- Structure
- Nomenclature
- Properties
- Physical state
- Molecular weight
- Melting point
- Density
- Solubility
- Dissociation constants
- Chemical properties
- Biochemical properties
- Obtaining
- Applications
- In motor vehicles and aircraft
- In the chemical industry
- In agriculture
- In the preparation of other chemical compounds
- In the explosives industry
- In biochemical laboratories
- In various uses
- Risks
- References
The sodium azide is a crystalline inorganic solid formed by sodium ion Na + and azide ion N 3 -. Its chemical formula is NaN 3. The compound NaN 3 is the sodium salt of hydrazoic acid HN 3. NaN 3 is a colorless to white crystalline solid.
Although it is a very toxic compound, one of its most widespread uses has been in air bags that inflate instantly during vehicle accidents. It is also used to quickly inflate the emergency slides of airplanes. However, its use is currently being highly questioned in both cases due to its toxicity.
Solid NaN 3 sodium azide. И.С. Непоклонов. Source: Wikimedia Commons.
It is used in chemical research laboratories to synthesize various types of compounds and in biochemical laboratories for studies with bacteria, fungi, or mammalian or human cells.
In some laboratories it is used to sterilize materials or equipment, but certain types of microorganisms resist its biocidal action.
It has also been used in agriculture to eliminate parasites from the soil or in the timber industry to prevent pine wood from being stained with fungi.
Structure
NaN 3 sodium azide is made up of a Na + sodium cation and a N 3 - azide anion.
Sodium azide is made up of the sodium ion Na + and the azide ion N 3 -. Lukáš Mižoch. Source: Wikimedia Commons.
The azide ion N 3 - is formed by 3 nitrogen atoms (N) joined together by covalent bonds that can be single, double or triple, since the electrons are shared between the three.
Said anion has a linear structure, that is, the three nitrogen atoms arranged in a straight line. Furthermore, the structure is symmetrical.
Possible Lewis structures of the azide anion. Author: Marilú Stea.
Nomenclature
- Sodium azide
- Sodium azide
Properties
Physical state
Colorless to white crystalline solid. Hexagonal crystals.
Molecular weight
65.01 g / mol
Melting point
It decomposes at 275 ° C.
Density
1.846 g / cm 3 at 20 ºC
Solubility
It is very soluble in water: 41.7 g / 100 mL at 17 ºC. It is slightly soluble in ethanol and insoluble in ethyl ether.
Dissociation constants
It has a pK b of 9.3. Aqueous solutions contain NH 3, which quickly escapes to the environment at 37 ºC.
Chemical properties
NaN 3 is very corrosive towards aluminum and moderately towards copper and lead.
According to a certain source, sodium azide is not explosive. It decomposes smoothly and completely when heated to 300 ° C or more, forming sodium metal Na and nitrogen gas N 2.
2 NaN 3 → 2 Na + 3 N 2 ↑
It is a nitriding agent, this means that it serves to nitrogenize or add nitrogen to other chemical compounds or to the surface of materials such as steel.
It is stable in neutral or alkaline water in the absence of light. It is decomposed by solar radiation.
Biochemical properties
Sodium azide inhibits an enzyme called cytochrome oxidase which is found in the mitochondria of cells and is significantly involved in respiration and energy generation.
Its action prevents the generation of ATP, a key compound in cellular activities and the cell deteriorates or damages.
If ingested, inhaled or in contact with sodium azide, it is very toxic and can be fatal.
Obtaining
Ammonia NH 3 is reacted with sodium metal Na at 350 ºC in a closed steel container, obtaining sodium amide NaNH 2.
The sodium amide NaNH 2 is reacted with dinitrogen monoxide N 2 O at 230 ° C in a nickel reactor, and thus a mixture of sodium azide NaN 3, sodium hydroxide NaOH and ammonia NH 3 is formed.
2 NaNH 2 + N 2 O → NaN 3 + NaOH + NH 3
It can also be obtained by reacting sodium amide with sodium nitrate NaNO 3 at 175 ºC:
3 NaNH 2 + NaNO 3 → NaN 3 + 3 NaOH + NH 3
To purify the azide, water is added to the mixture, the crystals of the azide are washed, and then the water is evaporated. The remaining crystalline material is sodium azide NaN 3 which is then dried at 110 ° C.
Applications
In motor vehicles and aircraft
Sodium azide has long been used in the automotive industry as a nitrogen generator to rapidly inflate safety airbags (airbags) on the steering wheels of cars and trucks when an impact occurs.
It has also been used in inflatable slides that are used to quickly escape from the interior of planes that have landed in emergency situations.
In both cases, the mechanism involves the action of a spark to produce an immediate reaction between sodium azide and certain compounds, generating nitrogen gas N 2 and sodium oxide Na 2 O.
