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5. The deuterated samples were synthesized by reacting the anhydrous forms of MSO4 and BaSiF6 in 99.6% D2O. The liquor obtained, after filtering off BaSO4, was concentrated by vacuum distillation and used for the production of single crystals. Throughout the processing, necessary precautions were taken for a minimum exposure to atmospheric moisture. The materials in Table II were prepared by reacting solutions of the mixed sulfates with BaSiF6. The latter is easily obtained, in high yield, from BaCl2 and Na2SiF6. The preparation of the metal fluotitanate proceeded in an analogous manner. The K2TiF6 used to prepare the barium salt was obtained (89% yield) by reacting TiO2 with 48% HF and the resultant mixture complexed with KF. Polyethylene wares were used for mixtures containing free HF. The metal fluostannate was prepared by the action of HF on the residue obtained by precipitation of a solution of the mixed metal chlorostannate with Na2CO3. The mixed metal chlorostannate solution was simply prepared by dissolving the three metal chlorides (Zn+2, Ni+2, and Sn+4) in HCl solution.