NITROUS OXIDE

Описание

dinitrogen monoxide’s (N2O) common name is nitrous oxide.Nitrous oxide is a colorless, nonfl ammable, nontoxic gas with a slightly sweet odor and taste. Nitrous oxide is produced by the thermal decomposition of ammonium nitrate at approximately 240°C: NH4NO3(g) → N2O(g) + 2H2O(g).Nitrous oxide is an important greenhouse gas. Its atmospheric residence time is 120 years. A molecule of N2O has 310 times the potential for absorbing heat compared to a molecule of CO2. Nitrous oxide is stable and unreactive on the earth’s surface, but it can be transported to the stratosphere where it absorbs energy and is converted into reactive forms of nitrogen such as nitric oxide and the nitrate radical contributing to ozone destruction.

Химические свойства

Nitrous oxide is a colorless gas. Slightly sweet odor. Shipped as a liquefied compressed gas.

Физические свойства

Colorless gas with faint sweet odor and taste; heavier than air, density in air 1.53 (air=1); gas density 1.977 g/L at 0°C; noncombustible gas; supports combustion; liquefies to a colorless liquid at -88.5°C; liquid density 1.226 g/mL at -89°C; freezes to a cubic crystalline solid at -90.8°C; dipole moment 0.166 ; critical temperature 36.5°C; critical pressure 71.7 atm; solubility in water: 130 mL gas dissolves in 100mL water at 0°C and 56.7 mL in 100 mL water at 25°C; soluble in alcohol, ether and sulfuric acid.

История

nitrous oxide was prepared in 1772 by Joseph Priestley (1733 1804) . Priestley called nitric oxide nitrous air, nitrogen dioxide nitrous acid vapor, and nitrous oxide phlogisticated nitrous air, but also referred to the dioxide. Priestley prepared nitric oxide by reacting nitric acid with a metal such as copper: 3Cu(s) + 8HNO3(aq) 2NO(g) + 3Cu(NO3)2(aq) + 4H2O(l).He prepared nitrous oxide by reducing nitric oxide using iron: 2NO(g) + H2O(l) + Fe(s) N2O(g) + Fe(OH)2(aq).For example, the year of discovery for nitrous oxide ranges between 1772 and 1793. Humphrey Davy (1778 1829) examined the physiological effects of nitrous oxide and in 1799 wrote Researches Chemical and Philosophical, Chiefly Concerning Nitrous Oxide.

Использование

Nitrous oxide was discovered by Priestley. It is found in the atmosphere in trace concentrations. The gas is used as an anesthetic, especially in dentistry and minor surgery. It produces mild hysteria and laughter preceding the anesthetic effect, for which reason it also is called “laughing gas.” It is used as an aerosol propellant, an aerating agent for whipped cream, and an oxidizing agent at high temperatures. Nitrous oxide also is used in the preparation of nitrites and as a flame gas in flame atomic absorption spectrometry of metals.

Определение

ChEBI: A nitrogen oxide consisting of linear unsymmetrical molecules with formula N2O. While it is the most used gaseous anaesthetic in the world, its major commercial use, due to its solubility under pressure in vegetable fats combined with ts non-toxicity in low concentrations, is as an aerosol spray propellant and aerating agent for canisters of 'whipped' cream.

Подготовка

Prepared by thermal decomposition of ammonium nitrate
NH₄NO₃ → N₂O↑ + 2H₂O

Методы производства

Nitrous oxide is prepared by heating ammonium nitrate to about 170°C. This reaction also forms water.

Общее описание

NITROUS OXIDE is a colorless, sweet-tasting gas. NITROUS OXIDE is also known as "laughing gas". Continued breathing of the vapors may impair the decision making process. NITROUS OXIDE is noncombustible but NITROUS OXIDE will accelerate the burning of combustible material in a fire. NITROUS OXIDE is soluble in water. Its vapors are heavier than air. Exposure of the container to prolonged heat or fire can cause NITROUS OXIDE to rupture violently and rocket. NITROUS OXIDE is used as an anesthetic, in pressure packaging, and to manufacture other chemicals.

Профиль реактивности

NITROUS OXIDE is an oxidizing agent. Nonflammable but supports combustion. Can explode at high temperature (after vaporization). Vapors can undergo a violent reaction with aluminum, boron, hydrazine, lithium hydride, phenyllithium, phosphine, sodium, tungsten carbide [Bretherick, 5th ed., 1995, p. 1686]. Contact of the cold liquefied gas with water may result in vigorous or violent boiling. If the water is hot, a liquid "superheat" explosion may occur. Pressures may build to dangerous levels if liquefied gas contacts water in a closed container [Handling Chemicals Safely 1980].

Опасность

Supports combustion, can form explosive mixture with air. Narcotic in high concentration. Central nervous system impairment, hematologic effects, and embryo/fetal damage. Questionable carcinogen.

Угроза здоровью

Toxicity and irritant effects of nitrous oxidein humans are very low. It is an anesthetic.Inhalation of this gas at high concentrationscan produce depression of the central nervous system, decrease in body temperature,and fall in blood pressure. The LC50 valueof a 4-hour exposure in mice is in the rangeof 600 ppm.