In this application, the instantaneous release of a cold and non-toxic gas is required, so nitrogen is the most appropriate gas.
Security bags that have already been used in vehicles. Author: Marcel Langthim. Source: Pixabay.
However, this use is decreasing due to the toxicity of sodium azide and less toxic compounds are being used instead.
In the chemical industry
It is used as a retarder in the manufacture of sponge rubber, to prevent the coagulation of styrene or butadiene latex when they are stored in contact with metals and to decompose nitrites in the presence of nitrates.
In agriculture
It has been used in agriculture: as a biocide and fumigant, it is also nematicide, that is, it is applied in soils to eliminate nematodes, which are parasites that attack some crops.
Damage caused by nematodes in the root of a plant. Author: RedWolf. Source: Wikimedia Commons.
It has also worked as a herbicide and to prevent rotting of fruits.
Recently NaN 3 has been used in the preparation of okra or okra seeds to observe their resistance to waterlogging conditions.
The seeds to which NaN 3 was previously applied generated seedlings that withstood the flood conditions better than the untreated ones, improved the height of the plants, increased the number of leaves and increased the number of roots even with excess water.
In the preparation of other chemical compounds
It is used as a chemical reagent in the synthesis of organic compounds, for example to prepare many organic azides, such as tosyl azide or azides of tertiary alkyl groups, which are important in chemical synthesis.
It is used to prepare hydrazoic acid (HN 3) and pure sodium (Na).
In the explosives industry
NaN 3 sodium azide is an intermediate in the manufacture of explosives, as it is used for the preparation of lead azide Pb (N 3) 2. The latter is a compound that explodes when struck with force, which is why it is used in the construction of detonating devices.
NaN 3 sodium azide is used to make the compound lead Pb (N 3) 2 azide that is part of blasting devices. Author: OpenClipart-Vectors. Source: Pixabay.
In biochemical laboratories
Sodium azide is used when sterile laboratory equipment is required, as it is capable of destroying different types of microorganisms.
It is a biocidal agent. However, some sources indicate that some types of bacteria are resistant to its action.
This is achieved by blocking the oxygen binding site in cytochrome oxidase, which is an enzyme involved in the energy production process of some microorganisms.
It is used in automatic blood counters, also in the differential selection of bacteria and to preserve laboratory reagent solutions as it prevents the growth of certain microorganisms in them.
In various uses
Sodium azide is used in the lumber industry to prevent the growth of brown fungal spots on pine wood.
It has also been used in the Japanese beer industry to prevent the development of a fungus that darkens beer.
Risks
Sodium azide is a toxic compound that inhibits an enzyme important for respiration and the life of human and animal cells. It has been found that it can severely affect the cells of the blood vessel tissue of the brain.
Its immediate effect after ingestion, inhalation or skin contact is to dangerously lower blood pressure, which can lead to death. Therefore, it must be handled with great care.
There are sources of information that call attention to the air bags of vehicles that are destroyed in waste areas.
In such cases, people who are unaware of the danger could access the NaN 3 deposits, this being a very toxic compound. In addition, there is a danger of contamination with NaN 3 of soils and waters.
Likewise, during accidents, collisions or vehicle fires, people could be exposed to NaN 3 and this can be underestimated or unknown by the medical personnel attending the emergency.
Attention has also been drawn to the exposure of laboratory personnel using it.
References
- Vwioko, ED et al. (2019). Sodium Azide Priming Enhances Waterlogging Stress Tolerance in Okra (Abelmoschus esculentus). Agronomy 2019, 9, 670. Recovered from mdpi.com.
- Kho, DT et al. (2017). Death of Blood Brain Barrier Endothelial Cells to Sodium Azide and Its Gaseous Products. Biosensors 2017, 7, 41. Recovered from mdpi.com.
- US National Library of Medicine. (2019). Sodium azide. Recovered from: pubchem.ncbi.nlm.nih.gov.
- Talavera, M. et al. (2019). Nematode Management in the Strawberry Fields of Southern Spain. Agronomy 2019, 9, 252. Recovered from mdpi.com.
- Okano, T. et al. (nineteen ninety five). Mechanism of cell detachment from temperature-modulated, hydrophilic-hydrophobic polymer surfaces. In The Biomaterials: Silver Jubilee Compendium. Recovered from sciencedirect.com.
- Ullmann's Encyclopedia of Industrial Chemistry. (1990). Fifth Edition. Volume A22. VCH Verlagsgesellschaft mbH.
- Cotton, F. Albert and Wilkinson, Geoffrey. (1980). Advanced Inorganic Chemistry. Fourth Edition. John Wiley & Sons.
- Chang, S. and Lamm, SH (2003). Human Health Effects of Sodium Azide Exposure: A Literature Review and Analysis. Int J Toxicol 2003, 22 (3): 175-86. Recovered from ncbi.nlm.nih.gov.