124 



platiiiiiiii spiral). Tlie spiral is then pressed down into a liorizonlal 

 position. The tube is now filled np with a solution of cadmium 

 sulphate of arbitrary concentration (the E. M. F. of the cell is in- 

 dependent of the strength of the solution). 



In order to produce the cadmium electrode a current of 1 or 2 

 inilliamp. (i or 2 milligrams Cd per hour) is passed from the amal- 

 gam fo the platinum spiral. At least 18 milligrams must be depo- 

 sited. The cell may then be sealed off. 



4. We specially call attention to the following passage in Hulett's 

 paper: ''The electromotive force of these cells is high when the 

 cadmium is freshly deposited, and the lengtii of time required to 

 reach the normal value seems to depend on the thickness of tiie 

 deposit. iVir free cells and those saturated with Cd(OH), behave like 

 the others and 1 have as yet no explanation of the high E. M. F. 

 of newly constructed cells." Our table I shows this decrease of 

 potential of newly constructed cells. It amounts to about 1 millivolt. 



T A B L E 1. 



Temperature 25°.0. 

 E. M. F. in Volts. 



2 E 



After 1 After 2 ' After 3 After 4 

 day days | days | days 



After 5 j After 7 i After i 

 days I days days 



a. 

 b. 



c. 

 d. 

 e. 



0.05156 I 0.05105 0.05084 0.05078 I 0.05070 0.05065 ; 0.05052 ! 0.05052 

 0.05143 ; 0.05099 0.05082 0.05076 ' 0.05068 0.05067 i 0.05054 0.05056 



0.05154 i 0.05103 , 0.05C84 

 0.05151 I 0.05099 j 0.05082 

 0.05162 I 0.05113 i 0.05090 



0.05076 



0.05070 



0.05076 0.05070 



0.05067 j 0.05056 0.05058 



0.05067 0.05056 



0.05084 I 0.05074 0.05070 0.05058 



0.05056 

 0.05058 



5. These determinations and those to be described below were carried 

 out by the Poggendorff compensation method. The resistances used 

 had been checked by the Physikalisch-Technische Reichsanstalt at 

 Charlottenburg-Berlin. The same was the case with the thermometers 

 used. Our two standardelements (Weston) were put into a thermostat 

 which was kept at 25°. 0. We used as a zero instrument a Desprez- 

 d'Arsonval galvanometer. It was mounted on a vibration free sus- 



