Some elementary solutions of the wave equation are obtained for electromagnetic waves in an ionized gas. The solutions demonstrate the importance of conductivity in controlling absorption. Improper computation of conductivity by conventional theory may lead to order of magnitude errors in estimating absorption. The theory of A.C. conductivity for a weakly ionized gas is reviewed. It is shown when and how the exact theory may be employed in conventional form and without error. The expression for the conductivity of a weakly ionized mixture of gases is formulated and analyzed in the low, intermediate and high pressure regions. The conductivity of the mixture is shown to be reducible to the sum of conductivities of gases of constant cross section but complex wave frequencies. Appropriate tables for the evaluation of these latter conductivities are being constructed. (Author).