1908. | The Alcoholic Ferment of Yeast~jwice. 307 
tions of phosphate the acceleration produced is so transient that no accurate 
measurements of rate can be made. As soon as the amount of phosphate 
added is sufficiently large, it is found that the rate of evolution of carbon 
dioxide suddenly increases from 5 to 10 times, and then rapidly falls 
approximately to its original value. 
As the concentration of phosphate is still further increased, it is first 
observed that the maximum velocity, which is still attained immediately 
on the addition of the phosphate, is maintained for a certain period before 
the fall commences, and then, as the increase in concentration of phosphate 
proceeds, that the maximum is only gradually attained after the addition, the 
period required for this increasing with the concentration of the phosphate. 
Moreover, with these higher concentrations the maximum rate attained is 
less than that reached with lower concentrations, and, further, the rate falls 
off more slowly. The concentration of phosphate which produces the 
highest rate, which may be termed the optimum concentration, varies very 
considerably with different specimens of yeast-juice. 
All these points are illustrated by the accompanying tables and curves. 
Experiment 19.—The following solutions were employed :— 
(1) 25 cc. yeast-juice +15 c.c. sodium bicarbonate solution. 
(2) 25 c.c. yeast-juice +10 c.c. of potassium phosphate solution (0°3 molar) 
+5 ¢.c. sodium bicarbonate solution. 
(3) 25 ce. yeast-juice+15 cc. potassium phosphate solution. All the 
solutions contained 4 grammes of glucose, and the experiment was carried 
out at 25° in the presence of toluene. The solution of bicarbonate added 
contained an amount of this salt equal to that formed by the action of carbon 
dioxide on an equal volume of the solution of potassium phosphate employed. 
| Carbon dioxide evolved in preceding 5 minutes with n | 
Time after | cubic centimetres of 0°3 molar potassium phosphate added. 
addition 
in minutes. | 
m=O... n= 10 c.c¢, n = 15 c.c. 
5 4 °O nT es Cae 
10 3 °2 16 ‘0 9°7 
15 A. 2 20 °2 12:1 | 
20 3°6 22°4 16: 
25 4 °3 17 °4 18 “4 
30 3 °6 66 19 °4 
35 4°3 4. °6 20-4 
40 3 °2 47 16 °7 
45 =a 4°5 12 °7 
50 Ses 4°2 6°0 
55 41 4, °0 
