Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium (Na+) and iodide (I−) in a crystal lattice. It is used mainly as a nutritional supplement and in organic chemistry. It is produced industrially as the salt formed when acidic iodides react with sodium hydroxide.[ It is a chaotropic agent.
]
Uses
Food supplement
Sodium iodide, as well as potassium iodide, is commonly used to treat and prevent iodine deficiency. Iodized table salt contains 10 ppm iodide.
Organic synthesis
Sodium iodide is used for conversion of into . This method, the Finkelstein reaction,
- :R–Cl + NaI → R–I + NaCl
Nuclear medicine
Some radioactive iodide salts of sodium, including Na125I and Na131I, have radiopharmaceutical uses for thyroid cancer and hyperthyroidism or as radioactive tracer 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
Sodium iodide activated with thallium, NaI(Tl), when subjected to ionizing radiation, emits (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 Dopant are used in X-ray detectors with high spectrometric quality. Sodium iodide can be used both as and as polycrystals for this purpose. The wavelength of maximum emission is 415 nm.
Radiocontrast
António Egas Moniz searched for a radiocontrast agent for cerebral angiography.
Solubility data
Sodium iodide exhibits high solubility in some organic solvents, unlike sodium chloride or even bromide:
|
| 1842 |
| 1620 |
| 150 |
| 625–830 |
| 618 |
| 249 |
504 |
| 570–850 |
| 323 (41.5 °C) |
| 37–64 |
0.09 |
Stability
Iodides (including sodium iodide) are detectably oxidized by atmospheric oxygen (O2) to molecular iodine (I2). I2 and I− complex to form the triiodide complex, which has a yellow color, unlike the white color of sodium iodide. Water accelerates the oxidation process, and iodide can also produce I2 by photooxidation, therefore for maximum stability sodium iodide should be stored under dark, low temperature, low humidity conditions.
See also
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Gamma spectroscopy
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Scintillation counter
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Teratology
Cited sources
External links
