Sodium iodide

Sodium iodide
Identifiers
CAS number	7681-82-5 Y,  13517-06-1 (dihydrate)
PubChem	5238
ChemSpider	5048 Y
UNII	F5WR8N145C Y
ChEBI	CHEBI:33167 N
ChEMBL	CHEMBL1644695 N
RTECS number	WB6475000
Jmol-3D images	Image 1
SMILES [Na+].[I-]
InChI InChI=1S/HI.Na/h1H;/q;+1/p-1 Y Key: FVAUCKIRQBBSSJ-UHFFFAOYSA-M Y InChI=1/HI.Na/h1H;/q;+1/p-1 Key: FVAUCKIRQBBSSJ-REWHXWOFAL
Properties
Molecular formula	NaI
Molar mass	149.89 g/mol
Appearance	white solid deliquescent
Density	3.67 g/cm3
Melting point	661 °C, 934 K, 1222 °F
Boiling point	1304 °C, 1577 K, 2379 °F
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 (39.9 g/100 mL)
Structure
Coordination geometry	Octahedral
Hazards
MSDS	[1]
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
N (verify) (what is: Y/N?) 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.

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 activated with thallium, NaI(Tl), when subjected to ionizing radiation, emits photons (i.e., scintillate) and is 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 yield of the commonly used scintillators. 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]

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]

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

See also

• Gamma spectroscopy
• Scintillation counter
• Teratology

External links

• International Chemical Safety Card 1009 - Sodium Iodide (Anhydrous)
• Material Safety Data Sheet (MSDS) - Safety data for sodium iodide
• Sodium Iodide Consumer Information