Dielectric Constants of Dilute Solutions of Polar Liquids in Nonpolar Solvents

Dielectric constants of solutions of methyl, ethyl, propyl and amyl alcohols in benzene and carbon tetrachloride.---Failure of the Debye theory to represent the behavior of such polar liquids as the alcohols is usually attributed to association. With hope of eliminating the effects of association, the dielectric behavior of dilute solutions of several alcohols in benzene have been studied. Dielectric constants were determined by a heterodyne beat method. Both dielectric and density data were obtained at each 10^∘{} temperature interval from freezing to boiling. The molecular polarization found for the dissolved alcohol was plotted against concentration; one such curve was plotted at each 10^∘{} interval. With hope of obtaining the polarization of the alcohol in the unassociated state, these curves were extended to cut the zero concentration axis. The resulting intercepts for the various temperatures were checked against theory.Electric moments of methyl, ethyl, propyl and amyl alcohol molecules.---By taking the contribution due to electron displacement from optical data, it was found that the zero concentration intercepts for methyl, ethyl, propyl, and amyl alcohol (using benzene as solvent) lead to values of the electric moment of the molecule which are essentially independent of temperature. This is in agreement with the Debye theory; it is in contrast to the behavior of the pure liquid alcohols. The moments found are 1.64, 1.74, 1.75, and 1.62×{}10^-18 for methyl, ethyl, propyl, and amyl alcohol, respectively. If use of the molecular refraction is avoided by plotting values of P₀T against T, where P₀ is the zero concentration intercept, it is apparent that the data can in no way lead to imaginary electric moments, as do data on the pure liquids. If straight lines with the extreme slopes justified by the data are drawn through the group of points for any alcohol, the zero temperature intercepts so found limit the electric moment to a range whose extremes differ by not more than 20 percent. In every case the moment obtained through use of the molecular refraction falls within this range.