Specific Isochoric Heat Capacity Measurements for Liquid Isobutane

Abstract

Experimental specific isochoric heat capacities (Cv) and P_ρT properties for isobutane are presented that were measured with a twin-cell type adiabatic isochoric calorimeter. The measurements were obtained for temperatures from 272 to 408 K and for pressures up to 30MPa. The sample purity was 99. 99 mol%. The expanded uncertainties (i.e., a coverage factor k= 2 ) are ±l3 mK for temperature, ±8k Pa for pressure, ±0.16% for density, and ±3.6% for Cv in the liquid phase. An evaluation and a comparison of the experimental data with highly reliable equations of state confirmed satisfactorily the thermodynamic consistency of the present measurements.