NITROUS OXIDE

Description

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.

Chemical Properties

Nitrous oxide is a nonflammable, colorless and odorless, sweettasting gas. It is usually handled as a compressed gas, stored in metal cylinders.

Chemical Properties

A colorless gas without appreciable odor or a slightly sweetish odor and taste. One L at 0°C and at a pressure of 760 mm of mercury weighs about 1.97 g. One volume dissolves in about 1.4 volumes of water at 20°C and at a pressure of 760 mm of mercury. It is freely soluble in alcohol and soluble in ether and in oils. It is prepared by thermal decomposition of ammonium nitrate.

Chemical Properties

Colourless gas with sweetish odour

Chemical Properties

Nitrous oxide has a slight sweetish, odor and taste. This gas is also reported as without appreciable odor. At 0°C and a pressure of 760 mm of mercury, 1 L weighs about 1.97 g.

Chemical Properties

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

Physical properties

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.

History

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.

Uses

Nitrous oxide is called laughing gas and has been used as a recreational inhalant, anesthetic, oxidizer, and propellant. Nitrous oxide is widely used as an anesthetic in dental surgery, which accounts for approximately 90% of its use. It is used by the dairy industry as a foaming agent for canned whipping creams.

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.

Uses

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.

Uses

Nitrous oxide is still commonly used in combination with a volatile agent to maintain anaesthesia. However, there is growing concern regarding its toxic effects and cost. Consequently, medical air in combination with oxygen is now being used increasingly during anaesthesia.

Uses

Nitrous Oxide is a noncombustible gas used as a propellant in certain dairy and vegetable fat whipped toppings contained in pressurized containers.

Uses

Nitrous oxide is used in the productionof nitrites, in rocket fuel, as an inhalationanesthesia and analgesic agent.

Preparation

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

Production Methods

Prepared (1) by reaction of silver hyponitrite Ag2N2O2 and hydrogen chloride in anhydrous ether, an evaporation of the resulting solution, (2) by reaction of hydroxylamine H2NOH plus nitrous acid HONO.

Definition

A colorless gas with a faintly sweet odor and taste. It is appreciably soluble in water (1.3 volumes in 1 volume of water at 0°C) but more soluble in ethanol. It is prepared commercially by the careful heating of ammonium nitrate:
NH₄NO₃(s) = N₂O(g) + 2H₂O(g)
Dinitrogen oxide is fairly easily decomposed on heating to temperatures above 520°C, giving nitrogen and oxygen. The gas is used as a mild anesthetic in medicine and dentistry, being marketed in small steel cylinders. It is sometimes called laughing gas because it induces a feeling of elation when inhaled.

Definition

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.

Production Methods

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

Biological Functions

N₂O (commonly called laughing gas) produces its anesthetic effect without decreasing blood pressure or cardiac output. Although it directly depresses the myocardium, cardiac depression is offset by an N₂O– mediated sympathetic stimulation. Likewise, respiration is maintained.Tidal volume falls, but minute ventilation is supported by a centrally mediated increase in respiratory rate. However, since the respiratory depressant effect of N₂O are synergistic with drugs such as the opioids opioids and benzodiazepines, N₂O should not be considered benign.
Deep levels of anesthesia are unattainable, even when using the highest practical concentrations of N₂O (N₂O 60–80% with oxygen 40–20%). Although unconsciousness occurs at these inspired levels, patients exhibit signs of CNS excitation, such as physical struggling and vomiting. If the airway is unprotected, vomiting may lead to aspiration pneumonitis, since the protective reflexes of the airway are depressed.
On the other hand, lower inspired concentrations (25–40%) of N₂O produce CNS depression without excitatory phenomena and are more safely used clinically. CNS properties of low inspired tension of N₂O include periods of waxing and waning consciousness, amnesia, and extraordinarily effective analgesia. N₂O 25% produces the gas’s maximum analgesic effect.With this concentration, responses to painful surgical manipulations are blocked as effectively as they would be with a therapeutic dose of morphine. Such low inspired concentrations of N₂O are used in dentistry and occasionally for selected painful surgical procedures (i.e., to relieve the pain of labor). Since the tissue solubility of N₂O is low, the CNS effects are rapid in onset, and recovery is prompt when the patient is returned to room air or oxygen.
The most common use of N₂O is in combination with the more potent volatile anesthetics. It decreases the dosage requirement for the other anesthetics, thus lowering their cardiovascular and respiratory toxicities. For example, an appropriate anesthetic maintenance tension for N₂O and halothane would be N₂O 40% and halothane 0.5%.With this combination in a healthy patient, anesthesia is adequate for major surgery, and the dose-dependent cardiac effects of halothane are reduced.

