Liquid Nitrogen

History

Nitrogen was discovered independently in 1772 by Swedish chemist Carl Scheele and Scottish botanist Daniel Rutherford. Priestly, Cavendish, and Lavoisier also obtained nitrogen independently more or less around the same time. Nitrogen was recognized first as an element by Lavoisier, who named it “azote”, meaning “without life.” The element was named nitrogen in 1790 by Chaptal. The name derived from the Greek name ‘nitre’ for potassium nitrate which contains nitrogen.

Occurance

Nitrogen is the principal component of air. The earth’s atmosphere constitutes about 78% nitrogen by volume. Nitrogen also occurs as nitrates in several minerals such as Chile saltpeter (sodium nitrate), niter or saltpeter (potassium nitrate) and minerals containing ammonium salts. Nitrogen is contained in many complex organic molecules including proteins and amino acids that occur in all living organisms.

Uses

Gaseous nitrogen has numerous uses in chemical, food, metal, and electrical industries. Nitrogen is needed in commercial production of ammonia (Haber process) and in preparation of many nitrides. It also is the starting material in making cyanamide salts, cyanides, and nitrogen oxides for producing nitric acid. Other applications are in gas chromatrography, as a carrier gas, to provide an inert atmosphere in chemical reactions, to prevent oxidation reactions, to reduce fire or explosion hazards, and to dilute a reacting gas.
In the food industry nitrogen is used to prevent mold growth, spoilage from oxidation, and insect infestation.
Other miscellaneous applications of nitrogen gas include pressurizing cable jackets, preventing carburization in welding and soldering, inflating balloons, agitating liquid baths, and cooling catalytic reactors in petroleum refining.

Uses

Nitrogen has many commercial and technical applications. As a gas, it is used in heat treating of primary metals; blanketing of oxygen- sensitive liquids and of volatile liquid chemicals; the production of semiconductor electronic components, as a blanketing atmosphere; the blowing of foam-type plastics; the deaeration of oxygen-sensitive liquids; the degassing of nonferrous metals; food processing and packing; inhibition of aerobic bacteria growth; magnesium reduction of aluminum scrap; and the propulsion of liquids through pipelines.
Gaseous nitrogen is also used in pressurizing aircraft tires and emergency bottles to operate landing gear; purging, in the brazing of copper tubing for air-conditioning and refrigeration systems; the purging and filling of electronic devices; the purging, filling, and testing of high-voltage compression cables; the purging and testing of pipelines and related instruments; and the treatment of alkyd resins in the paint industry.
Liquid nitrogen also has a great many uses, among them the freezing of highly perishable foods such as shrimp, hamburgers, and chicken; deflashing of rubber tires; cooling of concrete; and the cold-trapping of materials such as carbon dioxide from gas streams (commonly used in this way in systems that produce high vacuums). It is used as a coolant for electronic equipment, for pulverizing plastics, and for simulating the conditions of outer space. Other ways in which liquid nitrogen is used include: creating a very high pressure gaseous nitrogen (15 000 psig or 103 000 kPa) through liquid nitrogen pumping; in food and chemical pulverization; for the freezing of liquids in pipelines for emergency repairs; for low temperature stabilization and hardening of metals; for low temperature research; for low temperature stress relieving of aluminum alloys; for the preservation of whole blood, livestock sperm, and other biologicals; for refrigerating foods in local and long-distance hauling; for refrigeration shielding of liquid hydrogen, helium, and neon; for the removal of skin blemishes in dermatology; and for shrink fitting of metal parts.
Liquid nitrogen also has a number of classified applications in the missile and space programs of the United States, in which it is used in large quantities.

Description

Nitrogen makes up the major portion of the atmosphere (78.08 percent by volume, 75.5 percent by weight). It is a colorless, odorless, tasteless, nontoxic, almost totally inert gas, and is colorless as a liquid. Nitrogen is nonflammable, will not support combustion, and is not life supporting. It combines with some of the more active metals such as lithium and magnesium to form nitrides, and at high temperatures it will also combine with hydrogen, oxygen, and other elements. It is used as an inert protection against atmospheric contamination in many nonwelding applications. Nitrogen is only slightly soluble in water and most other liquids, and is a poor conductor of heat and electricity. As a liquid at cryogenic temperatures it is nonmagnetic. It is shipped as a nonliquefied gas at pressures of 2000 psig (13 790 kPa) or above, and also as a cryogenic fluid at pressures and temperatures below 200 psig (1380 kPa) and -261°F (-163°C).

Chemical Properties

Solid nitrogen has a hexagonal crystal structure. Nitrogen at standard conditions is a colorless, odorless, tasteless gas. The gas is slightly soluble in H2O (2.35 parts nitrogen in 100 parts H2O at 0°C), the solubility decreasing with increasing temperature (1.55 parts nitrogen in 100 parts H2O at 20°C). Nitrogen is slightly soluble in alcohol and is essentially insoluble in most other known liquids.

