1905.] Hie Alcoholic Ferment of Yeast- Juice. 



409 



The results (Table IV) show that in this way an almost inactive residue can 

 be obtained which is rendered active by the addition of the filtrate (Experi- 

 ments 1, 2, 3) or a boiled juice (Experiment 4). 



Table IV. — Filtration of Yeast-juice through the Martin Gelatin Filter. 

 15 c.c. residue + 3 grammes glucose + toluene. 



No. 



Water. 



Filtrate. 



Boiled juice. 



Time. 



Carbon dioxide. 





c.c. 



' c c. 



c.c. 



hours. 



gramme. 



1 



15 











48 



0-000 









15 







48 



035 



2 



15 











60 



0-001 









15 







60 



0-051 



3 



15 











60 



0-008 









15 







60 



0-064 



4 



15 











60 



024 













15 



60 



0-282 



The total fermentations observed even in the presence of the filtrate are 

 very low, this being, at all events in part, due to the fact that in this series 

 of experiments the original juices themselves happened to be of low 

 fermenting power. 



In a second set of experiments (Table V) a smaller quantity of juice was 

 placed in the filter and the filtration was continued until no more liquid 

 would pass through. The residue was then washed several times by adding 

 water and forcing it through the filter. The time occupied in this process 

 varied greatly with different juices, the limits for the filtration and washing 

 of 50 c.c. of juice, using two filters simultaneously, were about 6 to 12 hours. 

 The carbon dioxide was not estimated by absorption in potash as in the 

 previous cases, but was collected and measured over mercury, by means of 

 the apparatus described later on, the object of this procedure being to ascertain 

 not only the total amount of carbon dioxide produced, but the rate and 

 duration of the evolution. The residue was dissolved in water and made to 

 the same volume as the original juice, and the filtrate was evaporated down 

 to the same volume. All the solutions were saturated with carbon dioxide at 

 the temperature of the bath (25°) before the measurements were commenced, 

 and the observations were continued until all fermentation had ceased. 



The boiled juice added in Experiments 1, 3 and 4 (Table V) was obtained, 

 by boiling a portion of the same preparation as was used for the filtration. 

 The carbon dioxide is expressed in cubic centimetres under atmospheric 

 conditions. 



