Experimental evidence obtained in this study verifies reciprocal relations for two nonassociating ternary systems within the limits of experimental error. In addition, it demonstrates the applicability of hydrodynamic theory to multicomponent liquid diffusion. These conclusions are based on the fact that good agreement between the diffusion and phenomenological coefficients obtained by optical methods and those obtained from friction coefficients was found for the nonassociating systems studied.Hopefully experimental techniques will be developed in the future which will enable measurement of quaternary or higher diffusion coefficients, Dij, so that those calculated from friction coefficients, ui, can be checked. Since hydrodynamic theory requires fewer independent friction coefficients than independent diffusion coeficients to describe diffusion in systems of more than three components, such experimental techniques would be extremely valuable in checking the applicability of hydrodynamic theory to such systems.A study of the geometric and structural isomerization rates of chemically activated cis-1,2-dimethylcyclopropane formed by singlet methylene radical addition to the double bond of cis-2-butene is reported. The singlet methylene radicals were produced by diazomethane photolysis a t 4358 and 3660 d in the presence of added oxygen. The structural isomerization rate was determined by an internal comparison method that eliminates uncertainties due to pentene decomposition. The rates are in excellent agreement with RRKM theory calculations at an adjusted energy for each photolysis wavelength. The energies carried into the activated molecule by the methylene radical were 113.0 and 116.8 kcal/mol at 4358 and 3660 A, respectively. These values suggest that the methylene radical carries into the addition reaction a relatively small fraction (0.30) of the total excess energy available from its formation reaction. Energies determined in this work, applied to related systems, give results that differ by at most -3 kcal/moI from earlier determinations.