Specific heat capacity singularity and related weak anomalies in the nitroethane-cyclohexane critical binary mixture

Abstract

An adiabatic scanning calorimeter has been used to measure the specific heat capacity ${\mathit{C}}_{\mathit{p},\mathit{x}}$ of a critical nitroethane-cyclohexane binary liquid mixture in the one-phase and the two-phase region above and below the consolute point. The temperature dependence of the refractive index n has been measured with a grating interferometer. Also the change of the critical temperature with pressure has been measured. Combining these new results with existing results for the dielectric constant \ensuremath{\epsilon} and the density \ensuremath{\rho} allowed a broad inspection of several relationships among these physical quantities. From our analysis it followed that the data are fully consistent with scaling predictions. The critical exponent \ensuremath{\alpha} and the critical heat capacity amplitude ratio values agree very well with the theoretical values for the three-dimensional Ising universality class. Reasonable agreement was found between the critical amplitude from experimental density data and the value calculated from the specific heat capacity amplitude and the slope of the critical line. In contrast to the dielectric constant results, where a large intrinsic effect is present, a similar effect in the refractive index within the experimental uncertainties could not be detected. \textcopyright{} 1996 The American Physical Society.