Chemical Properties

Nitrogen occurs naturally as approximately 78% v/v of the atmosphere. It is a nonreactive, noncombustible, colorless, tasteless, and odorless gas. It is often used under refrigeration as a cryogenic liquid. The boiling point is -195.8 °C and -320 °F. Nitrogen is not combustible. Nitrogen can combine with oxygen at high temperatures to form oxides and may form ammonia in contact with hydrogen at elevated temperatures. Cyanides can form if nitrogen is heated with carbon in presence of alkalies or barium oxide. If nitrogen comes in contact with ozone, nitrogen can oxidize explosively.It is usually handled as a compressed gas, stored in metal cylinders.

Physical properties

In its natural gaseous state, nitrogen is a relatively inert diatomic molecule (N2) that iscolorless, odorless, and tasteless, yet it is responsible for hundreds of active compounds. Itmakes up about 78% of the air we breathe. We are constantly taking it into our lungs withno stimulation or sensation; therefore, we really do not detect its presence. When liquefied, itis still colorless and odorless and resembles water in density. The melting point of nitrogen is–209.86°C, its boiling point is –195.8°C, and its density as a gas is 0.0012506 g/cm³.

Isotopes

There are 19 isotopes of nitrogen, two of which are stable. The stable ones andtheir proportion to the natural abundance of nitrogen on Earth follow: N-14 = 99.634%and N-15 = 0.366%. The other 17 isotopes are radioactive and man-made in nuclearreactors and have half-lives ranging from a few nanoseconds to 9.965 minutes.

Origin of Name

From the two Greek words nitron and genes, which together stand for “soda or saltpeter forming.”

Occurrence

Nitrogen is the 30th most abundant element on Earth. There is an almost unlimited sourceof nitrogen available to us considering that our atmosphere constitutes 4/5, or over 78%, ofthe nitrogen by volume. Over 33 million tons of nitrogen is produced each year by liquefyingair and then using fractional distillation to produce nitrogen as well as other gases in the atmosphere. During this process the air is cooled and then slowly warmed to fractionaltemperature points at which each specific gas in the air will “boil” off. (Note: Oxygen, argon,carbon dioxide, and nitrogen all have specific boiling points and these gases can be used tocollect the specific gas during the fractionation process.) When the temperature –reaches–195.8°C, the nitrogen is boiled off and collected.
There is a balance of nitrogen with other gases in the atmosphere that is maintained bywhat is called the nitrogen cycle. This cycle includes several processes, including nitrogen fixationof bacteria in the soil by legumes (bean and pea plants). Lightning produces nitrogen, asdo industrial waste gases and the decomposition products of organic material (i.e., organicproteins and amino acids in plants and animals contain nitrogen). In time, these sourcesreplace the nitrogen in the atmosphere to complete the cycle.
Ammonia (NH₃) is the first binary molecule discovered in outer space of our galaxy, theMilky Way. It may also be the main compound that forms the rings of the planet Saturn.

Characteristics

There are approximately 4,000 trillion tons of gas in the atmosphere, and nitrogen makesup about 78% of these gases. It is slightly soluble in water and alcohol. It is noncombustibleand is considered an asphyxiant gas (i.e., breathing pure nitrogen will deprive the body ofoxygen).
Although nitrogen is considered an inert element, it forms some compounds that are veryactive. Of the diatomic molecules, such as CO₂ , it is difficult to separate the two atoms innitrogen’s molecules because of their strong binding energy. This is the reason that, along withcarbon dioxide, nitrogen gas is stable. However, once separated, the individual atoms of nitrogen(N) become very reactive and do combine with hundreds of other elements.
Nitrogen can be liquefied easily, making it useful in many applications wherein sustainedcooling is needed. At high temperatures, nitrogen reacts with many metals to form nitrides.

History

Nitrogen was discovered by Daniel Rutherford in 1772, but Scheele, Cavendish, Priestley, and others about the same time studied “burnt or dephlogisticated air,” as air without oxygen was then called. Nitrogen makes up 78% of the air, by volume. The atmosphere of Mars, by comparison, is 2.6% nitrogen. The estimated amount of this element in our atmosphere is more than 4000 trillion tons. From this inexhaustible source it can be obtained by liquefaction and fractional distillation. Nitrogen molecules give the orange-red, blue-green, blue-violet, and deep violet shades to the aurora. The element is so inert that Lavoisier named it azote, meaning without life, yet its compounds are so active as to be most important in foods, poisons, fertilizers, and explosives. Nitrogen can be also easily prepared by heating a water solution of ammonium nitrite. Nitrogen, as a gas, is colorless, odorless, and a generally inert element. As a liquid it is also colorless and odorless, and is similar in appearance to water. Two allotropic forms of solid nitrogen exist, with the transition from the α to the β form taking place at –237°C. When nitrogen is heated, it combines directly with magnesium, lithium, or calcium; when mixed with oxygen and subjected to electric sparks, it forms first nitric oxide (NO) and then the dioxide (NO2); when heated under pressure with a catalyst with hydrogen, ammonia is formed (Haber process). The ammonia thus formed is of the utmost importance as it is used in fertilizers, and it can be oxidized to nitric acid (Ostwald process). The ammonia industry is the largest consumer of nitrogen. Large amounts of gas are also used by the electronics industry, which uses the gas as a blanketing medium during production of such components as transistors, diodes, etc. Large quantities of nitrogen are used in annealing stainless steel and other steel mill products. The drug industry also uses large quantities. Nitrogen is used as a refrigerant both for the immersion freezing of food products and for transportation of foods. Liquid nitrogen is also used in missile work as a purge for components, insulators for space chambers, etc., and by the oil industry to build up great pressures in wells to force crude oil upward. Sodium and potassium nitrates are formed by the decomposition of organic matter with compounds of the metals present. In certain dry areas of the world these saltpeters are found in quantity. Ammonia, nitric acid, the nitrates, the five oxides (N2O, NO, N2O3, NO2, and N2O5), TNT, the cyanides, etc. are but a few of the important compounds. Nitrogen gas prices vary from 2￠ to $2.75 per 100 ft3 (2.83 cu. meters), depending on purity, etc. Production of elemental nitrogen in the U.S. is more than 9 million short tons per year. Natural nitrogen contains two isotopes, 14N and 15N. Ten other isotopes are known.

