Caesium dichloroiodate
Caesium dichloroiodate on a lab spatula
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| Names | |
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| IUPAC name
Caesium dichloroiodate(I)
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| Other names
Cesium dichloroiodide
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| EC Number |
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties[5] | |
| Cl2CsI | |
| Molar mass | 330.71 g·mol−1 |
| Appearance | trigonal orange-yellow crystals[1] |
| Density |
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| Melting point | 139 °C (decomposes)[3] |
| carbon tetrachloride: 0.00126 (25°C), water: soluble, ethanol: soluble[4] | |
| Structure[1] | |
| Trigonal | |
| R3m, No. 166 | |
a = 5.469(2) Å α = 70.67(3)°, β = 70.67(3)°, γ = 70.67(3)°
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Lattice volume (V)
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141.079 Å3 |
Formula units (Z)
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1 |
| Hazards | |
| GHS labelling:[6] | |
| Warning | |
| H315, H319, H335 | |
| P261, P264, P264+P265, P271, P280, P302+P352, P304+P340, P305+P351+P338, P319, P321, P332+P317, P337+P317, P362+P364, P403+P233, P405, P501 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
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Caesium dichloroiodate, also called caesium dichloroiodide is an inorganic compound with the formula Cs[ICl2]. This yellow-orange salt is a crystalline solid in its pure form at room temperature. Fractional crystallization of caesium dichloroiodate may be used to separate caesium from rubidium and purify it, as rubidium dichloroiodate (Rb[ICl2]) is much more soluble in hydrochloric acid. Furthermore, other metal impurities do not form dichloroiodate salts.[7][8][9][10] Caesium dichloroiodate is notable for containing the linear dichloroiodate anions [ICl2]−, with connectivity Cl-I-Cl, which is analog of triiodide anion [I3]−.
Structure
The resolution of the crystal structure of caesium dichloroiodate via X-ray diffraction, by Wyckoff in his 1919 Ph.D. thesis (published 1920), established the linearity of the dichloroiodate ion, one of the first complex ions to have its structure solved using X-ray crystallography.[11][12] The dichloroiodate ion is symmetric, with an I–Cl bond length of 2.548 Å.[1]
Properties
Caesium dichloroiodate readily dissolves in room temperature water, forming a dark yellow-purple solution. This color is due to the production of free iodine via the hydrolysis of caesium dichloroiodate to elemental iodine, hydrochloric acid, and caesium ions. Such hydrolysis also slowly occurs on contact with normal air, which contains moisture, however this change is negligible over the time scale of a few days to weeks.
Preparation
Caesium dichloroiodate may be synthesized via the reaction of caesium chloride (acidified using hydrochloric acid (or acetic acid[13])) with iodine monochloride. Thermolysis (ending at 450–500 °C) recovers the starting materials.[9] Additionally, caesium dichloroiodate may be synthesized in-situ via the addition of chlorine gas to an acidic solution containing elemental iodine and caesium chloride.[14]
References
- ^ a b c van Bolhuis, F.; Tucker, P. A. (15 November 1973). "Refinement of the crystal structure of caesium dichloride". Acta Crystallographica Section B. 29 (11): 2613–2614. doi:10.1107/S0567740873007144.
- ^ Standard X-ray Diffraction Powder Patterns (PDF). Vol. 3. National Bureau of Standards. 1953. p. 50.
- ^ Harris, G.S.; McKechnie, J.S. (January 1982). "Thermogravimetric analysis and dissociation pressure of caesium trihalides". Polyhedron. 1 (2): 215–216. doi:10.1016/S0277-5387(00)80991-2.
- ^ Справочник экспериментальных данных по растворимости солевых систем. - Т. 3. - Л.: ГНТИХЛ, 1961 pp. 2186 [Russian], Ефимов А.И. и др. Свойства неорганических соединений. Справочник. - Л.: Химия, 1983 [Russian], Ефимов А.И. и др. Свойства неорганических соединений. Справочник. - Л.: Химия, 1983 [Russian] (Respectively)
- ^ "cesium dichloroiodate(I)". chemister.ru. Retrieved 2025-07-31.
- ^ PubChem. "Cesium dichloroiodate". pubchem.ncbi.nlm.nih.gov. Retrieved 2025-07-31.
- ^ Baxter, Gregory Paul; Thomas, Joseph Smith (May 1934). "A Revision of the Atomic Weight of Cesium". Journal of the American Chemical Society. 56 (5): 1108–1110. doi:10.1021/ja01320a030.
- ^ Ishibashi, Masayoshi; Yamamoto, Toshio; Hara, Tadashi (1959). "On the Purification of Cesium Chloride". Bulletin of the Institute for Chemical Research, Kyoto University. hdl:2433/75692.
- ^ a b Simons, E.L.; Cairns, E.J.; Sangermano, L.D. (February 1966). "Purification and preparation of some caesium compounds". Talanta. 13 (2): 199–204. doi:10.1016/0039-9140(66)80026-7. PMID 18959868.
- ^ Niu, Heyue; Yu, Mingming; Mubula, Yusufujiang; Zeng, Ling; Xu, Kun; Zhu, Zhehan; He, Guichun (18 July 2025). "Extraction of Rubidium and Cesium from a Variety of Resources: A Review". Materials. 18 (14) 3378. doi:10.3390/ma18143378. PMC 12300911. PMID 40731586.
- ^ Pauling, Linus (1962). "Chapter 9. Problems of Inorganic Structures". In Ewald, Paul Peter (ed.). 50 Years of X-Ray Diffraction. International Union of Crystallography. p. 141.
- ^ Wyckoff, Ralph W. G. (June 1920). "The Crystal Structure of Cesium Dichloro-iodide". Journal of the American Chemical Society. 42 (6): 1100–1116. doi:10.1021/ja01451a005.
- ^ Course Hero. (2022, November). Experiment 2: The preparation of cesium dichloroiodide Grant MacEwan University. Retrieved September 25, 2025, from https://www.coursehero.com/file/178619164/Experiment-2-The-Preparation-of-Cesium-Dichloroiodidepdf/
- ^ "Chlorine, Bromine, Iodine", Handbook of Preparative Inorganic Chemistry, Academic Press, pp. 272–333, 1963-01-01, doi:10.1016/B978-0-12-395590-6.50013-2, retrieved 2026-02-23