A hydrated metal salt is dehydrated to its anhydrous form by dissolving the metal salt hydrate in an organic solvent and contacting the solvent solution of metal salt hydrate with a molecular sieve of a pore size sufficient to permit the absorption of water molecules but of a size too small to absorb solvent molecules. Thus, 2.79 G of hydrated ZnCl2 was dissolved in 250 ml of ethanol. Analysis of the solution showed it to be 0.046M in H2O and 0.076M in ZnCl2, thus indicating a hydrate composition of ZnCl2.1/2H2O. Fifty milliliters of the solution were contacted with 10 g of a commercial molecular sieve that is a type a synthetic zeolite having an effective pore size of 3 angstroms, which was activated by heating at 250 deg C. After 3 h, analysis of the solution indicated a salt composition of ZnCl2.1/7H2O. After 22 h, analysis showed anhydrous ZnCl2. Again, 1.53 G of hydrated MnCl2 was dissolved in ethanol. Analysis showed a content of 0.151M H2O and 0.060M MnCl2, for an overall composition of MnCl2.2-1/2H2O. After contracting with a molecular sieve for 2 h as described above, analysis showed a composition of MnCl2.1/2H2O and after 24 h the composition was MnCl2.0.12H2O.