Sodium azide

Overview

Sodium azide is a white, odorless crystalline powder that dissolves in water and explodes when it hits metal. The compound is extremely toxic which means that signs and symptoms can be observed immediately after exposure. Sodium azide is commonly used as a preservative of samples and in airbags in cars.

Health Hazards

Exposure
When sodium oxide is released from water or the pipeline within a setting, one can be exposed to it by drinking the polluted water. Also, exposure of sodium azide can be through consuming contaminated food, breathing polluted air, as well as through contact.
Chronic Health Effects
Sodium oxide is a mutagen, therefore, can cause genetic changes in the body that can lead to cancer. Moreover, exposure to the chemical can cause reproductive harm. The compound can also affect the nervous system leading to dizziness, weakness of muscles, tremor, anxiety, syncope, and even death.
Acute Health Effects
These include health effects that may be witnessed immediately after exposure to sodium azide. (5) When in contact with the eyes, it can irritate, burn, and even cause loss of vision. On the other hand, the chemical can cause redness of the skin and irritate the nose and throat when inhaled. In addition, sodium oxide can irritate the lungs, thus leading to shortness of breath and coughing. (5)Extreme inhalation of the chemical can cause pulmonary edema – the concentration of fluids in the lungs. Symptoms of exposure include nausea, headache, vomiting, dizziness, syncope, rapid heartbeat, dripping nose, weakness, and red eyes.

Stucture

Sodium azide has a body-centered rhombohedral structure with one molecule per unit cell, a sodium ion at the corners of the cell, and an azide ion arranged along the body diagonal of the cell; coordination is 6:6. The heavier alkali azides are all body-centered tetragonal with 4 molecules per unit cell and 8:8 coordination.

Storage and Transportation

Sodium azide should be stored in a cool, well-ventilated, dry area preferably in polythene or glass. Moreover, it should be stored away from open flames, water, or heat. The substance should be stored away from incompatible materials such as acid chlorides, metals, and hydrocarbons. During transportation, sodium azide should be sealed in tight containers.

Disposal

Destruction
Use freshly prepared nitrous acid to destroy solutions with less than 5% of sodium azide. It is noteworthy that the destruction must take place in an open container and one should wear a fume hood to prevent the effect of nitric oxide gas that is normally released during the reaction.
Waste Disposal
While labeling the container with hazardous waste before disposing of it, it is essential to spell out the full name of the substance. Sodium azide solutions must never be drained, as they can react with copper or lead pipes that can react to produce extremely explosive azide salt.

Chemical Properties

Sodium azide is a colorless to white, odorless, crystalline solid. Combustible solid above 300°C.

Chemical Properties

Colorless, hexagonal crystals. Decom- poses at about 300C. Soluble in water and in liquid ammonia; slightly soluble in alcohol; hydrolyzes to form hydrazoic acid. Combustible.

Physical properties

Colorless hexagonal crystals; density 1.846 g/cm³ at 20°C; decomposes on heating to produce sodium and nitrogen; also decomposes in vacuum; soluble in water partially converting to hydrazoic acid, solubility in water, 41.7 g/100mL; slightly soluble in alcohol, 0.316g/100mL at 16°C; soluble in liquid ammonia.

Uses

Sodium azide is used in making othermetal azides, therapeutically to control bloodpressure, as a propellant for automotivesafety bags, as a preservative for laboratoryreagents, as an analytical reagent, andin organic synthesis. It is also used as anantifading reagent for immunofluorescence(Boeck et al. 1985).

Uses

Biomedical Sciences
Sodium azide is a biocide that is used in making chemical preservatives that are used in laboratories and hospitals. In hospitals, it is used as a preservative in blood tests and diagnostic machines. Since the chemical is soluble, it can act as useful metabolic inhibitors that can affect the activities of numerous oxidative enzymes. Specifically, it inhibits oxidative enzymes that are involved in electron transport system respiration. However, accidents have occurred whenever sodium azide is used in a hospital setting; therefore, major bodies such as the CDC that deal with chemicals do not advise the use of the compound.
Automobiles Airbags
Before the 1990s, sodium azide was used in airbags. In airbags, when electricity heats sodium azide to approximately 300oC, it decomposes into two simple components, namely sodium and nitrogen gas. The decomposition of sodium azide happens very fast that the filling of the airbag with nitrogen gas occurs at a velocity of around 200 miles per hour.
Agriculture
Sodium azide is used for pest control due to its ready solubility in water. Nitrifying bacteria acts as a catalyst that decomposes the sodium azide solution to release nitrate, HN3, and NH4+ when added to the soil. It is noteworthy that these components have wide range of activity against nematodes, weeds, and phytopathogenic fungi that is soil-borne. The chemical is typically applied through drip irrigation to avoid reactivity of HN3 in the soil-air space that can eventually result in an active compound that can be ineffective for pest control.
Detonators
When combined with other metals such as copper (Cu), lead (Pb), and mercury (Hg), sodium azide becomes unstable and explosive. As such, it is mostly used as detonators due to its explosive nature.
A summary of main uses is listed in the table below:

Uses

In airbag inflation, as a preservative in diagnostic medicinals.Sodium azide is used in organic synthesis for the introduction of an azide group to prepare a desired compound. It acts as a precursor to prepare inorganic azides like lead azide and silver azide. In biochemistry, it is useful as a probe reagent and a preservative. It also acts as a nitridizing agent and cytochrome oxidase inhibitor. Further, it is used as a propellant in airbags.

