Measurements of the spin-lattice relaxation time,T1, for the75As nucleus are presented for solutions of potassium hexafluoroarsenate in acetonitrile, acetone, ethyleneglycol-dimethylether and diethyleneglycol-dimethylether. Viscosity and density data are given for each series of solutions. Plots of (T1)-1against viscosity are linear for each solution. The relaxation is interpreted in terms of the fluctuating quadrupole coupling of the75As nucleus, the mean square value of which is constant over the whole concentration range for a given solvent. Possible origins of the electric field gradients at the75As nucleus are discussed in the light of this and earlier work on similar systems. The viscosity and density data are used to obtain a set of ‘ solvation numbers ’.