Abstract
Equipotentials have been mapped out around the electrode and the tip of the capillary for the following arrangements: (a) capillary in front of the electrode; (b) capillary behind a finite electrode having an insulated back; (c) capillary through the back of the electrode and having its tip at the front surface. Arrangement (a) can be used for accurate measurements if the distance between the electrode and the capillary tip of radius r is 4r or more, and any appreciable IR drop subtracted. Arrangement (b) is unsatisfactory because the current density varies over the surface of the electrode. With arrangement (c) the current density is increased at the area nearest the capillary, hence the polarization measurement tends to be too high.