Alcohol

vessel, water, spirit, salt, vapour, bottom, distillation, process, pipe and passes

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m is the body of the still fixed in brick-work over a furnace ; a long perpen dicular neck proceeds from this as in the wash-still, the object of which is, that the aqueous part of the vapour may be condensed as it ascends, and fall back again into the still, while the more volatile and spirituous passes on through the tube n to the bottom of the vessel o. This last-mentioned vessel has a tub of cold water placed on the top of it, which is kept supplied by the service pipe p, and as the tube n passes through this tub, the greater part of the vapour at first condenses and is received into the vessel o in a liquid form ; but as the vapour is continually coming over from the still, the condensed liquor is at length made to boil : the vapour filling the upper part of the vessel, from thence passes up the tube r into the long cylindrical vessel s, which is partly immersed in a long cistern constantly supplied with cold water by the usual means. The cylindrical vessel i is divided by five vertical partitions into six compartments, but having a communication from one to the other by means of bent tubespro ceeding from the upper part of the first compartment, to the lower part of the second ; and, in the same manner, from the second to the third, the third to the fourth, and so on. It will now be readily seen that the most aqueous part of the vapour will be condensed in the first compartment, while the more vola tile passes to the second, where another portion of the vapour assumes a liquid form ; the more volatile still will proceed to the third, and thence to the fourth, fifth, and sixth, according as the spirit is more or less divested of aqueous particles, all depending, of course, upon the degree of heat employed in the furnace for raising the vapour in the stall m, and upon the degree of coldness of the water surrounding the condensing vessels. To ensure, however, the condensation of all the vapour, a tube g proceeds from the upper part of the sixth compart ment, rises to a considerable height, then takes a horizontal course, and, finally, descends into a spiral worm placed in a tub of cold water, where, making a long circuitous passage, it is delivered from the bottom into a receiver in so concentrated a form, as to be nearly in the state of pure alcohol. At the bottom of the cylindrical vessel 5, a separate short pipe, with a cock, pro ceeds from each compartment, leading into the long pipe u, which being also furnished with a cock at either end, the spirit contained in any compartment may be drawn off distinctly ; the contents of any, or all of the pipes, may like wise be drawn off by the pipe u into the vessel o for redistillation ; and the vessel o may be discharged back into the still when desired, by the pipe v having a cock for that purpose. Although this apparatus is well adapted for its intended purpose, and is new in this country (where the vexatious nature of the excise laws preclude, in a great measure, any improvements in the art of distillation) we must observe that little invention has been displayed on the part of the patentee, as almost every part of it is copied from apparatus long since invented, and in use in France. For a further account of distillatory appa ratus, we refer our readers to the article DISTILLATION, under which head will be found a description of a great variety of stills and apparatus connected there with, which the length to which we have extended the present article prevents our noticing in this place.

When, by repeated distillation, the alcoholic mixture is brought to a certain degree of concentration, the affinity of the alcohol for the water with which it is still combined, aided by the great excess in the proportion of the alcohol to the water, becomes so great, that no further separation of the constituent parts of the mixture can be effected by distillation. Alcohol being much lighter than

water, its spec. gray. is used as a test of its purity. Fourcroy considered it as rectified to the highest point when its spec. gray. was 829, that of water being 1000 ; and this is, perhaps, nearly as far as it can be carried by mere distil lation. Alcohol, however, is not in this state pure (nor, indeed, is any process known by which it may be rendered anhydrous, or perfectly free from water); but it may be freed from a further portion of water by means of an alkaline salt. For this purpose, muriate of soda (common salt), may be advantageously employed, by first depriving it of its water of crystallization by heat, and adding it hot to the spirit. It is, however, considered preferable to employ the sub-carbonate of potash. About a third part of the weight of the alcohol should be added to it in a glass vessel, be well shaken, and then allowed to subside. The salt will be found to have absorbed water from the alcohol, which being decanted, more of the salt is to be added, and the process con tinued until the salt falls dry at the bottom of the vessel. The alcohol must now be subjected to final distillation in a water-bath, to deprive it of the red tint derived from the potash, as well as to free it from the alkali held in solu tion. A most important improvement upon this method of rectification has been invented by a French chemist. It consists in placing a quantity of dry muriate of lime, or other deliquescent salt, in a large shallow-covered vessel ; in this is placed another vessel of smaller dimensions, and resting upon the bottom on short legs, and containing the diluted spirit (brandy for instance) to be concentrated; the outer, or larger vessel, is then covered down, and properly luted, to prevent the escape of the spirit. A series of double vessels are arranged beneath the former, charged with the deliquescent salt only; and pipes of communication lead from one to the other, and are furnished with stop cocks. These arrangements, as well as the process, will be perfectly well understood upon reference to the annexed diagram. a is the vend containing the deliquescent salt ; b, that containing the dilute spirit ; the cover of a being well closed and luted, it is left for several days to attract the water from the spirit; and when the former is supposed to be fully saturated with aqueous particles, the spirit in b (considerably improved in strength) is drawn off into d by turning the cock c. This second vessel being also provided with a stratum of muriate of lime, the process of concentration recommences by a farther abstrac tion of the water contained in the spirit. In like manner the spirit may be successively operated upon by the salts contained in the vessels e and f, and, if required, by an additional number of vessels, until alcohol of the greatest purity is obtained. As each vessel is successively emptied, the satu rated salt is taken away and replaced with a fresh of dry salt, when it is ready to operate upon another portion of spirit let on from above. There is another method by which the strongest alcohol may be obtained, although the process, as usually conducted, is rather dilatory. It has been ascertained that bladder is impervious to alcohol, although pervious to water; so that if a portion of alcohol be confined in a bladder, the water will be evaporated in the course of a few days, whilst the alcohol remains, but in a highly concentrated state. The following information on the subject is extracted from Ferrusac's Bulletin, Mai, 1828, and, we doubt not, may be turned to practical advantage.

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