Sodium iodide

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Sodium iodide
Sodium iodide Sodium iodide
CAS number 7681-82-5 YesY
13517-06-1 (dihydrate)
PubChem 5238
ChemSpider 5048 YesY
ChEBI CHEBI:33167 YesY
RTECS number WB6475000
Jmol-3D images Image 1
Molecular formula NaI
Molar mass 149.89 g/mol
Appearance white solid
Odor odorless
Density 3.67 g/cm3
Melting point 661 °C (1,222 °F; 934 K)
Boiling point 1,304 °C (2,379 °F; 1,577 K)
Solubility in water 178.8 g/100 mL (20 °C)
184 g/100 mL (25 °C)
294 g/100 mL (70 °C)
302 g/100 mL (100 °C)
Solubility soluble in ethanol and acetone (39.9 g/100 mL)
Acidity (pKa) 8-9.5
91 J·mol−1·K−1[1]
−288 kJ·mol−1[1]
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
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

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


Sodium iodide is manufactured from the reaction between iodine and sodium hydroxide.


Food supplement[edit]

Sodium iodide, as well as potassium iodide, is commonly used to treat and prevent iodine deficiency. Iodized table salt contains one part sodium or potassium iodide to 100,000 parts of sodium chloride.[2]

Organic synthesis[edit]

Sodium iodide is used in the Finkelstein reaction, for conversion of an alkyl chloride into an alkyl iodide. This method relies on the insolubility of sodium chloride in acetone to drive the reaction:

R-Cl + NaI → R-I + NaCl

Nuclear medicine[edit]

Some radioactive iodide salts of sodium, including [125I]NaI and [131I]NaI, have radiopharmaceutical uses, such as in the treatment of thyroid cancer and hyperthyroidism[3] or as radiolabeling tracers in imaging (see Isotopes of iodine > Radioiodines I-123, I-124, I-125, and I-131 in medicine and biology).

Thallium-doped NaI(Tl) scintillators[edit]

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. 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 wavelength of maximum emission is 415 nm.[4]

Solubility data[edit]

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 50.4425
Formamide 57 - 85
Acetamide 32.3
Dimethylformamide 3.7 - 6.4
Dichloromethane 0.009 [6]

See also[edit]


  1. ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A23. ISBN 0-618-94690-X. 
  2. ^ Lyday, Phyllis A. "Iodine and Iodine Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim, ISBN 978-3-527-30673-2 doi:10.1002/14356007.a14_381 Vol. A14 pp. 382–390.
  3. ^ The Free Dictionary: sodium iodide 131I
  4. ^ Scintillation Materials
  5. ^ Burgess, J. "Metal Ions in Solution" (Ellis Horwood, New York, 1978) ISBN 0-85312-027-7
  6. ^ Danil de Namor, A.F.; J. Chem. Soc., Faraday Trans. 1, 1989,85, 2705-2712 DOI: 10.1039/F19898502705

External links[edit]