The mathematical model/method/approach
To obtain the standard Gibbs energy of formation to estimate the equilibrium constants in the liquid phase, the molar thermodynamic functions at saturation pressure (Ps) were extracted from the studies cited before, for temperatures between 250 K and 550 K. The saturation pressure was obtained from the (2,4) form of the Wagner equation as it was done by Chirico and co-workers:
Ps 11.524ln A 1 Tr B 1 Tr C 1 Tr +D 1 Tr (1) Pc Tr
where Tr =T/Tc, Pc is the critical pressure, and Tc is the critical temperature. The required equation parameters (A, B, C, and D),Pc , Tc , and some other required properties, of each species, are presented in Table S2 in the SI.
Based on the values presented in Table S1 in the SI, the enthalpy (H) and entropy (S) in the standard state (i.e., atP0 ) were calculated at each temperature using Maxwell relations:
Integrating within the pressure range and assuming no variation of molar volume (V) in the liquid phase due to pressure, the following relations were obtained:
where ΔP=P0 Ps. Following the procedure of Chirico and co-workers, molar volumes were obtained by means of the molecular weight (M) and the densities (ρ) calculated with a form of the corresponding-states equation of Riedel: