The preparation of purified ScI₃ and ScI₃-Nal bi-component mixtures for use in metal halide lamps is described. The principles of controlled break-up of liquid jets are outlined, and applied to the preparation of precisely sized spheres of bi-component mixtures. Experimental optimization of the jet velocity and excitation frequency permit the attainment of high yields of precisely sized pellets. Lamp performance trials show much improved colour uniformity for lamps dosed with bi-component mixtures as compared to those dosed with individual components.