Chromium (III)hydroxide hydrate - a new hydroxide structure type with cross-linked hydrogen bonding
Precipitation of hexaquo chromium(III) solutions with OH- ions yields a hydroxide with analytical composition Cr(OH)3・3 H2O of the anti-bayerite type. The lattice constants of the pseudo-hexagonal unit cell are a0 = 5,047 and c0 = 4,73 Å. This lattice has vacancies where bayerite would have occupie...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | deu |
| Published: |
Swiss Chemical Society
1973-03-01
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| Series: | CHIMIA |
| Online Access: | https://www.chimia.ch/chimia/article/view/9077 |
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| Summary: | Precipitation of hexaquo chromium(III) solutions with OH- ions yields a hydroxide with analytical composition Cr(OH)3・3 H2O of the anti-bayerite type. The lattice constants of the pseudo-hexagonal unit cell are a0 = 5,047 and c0 = 4,73 Å. This lattice has vacancies where bayerite would have occupied octahedral sites, and vice versa, in a hexagonal closest arrangement of OH- and H2O. It consists of layers of isolated [Cr(OH2)3(OH)3] units. These are held together by a network of two kinds of hydrogen bonds. IR evidence gives O . . . HO distances of 2,7 and 2,9 Å, respectively. Precipitation experiments with H218O enriched solvent could be explained by a simple and fast deprotonation mechanism where the inner coordination sphere of the hexaquo chromium (III) ion remains unaltered. Upon ageing an amorphous phase of undefined composition is formed, where corner and/or edge sharing of hexaquo chromium (III) octahedra occurs. The solubility rate of this aged product in acids is distinctly lower, as the inner coordination sphere of the Cr3+ has to be attacked.
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| ISSN: | 0009-4293 2673-2424 |