Sodium iodide

Cubic

Well, I

V09FX02, V10XA01

Colorless solid

Fixed

• 3.67 g · cm -3 ( 20 ° C) (anhydrous )
• 2.45 g · cm -3 ( dihydrate)

662 ° C

1304 ° C

Well in water (1793 g · l-1 at 20 ° C)

1,774

Attention

4340 mg · kg -1 ( LD50, rat, oral)

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Sodium iodide (deprecated sodium ) is a white, crystalline salt with the chemical formula NaI, which is used for the detection of ionizing radiation for the treatment of iodine deficiency and for the production of alkyl iodides in the Finkelstein reaction.

Production and representation

The recovery can be effected by the reaction of sodium carbonate with iron iodide. It is thereby obtained as the dihydrate.

Properties

The salt may be present as anhydrous compound (anhydrous ), di - or pentahydrate. Above 65 ° C, the anhydrate crystallized from aqueous solutions. Crystallization at room temperature yields the dihydrate. At lower temperatures of between -13.5 ° C and -31.5 ° C. The pentahydrate can be obtained.

The standard enthalpy of formation of sodium iodide is ΔHf0 = -288 kJ / mol.

Use

Sodium iodide is commonly used to treat and as a precaution against iodine deficiency. The radioactive isotopes 123Iod and 131Iod are as sodium iodide for nuclear medical diagnosis - used - particularly for thyroid scintigraphy. 131Iod is used as sodium iodide in the context of radioiodine as a therapeutic agent.

Another field of application is the Finkelstein reaction. Here, an alkyl chloride or bromide is treated with sodium iodide in acetone.

This displaces the better leaving group iodide poorer leaving group chloride. The driving force of the reaction is the low solubility of sodium chloride in acetone, by which the equilibrium is shifted to the side of the alkyl iodide. Addition of acetone and acetonitrile and THF can be used as a solvent.

Furthermore, there are many of the Finkelstein reaction, analogous reactions such as the representation of trimethylsilyl iodide from trimethylsilyl, acetyl from acetyl chloride, etc.

In crystals doped with thallium on a portion of the sodium positions ( NaI: Tl ), caused by ionizing radiation photons and can thus be used as scintillation, traditionally in nuclear medicine, geophysics, nuclear physics, etc. NaI: Tl is the most prevalent scintillation because it produces the most light. The crystals are usually coupled with a photomultiplier and hermetically sealed because NaI is hygroscopic. Some parameters ( radiation hardness, afterglow, transparency) can be influenced by the conditions under which the crystal grows is controlled. Crystals with higher doping are used as X-ray detectors with high spectroscopic quality. Sodium iodide may be used as a single crystal or polycrystalline.