(98) 
Chemistry. — “The electromotive force of zinc amalgams”. By 
Prof. Ernst Cohen and W. Tombrock. (Communicated by 
Prof. P. van Romburgh). 
(Communicated in the meeting of May 29, 1909). 
1. After it had been found, in the development of the thermo¬ 
dynamics of the normal cells *), that the deviations which the E. M. F. 
of the WESTON-cell exhibits under definite circumstances must be 
attributed to the peculiar behaviour of the cadmium amalgam used 
therein, the researches of H. C. Bijl s ) have elucidated the matter 
so that we are now in a better position to judge. Yet, the latest 
researches of Ernst Cohen and H. R. Kruyt 8 ) have proved that 
the last word has not yet been spoken in this matter and that a 
continuation of the study of the cadmium amalgams in the direction 
indicated will be necessary before we arrive at the construction of 
an accurate temperature formula for that standard 1 2 * 4 ). 
2. An investigation of the zinc amalgams whose electromotive 
force will have to be known accurately if the CLARK-cell is really 
to be used as a standard, was undertaken by one of us some 
years ago s ). This field, however, is nearly' quite barren. The most 
confused ideas still reign, as may be shown by the fact that the 
American Electrochemical Society at the Meeting, May 1907 made 
the following theme a subject of discussion “If an electrode of zinc and 
another of amalgamated zinc be placed in a solution of zinc and 
the electrodes connected externally, a current will flow in the external 
circuit from the zinc plate to the amalgamated one and zinc will 
be deposited in the former. What is the source of energy of this 
battery ? It has been thought to be thermal, and that the liquid 
cools by virtue of this reaction, thereby absorbing heat from the 
air. If so, it would offer a direct means of changing the heat energy 
of the air into an electric current, and would seem to be contrary 
to the second law of thermodynamics.” 
We will again refer in detail to the theory of that phenomenon 
in our paper which will appear shortly in the Zeitschrift fur physi* 
kalische Chem ie. Here it may be pointed out that, first described by 
1 ) Ermst Cohen. Proc. 1900 Vol. Ill, p. 91. 
2 ) Zeitschr. fur physik. Chemie 41, 641 (1902). 
Zeitschr. fur physik. Chemie 65, 359 (1909). 
M Proc. 1900 Vol. Ill, p . 225. 
°) Electr °chemical and Metallurgical Industry, 5, 93 (1907). 
