What Is Sodium Azide?
Sodium azide is a white crystalline powder at room temperature with the molecular formula NaN3. It has a molecular weight of 65.01, a specific gravity of 1.85, a boiling point of about 300°C, and a melting point of 275°C. This compound is soluble in water and liquid ammonia but insoluble in ethanol and ether. It is potentially explosive when in contact with metals and is toxic, necessitating careful handling.
Properties of Sodium Azide
Sodium azide is well known for its toxicity and the risk of explosion. Inhalation or ingestion can cause serious health issues such as dizziness, breathing difficulties, and convulsions. Proper precautions must be taken to avoid fire, explosion, and exposure.
Uses of Sodium Azide
- Introduction of Azide Groups: Sodium azide is used to introduce azide groups into organic compounds, enabling cycloaddition reactions with alkynes in the presence of copper catalysts.
- Introduction of Amino Groups: The azide group can be converted to an amino group, for example, through palladium-catalyzed catalytic hydrogen reduction. Sodium azide was previously used in automobile airbags but is now being replaced due to toxicity concerns.
- Preservatives: It’s used as a preservative in commercial antibodies but is not included in antibodies labeled for horseradish peroxidase due to enzyme inhibition.
- Dissolved Oxygen (DO) Measurement: Used in the Winkler method for measuring DO in water, preventing inaccurate measurements due to nitrite ions.
Reactivity of Sodium Azide
Sodium azide decomposes into sodium and nitrogen at high temperatures and reacts with acids to produce hydrogen azide (HN3), which is both toxic and explosive.
Production of Sodium Azide
Industrially, sodium azide is produced through the Wislicenus process, involving the reaction of liquid ammonia with nitrous oxide (N2O) via sodium amide (NaNH2).