HEAT CAPACITY AND ENTROPY OF RUTILE (TIO2) AND NEPHELINE (NAALSIO4)

Abstract

From heat capacities measured adiabatically at low temperatures, the standard entropies at 298.15 K of synthetic rutile (TiO2) and nepheline (NaAlSiO4) have been determined to be 50.0 ± 0.1 and 122.8 ± 0.3 J mol-1 K, respectively. These values agree with previous measurements and in particular confirm the higher entropy of nepheline with respect to that of the less dense NaAlSiO4 polymorph carnegieite.