1908 - 9 .] 
167 
Note on a Study of Polarisation. 
Two of the more successful series of observations of the cotemporaneous 
variation of the potential difference between the electrodes and the 
electrolyte directly behind them are shown graphically in fig. 1. They 
are marked (a) and (b) respectively. The graphs were obtained by plotting 
the polarisation against the time for each of the four electrodes — the 
polarisation being the excess of the potential difference between the 
electrode and the electrolyte behind it over the potential difference just 
before starting the polarising current. 
The set of curves marked (a) was the first of the two obtained. It 
showed that the anode curves and cathode curves of the two cells were 
neither coincident nor of exactly the same form, although in the case of 
the cathode curves the difference in form was slight. Differences in 
form were to be expected, because of differences in the temperatures of the 
cells and in the convection currents in the neighbourhood of the electrodes, 
no precautions having been taken in these preliminary experiments to 
exclude such differences. These differences in form must prevent exact 
coincidence ; but there was obviously not even general coincidence, both 
the anode and cathode of the high-resistance cell being throughout more 
highly polarised than those of the low-resistance cell. This might be due 
either to the dependence of the polarisation on the potential difference 
of the electrodes or to differences in the current density at the electrodes 
caused by inequality of their area. If it was due to differences in the 
current density, interchanging the electrodes might be expected to change 
the relative positions of the curves. Accordingly, the anodes and cathodes 
respectively of the two cells were interchanged, and a set of observations 
represented by the curves marked (b) (fig. 1) obtained. As the polarising 
current in the two series of observations (a) and ( b ) would not be exactly 
the same, the two sets of curves might be expected on this account to differ 
slightly in form. It will be seen that this difference is very small in the 
case of the anode curves, while all the four cathode curves are of approxi- 
mately the same form. From the general agreement in form of the anode 
curves of the same cell, it would seem that the form of the curves was 
determined by the structure of the cell rather than by the electrode. 
Notwithstanding the differences in form, it is clearly seen from set (b) that 
after a short time (in which the disturbing influences might be expected 
to be most marked) the anode and cathode of the low-resistance cell 
are more highly polarised than those of the high-resistance cell, and 
approximately by the same amount as, in the case of set (a), the anode and 
cathode of the high-resistance cell were the more highly polarised. 
This shows us that the non-coincidence of the curves for the high- 
