Phase
equilibria of the ternary system (water + phosphoric acid
+ mesityl oxide) were investigated, and experimental tie-line data
of liquid–liquid equilibrium were obtained at T = (298.2, 308.2, and 318.2) K and atmospheric pressure. The mass
fractions of mesityl oxide and phosphoric acid were determined by
high-performance liquid chromatography and acid–base titration,
respectively. A limitation for the complete investigation of biphasic
regions was observed in the (water + phosphoric acid + mesityl oxide)
system, which was not detected in previous aqueous ternary systems
containing mesityl oxide and other weak acids. The unsaturated carbon–carbon
double bond of mesityl oxide is the cause of this limitation. Distribution
coefficients (0.05 up to 0.25) and separation factors (1.05 up to
2.58) were determined over the biphasic area and proved the efficiency
of mesityl oxide in the studied range. All the evaluated experimental
data of the ternary system were correlated using the Hand equation
to confirm the reliability of the endpoints. Temperature increments
increased the extraction ability of mesityl oxide. The nonrandom two-liquid
activity coefficient model was applied to correlate the measured tie-line
points. Binary interaction parameters were obtained in each temperature,
and temperature dependence of the parameters was investigated. The
root-mean-square deviation values (less than 1% in all correlations)
proved the quality of modeling, and the interaction parameters were
validated. Biphasic regions were predicted using the obtained interaction
parameters where experimental data could not be measured.