Range of Validity of Higashi's Equation for a Quick Determination of Dipole Moment in Solution

The present authors have discussed the range of validity of Higashi's equation for determining the electric dipole moment of a substance in a nonpolar solvent. Mathematical analysis shows that Higashi's equation is valid for the straight part of the curve showing the variation of the dielectric constant of the solution with the mole fraction of the solute. With the six organic solutes examined the above conclusion is found to be valid for four, viz., chlorobenzene, ortho-dichlorobenzene, nitrobenzene, and methylene chloride. Ethylene dichloride and ethylene dibromide whose molecules are subject to restricted rotation, show anomalous results. It is likely that Higashi's equation may not be applicable to such molecules. Benzene was used as a solvent throughout.