Sodium iodide

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Sodium iodide

General
Molecular formula	NaI
Molar mass	149.89 g/mol
Appearance	White solid.
CAS number	[7681-82-5]
Properties
Density and phase	3.67 g/cm³, solid
Solubility in water	184 g/100 ml (25°C)
Melting point	660°C
Boiling point	1304°C
Structure
Coordination geometry	Octahedral
Crystal structure	Halite
Hazards
MSDS	External MSDS
EU classification	Irritant (I).
R-phrases	R36, R38, R42, R43, R61
S-phrases	S26, S36, S37, S39
NFPA 704	0 2 1
Flash point	Non-flammable.
RTECS number	WB6475000
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other anions	Sodium fluoride Sodium chloride Sodium bromide
Other cations	Lithium iodide Potassium iodide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Sodium iodide is a white, crystalline salt with chemical formula Na I used in radiation dectection, treatment of iodine deficiency, and as a catalyst in the Finkelstein reaction.

Solubility of NaI in various solvents (g NaI / 100g of solvent at 25°C)
H₂O	184
Liquid ammonia	162
Liquid sulfur dioxide	15
Methanol	62.5 - 83.0
Formic acid	61.8
Acetonitrile	24.9
Acetone	28.0
Formamide	57 - 85
Acetamide	32.3
Dimethylformamide	3.7 - 6.4
Reference: Burgess, J. Metal Ions in Solution (Ellis Horwood, New York, 1978) ISBN 0-85312-027-7

1 Uses
2 Notes, references
3 See also
4 External links

[edit] Uses

Sodium iodide is commonly used to treat and prevent iodine deficiency.

Sodium iodide is used in polymerase chain reactions, and also (as an acetone solution) in the Finkelstein reaction, for conversion of an alkyl chloride into an alkyl iodide. This relies on the insolubility of sodium chloride in acetone to drive the reaction.

R-Cl + Na I → R-I + Na Cl

Solid crystals of sodium iodide can be used to detect radiation (e.g. radiation from uranium) - a solid crystal of sodium iodide creates a pulse of light when radiation interacts with it. ^[1]

Sodium iodide crystals doped with thallium, NaI(Tl), when subjected to ionising radiation, emit photons (scintillate) and are used in scintillation detectors, traditionally in nuclear medicine, geophysics, nuclear physics, environmental measurements, etc. NaI(Tl) is the most widely used scintillation material and has the highest light output. The crystals are usually coupled with a photomultiplier tube, in a hermetically sealed assembly, as sodium iodide is hygroscopic. Fine tuning of some parameters (radiation hardness, afterglow, transparency) can be achieved by varying the conditions of the crystal growth. Crystals with higher level of doping are used in X-ray detectors with high spectrometric quality. Sodium iodide can be used both as single crystals and as polycrystals for this purpose.