ALCOHOLS. 483 



Ethyl alcohol may also be obtained, as already mentioned, by treat- 

 ing ethyl chloride with potassium hydroxide : 



C 2 H 5 C1 + KOH KC1 + C 2 H 6 OH. 



While the above methods for obtaining alcohol are of scientific 

 interest, there is but one mode of manufacturing it on a large scale, 

 namely, by the fermentation of certain kinds of sugar, especially 

 grape-sugar or glucose, C 6 H 12 O 6 . A diluted solution of grape-sugar 

 under the influence of certain ferments (yeast) suffers decomposition, 

 yielding carbon dioxide and alcohol : 



C 6 H 12 6 = 2CO 2 + 2C 2 H 5 OH. 

 Glucose. Carbon Ethyl 



dioxide. alcohol. 



From 94 to 96 per cent, of the sugar is decomposed, according to 

 the above reaction, the rest forming glycerin (3 per cent.), succinic 

 acid (0.6 per cent.), and higher alcohols designated " fusel oil." 



Experiment 55. To a solution of 25 grammes of commercial glucose (grape- 

 sugar) in 1000 c.c. of water, add a little brewer's yeast and introduce this mix- 

 ture into a flask. Attach to the flask, by means of a perforated cork, a bent 

 glass tube leading into clear lime-water, contained in a small flask. After 

 standing (a warm place should be selected in winter for this operation) a few 

 hours fermentation will commence, which can be noticed by the evolution of 

 carbon dioxide, which, in passing through the lime-water, causes the precipi- 

 tation of calcium carbonate. 



After fermentation ceases connect the flask with a condenser and distil over 

 50 to 100 c.c. of the liquid. Verify in the distilled portion the presence of 

 alcohol by applying the tests mentioned below. For condensation of the dis- 

 tilling vapors a Liebig's condenser, represented in Fig. 70, may be used. 



The alcoholic strength of fermented sugar solutions is never over 

 14 per cent., since above this point the yeast ceases to act. On the 

 large scale this liquid is distilled in apparatus so arranged that the 

 vapors are repeatedly condensed and vaporized, thus yielding by a 

 single distillation an alcohol of about 90 per cent. This is further 

 purified by treatment with charcoal and rectifying in so-called column 

 stills, when alcohol containing as much as 94 to 95 per cent, is ob- 

 tained. To remove the last portions of water the liquid is distilled 

 over calcium oxide, which forms calcium hydroxide. 



The alcohol thus obtained, and containing not more than 1 per 

 cent, of water, is known as pure, absolute, or real alcohol (alcohol 

 absolutum). The alcohol of the U. 8. P. contains 92.3 per cent, by 

 weight or 94.9 per cent, by volume of real alcohol, and has a specific 

 gravity of 0.816 at 15.6 C. (60 F.). The diluted alcohol, is made 

 by mixing equal volumes of water and alcohol, and has a specific 



