CsI crystal
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Scintillating CsI crystal
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Crystal structure
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Names | |
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IUPAC name
Caesium iodide
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Other names
Cesium iodide
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Identifiers | |
3D model (JSmol)
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ChemSpider | |
ECHA InfoCard | 100.029.223 |
EC Number |
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PubChem CID
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RTECS number |
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
CsI | |
Molar mass | 259.809 g/mol[2] |
Appearance | white crystalline solid |
Density | 4.51 g/cm3[2] |
Melting point | 632 °C (1,170 °F; 905 K)[2] |
Boiling point | 1,280 °C (2,340 °F; 1,550 K)[2] |
848 g/L (25 °C)[2] | |
-82.6·10−6 cm3/mol[3] | |
Refractive index (nD)
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1.9790 (0.3 µm) 1.7873 (0.59 µm) 1.7694 (0.75 µm) 1.7576 (1 µm) 1.7428 (5 µm) 1.7280 (20 µm)[4] |
Structure | |
CsCl, cP2 | |
Pm3m, No. 221[5] | |
a = 0.4503 nm
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Lattice volume (V)
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0.0913 nm3 |
Formula units (Z)
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1 |
Cubic (Cs+) Cubic (I−) | |
Thermochemistry | |
Heat capacity (C)
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52.8 J/mol·K[6] |
Std molar
entropy (S⦵298) |
123.1 J/mol·K[6] |
Std enthalpy of
formation (ΔfH⦵298) |
−346.6 kJ/mol[6] |
Gibbs free energy (ΔfG⦵)
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-340.6 kJ/mol[6] |
Hazards | |
GHS labelling: | |
Warning | |
H315, H317, H319, H335 | |
P201, P202, P261, P264, P270, P271, P272, P273, P280, P281, P301+P312, P302+P352, P304+P340, P305+P351+P338, P308+P313, P312, P321, P330, P332+P313, P333+P313, P337+P313, P362, P363, P391, P403+P233, P405, P501 | |
Flash point | Non-flammable |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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2386 mg/kg (oral, rat)[1] |
Related compounds | |
Other anions
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Caesium fluoride Caesium chloride Caesium bromide Caesium astatide |
Other cations
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Lithium iodide Sodium iodide Potassium iodide Rubidium iodide Francium iodide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Caesium iodide or cesium iodide (chemical formula CsI) is the ionic compound of caesium and iodine. It is often used as the input phosphor of an X-ray image intensifier tube found in fluoroscopy equipment. Caesium iodide photocathodes are highly efficient at extreme ultraviolet wavelengths.[7]