Abstract
The equation of mass transport of a weakly ionized gas in a uniform electric field is solved giving initial corrections to the diffusion equation. The corrections arise because account is taken of the effect on the ion velocity distribution of both small density gradients and non-steady state. The Green's function in unbounded space of the resulting equation is found for two situations, one in the limit of vanishing electric fields and the other for finite fields. Generally initial deviations from the diffusion equation result in a skewed density distribution. The analysis is applied to the interpretation of drift velocities in drift tube experiments.