74 



VINEGAR, CIDER, AND FRUIT-WINES. 



air. 



Fig. 20. 



and hence a certain quantity of oxygen is withdrawn from the 

 This process being also continued in the lower parts of the 

 generator, a current of air already 

 deprived of a portion of its oxygen, 

 and hence less suitable for the fur- 

 ther formation of acetic acid, would 

 be sucked in the same direction 

 which the drops of alcohol take. 



The principal reason advanced 

 for the use of a current of air from 

 above to below is that by these 

 means a uniform temperature is 

 maintained in all parts of the gen- 

 erators, while it rises considerably 

 in the upper part of those in which 

 the air passes from below to above. 

 This rise of temperature is, how- 

 ever, agreeable to nature. The air 

 entering from below oxidizes the 

 alcohol to acetic acid, becoming 

 thereby poorer in oxygen and again 

 heated. By the higher temperature 

 it acquires, it is, however, capable 

 of a more vigorous chemical activity, 

 so that it will induce the process of 

 the formation of vinegar, even in 

 the uppermost portions of the gen- 

 erator. Besides, the warmer cur- 

 rent of air moving upwards has the 

 further advantage of yielding heat 



to the drops of alcoholic fluid trickling down. With the use oi 

 generators of moderate height, and with a suitable regulation ot 

 the draught of air, the maximum temperature will not be ex- 

 ceeded, even in the uppermost portions of the generator. 



If no rise of temperature is observed in the lower portions of 

 a generator in which the air passes from above to below, it only 

 proves that the air has lost too much oxygen to further effect a 

 vigorous oxidation of the alcohol. It will be readily understood 



Generator with Ventilation from 

 above to below. 



