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



of phosphate lowers the rate of fermentation. The rates obtained with 

 inannose and glucose in comparative experiments are approximately equal. 



These phenomena are illustrated by the following experiments : — 



Experiment 7. — Two quantities of 25 c.c. of yeast-juice + 5 c.c. of a solution 

 coutaining 1 gramme of the sugar were incubated until a constant rate had 

 been attained, and 5 c.c. of an approximately 03 molar solution of sodium 

 phosphate were then added. 



Experiment 8. — Two quantities of 25 c.c. of a different sample of yeast- 

 juice + 1 gramme of the sugar were incubated as above and 10 c.c. of the same 

 sodium phosphate solution (0 - 3 molar) were added. 



The readings made after the addition of the phosphate are tabulated below, 

 the numbers expressing the volume of carbon dioxide evolved in the 

 five minutes preceding the time given in the first column : — 



Table III. — Fermentation of Glucose and Mannose in presence of Phosphate. 



Time after addition. 



Carbon dioxide evolved 



in preceding 5 minutes. 



Experiment 7. 



Experiment 8. 



G-lucose. 



Mannose. 



G-lucose. 



Mannose. 



5 



4 -4 



6-4 



22-4 



22 -5 



10 



8-2 



6-0 



23 "8 



26 -7 



15 



9-1 



6-8 



22 -2 



22 -1 



20 



9-6 



7-0 



16 -8 



14 -5 



25 



7-9 



6-0 







30 



4-0 



4-8 







35 



1 -5 



2-7 







40 



1 -o 



1 -o 







45 



1 -1 



1 -o 







Experiment 9. Formation of a Hexosephosphate. — Twenty-five cubic 

 centimetres of yeast-juice were incubated until the rate of fermentation 

 became constant at 0*8 c.c. in five minutes. Ten cubic centimetres of a 

 - 3 molar solution of sodium phosphate were then added. The rate rose to 

 7'1 c.c. in five minutes, and incubation was continued until it had again 

 fallen. The liquid was then boiled and filtered, and the amount of free 

 phosphate estimated as Mg2P20 7 . The whole solution was found to yield 

 O0567 gramme of Mg 2 P 2 7 . The phosphate added corresponded to 

 - 3263 gramme Mg 2 P20 7 , and hence the difference between these quantities, 

 0*3263 — - 0567 = - 2696, corresponds to the minimum amount of phosphate 

 rendered non-precipitable by magnesium citrate mixture. 



Experiment 10. Equivalence of extra Carbon Dioxide evolved to the 



