302 FERMENTATION OF BEER. 



garded as a combination of a body composed of 

 C8 N2 H2 O8 with 2 equivalents of water, and 

 alloxantin as a combination of 3 atoms of water, 

 with a compound consisting of C8 N2 H2 O7. The 

 conversion of alloxan into alloxantin would in this 

 case result from its eight atoms of oxygen being 

 reduced to seven, while alloxan would be formed 

 out of alloxantin, by its combining with an addi- 

 tional atom of oxygen. 



Now, oxides are known which combine with 

 water, and present the same phenomena as alloxan 

 and alloxantin. But no compounds of hydrogen 

 are known which form hydrates ; and custom, which 

 rejects all dissimilarity until the claim to peculiarity 

 is quite proved, leads us to prefer an opinion, for 

 which there is no further foundation than that of 

 analogy. The woad (Isatis tinctoria) and several 

 species of the Nerium contain a substance similar 

 in many respects to gluten, which is deposited as 

 indigo blue, when an aqueous infusion of the dried 

 leaves is exposed to the action of the air. Now it 

 is very doubtful whether the blue insoluble indigo 

 is an oxide of the colourless soluble indigo, or the 

 latter a combination of hydrogen with the indigo 

 blue. Dumas has found the same elements in both, 

 except that the soluble compound contained 1 equi- 

 valent of hydrogen more than the blue. 



In the same manner the soluble gluten may be 

 considered a compound of hydrogen, which becomes 

 ferment by losing a certain quantity of this ele- 



