Thermodynamic studies of solvent extraction systems-V. The binary mixtures of dibutyl phosphate with benzene and chloroform

From total vapour pressures determined between 25 and 45°C, the activity coefficients and excess thermodynamic functions were evaluated in the dibutyl phosphate (HDBP)-benzene and HDBP-chloroform systems. The first system is adequately described by the regular associated mixture model of the type A+B+A₂, with the equilibrium constant of the dimerization reaction K = 0.301, on the molar fraction scale, and the interaction parameter α = 5 kJ/mole at 25°C. The HDBP-CHCL₃ system is characterized by negative deviations from ideality and as a first approximation, the obtained results can be interpreted in terms of 1:1 hydrogen bonded complex, with K = 0.724 at 25°C and K = 0.515 at 45°C and the with standard heat of formation ΔH° = -13.4 kJ/mole.