,524 FERMENTATION OF BEER. 



latter a combination of hydrogen with the indigo blue. Dumas 

 has found the same elements in both, except that the soluble 

 compound contained 1 equivalent of hydrogen more than the 

 blue. 



In the same manner the soluble gluten may be considered a 

 compound of hydrogen, w liich becomes ferment by losing a cer- 

 tain quantity of this element when exposed to the action of the 

 oxygen of the air under favorable circumstances. At all events, 

 it is certain that oxygen is the cause of the insoluble condition 

 of gluten ; for yeast is not deposited on keeping wine, or during 

 the fermentation of Bavarian beer, unless oxygen has access to 

 the fluid. 



Now, whatever be the form in which the oxygen unites with 

 the gluten — whether it combines directly with it, or extracts 'a 

 portion of its hydrogen, forming water — the products formed in 

 the interior of the liquid, in consequence of the conversion of 

 the gluten into ferment, will still be the same. Let us suppose 

 that gluten is a compound ^of another substance with hydrogen, 

 then this hydrogen must be removed during the ordinary fermen- 

 tation of must and wort, by combining with oxygen, exactly as 

 in the conversion of alcohol into aldehyde by erenmcausis. 



In both cases the atmosphere is excluded ; the oxygen cannot, 

 then, be derived from the air, neither can it be supplied by the 

 elements of water, for it is impossible to suppose that the oxygen 

 will separate from the hydrogen of water, for the purpose of 

 uniting with the hydrogen of gluten, in order again to form 

 water. The oxygen must, therefore, be obtained from the ele- 

 ments of sugar, a portion of which substance must, in order to 

 the formation of ferment, undergo a different decomposition fr m 

 that which produces alcohol. Hence a certain part of the sugar 

 will not be converted into carbonic a* id and alcohol, but will 

 yield other products containing less oxygen than sugar itself con- 

 tains. These products, as has already been mentioned, are the 

 cause of the great difference in the qualities of fermented iiquids, 

 and particularly in their quantity of alcohol. 



Must and wort do not, therefore, in ordinary fermentation, 

 yield alcohol in proportion to the quantity of sugar which they 

 hbW in solution, a part of the sugar being employed in the coo- 



