Measurement of Isochoric Specific Heat Capacity for Pure Alcohol with Adiabatic Twin-Cell Calorimeter

Abstract

Specific heat capacity at constant volume (cv) is one of the most important thermodynamic properties to develop and evaluate reliable equation of state. With this point of view, isochoric heat capacities of methanol and ethanol have been measured with a twin-cell type adiabatic calorimeter, which was modified to measure data more precisely. Temperatures were measured with a platinum resistance thermometer on the bottom of each cell and were reported on the ITS-90. Sample pressure measurements were made with a crystal quartz transducer. Densities were calculated from the volume of the calorimeter cell and sample mass. The experimental expanded uncertainty (with a coverage factor k = 2) of temperature measurements is ±13 mK, and that of pressure measurement is ±8kPa. The expanded relative uncertainty for isochoric heat capacity is estimated to be less than ±2% for liquid phase measurements, and for density it is about ±0.16%. This study obtained 91 points for methanol and 116 points for ethanol at the temperature range from 270 to 420 K and at presures up to 30 Mpa.