───────┬─────────┬──────────────────────┬────────────────────── Sugar │ Total │ Optimum Volume of │ Maximum Rate in Cubic in │ Volume. │ 0·6 Molar Phosphate │ Centimetres of CO{2} Grams.│ │ in c.c. │ per Five Minutes │ │ Glucose. │ Fructose. │ Glucose. │ Fructose. ───────┼─────────┼──────────┼───────────┼──────────┼─────────── 2 │ 35 │ 2 │ 5 │ 7·5 │ 32·2 4 50 1 10 5·4 28·4 1·6 23 2 5 8 17 1 25 1·75 5 5·2 25·9 2 25 5 7·5 16·2 31·2 2 20 2 3·5 7·9 22·6 2 22·5 0·75 2 3·4 22·2 ─────────────────────────────────────────────────────────────── [p074] It is interesting to note that the two high rates, 32·2 and 31·2 c.c. per five minutes, are equal to about half the rate obtainable with an amount of living yeast corresponding to 10 c.c. of yeast-juice, assuming that about 16 to 20 grams of yeast are required to yield this volume of juice, and that this amount of yeast would give about 56 to 70 c.c. of carbon dioxide per five minutes at 25°, which has been found experimentally to be about the rate obtainable with the top yeast employed for these experiments. III. EFFECT OF THE ADDITION OF FRUCTOSE ON THE FERMENTATION OF GLUCOSE OR MANNOSE IN PRESENCE OF A LARGE EXCESS OF PHOSPHATE. When the maximum rate of fermentation of glucose or mannose by yeast-juice in presence of phosphate is greatly lowered by the addition of a large excess of phosphate, the addition of a relatively small amount of fructose (as little as 2·5 per cent. of the weight of the glucose) causes rapid fermentation to occur. This induced activity is not due solely to the selective fermentation of the added fructose, since the amount of gas evolved may be greatly in excess of that obtainable from the quantity added. Another way of expressing the same thing is to say that the optimum concentration of phosphate (p. 71) is greatly raised when 2·5 per cent. of fructose is added to glucose, and that consequently the rate of fermentation rises. The effect is extremely striking, since a mixture of glucose and yeast-juice fermenting in the presence of a large excess of phosphate at the rate of less than 1 c.c. of carbon dioxide in five minutes may be made to ferment at six to eight times this rate by the addition of only 0·05 gram of fructose (2·5 per cent. of the glucose present), and to continue until the total gas evolved is at least five to six times as great as that obtainable from the added fructose, the concentration of the phosphate being the whole time at such a height as would limit the fermentation of glucose alone to its original value.