Sodium azide

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Sodium azide

General
Other names	Sodium trinitride
Molecular formula	NaN₃
Molar mass	65.01 g/mol
Appearance	White solid.
CAS number	[26628-22-8]
Properties
Density and phase	1.85 g/cm³, solid
Solubility in water	41.7 g/100 ml (17°C)
Melting point	275°C decomp.
Structure
Coordination geometry	?
Crystal structure	?
Hazards
MSDS	External MSDS
EU classification	Highly toxic (T+) Dangerous for the environment (N)
NFPA 704
R-phrases	R21, R26, R28, R32, R50, R53
S-phrases	S1, S2, S28, S45, S60, S61
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other anions	?
Other cations	Potassium azide
Related compounds	Sodium cyanide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Sodium azide (NaN₃) is a highly toxic chemical that exists as an odorless white solid. Its solution in water is slowly hydrolyzed into a very toxic gas, hydrogen azide (HN₃), which also forms when NaN₃ reacts with a strong acid. It may react with heavy metal ions such as copper, silver or lead to form metal azides which are very unstable, easily synthesized, and highly explosive. Care should be taken when disposing of this material in the presence of elementary metals as it may react with them. After use, this compound should be disposed of in a responsible manner, since it is very harmful to the environment.

When pure, it is a white crystalline solid, odorless, and easily soluble in water. It is slightly soluble in ethanol and starts to decompose vigorously to sodium metal and nitrogen gas at approximately 300 °C. It is very toxic to the aquatic environment, and so the disposal of this substance should be carefully regulated. It should be destroyed by oxidation or reduction before being released to the environment.

The common synthesis method involves using the Wislicenus process, which first reacts sodium metal, Na, with ammonia, NH₃, to get sodium amide,

2Na + 2NH₃ → 2NaNH₂ + H₂

then reacts the sodium amide with nitrous oxide.

2NaNH₂ + N₂O → NaN₃ + NaOH + NH₃

Sodium azide is best known as the chemical found in automobile airbags. An electrical charge triggered by automobile impact causes sodium azide to explode and release nitrogen gas inside the airbag. The chemical equation for this reaction is 2NaN₃ → 2Na + 3N₂. The sodium that is formed is a potential hazard itself and is converted by reaction with other ingredients, such as potassium nitrate (KNO₃) and silica (SiO₂), into an inert alkaline silicate 'glass'.

Sodium azide is also used as a chemical preservative in hospitals and laboratories. In this role, it is a biocide; it is especially important in bulk reagents and stock solutions which may be capable of supporting bacterial growth where the sodium azide acts as a bacteriostatic by inhibiting cytochrome oxidase in gram-negative bacteria, gram-positive (streptococci, pneumococci, lactobacilli) are resistant ^[1](a characteristic similar to antibiotic resistance). It is also used in agriculture (farming) for pest control, and in detonators and other explosives.

1 Toxic effects
- 1.1 Treatment
2 References
3 External links

[edit] Toxic effects

The toxicity of this material is often compared with that of cyanide salts as they give similar symptoms.

The seriousness of poisoning caused by sodium azide depends on the amount, route, and length of time of exposure, as well as the age and preexisting medical condition of the person exposed. Breathing the gas (hydrogen azide) that is formed from sodium azide causes the most harm, but ingesting (swallowing) sodium azide can be toxic as well. The gas formed from sodium azide is most dangerous in enclosed places where the gas will be trapped. The toxic gas quickly disperses in open spaces, making it less harmful outdoors. The gas formed from sodium azide is less dense (lighter) than air, so it will rise.

Azide anions prevent the cells of the body from using oxygen, inhibiting the function of cytochrome oxidase by binding irreversibly to the heme cofactor in a process similar to that of carbon monoxide. When this happens, the cells die. Sodium azide is more harmful to the heart and the brain than to other organs, because the heart and the brain require a constant supply of oxygen.

People exposed to a small amount of sodium azide by breathing it, absorbing it through their skin, or eating foods that contain it may have some or all of the following symptoms within minutes:

Rapid breathing
Restlessness
Dizziness
Weakness
Headache
Nausea and vomiting
Rapid heart rate
Red eyes (gas or dust exposure)
Clear drainage from the nose (gas or dust exposure)
Cough (gas or dust exposure)
Skin burns and blisters (explosion or direct skin contact)

Exposure to a large amount of sodium azide by any route may cause these other health effects as well:

Convulsions
Low blood pressure
Slow heart rate
Loss of consciousness
Lung injury
Respiratory failure leading to death

Showing these signs and symptoms does not necessarily mean that a person has been exposed to sodium azide. Survivors of serious sodium azide poisoning may have heart and brain damage.

[edit] Treatment

Sodium azide poisoning is treated with supportive medical care in a hospital setting. No specific antidote exists for sodium azide poisoning. The most important thing is for victims to seek medical treatment as soon as possible.