Improvements in the assessment of the thermodynamic properties of condensed and gaseous phases of the CsOH compound

• We reveal melting temperature discrepancies of CsOH and we select a new one.
• We propose a reliable dimerization energy for the gas phase.
• We completely re-interpret the gas phase thermodynamics including flame studies.
• New condensed and gaseous phases was proposed in view of data selection.

Thermodynamic properties of condensed and gas phases of the CsOH compound are assessed. Thermal functions of the condensed phase are those already selected in a preceding compilation with some important modification concerning the melting temperature of CsOH(s, γ) that has been re-evaluated to be T = 649 ± 2 K from recent mass spectrometric determination certifying the total lack of water impurity and from a comparison between the CsOH–H2O and the RbOH–H2O phase diagram shapes. The vapor phase thermodynamic properties – dealing mainly with the CsOH(g) and Cs2O2H2(g) molecules – are re-evaluated from the selection of a new dimerization equilibrium constant and a thorough analysis of preceding vaporization experiments. Besides, flame studies that give directly the dissociation energies of the CsOH bond are analyzed from the main assumed reactions as well as considering the different analytical methods as used. The reliability of flame results have also been analyzed in this work by thermodynamic adiabatic calculations of the flame. The mean formation enthalpies as retained in the present analysis are:ΔfH°(CsOH,g,298.15K)=-252.7±7.0kJ·mol-1, and ΔfH°(Cs2O2H2,g,298.15K)=-652.0±11.7kJ·mol-1.