Critical heat capacity in a 3-methylpentane + nitroethane mixture near its consolute point

A computerized high-resolution ac calorimetric technique has been used to measure the heat capacity Cₚₓ of a critical 3-methylpentane + nitroethane binary-liquid mixture. An analysis of these results yields universal parameters in good agreement with those expected for the $d=3$, $n=1$ (three-dimensional Ising) universality class. The critical exponent α=α^' lies in the range 0.11-0.12, the ratio A^'A of the amplitudes of the leading singularity in Cₚₓ above and below Tc is 1.79±{}0.06. The ratio of the corrections-to-scaling amplitudes D^'D is {~}1. The quantity Aᵥξ₀³kB, which relates the critical amplitude of the heat capacity to that of the correlation length, is also in agreement with the renormalization-group value for the three-dimensional Ising model as expected from two-scale-factor universality.