RICHARDS AND LEWIS. — ZINC AND CADMIUM AMALGAMS. 



93 



In the table, Cj and Cg represent the percentage by weight of cadmium 

 in the amalgam, which in the case of dilute amalgams is proportional 

 to the concentration by volume ; t is the Centigrade temperature. The 

 columns under E give the observed electromotive forces and those calcu- 

 late,d from equation (2). 



It was noticed by Meyer that the electromotive force of a cell of this 

 kind increases rapidly upon standing. A similar eflfect was noticed by 

 Jaeger* with solid cadmium amalgams. Although no explanation can 

 be given of this phenomenon, one may prevent it by using as electrolyte 

 a solution which has remained standing in contact with cadmium amal- 

 gam for several weeks before being used. The constancy thus reached 

 permits much greater accuracy than could otherwise be obtained. 



A study of the data of Table I. shows that the behavior of the last cell 

 containing nine per cent amalgam differs materially from the rest. Re- 

 garding the electromotive forces of the other cells, it is to be noticed that, 

 (1 ) at the same temperature they are all equal within limits of .0003 volt, 

 therefore the potential depends on the ratio of c^ to Cj, and not on their 

 absolute values; (2) they are proportional to the absolute temperature ; 

 (3) they are uniformly higher than the values calculated from the 

 formula, ranging from one percent to three per cent too high. In the first 

 two respects the amalgams obey rigidly the laws of dilute solutions. The 

 small apparent deviation from these laws, indicated by the difference 

 between the observed and calculated values, is therefore probably not a 

 real deviation, but the effect of some slight side reaction in the cell. 



The wide departure in the case of the last cell, on the other hand, 

 shows that in amalgams of concentration as great as nine per cent there 

 is a considerable deviation from the laws of dilute solution. 



Theoretically, the nature of the anion of the electrolyte or the con- 

 centration of the kation should be without effect upon the rcfult. This 



TABLE n. Varying Electrolytes. 



* Wied. Ann., LXV. 106, 1898. 



