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Examination of the solid phases in the system AgI–NaI–H 2 O
Author(s) -
Johnson L. R.,
Davis B. L.
Publication year - 1972
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889872009197
Subject(s) - monoclinic crystal system , crystallography , metastability , phase (matter) , diffraction , chemistry , x ray crystallography , transmission electron microscopy , analytical chemistry (journal) , materials science , crystal structure , physics , optics , nanotechnology , organic chemistry , chromatography
By means of several low temperature devices the solid hydrous phases of the AgI–NaI–H 2 O system have been extensively studied by X‐ray diffraction, transmission Laue photography, and polarizing microscopy. The density, composition and unit‐cell parameters have been determined for three distinct AgI–NaI hydrates for which the stability regions correspond to phases C , E , and F previously reported by Davis [ J . Atmos. Sci . (1969), 26 , 1042]. The cell assignments are based on determinations of axial ratios from the Laue photographs and interplanar spacing analyses utilizing the Hesse–Lipson technique, Cohen cell‐parameter refinement and the de Wolff cell‐reliability criteria. All phases are of the composition AgI–NaI– n H 2 O with phase C at 25 °C having n = 4, ρ = 3.0 g.cm −3 (measured and calculated) and indexing on the basis of a monoclinic cell with parameters a 0 = 7.573, b 0 = 9.454, c 0 = 12.403 Å, and β = 92.43° with Z = 4. Phase F at −10 °C is also monoclinic with a 0 = 5.757, b 0 = 13.563 and c 0 = 12.541 Å and β = 103.05° with Z = 4, and n = 4. Phase E appears to consist of two structures, very similar but differing in cell volume by 2.8%. We believe this to be due to varying water content, the n = 3 phase being metastable. The cell reliability factor is less than 10 for both cells and indexing is considered to be tentative.