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 wines; consisting of alcohol combined 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 proces3 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 invention 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 contained 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 proceeded 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 temperature 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 refrigerator 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 invention 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.
About the same time that Adam introduced the important improvement just described, M. Solimani, Professor of Natural Philosophy in the Central School of the Gironde, contrived to obtain the same results by a different method. The principle upon which his invention is based is, that water to exist in the state of vapour requires a temperature of 212° Fahr., whilst alcohol boils at about 165°; and that if a mixture of the two vapours be exposed to any temperature between these two points, a portion of the watery vapour will be condensed, which will be greater in proportion as the temperature is below 212°. The annexed figure represents Solimani's still, as improved by Curadau. a is the door of the furnace; b the ash-pit; c the boiler, with a large cylindrical head d; e the exit tube for the vapours, connected by a union joint to the worm f in the tub g. This tub is filled with water, which is to be maintained at a temperature depending upon the strength of the spirit required, and the spirituous vapour that passes upwards through the worm f along the tube h, then descends through the worm i i surrounded with wine, in the vessel k, where it becomes condensed.
The liquid spirit then runs through another worm l, surrounded by cold water, which completely cools it before it is discharged by the pipe n into the recipient o. To prevent the water in the tub g from becoming too hot by the passage of the heated vapours through the worm f, and to preserve it at an even temperature, cold water from an elevated cistern is introduced at the bottom by a pipe p, the quantity being regulated by a stop-cock; and the wine which surrounds the worm i % in the tub k is supplied from a vessel above, by means of the pipe q. This wine in the course of distillation grows hot: it is therefore used to charge the still as often as the former charge is worked off, and the spent wine drawn off by the cock t; and as it is economical to take off the hottest portion, the cock q is opened, when the cold wine from the cistern above enters at the bottom of k, and forces the upper or heated portion along the pipe u into the boiler of the still. The spirituous vapours formed in the tub k are conducted by the head r and the curved neck s into the worm f, where it takes the course of the vapours which proceed from the still. The tub m is kept as cold as possible by an ingenious contrivance of M. Curadau.