268 



CHYMISTRY APPLIED TO AGRICULTURE. 



in the water-bath of the condensers, and in the liquid in 

 which the worm is immersed, the product of the whole ope- 

 ration would be of the same specific gravity ; the degrees 

 may therefore be raised again when they begin to sink, by 

 changing the baths. 



When the operation is completed, the fire is covered, the 

 residuum of the wine removed, and the boiler cleansed and 

 again filled. 



Though the alcohol distilled in the course of the opera- 

 tion is not all of the same degree, it may be made 

 so by mixing the several portions ; the better way how- 

 ever is to redistil that which is produced last, and thus 

 raise the whole to the highest degree known. There is no 

 need in any case of having recourse to what is called the 

 water-hath. 



Alcohol should be colorless and destitute of any un- 

 pleasant odor ; any bad qualities it may have, may be re- 

 moved by a second distillation carefully performed; in- 

 deed it is often enough to filtrate it through well burnt 

 charcoal reduced to a very fine powder. The bad quality 

 of alcohol arises almost always from want of care in the 

 distillation of it, or from a fault in some one or more of 

 the different parts of the apparatus : sometimes, however, it 

 happens that it is owing to the wine's having begun to turn 

 sour. 



As fast as the vessels which receive the alcohol are full, 

 they are emptied into oaken casks set in a cool place to pre- 

 vent evaporation : from the casks the liquor acquires a yel- 

 lowish color, but is unchanged in any other respect. Bran- 

 dy loses by age the burnt taste which it often has when new, 

 and becomes milder and more agreeable. 



The instruments made use of for ascertaining the specific 

 gravity of alcohol, do not give it with mathematical precision, 

 but near enough for commercial purposes : previous to the 

 knowledge of these instruments the methods made use of 

 were very inexact. 



The regulation of 1729 ordered powder to be put into a 

 spoon and covered with alcohol ; the spoon was then placed 

 over the fire, and the strength of the alcohol was judged of 

 by the kindling or not kindling of the powder. To obtain by 

 this method exact results, it was necessary that the quantity of 

 powder and of alcohol should be always the same ; for a larger 

 proportion of spirit would leave, after combustion, a great- 

 er quantity of water, and this would prevent the powder from 

 taking fire. 



