Self-diffusion in molten lead and thallous chlorides

The tracer diffusion coefficients of both ions in PbCl₂ and TlCl have been measured using a technique involving diffusion of the tracer out of an open capillary into an inert bath. The results which are in good agreement with previous work, are described by the relations: in PbCl₂ D _Pb = 1.4x10^-3 exp (-7760±320)/RT, (515-588°C), D_Cl = 2.55x10^-3 exp (-7740±410)/RT, (515-580°C), in TlCl D_Tl = 7.3x10^-3 exp (-4540±240)/RT, (452-526°C), D_Cl = 7.9x10^-4 exp (-4560±460)/RT, (472-542°C). Different techniques which have been used for measuring tracer diffusion coefficients in fused salts are assessed and it is concluded that diffusion out of an open capillary into an inert bath is the most reliable method. The results are discussed in the light of theories of transport in ionic melts; the transport properties are largely determined by short-range forces and not by the coulomb potential.