Standard Gibbs energy of formation of Cs2CdI4

The vapor pressures of CdI₂ and Cs₂CdI₄ were measured below and above their melting points, employing the transpiration technique. The standard Gibbs energy of formation Δ_fG° of Cs₂CdI₄, derived from the partial pressure of CdI₂ in the vapor phase above and below the melting point of the compound could be represented by the equations Δ_fG°Cs₂CdI₄ (±6.7) kJ mol⁻¹=−1026.9+0.270 T (643 K≤T≤693 K) and Δ_fG°{Cs₂CdI₄} (±6.6) kJ mol⁻¹=−1001.8+0.233 T (713 K≤T≤749 K) respectively. The enthalpy of fusion of the title compound derived from these equations was found to be 25.1±10.0 kJ mol⁻¹ compared to 36.7 kJ mol⁻¹ reported in the literature from differential scanning calorimetry (DSC). The standard enthalpy of formation Δ_fH°_298.15 for Cs₂CdI₄ evaluated from these measurements was found to be −918.0±11.7 kJ mol⁻¹, in good agreement with the values −920.3±1.4 and −917.7±1.5 kJ mol⁻¹ reported in the literature from two independent calorimetric studies.