44 ALCOHOL 



Messrs. Ronalds and Richardson remark : ' ' the enormous amount of bread that is 

 baked in large towns in London, for instance, 8'8 millions of cwts. yearly would 

 render the small amount of alcohol contained in it of sufficient importance to be worth 

 collecting, provided this could bo done sufficiently cheaply.' In London it has been 

 estimated that in this way about 300,000 gallons of spirit are annually lost ; but the 

 cost of collecting it would far exceed its value. 



2. Distillation. By the process of distillation, ardent spirits are obtained, which 

 have likewise received different names according to the sources whence the fermented 

 liquor has been derived : viz. that produced by the distillation of wine being called 

 brandy, and in France cognac, or eau de vie ; that produced by the distillation of the 

 fermented liquor from sugar and molasses, rum. There are several varieties of spirits 

 made from the fermented liquor produced from the cereals (and especially barley), 

 known according to their peculiar methods of manufacture, flavour, &c. as whisky, 

 gin, Hollands the various compounds and liqueurs. In India, the spirit obtained 

 from a fermented infusion of rice is called arrack. 



3. Rectification ; preparation of absolute alcohol. It is impossible by distillation 

 alone to deprive spirit of the whole of the water and other impurities to obtain, in 

 fact, pure or absolute alcohol. 



This is effected by mixing with the liquid obtained after one or two distillations, 

 certain bodies which have a powerful attraction for water. The agents commonly 

 employed for this purpose are quicklime, carbonate of potash, anhydrous sulphate of 

 copper, or chloride of calcium. Perhaps the best adapted for the purpose, especially 

 where large quantities are required, is quicklime ; it is powdered, mixed in the retort 

 with the spirit (previously twice distilled), and the neck of the retort being securely 

 closed, the whole is left for 24 hours, with occasional shaking ; during this period the 

 lime combines with the water, and then on carefully distilling, avoiding to continue 

 the process until the last portions come over, an alcohol is obtained which is free 

 from water. If not quite free, the same process may be again repeated. 



In experiments on a small scale, an ordinary glass retort may be employed, heated 

 by a water-bath, and fitted to a Liebig's condenser cooled by ice-water, which passes 

 lastly into a glass receiver, similarly cooled. 



Although alcohol of sufficient purity for most practical purposes can be readily 

 obtained, yet the task of procuring absolute alcohol entirely free from a trace of water, 

 is by no means an easy one. 



Mr. Drinkwater 2 effected this by digesting ordinary alcohol of specific gravity '850 

 at 60 F. for 24 hours with carbonate of potash previously exposed to a red heat ; the 

 alcohol was then carefully poured off and mixed in a retort with as much fresh-burnt 

 quicklime as was sufficient to absorb the whole of the alcohol ; after digesting for 48 

 hours, it was slowly distilled in a water-bath at a temperature of about 180 F. This 

 alcohol was carefully redistilled, and its specific gravity at 60 F. found to be 7947, 

 which closely agrees with that given by Gay-Lussac as the specific gravity of 

 absolute alcohol. He found, moreover, that recently ignited anhydrous sulphate of 

 copper was a less efficient dehydrating agent than quicklime. 



Graham recommends that the quantity of lime employed should never exceed 

 three times the weight of the alcohol. 



Chloride of calcium is not so well adapted for the purification of alcohol, since the 

 alcohol forms a compound with this salt. 



Many other processes have been suggested for depriving alcohol of its water. 



A curious process was proposed many years ago by Soemmering,* which is depen- 

 dent upon the peculiar fact, that whilst water moistens animal tissues, alcohol does 

 not, but tends rather to abstract water from them. If a mixture of alcohol and water 

 bo enclosed in an ox bladder, the water gradually traverses the membrane and evapo- 

 rates, whilst the alcohol does not, and consequently by the loss of water the spirituoiifi 

 solution becomes concentrated. 



This process, though an interesting illustration of exosmose, is not practically ap- 

 plicable to the production of anhydrous alcohol ; it is, however, an economical method, 

 and well suited for obtaining alcohol for the preparation of varnishes. Smugglers, 

 who bring spirits into France in bladders hid about their persons, have long known, 

 that although the liquor decreased in bulk, yet it increased in strength ; hence the 

 people preferred the article conveyed clandestinely. Professor Graham ingeniously 

 proposed to concentrate alcohol as follows : 



' A large shallow basin is covered, to a small depth, with recently burnt quick- 

 lime, in coarse powder, and a smaller basin, containing three or four ounces of com* 



1 Chemical Technology, by Dr. P. Knapp : edited by Messrs. Konalds and Richardson. Vol. iii. 199* 



On the Preparation of Absolute Alcohol, and the Composition of Proof Spirit. See Memoirs of 

 the Chemical Society, vol. iii. p. 447. 



Soemmering : ' Denkschrif ten d. k. Akad. d. Wisscnscbaften zu MUnchcn,' 1711 to 1824. 



