This invention provides a process for reducing the amount of soluble halide in a solution comprising a liquid organic medium, at least one viscosity reducing agent, at least one dihydrocarbylmagnesium compound, and an initial amount of soluble halide. The process comprises mixing at least one alkali metal with the solution at a mole ratio of alkali metal to magnesium of less than about 1:2.5, thereby forming precipitated soluble halides. Also provided by this invention is a process for reducing the amount of soluble halide in a slurry comprising a liquid organic medium, at least one viscosity reducing agent, at least one dihydrocarbylmagnesium compound, solids from the formation of said dihydrocarbylmagnesium compound, and an initial amount of soluble halide. This process comprises mixing at least one alkali metal with the slurry at a mole ratio of alkali metal to magnesium of less than about 1:1.25, thereby forming precipitated soluble halides.