Upper critical solution temperatures for immiscible solvent systems with halide salts, carboxylic acids, surfactants and polynuclear aromatic compounds and benzene derivatives

Upper critical solution temperatures (UCSTs) of (water + phenol) systems are reported with 0.1 mol · kg−1 halide salts, carboxylic acids, 1.0% PEG 200 in water, and 0.01 mol · kg−1 surfactants and polynuclear aromatic compounds namely benzene, naphthalene, anthracene, chrysene; and benzene derivatives namely toluene and xylene solutions in phenol. Valence electrons and shell numbers, basicity, –CH3 and –CH2–, hydrophilic, hydrophobic and π conjugated electrons of respective additives have been noted to affect their UCSTs and mutual solubilities. The surfactants decrease the USCTs with higher mutual solubilities due to effective hydrophilic as well as hydrophobic interactions with aqueous and organic phases, respectively. A stronger structure breaking action of 3(-OH) of glycerol outweighs those of the 3(-COO−) and 1(-OH) of citric acid and urea does produce almost equal UCSTs as compared to glycerol. A decrease in UCSTs is noted with increasing number of conjugated π electrons of benzene, naphthalene, anthracene and chrysene. In general, dTc/dx2 values of salts for 0.20 to 0.16 mole fractions of phenol are found positive while for 0.055 to 0.052 mole fractions, the negative.