Absolute Alcohol. — Hydrate of oxide of Ethyle. Specific gravity, 0.794-6.
Spiritus Rectificatus. — Rectified spirit. Specific gravity, 0.835.
Alcohol Dilutum. — Proof Spirit. Diluted Alcohol. Specific gravity, 0.935.
Preparation. — Alcohol is a peculiar liquid, generated for the most part in vegetable juices and infusions, by a fermentation called the vinous or alcoholic. The liquids which have undergone it are called vinous liquors, and are of various kinds ; thus, the fermented juice of the grape is called Wine ; of the apple, Cider ; the fermented infusion of malt, Beer. This fermentation is owing to the presence of sugar in these liquids, and in other instances, to the conversion of starch into sugar, by some unknown spontaneous change.
In vinous liquors, the alcohol is diluted with abundance of water, and associated with coloring matter, volatile oil, extractive, and various acids and salts. In purifying it we take advantage of its volatility, which enables us to separate it by distillation, combined with some of the principles of the vinous liquors employed, and more or less water. The distilled product of vinous liquors forms the different varieties of ardent spirit of commerce. When obtained from wine, it is called Brandy ; from fermented molasses, Rum ; from cider, malted barley, or rye, Whisky ; from malted barley and rye-meal with hops, and rectified from juniper berries, Holland Gin ; from malted barley, rye or potatoes, rectified with turpentine, Common Gin ; and from fermented rice, Arrack. These spirits are of different strengths, that is, contain different proportionate quantities of alcohol,- and have various peculiarities by which they are distinguished by the palate. Their strength is accurately judged of by the specific gravity, which is always inversely proportionate to their concentration. When they have a sp. gr. of 0.920 they are designated in commerce by the term Proof Spirit. If lighter than this, they are said to be above proof; if heavier, below proof. Proof spirit may be considered as corresponding with the average strength of the weaker alcohol used in pharmacy.
Proof spirit is still very far from being pure ; being a dilute alcohol, containing about half its weight of water, together with essential oil and other foreign matters. It may be further purified and strengthened by re-distillation, or rectification as it is called. Whisky is the spirit usually employed for this purpose, and from every hundred gallons, between fifty-seven and fifty-eight will be obtained, of the average strength of rectified spirit, (sp. gr. 0.835,) corresponding to the alcohol of the United States Pharm., and the Spiritus Rectificatus of the London and Dublin Colleges. When this is once more cautiously distilled, it will be further purified from water, and attain the sp. gr. of about 0.825, which is the lightest spirit which can be obtained by ordinary distillation. It still, however, contains eleven per cent, of water. In the meanwhile, the spirit, by these repeated distillations, becomes more and more freed from essential oil, called Grain, or Fusel Oil.
If it be desired to obtain alcohol of still greater concentration, (Absolute alcohol), it is necessary to avail ourselves of certain substances which have a powerful affinity for water. Of this nature, are lime, carbonate of potassa, and chloride of calcium. These, being mixed with the rectified spirit, unite with water and sink, while the purer spirit floats above, and may be separated by decantation or distillation. By availing themselves of substances of this nature, the London and Dublin Colleges are enabled to produce their strongest spirit, which they denominate Alcohol.
Souberain recommends the following as an easy method for obtaining alcohol free from water, abundantly and economically : — "1st. Rectify alcohol, marking 86° of the centesimal alcoholmeter of Gay-Lussac (rectified spirit) by distilling it from carbonate of potassa. This operation raises its strength to 94° or 95°. 2d. Raise this alcohol to 97°, by distilling it with fused chloride of calcium, or by digesting it with quicklime, from which it must be afterward poured off, in the proportion of a pint of the alcohol to 1½ ounces of the chloride, or 2¼ ounces of the lime. 3d. Distil the product of this operation slowly with quicklime, in the proportion of 3¾ ounces to the pint. The product will be absolute alcohol. The operation may be shortened to two steps, by distilling the alcohol of 94° or 95°, with an excess of quicklime (7½ ounces to the pint). In all cases, before decanting or distilling, the alcohol must be digested for two or three days with the lime, at a temperature between 95° and 100° F. Lime will not answer as a substance to be distilled from, unless it be in sufficient excess ; for otherwise, toward the end of the distillation, the hydrate of lime formed, will yield up its water to the alcohol, and weaken the distilled product."
