Азид натрия

Химические свойства

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

Физические свойства

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.

Использование

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).

Определение

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.

Методы производства

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.

Подготовка

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.

Профиль реактивности

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].

Опасность

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.

Угроза здоровью

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.

Пожароопасность

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.

Воспламеняемость и взрывоопасность

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

Профиль безопасности

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.

Возможный контакт

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.

хранилище

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.

Перевозки

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

Методы очистки

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.

Несовместимости

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

Утилизация отходов

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.