123 



Solution of cadiiiiiim siilpliatc (M-ainaIi>;am 



Cd 



of arbitrary concentration ri.ö'Vo ofCd by weigiit 



The electromotive force of this combination is 0.0505 Volt at 

 25°. 0. The reproducibility is about 0.5 millivolt. The cadmium elec- 

 trode of this cell has to be electrolytically deposited, as Th. W. 

 Richards and Lewis ^) have proved, that only this kind of electrodes 

 give a definite potential. Ernst Cohen and Sinnige'), who used these 

 cells in their piez,ochemical investigations also found that they arc 

 reproduceable. 



3. Some points in the constrnclion of such cells which play an 

 important role in the experiments, to be described below, may be 

 given here. (Fig. 1 A). 



"A^- 



+ 



Fio-. 1. 



The glass part is a thin walled tube about 8—10 mm. in dia- 

 meter, closed at one end and pro\ ided with a platinum wire; two 

 or three centimeters above the closed end is a platinum spiral, with 

 ils end fused through the side of the tube (the wires are thoroughly 

 cleaned with aqua regia before tilling the cell). 



In filling, the spiral is pressed to one side and some 0.5 cc. of 

 12.5 percent cadmium amalgam is brought into the lower part and 

 jnelted (carefully avoid bringing the amalgam in contact with the 



1) Zeitsclir. f. physik. Chemie 28, 1 (18!)9). 



2) Zeitschr. f. physik. Chemie 67, 1 (1909). 



