Syntheses and Structures of Na2Mg3(OH)2(SO4)3·4H2O and K2Mg3(OH)2(SO4)3·2H2O |
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| Authors: | Frank Kubel Marie Cabaret‐Lampin |
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| Institution: | 1. Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/164‐SC, 1060 Vienna, Austria;2. INSA de LYON, Département Science et Génie des matériaux, 20 Avenue Albert Einstein, 69621 Villeurbanne cedex, France |
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| Abstract: | The crystal structures of Na2Mg3(OH)2(SO4)3 · 4H2O and K2Mg3(OH)2(SO4)3 · 2H2O, were determined from conventional laboratory X‐ray powder diffraction data. Synthesis and crystal growth were made by mixing alkali metal sulfate, magnesium sulfate hydrate, and magnesium oxide with small amounts of water followed by heating at 150 °C. The compounds crystallize in space group Cmc21 (No. 36) with lattice parameters of a = 19.7351(3), b = 7.2228(2), c = 10.0285(2) Å for the sodium and a = 17.9427(2), b = 7.5184(1), c = 9.7945(1) Å for the potassium sample. The crystal structure consists of a linked MgO6–SO4 layered network, where the space between the layers is filled with either potassium (K+) or Na+‐2H2O units. The potassium‐bearing structure is isostructural to K2Co3(OH)2(SO4)3 · 2(H2O). The sodium compound has a similar crystal structure, where the bigger potassium ion is replaced by sodium ions and twice as many water molecules. Geometry optimization of the hydrogen positions were made with an empirical energy code. |
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| Keywords: | Sodium magnesium hydroxide sulfate tetrahydrate Potassium magnesium hydroxide sulfate dihydrate X‐ray diffraction Empirical energy evaluations |
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