CORRIGENDUM Accurate Representation of Thermodynamic Properties near the Critical Point By G. A. CHAPELA and J. S. ROWLINSON J.C.S. Faraday I, 1974, 70, 584 The calculated heat capacities at constant volume shown in fig. 2 are wrong, because of an error in a computer programme. At 305.15 K the correct curves shows a larger peak (1.8 J g-' K-l) at the critical density and also agrees better with the experimental results at higher densities. At 306.15 K, an isotherm which passes close to the upper end of the critical region (as defined by the contour r = 0.01), the peak is lowered and the calculated values at higher densities fall to about 0.6 J g-l K-l at a density of 1 g ~ m - ~ . This discrepancy suggests that the precise form of the switching function (27) must be chosen with greater care if good values of C, (a second derivation of the free energy) are to be obtained on iso- therms which just " cut " the critical region. The calculated pressure is unaffected, and no sensible change is made in the calculated value of the energy or entropy.We are indebted to Mr. B. Armstrong of the I.U.P.A.C. Thermodynamic Tables Project Centre for discovering this error. A full account of the use of the equations of this paper will be published : S. Angus, B. Armstrong and K. M. de Reuck, International Thermodynamic Tables of the Fluid State, Carbon Dioxide, 1973 (Butterworth, to be published). 2368 CORRIGENDUM Accurate Representation of Thermodynamic Properties near the Critical Point By G. A. CHAPELA and J. S. ROWLINSON J.C.S. Faraday I, 1974, 70, 584 The calculated heat capacities at constant volume shown in fig. 2 are wrong, because of an error in a computer programme.At 305.15 K the correct curves shows a larger peak (1.8 J g-' K-l) at the critical density and also agrees better with the experimental results at higher densities. At 306.15 K, an isotherm which passes close to the upper end of the critical region (as defined by the contour r = 0.01), the peak is lowered and the calculated values at higher densities fall to about 0.6 J g-l K-l at a density of 1 g ~ m - ~ . This discrepancy suggests that the precise form of the switching function (27) must be chosen with greater care if good values of C, (a second derivation of the free energy) are to be obtained on iso- therms which just " cut " the critical region. The calculated pressure is unaffected, and no sensible change is made in the calculated value of the energy or entropy. We are indebted to Mr. B. Armstrong of the I.U.P.A.C. Thermodynamic Tables Project Centre for discovering this error. A full account of the use of the equations of this paper will be published : S. Angus, B. Armstrong and K. M. de Reuck, International Thermodynamic Tables of the Fluid State, Carbon Dioxide, 1973 (Butterworth, to be published). 2368