Thermodynamics of alkali alkanoates VII. Heat capacity and thermodynamic functions of potassium acetate from 4 to 585 K

Abstract

The heat capacity of potassium acetate was measured by equilibrium adiabatic calorimetry from near 4 K up to 350 K and by d.s.c. from 325 K through melting (solid to isotropic liquid) to 585 K. No transition or anomaly was observed below 300 K in the heat-capacity curve but four anomalies were observed at super-ambient temperatures including a broad and diffuse hump extending from 300 to 375 K. A bifurcated peak was observed between 375 and 436.5 K with peak temperatures at 411 and 425 K and with enthalpy increments ([Delta]trsHmo) of 41.7 and 22.8R[middle dot]K and entropy increments ([Delta]trsSmo) of 0.097R and 0.05R, respectively. A peak believed to be of first order (solid-to-solid transformation) was observed at 474 K having [Delta]trsHmo and [Delta]trsSmo of 194R[middle dot]K and 0.407R. Finally, a solid-to-(isotropic) liquid transition occurred at 582 K having [Delta]trsHmo and [Delta]trsSmo of 920R[middle dot]K and 1.58R.