Adiabatic heat capacity and related properties of ammonium hexachlororuthenate, (NH4)2RuCl6, at temperatures from 5 ⩽ T/K ⩽ 325

Abstract

The heat capacity of ammonium hexachlororuthenate, (NH4)2RuCl6, was measured over the temperature range 5⩽T/K⩽325 using adiabatic calorimetry. Our results show that a structural phase transition is not present. However, an anomalous increase in the heat capacity Cp,m occurs in the region 70⩽T/K⩽105 and the heat capacity reaches its maximum at T=(93.5±0.1) K. The molar entropy change associated with this increase amounts to ΔSm=(0.465±0.006)R. Standard molar thermodynamic functions are presented at selected temperatures from 5K to 325K.