PoLARIZATION OF CapMIUM CELLS. 
By BR: BR. RAMSEY: 
While working on another problem (Phys. Rev. Vol. 16, p. 105) it 
was noted that the E. M. F. of a cadmium cell was greatly decreased and 
at times apparently reversed after a considerable quantity of electricity 
had passed through it. 
To investigate the cause of this phenomenon the experiments de- 
seribed below were undertaken. Work of a similar nature has been car- 
ried out by F. E. Smith (Phil. Trans. Roy. Soc. Lon., Series A, Vol. 207, 
p. 393); by S. J. Barnett (Phys. Rev. Vol. 18, p. 104, 1904), and by P. I. 
Wold (Phys. Rey., Vol. 27, p. 182, 1909). However, in their experiments 
the time of polarization was comparatively small, the attention of the 
investigators being directed to the initial polarization or to the rate of 
recovery. In my work I have attempted to find the cause of this polariza- 
tion. 
Cells were constructed of the H type and according to the accepted 
formula for cadmium cells. The chemicals used were C. P. chemicals of 
commerce. With ordinary care a cell could be obtained whose HE. M. F. 
did not differ more than .001 volt from the standard value. Measurements 
of EK. M. F. were made by means of a potentiometer. At times where 
rapid measurements were desirable and great accuracy was not necessary 
a voltmeter was used, the readings being corrected for the internal re- 
sistance of the cell. Current was measured with a milliameter and time 
was measured with a watch. At first it was thought that the polarization 
was a surface effect, that a relation existed between the area of the sur- 
face of the electrode and the quantity of electricity required to polarize 
a cell to some standard amount. Cells were made with electrodes of vari- 
ous diameters. The current was noted at stated intervals, so that the 
total quantity could be caluclated. This was found to differ in different 
cells, but it appeared to depend more upon the past history of the cell 
than upon the electrode surface exposed. 
It was found that after a cell has been polarized once and has re- 
gained its normal E. M. F. again it required less quantity of electricity 
to polarize it than it did during the first run. A cell with three legs was 
