1909.] 



The Alcoholic Ferment of Yeast-juice. 



345 



the total fermentation of l - 3 grammes of sugar, it is obvious that the 

 addition of the fructose must have induced the fermentation of the glucose. 



Experiment 30. — Similar results were obtained in another way by 

 employing so large an excess of phosphate that the fermentation observed 

 did not reduce the concentration of phosphate to the limit at which the rapid 

 fermentation of glucose in the absence of added fructose became possible. 



Four quantities of 15 c.c. of yeast-juice +5 c.c. of a solution containing 

 2 grammes of glucose were employed — 



1. 5 c.c. of - 6 molar potassium phosphate solution were added. 



2. 7/5 c.c. of phosphate solution were added. 



3. 15 c.c. of phosphate solution were added. 



4. 15 c.c. of phosphate solution and 0'5 c.c. of a solution containing 

 0"05 gramme of fructose were added. 



The following observations were then made : — 



Time. 



Rate for 5 minutes. 



• 





















1. 



2. 



3. 



4 





5 minutes 



,2 



■o 



1 



■9 



0-8 



4 



■2 



10 „ . 



2 



•6 



1 



•6 



1-1 



4 



•o 



15 „ 



3 



•7 



2 



•2 



0-6 



6 



•6 



20 



3 



■7 



2 



•1 



0-8 



8 



•9 



25 



5 



•2 



2 



•6 



0-7 



11 



■6 



30 „ 



6 



•4 



2 



•9 



0-6 



14 



•2 



• 35 „ 



9 



•6 



3 



•5 



0-7 



14 



•8 



Total evolved 



33 



•2 



16 -8 



5-3 



64 



■3 



In this case the amount of gas evolved in No. 4 is equivalent only to 

 4 - 8 c.c. of the phosphate solution, and the final concentration is therefore 

 10*2 c.c. of phosphate in 35 c.c. The concentration of phosphate, therefore, 

 never falls as low as that present in No. 2 (7'5 in 27'5 or 9'5 in 35), and yet 

 the fermentation is much more rapid than in this flask, which itself contains 

 a concentration of phosphate greatly in excess of the optimum, as shown by 

 a comparison with No. 1. The amount of carbon dioxide yielded by the 

 complete fermentation of - 05 gramme of fructose is only 13'5 c.c, so that 

 there can be no doubt that most of the gas evolved was derived from the 

 glucose. 



(Note. — Experiments 1, 2, and 4 are not strictly comparable, since the 

 contents of the flasks were not made up to the same volume, but the 

 difference in rate due to this is negligible.) 



