DISTILLATION. The evaporati and subsequent condensation of liquids by means of a still and refrigeratory, or of a retort and receiver.
The discovery of the art of distillation is generally ascribed to the alchemists ; but it was doubtlessly known in more re mote ages to the Arabians, and by them probably derived from nations further east.
The process of distillation, though in continual use in the chemical and phar maceutical laboratory, is carried on upon the most extensive scale for the produc tion of ardent spirits in the distilleries. Under the words ALCOHOL, Br tsar, FER MENTATION, WINE, &c., will be found some details bearing upon the nature, sources, and production of spirituous liquors.
There are two distinct operations in the production of ardent spirits ; the one is the conversion of certain vegetable prin ciples into alcohol ; and the other, the separation of the alcohol from the other substances with which it is necessarily blended during its production.
All those species of corn which are em ployed in breweries answer for distil leries ,• as wheat, rye, barley, and oats ; as well as buckwheat, and maize or In dian corn. The product of spirits which these different grains afford, depends upon the proportion of starch they con tain, including the small quantity of en crystallizable sugar present in them. Hermstaedt, who has made exact experi ments upon the subject, reckons a quart, (Prussian or British) of spirits, contain mg 30 per cent. of the absolute alcohol of Richter, for two pounds of starch. Hence 100 pounds of starch should yield 85 pounds of alcohol ; or 4.375 gallons imperial, equal to 7.8 gallons of spirits, excise proof.
100 pounds of the following grains i afford in spirits of specific gravity 0.9427, containing 45 per cent. of absolute alco hol, (= 9-11 of British proof,) the follow ing quantities :— Wheat, 40 to 45 pounds of spirits ; rye, 86 to 42 ; barley, 40 ; oats, 36 ; buck wheat, 40; maize, 40. The mean of the whole may be taken at forty pounds, equal to 4} gallons imperial, of 0.0427 specific gravity = 3.47 gallons, at excise proof. The chief difference in these sev eral kinds of corn consists in their differ ent bulks under the same weight ; a mat ter of considerable importance ; for since a bushel of oats weighs little more than the half of a bushel of wheat, the former becomes for some purposes less conve nient in use than the latter, though it affords a good spirit.
Barley and rye are the species of grain most commonly employed in the Euro pean distilleries for making whiskey. On this continent corn and potatoes are the chief materials used for producing alcohol.
The vegetable principle which is es sential to the formation of alcohol is sugar; and this is sometimes used directly, as where molasses and analogous saccharine products are subjected to immediate fer mentation ; or it is indirectly obtained by subjecting amylaceous grains to certain processes, by which the starch they contain is first converted into sugar, and then that sugar afterwards alcoho find.
In distilleries the latter alternative is adopted ; and various kinds of grain, but chiefly barley, wheat, and rye, with more or less malt, are subjected to the opera tion of mashing. For this purpose the ground grain and the bruised malt are duly mixed, and infused under constant agitation in a proper quantity of hot water in the mach-tub; the wort is then run off, and fresh water added, till the soluble materials of the grain are ex tracted.
In this way the mixed worts or wash is obtained, which is afterwards to be sub jected to fermentation ; but in the dis tilleries of Great Britain the operator is not, as in the brewery, left to his own judgment or convenience, but enforced to conform to the excise laws, which are of a very peremptory and often of a very unscientific character. By these laws the distiller is restricted in the density of his worts to specific gravities between 1050 and 1090 ; and in Scotland between 1030 and 1075. It is presumed that as those specific gravities, which are called 50 and 90, and 30 and 75, the actual quan tity of saccharine or saccharifiable matter contained in each barrel (or 36 imperial gallons) amounts respectively to from 47} lbs. to 85 lbs., and from 28 lbs. to 79 3-10 lbs. In this country the distiller is untrammelled.