Пожароопасность

Behavior in Fire: Will support combustion, and may increase intensity of fire. Containers may explode when heated.

Использование в материалах

Nitrous oxide is noncorrosive and may therefore be used with any of the common, commercially available metals. Because of its oxidizing action, however, all equipment being prepared to handle nitrous oxide, particularly at high pressures, must be free of oil, grease, and other readily combustible materials. Nitrous oxide may cause swelling ofsome elastomers.

Клиническое использование

The low potency of nitrous oxide (MAC＝ 104%) precludes it from being used alone for surgical anesthesia.To use it as the sole anesthetic agent the patient wouldhave to breathe in pure N₂Oto the exclusion of oxygen. Thissituation would obviously cause hypoxia and potentially leadto death. Nitrous oxide can inactivate methionine synthase, aB12-dependent enzyme necessary for the synthesis of DNAand therefore should be used with caution in pregnant andB12-deficient patients. Nitrous oxide is also soluble in closedgas containing body spaces and can cause these spaces toenlarge when administered possibly leading to adverse occurrences(occluded middle ear, bowel distension, pneumothorax).Nitrous oxide is a popular anesthetic in dentistrywere it is commonly referred to as “laughing gas.” It is usedin combination with more potent anesthetics for surgicalanesthesia and remains a drug of recreational abuse.Nitrous oxide undergoes little or no metabolism.

Профиль безопасности

Moderately toxic by inhalation. Human systemic effects by inhalation: general anesthetic, decreased pulse rate without blood pressure fall, and body temperature decrease. An experimental teratogen. Experimental reproductive effects. Mutation data reported. An asphyxiant. Does not burn but is flammable by chemical reaction and supports combustion. Moderate explosion hazard; it can form an explosive mixture with air. Violent reaction with Al, B, hydrazine, LiH, LiC6H5, PH3, Na, tungsten carbide. Also self-explodes at high temperatures.

Безопасность

Nitrous oxide is most commonly used therapeutically as an anesthetic and analgesic. Reports of adverse reactions to nitrous oxide therefore generally concern its therapeutic use, where relatively large quantities of the gas may be inhaled, rather than its use as an excipient.
The main complications associated with nitrous oxide inhalation occur as a result of hypoxia. Prolonged administration may also be harmful. Nitrous oxide is rapidly absorbed on inhalation.

Возможный контакт

Used as an anesthetic in dentistry and surgery; used as a gas in food aerosols, such as whipped cream; used in manufacture of nitrites; used in rocket fuels; in firefighting; diesel emissions. Large amounts of nitrous oxide will decrease the amount of available oxygen. Nitrous Oxide 2231 Oxygen should be routinely tested to ensure that it is at least 19% by volume.

Канцерогенность

The possible carcinogenicity of nitrous oxide has been studied in dentists and chairside assistants with occupational exposures. No effect was observed in male dentists, but a 2.4- fold increase in cancer of the cervix in heavily exposed female assistants was reported.7 Other epidemiological reports of workers exposed to waste anesthetic gases have been negative.1 Carcinogenic bioassays in animals have yielded negative results. Nitrous oxide was not genotoxic in a variety of assays.

хранилище

Nitrous oxide is essentially nonreactive and stable except at high temperatures; at a temperature greater than 500°C nitrous oxide decomposes to nitrogen and oxygen. Explosive mixtures may be formed with other gases such as ammonia, hydrogen, and other fuels. Nitrous oxide should be stored in a tightly sealed metal cylinder in a cool, dry place.

Перевозки

UN1070 Nitrous oxide, compressed, Hazard Class: 2.2; Labels: 2.2-Nonflammable compressed gas; 5.1-Oxidizer; UN2201 Nitrous oxide, refrigerated liquid, Hazard Class: 2.2; Labels: 2.2-Nonflammable compressed gas; 5.1-Oxidizer. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner.

Методы очистки

Wash the gas with concentrated alkaline pyrogallol solution, to remove O2, CO2, and NO2, then dry it by passing it through columns of P2O5 or Drierite, and collecting in a dry trap cooled in liquid N2. It is further purified by freeze-pump-thaw and distillation cycles under vacuum [Ryan & Freeman J Phys Chem 81 1455 1977, Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I pp 484-485 1963].

Несовместимости

Nitrous oxide is a weak oxidizer. Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides. Violent reactions with organic peroxides, hydrazine, hydrogen, hydrogen sulfide; lithium, boron, lithium hydride, sodium, aluminum, phosphine. This chemical is a strong oxidizer @ .300C and self-explodes at high temperature. May form explosive mixtures with ammonia, carbon monoxide; hydrogen sulfide; oil, grease and fuels.

Утилизация отходов

Disperse in atmosphere or spray on dry soda ash/lime with great care; then flush to sewer.

Регуляторный статус

GRAS listed. Accepted for use as a food additive in Europe. Included in nonparenteral medicines licensed in the UK and USA. Included in the Canadian List of Acceptable Non-medicinal Ingredients.