1184 



Cohb:n concluded that an actual transformation of Cda into Cd,3 

 occurs in the neighbourhood of 60°," mentioned above, Getman 

 writes: "The author's data for cells .4-1 and B-\ appear to confirm 

 this conclusion, but when the e. m. f. of these cells was determined 

 at close intervals of temperature from 0° to 70° no evidence of a 

 transition temperature in the vicinity of 60° was obtained. On the 

 other hand, distinct discontinuities in the e. m. f.-temperature 

 curves were obtained at 39" with .1-1 and at 36". 8 with B — 1. 

 Since the agreement between Cohkn's cells and the author's at 25° 

 and 64°. 5 is satisfactory, it is highly [)robable that equally close 

 agreement would have been obtained at other temperatures and that 

 had CoHKN measured his cells over a wider range of temperatures 

 and plotted the values of e. m. f against the temperatures he would 

 have obtained no evidence of a transition point at 60^." 



There is a mistake in this conclusion, as we shall now demonstrate. 



C/OHKN and HKi,i)Kini.\N's experiments as well as those of Getman, 

 which have been described in § 10, have been carried out on the 

 assumption (the correctness of which has been proven by the 

 measurements) that Cd^ may be heated above its transition temperature 

 without transformation into Cd^3, nay, what is more, it woidd have 

 been impossible to carry out the measurements ,if there had not 

 taken place a strongly marked retardation. Consequently it is obvious 

 that Gktman could not tind a transition point using his B-i cell 

 (which contained Cd„) in the nuinner he described. 



On the other hand also, his A-1 cell which contained Cd^ at 

 all temperatures between 0° and 70°, coidd not show a discontinuity 

 at 60°. 



Moreover, we see from our diagram (Fig. 2) that the discontinuity of 

 the e. m. f of cell B-\ which contained Cd« must occur at a lower 

 temperature than that of cell A-1 where Cdj is present. As a 

 matter of fact Getman got this result. With the B-1 cell this 

 temperature is 36°. 8, with the .1-1 cell it was found to be 39°. ') 

 The discontinuity itself has nothing to do with the transformation 

 of Cda into Cd^ but again is to be ascribed to the change of the 

 heterogeneous phase of the amalgam into the homogeneous liquid one. 



13. Finally I want to point out a mistake which has been made 



1) That these temperalures have not been iound to be 37°.49 and 40^ 7 respectively, 

 may probably be ascribed to the fact, that only one single cell has been used in 

 this case for the determination. On the other hand a small difference in the 

 composition of the positive poles of the cells may have been the reason of this 

 deviation. 



