Effect of pressure on the conductivity of calcium nitrate tetrahydrate

Abstract

The conductivity of liquid Ca(NO₃)₂·4.17H₂O has been measured as a function of pressure and temperature over the range 250–1000 atm and 21.6–84°C. The data points were fitted to the empirical VTF equation. It was found that T₀, the theoretical glass-transition temperature, rises with pressure, and also that the ‘constants’ A and B in the VTF equation change with pressure. It has previously been suggested that A and B might be pressure dependent, but such changes have not previously been observed. The change in A is attributed to the formation of ion pairs under pressure, while the change in B is less easy to interpret, but may also be due to ion pair formation.