FERMENTATION. 83 



globules (of ferment) retained their form even under 

 the influence of potash. Quevenne was not, however, 

 acquainted with the properties of ferment. 



Eerment of wine is designated by Bouchardat* 

 " ferment noir." He obtained from white wine, 

 ferment consisting of round particles, characterised by 

 a black spot. 



The globules are mostly homogenous, perfectly 

 round, and have a diameter of from aib to aio milli- 

 meter. Put into sugar and water at a temperature of 

 from 10 (50 F.) to 12 (53 6'F.), the ferment put an 

 end to fermentation, which had been carried on during 

 a period of six months ; and more than 17 per cent, 

 alcohol was found in the fermented liquid. According 

 to Bouchardat tannic acid exercises a considerable 

 influence upon fermentation. The white of 4 eggs 

 and 1 kilogramme (2*2 pounds) of sugar were dis- 

 solved in 7 pints (4 litres) of water, which contained 

 nroo of muriatic acid. The mixture was divided into 

 two equal portions, and to one-half was added, 10 

 grammes (154 grs.) of tannic acid, dissolved in 100 

 grammes (1543 grs.) of water. A copious precipitate 

 was formed, and the slow fermentation, begun by 

 means of the black ferment, was completed at the end 

 of 40 hours, in a temperature of 25 C., 77 P. In 

 the other half of the liquid not a trace of alcohol 

 could be detected. But how can tannic acid, which 



* Compt. Rend. torn, xviii. p. 1120. 



