserve anatomical preparations, its effect being to combine with the moisture, and so prevent this from acting upon the animal substance to produce decay.

To the chemist it is valuable as a convenient fuel, producing in his lamp much heat with no annoyance from smoke; and it is of frequent use as a reagent for separating salts, one of which is soluble and the other insoluble in it. - The quantity of alcohol in wine, beer, and other fermented liquors, is very variable. Prof. Brande found from 1 to 2 per cent, only in small beer; 4 in porter; from 6 to 9 in ales; about 12 in the light wines of France and Germany; from 19 to 25 in port, sherry, and other strong wines; and from 40 to 50 per cent., and occasionally more, in brandy, gin, and whiskey. The strength of these liquors is ascertained by various expedients; but the process is sometimes complicated by reason of the different ingredients intermixed to color, sweeten, or flavor the liquor, or fraudulently added to alter the specific gravity, or to substitute a cheaper material. Mixtures thus complicated require to be first distilled, before their strength can be ascertained by the usual process of specific gravity. Common modes of judging of the strength are by tasting, observing the size and appearance of the bubbles when shaken, the sinking or floating of olive oil in them, and the appearances they exhibit when burned.

If cotton or gunpowder immersed in them is inflamed by their combustion, the spirit is considered pure. - Alcohol is decomposed by passing through a red-hot glass or porcelain tube, into carbonic acid, water, hydrogen, defiant gas, marsh gas, naphthaline, empyreumatic oil, and charcoal. By electrolysis, on adding potash, hydrogen is given off at the negative pole and aldehyde resin is formed at the positive pole. The product of its combustion in the air is carbonic acid and water. The vapor of alcohol mixed with air explodes by contact with flame or an electric spark. On contact with platinum black it is imperfectly oxidized, forming carbonic acid, water, aldehyde, acetic acid, formic acid, acetal, and a peculiar compound with an excessively pungent odor. Chlorine gas converts alcohol into aldehyde, chloral, chloride of ethyl, and acetate of ethyl. One of these products, chloral, has recently been introduced as a valuable hypnotic medicine. Concentrated chloric acid ignites alcohol; dilute, forms acetic acid. Alcohol unites in definite proportions with several salts, forming crystallizable compounds in which it plays a part analogous to the water of crystallization.

The methylated spirit of commerce consists of a mixture of alcohol of specific gravity 0.830 with 10 per cent, of common wood spirit. This addition of wood spirit scarcely interferes with the employment of the spirit as a solvent, though it renders it unfit for use afterward as a stimulant drink. - Alcohol or spirit of wine is the most important member of a group of compounds which manifest a close analogy with each other, both in chemical composition and in the decompositions of which they are susceptible. The general doctrine of alcohols was introduced into science by MM. Dumas and Peli-got. These iflustrious chemists, in the course of their investigations into the properties of wood spirit, discovered that vinic alcohol was not a unique body, but that in wood spirit was to be found a compound of similar character, which they therefore called methylic alcohol. Subsequently a long list of bodies properly classed under the generic term of alcohols was discovered by European chemists. As these bodies were found to be closely related to each other and to differ by a common multiple CH2, they were said to be homologous, because a like description is applicable to each member of the series.

The following table includes the most important homologous alcohols:

Methylic alcohol...............

CH4O

Ethylic

" ........................

C2 H6 O

or

CH4O

+

(CH2)

Propylic

" ........................

C3 H8O

or

CH4O

+

2(CH2)

Butylic

" ........................

C4 H10O

or

CH4O

+

3(CH2)

Amylic

" ..........................

C5 H12O

or

CH4O

+

4(CH2)

Caproic

" ..........................

C6 H14O

or

CH4O

+

5(CH2)

Caprylic

" ..........................

C8 H18O

or

CH4O

+

7(CH2)

Laurylic

" ..........................

C12H26O

or

CH4O

+

11(CH2)

Cetyiic

" ..........................

C16H34O

or

CH4O

+

15(CH2)

Cerylic

" ..........................

C27H56O

or

CH4O

+

26(CH2)

Melyssylic

" ...........................

C30H62O

or

CH4O

+

29(CH2)