Specific heat capacities at constant volume (c v ) of water, methanol, and their mixtures were measured with a new adiabatic calorimeter. Temperatures ranged from 300 K to 400 K, and pressures ranged to 20 MPa. Densities were determined at the initial and final end points during each calorimetric experiment. The calorimeter is a twin-cell type whose sample and reference cells (33 cm 3 ) and their shields are heated by electric power. The cells are surrounded by a high vacuum. During the experiment, the heating power was carefully controlled so that the cell temperature increased uniformly. The reference cell was always evacuated and was heated with a constant current. The temperature of the sample cell tracked that of the reference cell temperature by means an automatic control system. Automated sample pressure measurements were made with a crystal quartz transducer. The expanded relative uncertainty for c v is estimated to be 1% for liquid-phase measurements, and for density it is about 0.2%.

Isochoric heat capacities (c v ) of methanol, ethanol, and 1-propanol and binary mixtures of water with each of these alkanols were measured in the temperature range from 280 to 420 K and at pressures up to 30 MPa. The measurements were carried out on liquid-phase samples with a twin-cell type adiabatic calorimeter. Liquid densities were also reported in this work on the basis of the mass of the sample and the volume of the calorimetric cell. The experimental expanded uncertainty (with a coverage factor k ) 2) of temperature measurements is (13 mK, and that of pressure measurements is (8 kPa. The expanded relative uncertainty for isochoric heat capacity is estimated to be (2.2% for the liquid-phase measurements, and for density it is (0.16%. The behavior of c v is anomolous, indicating that alkanol + water mixtures are strongly associated due to the influence of hydrogen bonds.

The isochoric heat capacity (c v ) and pressure-volume-temperature-composition (pvTx) properties were measured for propane + isobutane mixtures in the liquid phase and in the supercritical region. The expanded uncertainty (k = 2) of temperature measurements is estimated to be ±13 mK, and that of pressure measurements is ±8 kPa. The expanded relative uncertainty for c v is ±3.2% for the liquid phase, increasing to ±4.8% for near-critical densities. The expanded uncertainty for density is estimated to be ±0.16%. The present measurements for {xC 3 H 8 + (1 − x)i-C 4 H 10 } with x = 0.0, 0.498, 0.756, and 1.0, were obtained at 659 state points at temperatures from 270 to 420 K and at pressures up to 30 MPa. The experimental data were compared with a published equation of state.

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