Thermodynamical Studies on Binary Systems Consisting of Polar and Non-polar Liquids. II. The Measurement of the Heats of Mixing for Binary Systems of Polar and Non-polar Liquids

The heats of mixing were measured for 22 binary systems of polar and non-polar liquids where the pairs of liquids have similar molecular sizes.For the systems in which the non-polar components are non-aromatic, the van Laar coefficients α are positive and increase smoothly as the concentration of polar liquids decrease. This variation of α with concentration is attributed to the effect of dipole of the polar component.However, for the systems where the nonpolar components are aromatic, the values of α are smaller than that of the corresponding non-aromatic system and are even negative for most of the cases and decrease with concentration of polar component in most concentration ranges.The sharp difference between two groups of the binary systems, was attributed to the structural difference of aromatic and non-aromatic non-polar components.The effect presumably due to the quadrupole of the non-polar components was noticed.