The results of electrical conductivity measurements in heavily doped RbCl:CoCl₂ crystals with 2500 and 6000 ppm of cobalt are being reported in this paper. The different regions of the conductivity plots for the crystals with the two concentrations of cobalt have been explained and relevant energy parameters determined. The crystals with 6000 ppm of cobalt have been found to contain two types of precipitates one of these being of the same type as that existing in RbCl crystals with 2500 ppm of cobalt while the other being of a different composition.

Further, it has been found that the crystals appear blackened after heating during measurements. The blackening has been attributed to the expulsion of cobalt from the bulk of the crystal which forms an oxide at the surface.

Electrical conductivity studies in NaNO₂ single crystals with inherent impurities and also in crystals with added Mn²⁺ impurities have been reported. The heating conductivity runs of undoped and doped NaNO₂ crystals have been compared. The decrease in conductivity in cooling following a heating run has been attributed to the oxidation during heating leading to the bulk precipitation of impurities in the host. Above 170°C however the intrinsic defects are responsible for conduction. An anomaly is noticed in both the heating and cooling conductivity runs of the sample at about the Curie temperatures and has been found to show thermal hysteresis.