1909.] 



The Alcoholic Ferment of Yeast-juice. 



339 



Phosphate added. — Parallel experiments with glucose, mannose, and fructose 

 were made with yeast-juice from the same preparation, the method being 

 that previously described.* Three quantities of 25 c.c. of yeast-juice + 5 c.c. 

 of a solution containing 1 gramme of the sugar to be examined were incubated 

 with toluene at 25° for one hour, and to each were then added 5 c.c. of 

 a solution of sodium phosphate corresponding to - 1632 gramme of Mg^O? 

 and equivalent to 32"6 c.c. of carbon dioxide at N.T.P. The rates of 

 fermentation were then observed until they had again fallen and attained 

 a steady value, the gases being measured moist at 19°"3 and 760*15 mm. 



Table IV. — Eelation of Carbon Dioxide evolved to Phosphate added for 

 Glucose, Mannose, and Fructose. 





Glucose. 



Mannose. 



Fructose. 





9-6 

 1 -1 

 49-7 

 12 -1 

 37 -6 

 34 -4 



7 



0-96 

 47 -8 

 10 -6 

 37 -2 

 34 -0 



11 3 



1 -08 

 47 -6 

 11 -9 

 35 -7 

 32 -6 



Total evolved in 55 minutes after addition of phosphate... 

 Correction for rate of juice in absence of phosphate 



„ „ at N.T.P 



These numbers agree well with the value calculated from the phosphate 

 added, viz., 32 - 6 c.c. 



Experiment 11. Effect of an Excess of Phosphate. — Two quantities of 

 15 c.c. of yeast-juice + 7 c.c. of a solution of mannose containing 1 gramme 

 of the sugar were treated with 10 and 15 c.c. respectively of a - 6 molar 

 solution of potassium phosphate, K 2 HP0 4 . The following readings were 

 obtained, showing that in presence of 15 c.c. of the phosphate solution the 

 rate is less than in presence of 10 c.c, and that in neither case is a high 

 maximum rate attained : — ■ 



Table V. — Effect of an Excess of Phosphate on the Fermentation of 



Mannose. 



Time after 

 addition in 

 minutes. 



Rate in preceding 5 minutes. 



10 c.c. phosphate. 



15 c.c. phosphate. 



10 



2-2 



2 1 



20 



1 -9 



1 -6 



30 



2 '4 



1 -4 



40 



3 -0 



1 -5 



60 



4-2 



1 7 



* 'Boy. Soc. Proc.,' B, 1906, vol. 77, p. 414. 

 VOL. LXXXI. — B. 2 C 



