Dielectric Measurements at High Pressures and Low Temperatures. II. The Dielectric Constant of Acetonitrile

The dielectric constant of acetonitrile is studied at temperatures between −60°C and +30°C up to pressures of 3 kbar. The electrode set developed is described. The dielectric constant of liquid acetonitrile together with recently determined PVT ‐ data allow the calculation of the Kirkwood correlation factor g . This g ‐factor decreases on approaching the melting curve to a constant value of approximately 0.7, independent of the pressure. On freezing the dielectric constant falls off from 49 to about 4 at atmospheric pressure and from 45.5 to about 4 at 3 kbar. In the solid state the dielectric constant is fairly independent of temperature and pressure, however, a small change is observed at a lower solid‐solid transition.