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

Abstract

Electric conductivities of the PbCl₂-ZnCl₂ binary melts have been measured by the use of a U-shaped cell having a relatively high cell constant. Viscosities of these melts have also been determined by using the oscillating vessel method for the low viscosity melts and the falling body method for the higher viscosity melts.
Changes in the liquid structure or the constituent ionic species have been estimated on the basis of the results obtained. The results are summarized as follows:
(1) Molten ZnCl₂ exhibits much lower electric conductivity and very high viscosity as compared with other chlorides. This seems to indicate the associating property as previously suggested by others workers.
(2) Electric conductance does not obey the Rasch-Heinrichsen equation, κ=A_κexp(−E_κ⁄RT), at any composition due mainly to the thermal decomposition of large structure units.
(3) Specific conductivity increases and viscosity markedly decreases as the content of PbCl₂ mcreases.
(4) Apparent activation energies for electric conductance and viscous flow drastically decrease by the addition of PbCl₂ to ZnCl₂ but they become nearly constant values which are similar to the values for pure PbCl₂ in the range of 50∼100 mol% PbCl₂.
(5) It is estimated from the results that the associating property of ZnCl₂ is weakened by the addition of PbCl₂ which is considered as a salt with a relatively high ionic dissociation tendency and also that single ions become predominant ionic species in the PbCl₂ rich side.