B40 



STUDIES ON FERMENTATION. 



excess of air, and also that they always take into solution a little 

 less air than saturated pure water contains under the same con- 

 ditions of temperature and pressure. At a temperature of 25° C. 

 (77° F.) therefore, if we adopt the coefficient of the solubility of 

 oxygen in water given in Bunsen's tables, we find that 1 litre 

 (If pints) of water saturated with air contains 5"5 c.c. (0'3 cubic 

 inch) of oxygen. The three litres of yeast-water in the flask, 

 supposing it to have been saturated, contained less than 16.5 c.c. 

 (1 cubic inch) of oxygen, or, in weight, less than 23 milli- 

 grammes (0"35 grains). This was the maximum amount of 

 oxygen, supposing the greatest possible quantity to have been 

 absorbed, that was required by the yeast formed in the fermenta- 

 tion of 150 grammes (4"8 Troy ounces) of sugar. We shall 

 better understand the significance of this result later on. Let us 

 repeat the foregoing experiment, but under altered conditions. 

 Let us fill, as before, our flask with sweetened yeast- water, but 

 let this be first boiled, so as to expel all the air it contains. To 

 efiect this we arrange our apparatus as represented in the 

 accompanying sketch (Fig. 60). "We place our flask. A, on a 



Fig. 60. 



