The specific electrical conductivity Ï of compacted polycrystalline CuCl has been studied at T= 370â 670° K and at 10â 55 kb. The graph of log Ï against 10³/T showed low and high temperature straight lines attributed respectively to predominantly electronic and ionic mechanisms. The activation energy in the low temperature region falls slightly, and in the high temperature region rises, with increase in pressure. Doping with CdCl2 up to 1 mole % had little effect on conductivity, but doping with CuCl2 up to 2 mole % greatly increased conductivity and removed the â kneeâ in the (log Ï , 10³/T) plots at high pressures. Phase transitions have been studied, and the thermoelectric power with respect to Pt has been measured over a range of pressure and temperature.