The spin Hamiltonian parameters of [Cr(NH3)5X]Z, where X is H20, C1-, Br-, NCS-, or NO3-, and of cis-[Cr(NH3)4XY]Z, where XY is HzO-CI-or C20d2-, have been determined at 295 and 77 K. Some complexes showed considerable variations in the parameters with temperature. For [Cr(NH3)jH20]Z3, where Z is NO3-or clod-, the effect of the counterion on the parameters was investigated. It appeared that the counterion had a considerable influence. Within a tetragonal ligand field model the spin Hamiltonian parameters were calculated by means of second-order perturbation theory. It was found that there was reasonable agreement between the calculated and experimental axial zero-field parameter D if the ligands did not have large spin-orbit constants.

Relative Cottrell measurements of the diffusion coefficients of eight ions in various supporting electrolytes are reported. A value of 0.70o X 10-6 cm.2 3/sec. was adopted as the diffusion coefficient of cadmium ion in 0.1 M KC1. The Cottrell cell was calibrated by a cadmium run prior to each determination. This procedure obviated any necessity for using a physically measured electrode area in the calculations. A 13% difference between measured and effective electrode areas resulting in a 28% difference between "absolute" and "secondary" diffusion coefficients was found in the present study.

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