Static and dynamic thermal quantities near the consolute point of the binary liquid mixture aniline–cyclohexane studied with a photopyroelectric technique and adiabatic scanning calorimetry

Abstract

We studied the thermal conductivity, thermal effusivity, and specific heat capacity at constant pressure of the critical binary liquid mixture aniline-cyclohexane near the consolute point, using a photopyroelectric (PPE) technique and adiabatic scanning calorimetry (ASC). According to recent theoretical predictions based on renormalization group theory calculations, a substantial (but not diverging) enhancement in the thermal conductivity in the homogeneous phase near the critical temperature was expected for this binary system near the consolute point. However, within an experimental precision of 0.05%, we found no deviation from linear behavior in the range of 5 K above Tc down to Tc. The specific heat capacity calculated from the results for the thermal conductivity and effusivity is in good agreement with that measured by ASC. For the ASC results, the theoretical power law expression with the Ising critical exponent was fitted to the specific heat capacity both above and below the transition temperature. Good agreement with theory was found both for the amplitude ratio and the two-scale universality.

Critical behaviour of binary mixture of {xC6H5CN+(1−x)CH3(CH2)7CH3}: Measurements of coexistence curves, light scattering, and heat capacity

“…It was reported that the critical temperature was determined by fitting the experimental heat capacity data to Eqs. (27) and (28) simultaneously [26,28,29]. Unfortunately we failed to do so because of the strong correlation among the adjusting parameters.…”

“…The temperature at the maximum point as postulated critical temperature was substituted into Eqs. (27) and (28), and then the experimental heat capacities within a range of ±3 K from the maximum point were fitted to Eqs. (27) and (28) with D + = D À = 0, and the standard deviation of the fit was calculated by:…”

“…(27) and (28) simultaneously, and the weighing factor was chosen as the reciprocals of the total squares of uncertainties of the heat capacities. It was found that even if the term of D ± was neglected and T c and E were fixed at the values determined by the method described above, the fit of the experimental heat capacities to Eqs.…”

“…It was found that even if the term of D ± was neglected and T c and E were fixed at the values determined by the method described above, the fit of the experimental heat capacities to Eqs. (27) and (28) with the rest of parameters being adjustable was unsuccessful. Particularly we failed to determine the critical exponent a and the amplitude ratio A + /A À simultaneously, because of the strong correlation between them.…”

“…(27) and (28) for the range (T À T c ) = (À2.8 to 2.8) K with T c , E, A + /A À , and D ± being fixed at 284.264 K, 0.1221 J Á K À1 Á cm À3 , 0.53, and 0, respectively. The uncertainties of adjusting parameters listed in table 10 are the standard errors from the fit, which are small; however, it was found that the variation of 0.01 in A + /A À caused the changes of about 3% in a, 4% in A + , 6% in A À , and 0.6% in C p0 , while the variations of T c and E within their uncertainties hardly changed the values of the adjusting parameters.…”