Haceett and Feui.y — The Polarisation of a Leclanche Cell. 287 



We shall consider here those by S. J. Barnett, who has given the polari- 

 sation as a percentage of the initial value of the E.M.F. of the cell. The 

 E.M.F. was measured by a modification of the sum and difference method, 

 using a second cadmium cell with a heavily damped galvanometer whose 

 deflections became steady 6 seconds after closing the circuit. As will be seen 

 in fig. 4, the inverse of the polarisation percentage bears a linear relation to the 



0-05 



H 



0-10 



0-15*— <& 





I 2 3 4 5 6 



Time (minutes). 



Fig. 4. 



time. The graphs indicated by I refer to a cell not previously used, except 

 for potentiometer measurements, which had a resistance of 351 ohms. The 

 graph shows its recovery from a short circuit for 15 minutes. The graphs 

 indicated by II refer to a cell which had a resistance of 401 ohms. This cell 

 had already been used for polarisation experiments a month previously. It 

 was on short circuit for 3 minutes. After allowing 23 minutes for recovery 



SOLENT. PBOO. R.D.S., VOL. XV., NO. XXVI. 8 A 



