1911.] 



The Permeability of the Yeast-Cell. 



305 



and to 1/10 of the total amount in the liquid, have been transferred from the 

 liquid to the yeast. The influence of this solution upon the fermentation of 

 yeast was studied according to the method described in a preliminary 

 communication by Harden and Paine (15), and, although the initial rate of 

 auto-fermentation was increased, the total volume of gas yielded was not 

 greater than that given by a water control, and, moreover, the rate of auto- 

 fermentation produced was exactly comparable to the rate under the influence 

 of sodium phosphate of the same normality. It would seem from this that, 

 although this substance is capable of entering the yeast-cell, it is not able to 

 penetrate through to the sphere of activity of the hydrolysing enzyme. 



Soclmm Arsenate. 



Sodium arsenate was specially interesting, since Harden and Young (16) 

 have found that solutions of arsenates have an enhancing influence on the 

 rate of fermentation of sugar by yeast-juice. 



The following table gives results of three experiments. The estimations 

 were made by digesting the yeast and liquid with nitric and sulphuric 

 •acids, and, after dispelling the nitric acid, reducing the arsenic acid with 

 hydriodic acid. The liberated iodine was removed by titration with thio- 

 sulphate and the arsenious acid precipitated with sulphuretted hydrogen, 

 collected on a tared filter, washed successively with water, alcohol and 

 carbon bisulphide, dried at 100° and weighed. The results are expressed 

 in terms of anhydrous sodium arsenate. 



Table XII. — Diffusion of Sodium Arsenate. 



No. 



Conditions. 





Yeast. 



Liquid. 



P. 



Pi- 



K. 





Initial. 



Final. 



Initial. 



Final. 



164 



Concentration, 2 - 02 

 per cent. = "11 

 molar. Stood 20 

 hrs. in cold room 



Total ... 

 Arsenate 



100-00 

 nil 



102 -40 

 0-15 



100 -oo 



2-02 



97 -60 

 1 -86 



0-22 



1-95 



0-11 



165 





Total ... 

 Arsenate 



100 -00 



nil 



97 '90 

 0-26 



100 -oo 



2 '02 



102 -10 

 2-10 



0-39 



2-12 



0-18 



166 



Concentration, 3 - 35 

 per cent. = - 18 

 molar 



Total ... 

 Arsenate 



100 -00 

 nil 



88 -20 

 0-28 



100 -oo 

 3-35 



111 -80 

 3-27 



0-49 



3 -03 



0-16 



These results are essentially similar to those obtained with sodium chloride 

 and ammonium sulphate, the factor K shows a fair degree of uniformity and 

 indicates definite but very imperfect diffusion of the substance. 



