Dielectric-constant anomaly near the critical solution point in polystyrene + cyclohexane

We present measurements of the static dielectric constant $\epsilon$ near the liquid-liquid critical point in polystyrene + cyclohexane. The data show an anomalous decrease in $\epsilon$ as a function of temperature as the critical temperature is approached from the one-phase region at the critical composition. The anomaly reaches an amplitude of about $7\times {10}^{-5\mathrm{}}$ in $\epsilon$ at a few millikelvins from the critical temperature. The data are consistent with the theoretical predictions of a critical exponent for ${\rho }^{-1\mathrm{}}\epsilon$ of ($1-\alpha$), where $\rho$ is the density and $\alpha$ is the specific-heat exponent.