ALCOHOL. 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 fer mented 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 of : 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 100 above the freezing point, and leaves no residue except a little water, when not quite pure. It boils at about 1650 Fehr., 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 ; 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, &c. The following substances are insoluble in alcohol: the alkaline carbonates ; all the sulphates ; some of the nitrates and mitriates; 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 most accurate method is to find its specific gravity by a hydrometer, noting carefully at the same time its temperature. The uses of alcohol are very numerous, and it is extensively employed in medicine and the arts. In com bination with copal, resin, &c. 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 ehgible 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 Anployed, 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 71° Fahr. the fermen tation will be too rapid; if below 600 Fahr. the fermentation will cease. The mean between these points is considered as the most favourable, and the fer mentation 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 fire place. 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. The worm is a long tube, generally made of pewter, of a gradually decreasing diameter, and is curled round into a spiral form ; it is enclosed in a tub which is kept filled with cold water during the distillation. The produce of the first distillation forms what is termed low urines; consisting of alcohol com bined with a large portion of water, on an average about one part of alcohol to five parts of water. This is re-distilled, and affords proof spirit, consisting of equal portions of spirit and water. The proof spirit being returned to the still and re-distilled, the product is called spirits of wine or alcohol, being alcohol combined with a very small portion of water, from which it is impossible to free it by distillation, but which may be wholly or in great part removed by other processes, to be hereafter described. The first important improvement in the process of obtaining alcohol was introduced by a French chemist named Adam, who, by a happy application of scientific principles, was enabled to dispense with the tedious re-distillations, and to obtain alcohol highly concentrated by a single operation ; economising time, labour, fuel, and (what in many situations is highly important,) water for condensation; besides obtaining spirits of a superior quality, with an increase in the quantity produced. The principle of his in vention consists in causing the vapour of the wine, with which the still is charged, to pass through a quantity of wine contained in a vessel placed between the still and the refrigerator, by which the vapour is condensed, and imparts its heat and alcohol to the wine, until at length it enters into ebullition ; and as this wine, besides its natural portion of alcohol, has received the alcohol con tained in the vapour of the wine in the still, its vapour will be more highly charged with alcohol than the former, and this vapour in its turn is condensed in another vessel similar to the former, and so on through a number of vessels in succession, until it arrives at the refrigerator highly concentrated. His apparatus in its arrangement resembled " Wolfe's apparatus:" between the still and the refrigerator were placed three or four strong copper vessels, named eggs, from their shape. From the head of the still a pipe proceeded to nearly the bottom of the first egg, and from the top of each egg, a similar pipe ceeded to nearly the bottom of the next egg in succession, the pipe from the top of the last egg being connected to the worm, which first traversed a vessel or reservoir containing wine, and then passed through a vessel containing cold water. From the wine reservoir a pipe went to the still, communicating also with the bottom of the eggs, by means of cocks, for the purpose of charging the still and eggs with the liquid for distillation, the several vessels being each filled about three-fourths. When ebullition takes place in the still, the vapour issuing from it is condensed by the wine in the first egg gradually raising its tem perature until it likewise boils, and its vapour (which is richer in alcohol than the vapour from the still) is in like manner condensed in the wine of the second egg, and so on through the remaining eggs, the vapour issuing from the last into the refrigerator being highly concentrated. The upper part of the refri gerator being immersed in the wine reservoir, the alcoholic vapour in its passage through the refrigerator gives out a portion of its heat to the wine by which it is surrounded, and is finally condensed by the cold water in which the lower portion of the refrigerator is immersed. When the vapour from the still no longer contains alcohol, the contents of the still are discharged, and the still is re-charged from the first egg, which is charged in its turn from the second, and so on throughout the series, the last egg being charged from the wine reservoir, the wine in which has been already considerably heated by the passage of the alcoholic vapour through the refrigerator. Although the principle of this in vention is admirable, and has served as the basis of a great part of the subsequent improvements in distillatory apparatus, yet, as was to be expected, improvements have been introduced in the construction and arrangement of the parts, several of which we shall lay before our readers, for which reason we omit giving a drawing of the original.