Sodium iodide
Identifiers
CAS number	7681-82-5 Y, 13517-06-1 (dihydrate)
PubChem	5238
RTECS number	WB6475000
Properties
Molecular formula	NaI
Molar mass	149.894 g/mol
Appearance	white solid deliquescent
Density	3.67 g/cm3
Melting point	661 °C
Boiling point	1304 °C
Solubility in water	178.8 g/100 mL (20 °C) 184 g/100 mL (25 °C) 294 g/100 mL (70 °C)
Solubility	soluble in ethanol and acetone
Structure
Coordination geometry	Octahedral
Hazards
MSDS	ICSC 1009
EU Index	Not listed
Main hazards	Irritant, can harm the unborn child
Flash point	Non-flammable
Related compounds
Other anions	Sodium fluoride Sodium chloride Sodium bromide
Other cations	Lithium iodide Potassium iodide Rubidium iodide Caesium iodide
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium iodide is a white, crystalline salt with chemical formula NaI used in radiation detection, treatment of iodine deficiency, and as a reactant in the Finkelstein reaction.

Contents 1 Uses 2 Solubility data 3 References 4 See also 5 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 + NaI → R-I + NaCl

Sodium iodide crystals doped with thallium, NaI(Tl), when subjected to ionizing radiation, emit photons (i.e., scintillate) and are used in scintillation detectors, traditionally in nuclear medicine, geophysics, nuclear physics, and environmental measurements. 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 (i.e., radiation hardness, afterglow, transparency) can be achieved by varying the conditions of the crystal growth. Crystals with a 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.

The radioactive iodide salt of sodium, Na¹³¹I, is used for the treatment of thyroid cancer and hyperthyroidism.^[1]

[edit] Solubility data

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
[2]

[edit] References

1. ^ The Free Dictionary: sodium iodide 131I
2. ^ Burgess, J. "Metal Ions in Solution" (Ellis Horwood, New York, 1978) ISBN 0-85312-027-7

[edit] See also

• Gamma spectroscopy
• Scintillation counter
• Teratology

[edit] External links

• International Chemical Safety Card 1009 - Sodium Iodide (Anhydrous)
• Material Safety Data Sheet (MSDS) - Safety data for sodium iodide
• Sodium Iodide Consumer Information
• Surveillance and Measurement (SAM) Model 940 Radioactive Isotope Identification Device

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