Isobaric heat capacity measurements for the n-pentane-acetone and the methanol-acetone mixtures at elevated temperatures and pressures

Isobaric heat capacities for the n-pentane-acetone and the methanol-acetone binary mixtures were measured with a flow calorimeter at selected temperat ures from 423.1 K to 523.1 K as a function of pressure up to 10 MPa. The co mpositions of each mixture were 0.25, 0.50, and 0.75 mole fractions. The un certainties of c(p) measurements were less than 0.4%, depending on the magn itude of the temperature differences. As part of the measurement process, l iquid densities at elevated pressure and 303.1 K were also determined and r eported. Experimental c(p) data were compared to the c(p) values calculated using several equations of state. In general none of the equations of stat e were able to reliably predict the heat capacities in the supercritical re gion for either mixture. For both mixtures, the use of binary interaction p arameters improved the c(p) representation in the critical region, by effec tively translating the pressures that correspond to cp maxima. However, ver y close to a maxima, deviations of the calculated c(p) were still as large as 50%, due to the deficiencies of cubic equations of state in the critical region. Comparison results are specifically presented for the Peng-Robinso n equation of state (C) 1999 Elsevier Science B.V. All rights reserved.