342 Messrs. A. Harden and W. J. Young. [June 10, 



of varying volumes of a - 6 molar solution of potassium phosphate, K2HPO4, 

 to yeast-juice and fructose. In all comparable experiments the total 

 volumes were kept equal by the addition of a solution of potassium 

 bicarbonate as previously explained for glucose ;* in each case 2 grammes of 

 fructose were employed. The maximum obtained and the optimum 

 concentration are printed in thick type : — 



Table VIII. — Maximum Eates of Fermentation and Optimum Concen- 

 trations of Phosphate for Fructose. 



No. of 

 experiment. 



Volume of 

 yeast-juice. 



Total volume. 



Cubic centimetres of 

 "6 molar solution 

 of E 2 HP0 4 added. 



Maximum rate 

 per 5 minutes. 





c.c. 



c.c. 





c.c. 



19a 



5 



25 







0-5 



b 



5 



25 



5 



14 2 



c 



5 



25 



10 



5-5 



d 



5 



25 



15 



1 -8 



20a 



15 



40 



3 



22 -5 



b 



15 



40 



7 5 



25 4 



c 



15 



40 



10 



20 -7 



d 



15 



40 



15 



11 -3 



e 



15 



40 



20 



7-4 



21a 



10 



35 



3 



31 -5 



b 



10 



35 



5 



32 2 



c 



10 



35 



7-5 



28 -5 



d 



10 



35 



10 



20-2 



e 



10 



35 



15 



9-2 



f 



10 



35 



20 



5 7 



It thus appears that, precisely as in the case of glucose, progressive increase 

 in the concentration of phosphate beyond the optimum produces a corre- 

 sponding decrease in the rate of fermentation, and at a high concentration 

 the rate becomes extremely slow. 



(e) Comparison of the optimum concentrations of phosphate and of the 

 maximum rates produced at those concentrations for fructose and glucose. 



The following results, which all refer to 10 c.c. of yeast-juice, clearly 

 show that the optimum concentration of phosphate for the fermentation of 

 fructose is from To to 10 times that for glucose, and that the maximum rate 

 of fermentation for fructose is two to six times that of glucose. 



* 'Hoy. Soc. Proc.,' B, 1908, vol. 80, p. 307. 



