366 Dr. H. J. S. Sand. The Eole of Diffusion during [Nov. 22, 



The Application of Equation 14 to Bredig's Results Shows that they 

 contradict Nernst's Hypothesis. Equation No. 12 is identical in form 

 with No. 1 which Bredig found to represent his experimental results. 

 As the constant K is a measure for reaction velocities under corre- 

 sponding conditions (see Equation 2), we can submit Nernst's hypothesis 

 to the test we have outlined above by a comparison of the theoretical 

 minimum value for K of Equation 14 with the experimental values 

 found by Bredig. 



We employ the results given by him in Table 7 'Zeitschrift f. 

 Physikalische Chemie,' vol. 31, p. 285. The concentration of the 

 platinum was here 31500" 1 g-atom of platinum per litre, which is 

 approximately 3150000" 1 c.c. of platinum per c.c. We thus have 

 to substitute K = 10~ 5 cm 2 /sec, L = 5 x 10- 5 cm, and v = 3150000" 1 into 

 Equation 14, and find 



K = (5xl0 



Whereas the average value of Bredig's experiments in which 

 2QQQ Na 2 HP0 4 was present amounted to only Q^jg =0'037 min." 1 , 



that is about one twenty-fifth of the calculated minimum number, and 

 the average value in a solution containing no electrolyte whatever was 



- = 0*055 min.' 1 , that is about one-sixteenth of the calculated 



value. 



Even in alkaline solution in which the reaction proceeds very much 

 faster, the velocity is smaller than the calculated value, whereas on 

 Nernst's hypothesis it ought, as already explained, to be much greater. 

 We employ the numbers given by Bredig in Table 12, p. 297, for a 



N 



2 NaOH solution, which probably correspond to the very greatest 



velocity measured by him. Here we have v = 300000" 1 g-atom 

 of platinum per litre, that is approximately v = 30000000" 1 c.c. 

 per c.c., the other quantities being the same as above. By Equation 14 

 we thus calculate 



R = 0-0016 sec.- 1 = 0-096 min.- 1 , 



whereas the average value of the constant given by Bredig amounts to 



0-0205 



0-4343 = 0-0472 min. *, that is about half of the calculated minimum 



value. We thus see that Bredig's reactions proceed far too slowly to 

 allow us to reconcile them with Nernst's hypothesis. 



An Equation of the Form of No. 1 expresses the Result if the Velocity 

 of the Reaction Occurring on the Surface of the Particles is Proportional 

 to the Concentration of the Solution in Immediate Contact with them. 

 The fact that the law obeyed by Bredig's reactions differs only in 



