Large heat capacity anomaly near the consolute point of the binary mixture nitromethane and 3-pentanol

The large critical anomaly in the isobaric heat capacity C-p,C-x(T) of the binary mixture nitromethane + 3-pentanol is measured using high-resolution adiabatic scanning calorimetry. The unique features of this technique provided an alternative approach to the study of the critical behavior of C-p,C-x(T), providing further C-p,C-x(T) related quantities from which valuable information could be extracted. Our data are in full agreement with the predictions of the Modern Theory of Critical Phenomena; specifically, 3D-Ising model values for the critical exponent alpha and the universal amplitude ratio values of the leading critical amplitudes, as well as for the first correction-to-scaling ones, provide the optimum fits to represent the experimental data. Evidence for the need of higher-order terms, i.e., first correction-to-scaling term, is given. The large value of the coefficient E for the linear temperature dependence of the background obtained is ascribed to a possible contribution of the regular linear background term, of a higher-order asymmetry term, and of the second correction-to-scaling term. Internal consistency of C-p,C-x(T) and its related quantities is successfully checked. (C) 2011 American Institute of Physics. [doi:10.1063/1.3535567]status: publishe