In Search of the True Structure of the Sodium Chromium Alum II: Crystal Growth and Structure of the Double Salt NaCr(SO4)2(H2O)6·(CH3OH)0.6(2)· (H2O)1.5(5)

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Attempts to crystallize the sodium chromium alum, NaCr(SO4)2(H2O)12, from water=methanol solutions at temperatures around 281 K yielded crystals of the title compound instead. Their monoclinic structure can be described as a centered rectangular array of linear {1 ∞}[Na(SO4)2]3- rods aligned parallel to [001] with vicinal rods held together by columns of isolated [Cr(H2O)6]3+ complexes. The structure forms channels parallel to [001] which are occupied by methanol and water molecules with atomic site occupancy factors of 1/5 and less. Various attempts to crystallize the compound or the sodium chromium alum from purely aqueous solutions remained unsuccessful