ENERGY CHANGES INVOLVED IN DILUTION OF AMALGAMS. 



electromotive force. When the proportion of zinc was reduced to four- 

 tenths of i per cent the electromotive force sank to nine-tenths of its orig- 

 inal value. It is interesting to note that he considered the phenomena 

 observed by Gaugain as quite analogous to the decrease of electromotive 

 force in a cell, due to polarization. 



In 1879 Hockin and Taylor * made extended observations on the electrical 

 behavior of solid and liquid amalgams. Unfortunately their original paper 

 is inaccessible. Their work, however, does not seem to have extended appre- 

 ciably the theoretical knowledge of these concentration effects. 



Three years later Helmholtz 6 published his masterly paper on the " Gal- 

 vanic current caused by differences in concentration." The relation between 

 the vapor tensions over two different aqueous solutions of a given electrolyte 

 was made the basis for the calculation of the electromotive force between 

 them. It was also pointed out that the latter should vary as the absolute 

 temperature. Measurements on cells of copper sulphate and of zinc sul- 

 phate were in good agreement with the predicted values. 



Elements consisting of concentrated amalgam as one electrode, and dilute 

 amalgam as the other, with an interposed solution of metallic salt, although 

 analogous to aqueous concentration cells, appear to have been altogether 

 disregarded up to this time, and, in fact, for eight years after it. Gaugain, 

 Becquerel, and the others had all aimed to improve the galvanic cell as a 

 practical source of electricity. So when they attempted to explain the 

 peculiar behavior of amalgams they always considered these separately in 

 their relation to copper, platinum, zinc, or pure mercury, and never in 

 relation to each other. Naturally little progress could be made by such 

 considerations. 



In 1888 Lindeck determined the potential of various amalgams of zinc, 

 cadmium, lead, tin, and silver against amalgamated zinc in zinc sulphate solu' 

 tion. His measurements on zinc and silver amalgams are the most im- 

 portant. A part of them are given below. 



(2) Silver amalgams . 



Journ. Soc. Tal., 8, 282 (1879). " The Voltaic Cell," by Park Benjamin, pp. 148-151. 

 'Abstract, Chem. Cent. Blatt, [3] 13, 648 (1882). 



