60 FERMENTATION. 



large admission of air engenders from the wine. An 

 experiment by De Saussure has proved this also. 



The reaction of the must was acid before the experi- 

 ment, so that 0'81 grammes (12*5, grains) of ammonia 

 were necessary to saturate the acid in 375 grammes 

 (5787*7 grains) of must. Now, after the experiment 

 narrated above, it was necessary to add to the juice 

 which had fermented without air, in order to neu- 

 tralize its acidity, 0*76 grammes (11'7 grains) am- 

 monia, but to that which had fermented in the air, 

 from 5 to 6 grammes (77 to 92 grains), that is six 

 times as much. The acid was acetic acid. That is 

 to say, the freer admission of air caused the formation 

 of acetic acid in the same proportion in which alcohol 

 disappeared from the liquid. 



The action of the oxygen in the air changes the 

 alcohol into acetic acid. 



Though on the large scale the result might be dif- 

 ferent, the experiment teaches sufficiently that but 

 very little air is required for the preparation of wine. 

 These inferences do not, however, render it impossible 

 that under favourable circumstances certain kinds of 

 grapes might produce a better flavoured wine, if dur- 

 ing fermentation a certain portion of air were admitted. 

 This is clear from the method used in the preparation 

 of Bavarian beer, as opposed to that common among 

 us. And it is my conviction that Liebig's opinion 

 ought not to have been so severely attacked as it has 

 been. 



