Heat capacities of bis-tetraethylammonium tetrachloronickelate and tetrachlorozincate I. Structural transitions and thermophysical results

Abstract

The heat capacities of bis-tetraethylammonium tetrachloronickelate () and tetrachlorozincate () were measured over the temperature range 5 to 350 K by adiabatic calorimetry. Bifurcated anomalies were found for both compounds with the temperatures of the maxima occurring at (222.1 +/- 0.1) K and (222.7 +/- 0.1) K for and at (227.9 +/- 0.2) K and (228.9 +/- 0.2) K for . The excess entropies associated with the transition regions were 9.16 and 9.96 calth K-1 mol-1 respectively. Both transition regions were characterized by equilibrium times of several days. Selected thermal functions Cpo, So, and -{Go(T) - Ho(0)}/T at 298.15 K are, respectively, 151.7, 185.33, and 92.16 calth K-1 mol-1 for and 153.0, 181.52, and 88.53 calth K-1 mol-1 for .