General Description

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.

General Description

Nitrous oxide is a gas at room temperature and is supplied asa liquid under pressure in metal cylinders. Nitrous oxide is a“dissociative anesthetic” and causes slight euphoria and hallucinations.

Reactivity Profile

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].

Hazard

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

Health Hazard

Inhalation causes intense analgesia; concentrations of over 40-60% cause loss of consciousness preceded by hysteria. Contact of liquid with eyes or skin causes frostbite burn.

Health Hazard

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.

Fire Hazard

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

Pharmaceutical Applications

Nitrous oxide and other compressed gases such as carbon dioxide and nitrogen are used as propellants for topical pharmaceutical aerosols. They are also used in other aerosol products that work satisfactorily with the coarse aerosol spray that is produced with compressed gases, e.g. furniture polish and window cleaner.
The advantages of compressed gases as aerosol propellants are that they are less expensive, of low toxicity, and practically odorless and tasteless. In contrast to liquefied gases, their pressures change relatively little with temperature. However, there is no reservoir of propellant in the aerosol, and as a result the pressure decreases as the product is used, changing the spray characteristics.
Misuse of a product by the consumer, such as using a product inverted, results in the discharge of the vapor phase instead of the liquid phase. Since most of the propellant is contained in the vapor phase, some of the propellant will be lost and the spray characteristics will be altered. Additionally, the sprays produced using compressed gases are very wet. However, recent developments in valve technology have reduced the risk of misuse by making available valves which will spray only the product (not propellant) regardless of the position of the container. Additionally, barrier systems will also prevent loss of propellant, and have found increased use with this propellant.
Therapeutically, nitrous oxide is best known as an anesthetic administered by inhalation. When used as an anesthetic it has strong analgesic properties but produces little muscle relaxation. Nitrous oxide is always administered in conjunction with oxygen since on its own it is hypoxic.

Materials Uses

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.

Clinical Use

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.

Safety Profile

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.

Safety

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.

Potential Exposure

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.

Physiological effects

Nitrous oxide's primary physiological effect is central nervous system (CNS) depression. At high concentrations, anesthetic levels can be obtained, but the low potency of nitrous oxide necessitates concomitant administration of other depressant drugs. Nitrous oxide has been associated with several side effects from longterm exposure. The most strongly substantiated effect is neuropathy. Epidemiological studies also suggest feto-toxic effects and higher incidents of spontaneous abortion in exposed personnel.Although no cause-and-effect relationship has been firmly established, exposure to the gas should be minimized.
Inhalation of nitrous oxide without the provision of a sufficient oxygen supply may be fatal or cause brain damage. Due to the concern over longterm exposure effects, release of the product into general work areas should be minimized. NIOSH has recommended a maximum exposure on an 8-hour Time-Weighted Average (TWA) of 25 parts per million for anesthetic and analgesic administration. ACGIH recommends a Threshold Limit Value-Time-Weighted Average (TLV-TWA) of 50 ppm (90 mglm3) for nitrous oxide. The TLV- TWA is the time-weighted average concentration for a normal 8-hour workday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.
Warning: The misuse of nitrous oxide can cause death by reducing the oxygen necessary to support life. Nitrous oxide abuse can impair an individual's ability to make and implement lifesustaining decisions.

Carcinogenicity

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.

storage

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.

Shipping

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.

Purification Methods

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].

Toxicity evaluation

Large amounts of released nitrous oxide can decrease the amount of available oxygen. Medical complications of nitrous oxide inhalation are due to varying degrees of hypoxia affecting primarily the heart and brain. By inactivating vitamin B12, a critical cofactor in hematopoiesis and lipid membrane formation, nitrous oxide can cause anemia and neuropathy via selective inhibition of methionine synthase, a key enzyme in methionine and folate metabolism.

Incompatibilities

Nitrous oxide is generally compatible with most materials encountered in pharmaceutical formulations, although it may react as a mild oxidizing agent.

Incompatibilities

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.

Waste Disposal

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

Regulatory Status

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.

GRADES AVAILABLE

Nitrous oxide is available in medical, commercial, and high-purity grades. The medical (USP) grade is the most widely used. Manufacturers typically produce nitrous oxide for this use to the specification published in the United States Pharmacopeia/National Formulary. CGA G-8.2, Commodity Specification for Nitrous Oxide, describes the requirements for particular grades of nitrous oxide. Other specifications to meet particular requirements are available from suppliers. The absence of a value in a listed quality verification level does not mean to imply that the limiting characteristic is or is not present, but merely indicates that the test is not required for compliance with the specification.