Studies on Aging of Precipitates and Coprecipitation XXXIX. Low Temperature Conductivity of Silver Bromide

The following expression is proposed for the electrical conductivity of silver bromide $${\mathrm{\chi =(Ae}}^{\text{−W/2kT}}{\mathrm{+KS)e}}^{\mathrm{-U/kT}},$$ in which S is the magnitude of the active surface. When ${\mathrm{Ae}}^{\text{−W/2kT}}\mathrm{\gg KS}$ the high temperature kind of conductivity predominates. In the opposite case the low temperature kind of conductance predominates. Conductivity‐temperature curves of fresh (large S) and well‐aged (small s) silver bromide have been determined. In agreement with theoretical expectations it is found that $${\text{χ=3.0×10}}^5{e}^{\text{−18,000/RT}}{\mathrm{+A}}_i{e}^{\text{−8300/RT}}$$ in which A_i varies in proportion to the active surface of the product. A pellet prepared from freshly precipitated silver bromide was found to have about 500 times as large a conductance as a pellet prepared from the fused product. At a given temperature the following relation exists between χ and the pressure p applied to the pellet: $d\ln \mathrm{\chi /dp=-k}$ . The value of k increases with decreasing active surface and with increasing temperature. The temperature effect is accounted for by the contribution of the active surface.