Thermodynamics Research Center / ThermoML | Thermochimica Acta

ABSTRACT

Abstract: One- and two-phase isochoric heat capacities and saturated liquid and vapor properties of sec-butanol in the wide temperature and density ranges including near- and supercritical conditions have been measured with a high-temperature and high-pressure nearly constant-volume adiabatic calorimeter. The measurements were made in the temperature range from 307 K to 551 K for 22 liquid and vapor isochores from 76.44 kg - -3. The isochoric heat capacity jump (quasi-static thermograms) technique have been used to accurately measure of the phase transition parameters near the critical point. The total experimental uncertainty of density, temperature, and isochoric heat capacity measurements at the 95 % confidence level with a coverage factor of k=2 were estimated to be 0.06 %, 15 mK, and 2 % to 3 %, respectively. The critical temperature for sec-butanol were determined from the measured saturated properties ( , ) near the critical point. The measured and saturated density data near the critical point have been analyzed and interpreted in terms of "complete" scaling theory to accurately determine the Yan-Yang anomaly strength parameter. A new technique of the Yang-Yang anomaly strength parameter determination from the direct simultaneously two-phase isochoric heat capacity and specific volumes measurements at saturation have been proposed. The values of the "complete" scaling asymmetric parameter of the liquid-gas coexistence curve for sec-butanol has been determined using the measured saturated liquid and vapor densities near the critical point.