DISTILLATION is a chemical process for applying a regulated heat to fluid substances in covered vessels, in order to separate their more volatile constituents in vapour : and for condensing them immediately by cold into the liquid state. The distillation of aromatic wa ters was known to the Greeks and Romans, and to the Arabians from very remote times. Arnoldus he Villa Nova and Raymond Lolly both noticed in the 13th century, a mode of producing intoxicating spirits by distillation. The alchemists of those days imagined that spirit derives its ardent qualities from the fire employed to heat the vessels.
The only substances employed in this country in the manufacture of ardent spirits upon the great scale (which is the chief ex ample of distillation) are different kinds of corn, such as barley, rye, wheat, oats, buck wheat, and maize. Peas and beaus also have been occasionally used in small quantity. The principles in these grains from which the spi rits are indirectly produced are starch and a little sweet mucilage, which, by a peculiar pro cess called mashing, are converted into a spe cies of sugar. It is the sugar so formed which is the immediate generator of alcohol, by the process of fermentation. In mashing one or more kinds of corn, a greater or smaller pro portion of malt is always mixed with the raw grain, and sometimes malt alone is used, as in the production of malt-whiskey.
The manufacture of ardent spirits consists of three distinct operations : first, mashing ; second, fermentation ; third, distillation.
..ilashing.—Either malt alone, or malt mixed with other grain, and coarsely ground, is put into the mash-tun, along with a proper propor tion of hot water, and the mixture is subjected to agitation by a mechanical revolving appa ratus. The water is applied at a temperature varying from 145° to 165° Fahr. After two or three hours' agitation, the whole is left to repose for an hour and a half, and then the worts (as the liquor is called) are drawn off to about one-third the volume of water employed, the rest being entangled in a pasty state among the farina. About two-thirds of the first quantity of water is now let into the tun, but at a temperature somewhat higher, and the mashing motion is renewed for nearly half an hour. A second period of infusion or re pose ensues, after which these second worts are drawn off. Both infusions must be cooled as quickly as possible down to about Fahr.:
this is usually effected by exposing the wort for some time in large shallow cisterns, called coolers, freely exposed to aerial currents ; but the liquor is sometimes cooled by being passed through serpentine tubes surrounded with cold water, or by the agency of ventilators blowing over its surface in extensive cisterns only three or four inches deep. A third mash ing is conducted with a fresh portion of water in order to extract the remaining saccharine matter from the grain.
The specific gravity of the first and second worts, when mixed, is about 1.060; and the liquor contains about GO lbs. of saccharine ex. tract per barrel of 36 gallons. The three mashings employ about 27 gallons of water to every bushel of ground meal.
Fermentation.— This consists in bringing the worth to a fermented state. The worts are drawn off into a fermenting vessel; and yeast or ferment is added, sufficient to decompose the sugar in the liquor. The process is com menced at a temperature between and 70° which soon afterwards rises to 85° or The first appearance of fermentation shows itself by a ring of froth round the edge of the vat usually within an hour after the addition of the yeast ; and in the course of five hours the extrication of carbonic acid from the particles throughout the whole body of the liquor causes frothy bubbles to cover its entire surface. The yeasty froth begins to subside in about 36 hours, and, when the attenuation gets more athianced, the greater part of it falls to the bottom on account of its density relatively to the subjacent fluid. In from forty-eight to sixty hours the liquor begins to grow clear, and becomes comparatively tranquil. The li quor is stirred up occasionally during the fer mentation, and the vessel is kept mostly closed after the first violence of the action. The specific gravity of the liquor diminishes as the process advances ; the fermentation converts the sugar into alcohol or spirit ; and, as the alcohol is lighter than water, it diminishes the specific gravity of the whole. The liquor itself is now called wash. 100 gallons of this wash contain about 12 gallons of proof spirit ; if the whole of the sugar were decomposed (which it never is in practice), the produce of spirit would be greater. In the great distille ries, where the quantity of liquor operated on at once is very large, the duration of the fer menting process is longer than that above named.