Chemistry:Caesium dichloroiodate

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Short description: Chemical compound
Caesium dichloroiodate
A few mg of caesium dichloroiodate on a lab spatula, displaying its vibrant yellow-orange color
Caesium dichloroiodate on a lab spatula
Names
IUPAC name
Caesium dichloroiodate(I)
Other names
Cesium dichloroiodide
Identifiers
3D model (JSmol)
ChemSpider
EC Number
  • 239-686-3
Properties[5]
Cl2CsI
Molar mass 330.71 g·mol−1
Appearance trigonal orange-yellow crystals[1]
Density
  • 3.86 g·cm-3 (20 °C)
  • 3.888 g·cm-3 (26 °C)[2]
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)°
141.079 Å3
1
Hazards
GHS pictograms GHS07: Harmful
GHS Signal word Warning
HH315Script error: No such module "Preview warning".Category:GHS errors, HH319Script error: No such module "Preview warning".Category:GHS errors, HH335Script error: No such module "Preview warning".Category:GHS errors
PP261Script error: No such module "Preview warning".Category:GHS errors, PP264Script error: No such module "Preview warning".Category:GHS errors, PP264+P265Script error: No such module "Preview warning".Category:GHS errors, PP271Script error: No such module "Preview warning".Category:GHS errors, PP280Script error: No such module "Preview warning".Category:GHS errors, PP302+P352Script error: No such module "Preview warning".Category:GHS errors, PP304+P340Script error: No such module "Preview warning".Category:GHS errors, PP305+P351+P338Script error: No such module "Preview warning".Category:GHS errors, PP319Script error: No such module "Preview warning".Category:GHS errors, PP321Script error: No such module "Preview warning".Category:GHS errors, PP332+P317Script error: No such module "Preview warning".Category:GHS errors, PP337+P317Script error: No such module "Preview warning".Category:GHS errors, PP362+P364Script error: No such module "Preview warning".Category:GHS errors, PP403+P233Script error: No such module "Preview warning".Category:GHS errors, PP405Script error: No such module "Preview warning".Category:GHS errors, PP501Script error: No such module "Preview warning".Category:GHS errors
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Caesium dichloroiodate, also called caesium dichloroiodide is an inorganic compound with the formula Cs[[[Chemistry:Iodine|I]]Cl
2]. 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 [ICl
2]−
, with connectivity Cl-I-Cl, which is analog of triiodide anion [I
3]−
.

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

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

  1. ↑ 1.0 1.1 1.2 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. 
  2. ↑ Standard X-ray Diffraction Powder Patterns. 3. National Bureau of Standards. 1953. p. 50. https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular539v3.pdf#page=54. 
  3. ↑ 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. 
  4. ↑ 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)
  5. ↑ "cesium dichloroiodate(I)". https://chemister.ru/Databases/Chemdatabase/properties-en.php?id=2945. 
  6. ↑ PubChem. "Cesium dichloroiodate" (in en). https://pubchem.ncbi.nlm.nih.gov/compound/23685551. 
  7. ↑ 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. 
  8. ↑ "On the Purification of Cesium Chloride". Bulletin of the Institute for Chemical Research, Kyoto University. 1959. 
  9. ↑ 9.0 9.1 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. 
  10. ↑ 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). doi:10.3390/ma18143378. PMID 40731586. 
  11. ↑ "Chapter 9. Problems of Inorganic Structures". 50 Years of X-Ray Diffraction. International Union of Crystallography. 1962. p. 141. https://archive.org/details/fiftyyearsofxray00ewal/page/141/mode/2up?q=wyckoff+cesium+dichloroiodide. 
  12. ↑ 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. 
  13. ↑ 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/
  14. ↑ "Chlorine, Bromine, Iodine" (in en-US), Handbook of Preparative Inorganic Chemistry (Academic Press): pp. 272–333, 1963-01-01, doi:10.1016/B978-0-12-395590-6.50013-2, https://www.sciencedirect.com/science/chapter/edited-volume/abs/pii/B9780123955906500132, retrieved 2026-02-23 



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