Although freed from water by the processes named, alcohol may still be impregnated with a portion of the essential oil, called grain or fusel oil. This is usually removed by digesting the spirit with charcoal, especially animal charcoal. The same end may be attained on a small scale, by adding a little of the solution of nitrate of silver to the spirit, and exposing it to a bright light. By the action of the oxide of silver on the oil, it is converted into a black powder, and by a new distillation, the spirit is obtained pure.
With the exception of alcohol and whisky, but very little pure liquors are to be had in this country, as they are superseded by the domestic articles manufactured by liquor dealers. The following formulas for the manufacturing of domestic liquors, are from an old dealer and manufacturer.
Domestic Gin is made of neutral spirits forty gallons, good Holland fin four gallons, oil of Juniper three ounces, oil of Anise one ounce; mix together. Domestic brandy consists of neutral spirits one gallon, good brandy one pint, molasses, q. s. to color, sweet spirits of nitre eight ounces.
History. — Alcohol is a colorless, transparent, volatile liquid, of a penetrating, agreeable odor, and strong burning taste. When free from water of dilution, it is called anhydrous or absolute alcohol, and has the specific gravity of 0.793 at the temperature of 60°. If a piece of anhydrous baryta be dropped into the liquid, if any water be present it will fall to powder ; otherwise, it will not. Alcohol is inflammable, and burns without smoke or residue, the products being water and carbonic acid. When strong, the flame is bluish, but yellowish when weak. It combines with water and ether in all proportions, and is capable of dissolving a great number of substances, as sulphur, phosphorus, iodine, ammonia, caustic potassa, soda, and lithia ; also the organic vegetable alkalies, urea, tannic acid, sugar, mannite, camphor, resins, balsams, soap, castor oil, and volatile oils ; also most of the chlorides that are readily soluble in water; some nitrates, none of the metallic sulphates, nor the insoluble efflorescent salts. It dissolves fixed oils sparingly, acts on most acids, forming ethers with some, and effecting the solution of others, and dissolves all deliquescent salts, except carbonate of potassa. Alcohol is represented by C4 H4 + 2HO — equivalent 46.
Properties and Uses. — A powerful, diffusible stimulant, and is the intoxicating ingredient in all malt, spiritous, and vinous liquors. It is never used in its pure state in medicine, but when diluted forms a menstruum for many remedies. In the form of brandy, it is useful in all cases of prostration or sinking, especially in typhus. Brandy is said to be cordial and stomachic ; rum, heating and sudorific ; gin and whisky, diuretic. The danger of manufacturing drunkards by the administration of wine or brandy, bitters, cordials, and the like, which was so common a few years since, we are glad to say, has now almost entirely ceased ; and although alcoholic tinctures are sometimes prescribed, yet it is in such small doses, and so well diluted with water, that no fear of intemperance can arise in the mind of the physician. There are very few cases in which alcoholic stimulants are given, and those are never of a chronic character, or in which these fluids have to be used longer than a few days. The discovery of our concentrated preparations, and improved modes of treating disease, have done much to set aside this dangerous and unscientific practice.
Externally, alcohol is sometimes applied to produce cold by evaporation, or to stimulate where its evaporation is repressed ; and enters into many discutient and stimulating lotions. A mixture of equal parts of white of egg and rectified spirit, is said to be an excellent application to excoriations from pressure, during their early stage, occurring in protracted diseases. To be applied frequently with a fine brush or feather, and renewed as it dries, until an albuminous coating is formed over the excoriated surface.
Alcohol is extensively employed in pharmacy, either rectified or diluted, for the manufacture of tinctures, spirits, ether, essences, resinous and alcoholic extracts, and for many other purposes.