Behavior of the dielectric constant of fluids near a critical point

Thermodynamic and statistical mechanical arguments indicate that the temperature derivative of the dielectric constant of fluids diverges weakly at the critical point. Following a thermodynamic procedure proposed by Mistura, we derive an expansion for the static dielectric constant of fluids near the gas-liquid critical point and of binary liquids near the critical point of mixing, which includes correction terms to the asymptotic critical behavior. The relationship with the statistical mechanical derivation of the critical behavior of the dielectric constant is discussed. The paper concludes with an assessment of the current experimental situation.