FERMENTATION 567 



red cloud of vapour due to the presence of nitrogen dioxide is observed 

 to hang over the massecuites ; this is ascribed to decomposition of the 

 potassium nitrate present under the influence of bacteria, but really very 

 little is known on the subject. The writer is unaware of any similar phe- 

 nomenon being observed in cane sugar factories. 



Foaming Fermentation of Massecuites. Low grade massecuites and 

 molasses frequently exhibit the phenomenon of suddenly producing large 

 volumes of gases giving rise to foaming and frothing. In the cane sugar 

 industry the matter was first studied by Geerligs 16 who believed the cause 

 was the spontaneous decomposition of the glucinates or bodies formed by 

 the action of lime on reducing sugars. A similar condition happens not 

 infrequently in the beet houses, where reducing sugars are mostly absent, 

 and Lafar 17 believes the cause in this case is that due to yeasts acting on 

 the amides present. He also accepts the possibility of purely chemical 

 causes such as the interaction of amides, water and reducing sugars. That 

 organic action is possible in so high a concentration follows from the isolation 

 by Ashby 18 (Jamaica) of a yeast active in molasses of 80 Brix, and also by 

 von Richten 19 of a conjugating yeast from honey. Two types of bacteria 

 have also been obtained by Gillet 20 from foaming beet massecuites, one of 

 which was thermophilous and active at 70 C. A third cause is proposed 

 by Kraisy 21 , who suggests that dissolved carbon dioxide is responsible, 

 and that the gas is released only when the supersaturation of the mother 

 liquor disappears. Possibly .all three causes contribute, since they are not 

 incompatible as between each other. 



Molasses as a Source of Alcohol. Fermentation proceeds according to 

 the equation : 



C 6 H 12 6 = 2 C 2 H 5 OH + 2C0 2 



Glucose Alcohol Carbon dioxide. 



Following on this equation lib. of glucose or o 95lb. of cane sugar should pro- 

 duce o-5iilb. of alcohol and 0-489!^ carbon dioxide. This yield is never 

 obtained in practice even when the distillation losses are disregarded. Peck 

 and Deerr 3 fermented in pure culture a number of molasses with tropical 

 yeasts, and found that on an average 90 per cent, of the fermentable sugars 

 were recovered in alcohol, the amount as indicated from the above equation 

 being put equal to 100. In addition, in Hawaiian molasses they found 

 from 4-05 per cent, to 7*32 per cent, of the sugars were unferrnentable. 

 Previously Pellet and Meunier 22 had observed in Egyptian molasses 2-40 

 per cent, of " glutose," and Deerr 23 had found up to 3 per cent, in Demerara 

 molasses. The total amount of sugars in cane molasses varies from 45 per 

 cent, to 65 per cent., so that it is impossible in the absence of an analysis 

 to state what quantity of alcohol can be obtained from a molasses. 



In the very best practice employing pure specially selected yeasts as much 

 as 90 per cent, of the theoretical yield may be obtained, falling to 70 per cent, 

 with the indifferent methods usually found. Referred to volume measure- 

 ments and to a molasses containing 55 per cent, of sugars, superior, good and 

 indifferent operation is represented by 2, 2-5, and 3 gallons of molasses per 

 gallon of 95 per cent, alcohol. 



Manufacture of Rum. The manufacture of rum as a product of the 

 fermentation of cane juice or of molasses forms an important part of the 

 cane sugar industry in Demerara, Trinidad, Jamaica, Cuba, the Leeward 



