Effect of pressure on the viscosity of liquid ZnCl2

The effect of pressure on the viscosity of liquid ZnCl2 has been measured in the range 663 less than or equal to T/K less than or equal to 719 and 50 less than or equal to P/atm less than or equal to 1000, using a falling-weight viscometer with a ceramic falling weight with a diameter considerably smaller than that of the fall tube, allowing the measurement of absolute viscosity. This viscometer has an accuracy of ca. +/-5%. The viscosity at 670-720 K was found to drop with pressure, to ca. 600-709 atm, and then to rise at higher pressures. The initial drop in viscosity is interpreted as due to a partial break-up of the network structure of liquid ZnCl2, while the rise in viscosity at higher pressures is probably due to the effect of pressure in suppressing ionic mobility.