128 DISEASES OF WINE. 



formed into grape sugar, and sugar disappears entirely 

 when carbonic acid ceases to be resolved. Three 

 substances in particular are thus produced lactic 

 acid, mannite, and vegetable mucus, but only a 

 trace of alcohol. The lactic acid, C 6 H 5 O 5 , and the 

 vegetable mucus, C 24 H 19 O 19 , are, together, equal to 

 sugar minus water. The mannite, C 6 H 7 O 6 , has 

 1 equivalent oxygen less than sugar, and this equiva- 

 lent oxygen may have passed over to the albuminous 

 matters of the vegetable juice, which consequently 

 become oxidised. 



According to Desfosses and Pelouze, this alter- 

 ation, which is called mucus fermentation, may be pro- 

 duced at will by boiling beer ferment or gluten with 

 water, dissolving sugar in it, and keeping it in a tem- 

 perature of from 30 (80 F.) to 40 (104 E.). 



Maclagan and Tilley* have analysed the substance 

 which is produced in ginger beer by this disease, and 

 which is identical with that in wine. They found it 

 to contain two equivalents of water more than vege- 

 table mucus, namely 



Eq. Reckoned. 



C. 43-9 43-3 24 43'7 



H. 6-1 6-8 21 6-3 



O. 50-0 49-9 21 50-0 



This substance was insoluble in cold water, but swelled 

 up very much when left in it. 



As those wines which are subject to this disease are 



* Phil. Mag. vol. xviii. p. 12. 



