Abstract
The author considers a fringe effect upon the electric field in the Gerdien condenser. The potential field in the neighborhood of the edge of the electrodes is numerically calculated by the relaxation method to solve the difference equations deduced from a Laplace equation. Solving the equation of motion of an atmospheric ion under the effect of the field, he investigates what portion of ions with arbitrary initial conditions should be removed by the stray flux of the electric lines of force at the entrance of the Gerdien condenser.
The correction for this fringe effect is evaluated for various measurements with actual instruments. It is shown that this effect should be small when using an electric conductivity meter or an ion mobility spectrometer but very large on a total small ion number density meter.
