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.


Food supplementEdit

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.[1]

Organic synthesisEdit

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

Radiation physics and medicineEdit

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.[2]

Solubility dataEdit

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

See alsoEdit


  1. Lyday, Phyllis A. "Iodine and Iodine Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim, ISBN 9783527306732 DOI:10.1002/14356007.a14_381 Vol. A14 pp. 382–390.
  2. The Free Dictionary: sodium iodide 131I
  3. Burgess, J. "Metal Ions in Solution" (Ellis Horwood, New York, 1978) ISBN 0-85312-027-7

External linksEdit

This page uses content from Wikipedia.
The original article was at Sodium Iodide. The list of authors can be seen in the page history. As with Chemistry, the text of Wikipedia is available under the GNU Free Documentation License.

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