On the Autofermentation of Yeast. 449 



were 10-6, 8-4, 6-6, 4-9, 4'8, 4"8 c.c, as against 4-9, 4-2, 3'3, 2"9, 2"8, 27 c.c. 

 when the same weight of yeast was immersed in water. In the former case 

 fermentation practically came to an end after six hours, at which time 

 60 c.c. of gas had been collected as against 31 c.c. from the water control 

 (Table I). In the latter case evolution of gas continued steadily until, after 

 about 60 hours, the volume of gas was identical with that from the sodium 

 chloride experiment. 



Table I. — Effect of Sodium Chloride upon the Autofermentation of Yeast. 





Cubic centimetres of carbon dioxide evolved by 



Time, 



3 grin, of yeast and 20 c.c. of solution. 



















Sodium chloride, molar. 



Water control. 



1 



25 -6 



12 



4 



2 

 3 



40-1 

 49 6 



20 

 24 



8 

 6 



4 



55 7 



27 



4 





58 -8 



29 



4 



6 



59 -7 



31 



2 



24 



65 -0 



49 



5 



48 



67 -0 



61 



5 



64 



67 -5 



67 



5 



This experiment shows that, under the influence of molar sodium chloride, 

 the whole of the fermentable material was decomposed in one-tenth of the 

 time required by the water control. 



Experiments were next made in order to determine the optimum 

 concentration of this substance, which would give a maximum rate of 

 autofermentation at the temperature employed. 



Table II. — Effect of Varying Concentrations of Sodium Chloride. 



No. 



Cubic centimetres of carbon dioxide evolved during the first hour from 4 grm. of yeast 

 + 10 c.c. solution 



Water. 



NaCl. 

 0-5 M. 



NaCl. 

 0-6 M. 



NaCl. 

 0-7 M. 



NaCl. 

 0-8 M. 



NaCl. 

 0-9 M. 



NaCl. 

 1-0 M. 



NaCl. 

 1-1 M. 



NaCl. 

 1-2 M. 



NaCl. 

 1 -5 M. 



NaCl. 

 1 -7 M. 



NaCl. 

 2 M. 



42 

 47 

 48 



48 a. 



21-7 

 7-5 



19-5 



37 -4 



41-7 

 49-0 

 24 -5 



43 -1 

 50 -6 



44 -1 

 50-1 

 24 -7 



82 -0 

 42 -9 

 44 -7 

 27 -2 



44-2 

 23 "6 



68-5 

 41 -9 



57 7 

 22 -2 



42 -5 



42 -5 

 12-3 



These results indicate that the optimum concentration varies slightly for 

 different samples of yeast, but that it approximates to molar ; moreover, very 