Definition

sodium azide: A white or colourlesscrystalline solid, NaN₃, soluble inwater and slightly soluble in alcohol;hexagonal; r.d. 1.846; decomposes onheating. It is made by the action ofnitrogen(I) oxide on hot sodamide(NaNH₂) and is used as an organicreagent and in the manufacture ofdetonators.

Production Methods

Sodium azide can be prepared from sodium metal and liquid ammonia in the presence of ferric chloride. The amide formed is treated with nitrous oxide to produce the azide.

Preparation

Sodium azide is prepared by reacting sodium amide with nitrous oxide. The amide is heated with nitrous oxide at 200°C or its solution in liquid ammonia is treated with nitrous oxide at ambient temperature: 2NaNH₂ + N₂O → NaN₃ + NaOH + NH₃.

Reactivity Profile

Sodium azide is unstable. Decomposes rapidly or explosively at about 300°C [Hawley]. May explode if shocked. Forms violently explosive products if exposed to carbon disulfide. Can be sensitized toward decomposition by metal salts (especially heavy metal salts such as silver chloride) or by traces of strong acids [Sax, 9th ed., 1996, p. 298].

Hazard

Sodium azide is a toxic as well as an explosive substance (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2_np ed. New York: John Wiley & Sons). Although inert to shock, violent decomposition can occur when heated at 275°C. Contact of solid or solution with lead and copper must be avoided. Reactions with halogens, carbon disulfide, or chromyl chloride can be explosive. Dissolution in water produces toxic vapors of hydrazoic acid. The salt is an acute poison causing headache, hypotension, hypothermia, and convulsion. LD₅₀ oral (rats): 27 mg/kg.

Health Hazard

Can cause death by affecting the central nervous system. Contact may cause burns to skin and eyes.

Health Hazard

Sodium azide is a highly toxic compound;the order of toxicity is the same as that ofhydrazoic acid. It is converted to hydrazoicacid in water. The aqueous solutions ofsodium azide contains hydrazoic acid, whichescapes at 37°C (98°F), presenting a dangerof inhalation toxicity.
Sodium azide, by itself, is a severe acutetoxicant causing hypotension, headache,tachpnea, hypothermia, and convulsion.The toxic symptoms from ingestion of100–200 mg in humans may result inheadache, respiratory distress, hypermotility,and diarrhea. An oral intake of 10–20 g may be fatal to humans. The target organsare primarily the central nervous system andbrain. There are reports on azide poisoningof brain and nerve tissue (ACGIH 1986;Mettler 1972). Owing to the availability ofelectron pairs in azide ion for coordinatebonding, azide forms strong complexes withhemoglobin, which blocks oxygen transportto the blood (Alben and Fager 1972).
LD50 value, oral (rats): 27 mg/kg
Sodium azide is strongly mutagenic in theAmes test. However, it shows a very weakmutagenic effect on Saccharomyces cerevisiaeC658-K42 (Morita et al. 1989). Macoret al. (1985) found that light decreased themutagenic effect of sodium azide to inducehereditary bleaching of Euglena gracilis.Carcinogenicity of this compound on animalsor humans has not yet been fully established,although skin and endocrine tumors in ratshave been observer (NIOSH 1986).

Health Hazard

The acute toxicity of sodium azide is high. Symptoms of exposure include lowered blood pressure, headache, hypothermia, and in the case of serious overexposure, convulsions and death. Ingestion of 100 to 200 mg in humans may result in headache, respiratory distress, and diarrhea. Target organs are primarily the central nervous system and brain. Sodium azide rapidly hydrolyzes in water to form hydrazoic acid, a highly toxic gas that can escape from solution, presenting a serious inhalation hazard. Symptoms of acute exposure to hydrazoic acid include eye irritation, headache, dramatic decrease in blood pressure, weakness, pulmonary edema, and collapse. Solutions of sodium azide can be absorbed through the skin. Sodium azide has not been found to be carcinogenic in humans. Chronic, low-level exposure may cause nose irritation, episodes of falling blood pressure, dizziness, and bronchitis.

Fire Hazard

Flammability hazard is low, but violent decomposition can occur when heated to 275 °C. Decomposition products include oxides of nitrogen and sodium oxide.

Fire Hazard

When heated to decomposition, Sodium azide emits very toxic fumes of nitrogen oxides; explosive. Forms explosive-sensitive materials with some metals such as lead, silver, mercury or copper. May form toxic hydrazoic acid fumes in fire. Containers may explode in fire. Avoid acids, benzoyl chloride and potassium hydroxide; bromine; carbon disulfide; copper; lead; nitric acid; barium carbonate; sulfuric acid; chromium (II) hypochlorite, dimethyl sulfate, water, dibromomalononitrile, lead, silver, copper, mercury. Hazardous polymerization may not occur.

