The first apparatus to fulfil these conditions was devised by Coffey. Although a variety of apparatus for distilling have been constructed by Savalle, Siemens Brothers, and others, yet some form or modification of Coffey's still is most commonly used in this country. It is constructed largely of wood and sheet copper; the wood being a bad conductor, prevents loss of heat, but it is liable in turn to give rise to leakage, and requires frequent renewal. The wash is-raised by a pump to the top of a column, the upper half of which is a condenser, and the lower a dephlegmator; by means of a zigzag copper tube, the wash passes downwards, and upwards again, to the top of a second column, into which it is discharged, where it undergoes a process of distillation, by means of steam rectification, on a series of perforated shelves connected with each other by over-flow pipes. Such stills may be built of any size, even of such dimensions that the pumps of each still are capable of passing 8000 gal. of wash per hour. (Prof. W. N. Hartley.)
The simplest form of spirit still is shown in Fig. 109, and consists of 2 essential parts, the still or boiler A, which is made of tinned copper, and enters the furnace, and the cooler or worm B, a pipe of block-tin or tinned copper, bent into a spiral and connected with the top of the still. The liquid is boiled in the still, and the vapours passing over are condensed in the pipe, which is placed in a tub or vessel containing cold water. This simple apparatus is not much employed in distilling, as it is impossible to get sufficiently pure products from it on a commercial scale. In an arrangement of this kind, the vapours of alcohol and water are condensed together. But if, instead of filling the cooler with cold water, it be kept at a temperature of 176° F. (80° C.), the greater part of the water will be condensed; but the alcohol, which boils at 172 1/2° F. (78° C), passes through the coil uncondensed. If, therefore, the water be condensed and collected separately in this manner, and the alcoholic vapours be conducted into another cooler, kept at a temperature below 172 1/2° F. (78° C), the alcohol will be obtained in a much higher state of concentration than it would be by a process of simple distillation.
Supposing, again, that vapours containing but a small quantity of alcohol are brought into contact with an alcoholic liquid of lower temperature than the vapours themselves, and in very small quantity, the vapour of water will be partly condensed, so that the remainder will be richer in alcohol than it was previously. But the water, in condensing, converts into vapour a portion of the spirit contained in the liquid interposed, so that the uncondensed vapours passing away are still further enriched by this means. Here, then, are the results obtained: the alcoholic vapours are strengthened, firstly, by the removal of a portion of the water wherewith they were mixed; and then by the admixture with them of the vaporised spirit placed in the condenser. By the employment of some such method as this, a very satisfactory yield of spirit may be obtained, both with regard to quality, as it is extremely concentrated, and to the cost of production, since the simple condensation of the water is made use of to convert the spirit into vapour without the necessity of having recourse to fuel.
The construction of every variety of distilling apparatus now in use is based upon the above principles.
Adam's apparatus for the production of strong alcohol on an industrial scale is shown in Fig. 110, in which is a still A to contain the liquor. The vapours are conducted by a tube into the egg-shaped vessel B, the tube reaching nearly to the bottom; they then pass out by another tube into a second egg C; then, in some cases, into a third, not shown in the figure, and finally into the worm D. The liquor condensed in the first egg is stronger than that in the still, while that found in the second and third is stronger than either. The spirit which is condensed at the bottom of the worm is of a very high degree of strength. At the bottom of each of the eggs, is a tube connected with the still, by which the concentrated liquors can be run back into it. In the tube, is a stop-cock a, by regulating which, enough liquor can be kept in the eggs to cover the lower ends of the entrance pipes, so that the alcoholic vapours are not only deprived of water by the cooling which they undergo in passing through the eggs, but are also mixed with fresh spirit obtained from the vaporisation of the liquid remaining in the bottom of the eggs, in the manner already described.
Adam's arrangement fulfils, therefore, the 2 conditions necessary for the production of strong spirit inexpensively; but unfortunately it has also serious defects. The temperature of the egg cannot be maintained at a constant standard, and the bubbling of the vapours through the liquor inside creates too high a pressure. It was, however, a source of great profit to its inventor for a long period, although it gave rise to many imitations and improvements of greater or less merit. Among these are the stills of Solimani and Berard, which more nearly resemble those of the present day.
Utilising the experience which had been gained by Adam, Solimani, and Berard, and avoiding the defects which these stills presented, Cellier-Blumen-thal devised an apparatus which has become the basis of all subsequent improvements; indeed, every successive invention has differed from this arrangement, merely in detail, the general principles being in every case the same. The chief defect in the 3 stills above-mentioned is that they are intermittent, while that of Cellier-Blumenthal is continuous; that is to say, the liquid for distillation is introduced at one end of the arrangement, and the alcoholic products are received continuously, and of a constant degree of concentration, at the other. The saving of time and fuel resulting from the use of this still is enormous. In the case of the previous stills, the fuel consumed amounted to a weight nearly 3 times that of the spirit yielded by it; whereas the Cellier-Blumenthal apparatus reduces the amount to 1/4 of the weight of alcohol produced. This latter apparatus, however, is adapted only to the needs of large distilleries, and a description of it would be out of place in the present volume.