Critical Solution Temperatures for Two Phase Solvent Systems with Halide Salts,Carboxylic Acids,Surfactants, and Polynuclear Aromatic Compounds

Upper critical solution temperatures (UCST) 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 solutions in phenol. The valence electrons and shell numbers, bascity, ‐CH₃ and ‐CH₂‐, hydrophilic, hydrophobic and π conjugated electrons of respective additives have been noted to affect the UCST values and mutual solubilities of the water and phenol. The surfactants decrease the UCST values with higher mutual solubilities due to effective hydrophilic as well as hydrophobic interactions with aqueous and organic phases, respectively. The stronger structure breaking action of the 3(‐OH) of the glycerol outweighs than those of the 3(‐COO^?) and 1(‐OH) of the citric acid and the urea does produce almost equal UCST values as compared to glycerol. A decrease in the UCST values is noted with number of conjugated π electrons of the benzene, naphthalene, anthracene, and chrysene. In general, the dTc/dx₂ values of salts for 0.20–0.16 mole fractions of phenol are found positive while for 0.055–0.052 mole fractions, the negative.