Dielectric behaviour of methanol and related polar fluids at high pressures and temperatures

Abstract

The dielectric constant (permittivity), ε, of liquid methanol has been measured from 32 to 252 °C and at pressures up to 2000 bar (critical temp: 240 °C). Details of apparatus and method are given. At 32 °C, ε(1 bar)= 31.9 and ε(2000 bar)= 36.4. At 252 °C, ε(200 bar)= 7.2 and ε(2000 bar)= 12.3. Kirkwood correlation factors, g, are derived and presented as functions of temperature and density. At 32 °C, g is about 3.0 with negative isothermal density dependence. At 252 °C, g= 1.9 at low density (200 bar) and increases showing a maximum at higher density. A comparative discussion with results for CH₃CN, CH₃F, CHF₃, H₂O, HCl and NH₃ is given.