A method of synthesising gallium or indium alkoxide from the corresponding gallium or indium halide, the method comprising the step of reacting the gallium or indium metal halide with the alkoxide of an alkali earth metal, to produce the desired metal alkoxide essentially free of chlorine contamination. The method provides a composition comprising a solution of gallium or indium alkoxide of high purity, the composition having a chloride content of less than 30 ppm, a barium or strontium content of less than 30 ppm, and a sodium or potassium content of less than 30 ppm, without requiring any additional steps.