Electric Conductivity and Viscosity of the Molten PbCl₂–ZnCl₂ Binary System

Abstract

Electric conductivities of PbCl₂–ZnCl₂ binary melts have been measured by using a cell specially designed to have a large cell constant. Viscosity coefficients have also been determined by the oscillating vessel method for the PbCl₂-rich melts and the falling body method for the high viscosity melts. Variation of the ionic species present in the melt with composition has been estimated on the basis of the data obtained. The results are summarized as follows:
(1) Molten ZnCl₂ exhibits very low specific conductivity and high viscosity as compared with other chlorides. This may be attributed to the associating property of ZnCl₂ as previously suggested by others.
(2) Apparent activation energy for specific conductivity decreases with rising temperature, which is particularly conspicuous in the ZnCl₂-rich side of the system, due probably to the thermal dissociation of complex species.
(3) Specific conductivity increases and viscosity coefficient markedly decreases when PbCl₂ is added to ZnCl₂.
(4) Apparent activation energies for both transport properties are decreased by the addition of PbCl₂ to ZnCl₂, but they become nearly constant and show the values similar to those of pure PbCl₂ at the compositions of more than 50 mol% PbCl₂.
(5) It is estimated that the associating property of ZnCl₂ is weakened by the addition of PbCl₂ having a comparatively strong ionic character in the ZnCl₂-rich side and also that single ions become predominant species in the PbCl₂-rich side of the system.