The equivalent generalised permittivity of a system composed of dielectric spheres in a conductive continuum is calculated. The diffusion effects are taken into account by characterising the continuous phase by its ion charges, mobilities and equilibrium concentrations. The results obtained, which reduce to the Maxwell-Wagner results in the limit of low diffusion at constant conductivity or large dispersion radii, do not agree with those deduced by Bonincontro et al (1980). They show the Maxwell-Wagner approximation always leads to an overestimation of both the dielectric increment and the relaxation time. These differences could be important in some cases of interest.

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The dipole moments of 21 aromatic and aliphatic aldehydes were determined. Permittivity measurements were performed on highly diluted cyclohexane solutions at 20 °C. The limiting forms of Debye's, Onsager's, and Bordewijk's expressions were used. The influence of the solvent on the dipole moment values was studied using decalin and heptane mixtures. Only the Debye's values presented an apparent solvent effect while the Onsager's and Bordewijk's values remained independent of the solvent. Dipole moment values obtained using the refractive indexes of the components were also compared with those derived using the refractive indexes of the mixtures. This permitted one to estimate in 0.07 the relation between atomic and electronic polarization.

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