A direct synthesis route for high-purity, anhydrous binary salt mixtures has been developed. This atom efficient, solvent-free process is easily scalable, with the potential to produce salt mixtures that meet the purity standards required for industrial heat transfer and nuclear applications. The essence of the methodology lies in mechanochemical synthesis of carnallite precursors that can mitigate the hydrolysis of MgCl2 center dot 6H(2)O under direct heating. Each dehydrated salt carnallite was then analyzed for purity and oxide content through subsequent powder X-ray diffraction, and strong acid titration. This process presents a more effective alternative route compared to previous methods for obtaining low-oxide, high-purity chloride salt mixtures.