146 - 



Such a substance can give rise to acetaldehyde (Drechsel, 

 loc, cit.); it may be that in presence of formic acid this latter 

 reaction takes place to a more limited extent ; certainly the fact 

 remains that the presence of formates strongly diminishes the 

 amount of acetaldehyde produced in alcoholic fermentation. 



" Our experiments conclusively show that the amount of alde- 

 hyde is markedly diminished by the presence of formates during 

 fermentation, and although Schade's original theory as to the r&le 

 played by formic acid in fermentation may need modification, it 

 should not too lightly be set on one side. " 



A. SLATOR and H. J. SALOMON SAND (University College, Notting- 

 ham). Studies in Fermentation: Part III. The Rdle of Dif- 

 fusion in Fermentation by Yeast Cells. Jour?tal of the 

 Chemical Society. Trans., May 1910. Pp. 922-927. 



A consideration of the influence of various factors on the rate 

 of alcoholic fermentation, shows that under ordinary conditions, 

 diffusion supplies the yeast cells rapidly and efficiently with sugar. 

 The high temperature-coefficient and the constancy of the velocity 

 with different concentrations of the sugar, constitute, practically 

 conclusive evidence on this point. In the present investigation the 

 limiting conditions have been examined under which diffusion alone 

 would no longer be capable of supplying the yeast cells efficiently 

 with sugar, and under which the apparent velocity of the reaction 

 would thus be influenced by convection currents produced either 

 owing to the evolution of gas in the liquid or by external means. 

 From these experiments the conclusion can be drawn that during 

 fermentation diffusion supplies the yeast cells very efficiently with 

 sugar and further, it is unlikely that conditions could be experi- 

 mentally realised under which diffusion becomes a controlling factor 

 of the rate of fermentation. 



