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Crystal Structure of Strontium Potassium Arsenate Octahydrate



M Mathew


The crystal structure of strontium potassium arsenate octahydrate, SrKAsO4.8H2O, has been determined by single crystal x-ray diffraction. The crystals are tetragonal, a = 7.144(1){Angstrom}, c = 23.613(2){Angstrom}, space group I41md (No. 109), Z = 4, V = 1205.1(1){Angstrom}3, dc = 2.258 Mg. M-3. The structure was refined by full-matrix least-squares techniques to R = 0.31, Rw = 0.052, for 317 reflections with I {greater than or equal} 3ς(I). All cations and anions in this compound are completely surrounded by water molecules. Sr and K ions are each coordinated to eight water molecules arranged in an approximately square antiprism. The [Sr(H2O)8] polyhedron shares one face of four water molecules with a [K(H2O)8] polyhedron forming O4-Sr-O4-K-O4 polyhedra. The O4-Sr-O4-K-O4 units are linked together through a pair of edge-sharing linkages of the outer water molecules, alternating along a-axis and b-axis. The hydrated cation polyhedra appear to define the host lattice, which accommodates the AsO4 ion in the interstitial space. The environment of the AsO4 ion consists of 16 water molecules; each oxygen atom is the acceptor in four hydrogen bonds from four water molecules. The pair distances associated with this environment may be used in investigations of the structure of hydrated XO4 ions in solutions. Each water molecule is coordinated to one Sr and one K and hydrogen bonded to two O atoms of two different AsO4 ions. There is no hydrogen bonding between water molecules.
Journal of Chemical Crystallography
No. 10


crystal structure, hydrated ions, ionic hydration, strontium arsenate, struvite-type structure, struvites


Mathew, M. (1998), Crystal Structure of Strontium Potassium Arsenate Octahydrate, Journal of Chemical Crystallography (Accessed May 24, 2024)


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Created September 1, 1998, Updated February 17, 2017