Flammability and Explosibility

Flammability hazard is low, but violent decomposition can occur when heated to 275 °C. Decomposition products include oxides of nitrogen and sodium oxide.

Biochem/physiol Actions

Sodium azide is a preservative for laboratory reagents. It also works as a plant mutagen. It is a F-type ATPase inhibitor and selectively inhibits ceruloplasmin.Sodium azide 0.1M solution is an additive screening solution of Additive Screening Kit. Additive Screen kit is designed to allow rapid and convenient evaluation of additives and their ability to influence the crystallization of the sample. The Additive Kit provides a tool for refining crystallization conditions.

Safety Profile

Poison by ingestion, skin contact, intraperitoneal, intravenous, and subcutaneous routes. Human systemic effects by ingestion: general anesthesia, somnolence, and hdney changes. Questionable carcinogen with experimental tumorigenic data. Human mutation data reported. Violent reaction with benzoyl chloride combined with KOH, Br2, barium carbonate, CS2, Cr(OCl)2, Cu, Pb, HNO3, BaCO3, H2SO4, hot water, (CH3)2SO4, dibromomalononitrile, sulfuric acid. Incompatible with acids, ammonium chloride + trichloroacetonitrile, phosgene, cyanuric chloride ,2,5 -dinitro3 methylbenzoic acid + oleum, trifluroroacryloyl chloride. Reacts with heavy metals (e.g., brass, copper, lead) to form dangerously explosive heavy metal azides, a particular problem in laboratory equipment and drain traps. When heated to decomposition it emits very toxic fumes of NOx and Na2O. See also AZIDES.

Potential Exposure

Sodium azide is used as preservative and diluent. It has been used for a wide variety of military, laboratory, medicine, and commercial purposes. It is used extensively as an intermediate in the production of lead azide, commonly used in detonators, and other explosives. Reported to be used in automobile air-bag inflation. One of the largest potential exposure is that to automotive workers, repairmen, and wreckers, if sodium azide is used as the inflation chemical. Commercial applications include use as a fungicide, nematocide, and soil sterilizing agent and as a preservative for seeds and wine. The lumber industry has used sodium azide to limit the growth of enzymes responsible for formation of brown stain on sugar pine, while the Japanese beer industry used it to prevent the growth of a fungus which darkens its product. The chemical industry has used sodium azide as a retarder in the manufacture of sponge rubber, to prevent coagulation of styrene and butadiene latexes stored in contact with metals; and to decompose nitrites in the presence of nitrates.

storage

In particular, work with sodium azide should be conducted in a fume hood to prevent exposure by inhalation, and appropriate impermeable gloves and splash goggles should be worn at all times to prevent skin and eye contact. Containers of sodium azide should be stored in secondary containers in a cool, dry place separated from acids.

Shipping

UN1687 Sodium azide, Hazard Class: 6.1; Labels: 6.1-Poisonous materials.

Purification Methods

Crystallise sodium azide from hot water or from water by adding absolute EtOH or acetone. Also purify it by repeated crystallisation from an aqueous solution saturated at 90o by cooling it to 10o, and adding an equal volume of EtOH. The crystals are washed with acetone, and the azide is dried at room temperature under vacuum for several hours in an Abderhalden pistol. Its solubility in H2O is 42% at 18o, and in EtOH it is 0.22% at 0o. [Das et al. J Chem Soc, Faraday Trans 1 78 3485 1982, Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I pp 474-475 1963, Browne Inorg Synth 1 79 1939, Frierson Inorg Synth II 139 1946.] HIGHLY POISONOUS and potentially explosive.

Incompatibilities

Reacts explosively and/or forms explosive and/or shock sensitive compounds with acids and many metals. Contact with water forms hydrazoic acid. Combustible solid (if heated above 275C). May explode when heated above its melting point, especially if heating is rapid. Reacts with acids; producing toxic, shock-sensitive, and explosive hydrogen azide. It forms explosive compounds with phosgene, brass, zinc, trifluoroacrylol fluoride, and nitrogendiluted bromine vapor. Reacts with benzoyl chloride and potassium hydroxide, bromine, carbon disulfide; copper, lead, nitric acid; barium carbonate; sulfuric acid; chromium (II) hypochlorite; dimethyl sulfate; dibromomalononitrile, silver, mercury. Over a period of time, sodium azide may react with copper, lead, brass, or solder in plumbing systems to form an accumulation of the highly explosive and shock-sensitive compounds of lead azide and copper azide

Waste Disposal

Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform to EPA regulations governing storage, transportation, treatment, and waste disposal. Disposal may be accomplished by reaction with sulfuric acid solution and sodium nitrate in a hard rubber vessel.Nitrogen dioxide is generated by this reaction and the gas is run through a scrubber before it is released to the atmosphere. Controlled incineration is also acceptable (after mixing with other combustible wastes) with adequate scrubbing and ash disposal facilities.