1911.] Decomposition of Organic Compounds. 



2Go 



Varying Amounts of Yeast. 



Fig. 3 gives the results of experiments to determine the effect of using 

 different amounts of yeast. The three cells here given as an example were 

 charged at the same temperature (23*5° 0.) from the same solution of glucose, 

 and to the first was added 5 grm. of yeast, to the second 2 - 5 grm., and to the 

 third 05 grm. With 5 grm. of yeast the voltage rose rapidly to its 

 maximum of 036 in 10 minutes. With 2 - 5 grm. the gradient of the curve 



Fig.3 



io zo 30 40 Time so in eominufesro 80 



Curves showing development of E.M.F. with different amounts of yeast, in a uniform 

 10-per-cent. solution of glucose. I, 5 grm. of yeast ; II, 2"5 grm. ; III, 0"5 grm. 

 Initial temperature 23 - 5° C. 



was much more gradual, reaching 0-3 volt at the end of 2 hours. With the 

 minimum of 05 grm. the curve rose very slowly ; at the end of 80 minutes 

 it only showed 0'04 volt, and did not reach the maximum of 0"3 volt until 

 after a period of 3 hours. A comparison of these curves gives striking 

 evidence of the greater speed of reaction corresponding to the more active 

 fermentation, i.e., the greater number of active yeast-cells present. 



Different Conditions of Temperature. 

 Under different conditions of temperature the results vary in a corre- 

 sponding manner. This is well exemplified by the curves shown in fig. 4. 

 When the yeast is introduced into a 10-per-cent. glucose solution at 25° C. a 

 voltage of 0-3 is attained in 9 minutes, and the maximum, 0-32, in 15 minutes. 

 But at 17° C. a voltage of 0-3 is not reached until after 20 minutes, and the 

 maximum, 0-32, after 25 minutes. At 10° C. the start was very slow, and 

 there was a much more gradual approach to the maximum, 34 minutes being 

 required for the development of 0\3 volt and 45 minutes for the maximum. 



x 2 



