If I is the current through unit area of the gas and if we neglect any diffusion except that caused by the electric field,

n1ek1X + n2ek2X = I   (2).

From equations (1) and (2) we have

n1e = 1 (I + k2 dX)   (3),
k1 + k2 X dx
n1e = 1 (I - k2 dX)   (4),
k1 + k2 X dx

and from these equations we can, if we know the distribution of electric intensity between the plates, calculate the number of positive and negative ions.

In a steady state the number of positive and negative ions in unit volume at a given place remains constant, hence neglecting the loss by diffusion, we have

d (k1n1X) = q − αn1n2   (5).
dx
- d (k2n2X) = q − αn1n2   (6).
dx

If k1 and k2 are constant, we have from (1), (5) and (6)