Uses

Nitrogen serves the important function of diluent in the earth’s atmosphere, controlling natural burning and respiration rates that otherwise would proceed much faster with higher concentrations of oxygen. Nitrogen is an important ingredient of numerous inorganic and organic compounds, including alkaloids, amides, amines, cyanides, cyanogens, diazo compounds, hydrazines, imides, nitrates, nitrides, nitrites, nitriles, oximes, purines, pyridines, and ureas. In terms of high-tonnage production, the nitrogen compound NH3 (ammonia) ranks first with worldwide production exceeding 50 million tons annually.

Uses

Nitrogen has many uses. It is the second most commonly produced chemical in the UnitedStates. Its chemical and physical properties, along with the five electrons in its outer shell,make it a versatile element that can react as a metal or nonmetal to produce numerous compounds.Some of its uses are based on its inertness as a gas (N₂) and its ability to be liquefiedto provide very low temperatures.
When recovered as a gas in the atmosphere, it is used to produce anhydrous ammonia(NH₃), which is the fifth most commonly produced chemical in the United States. It is alsoused as the basis for making many nitrogen compounds. At one time it was believed to beimpossible to combine hydrogen with nitrogen to form ammonia, a natural product of animalwaste that was used as a fertilizer and textile bleach, among other things.
Nitric acid (HNO3) is an important commercial chemical and was manufactured commerciallyto produce fertilizers and explosives as well as plastics and many other products. In1902 a German chemist, Wilhelm Ostwald (1853–1932), developed a process wherein at hightemperatures he used platinum catalysts to convert ammonia into nitric acid. When nitric acidis reacted with glycerol, the result is nitroglycerine—an unstable explosive unless dissolved ininert material, such as clay. It can then be stabilized as dynamite.

Uses

In manufacture of ammonia, nitric acid, nitrates, cyanides, etc.; in manufacture of explosives; in filling high-temp thermometers, incandescent bulbs; to form an inert atm for preservation of materials, for use in dry boxes or glove bags. Liquid nitrogen in food-freezing processes; in the laboratory as a coolant. Pharmaceutic aid (air displacement).

Definition

Nitrogen, N2, is a colorless,odorless, inert gas that comprises 80%of the earth's atmosphere. It serves as a diluent and controls natural burning and respiration rates, which would be much faster in higher concentrations of oxygen. Nitrogen is soluble in water and alcohol, but is essentially insoluble in most other liquids. It is essential to practically all forms of life and its compounds serve as foods or fertilizers. Nitrogen is used in the manufacture of ammonia and nitric acid. Nitrogen is essentially an inert gas at ambient and moderate temperatures. Therefore, it is easily handled by most metals.At elevated temperatures, nitrogen can be aggressive to metals and alloys.

Production Methods

Nitrogen is obtained commercially, in large quantities, by the fractional distillation of liquefied air.

Definition

Dinitrogen: the normal form ofmolecular nitrogen, N₂ used to distinguishit from nitrogen atoms.

Definition

nitrogen: Symbol N. A colourlessgaseous element belonging to group15 (formerly VB) of the periodictable; a.n. 7; r.a.m. 14.0067; d. 1.2506g dm–3; m.p. –209.86°C; b.p. –195.8°C.It occurs in air (about 78% by volume)and is an essential constituent of proteinsand nucleic acids in living organisms.Nitrogen is obtained for industrialpurposes by fractional distillation ofliquid air. Pure nitrogen can be obtainedin the laboratory by heating a metal azide. There are two naturalisotopes: nitrogen–14 and nitrogen–15 (about 3%). The element isused in the Haber process for makingammonia and is also used to providean inert atmosphere in weldingand metallurgy. The gas is diatomicand relatively inert – it reacts withhydrogen at high temperatures andwith oxygen in electric discharges. Italso forms nitrides with certainmetals. Nitrogen was discovered in1772 by Daniel Rutherford (1749–1819).

General Description

A colorless odorless gas. Noncombustible and nontoxic. Makes up the major portion of the atmosphere, but will not support life by itself. Used in food processing, in purging air conditioning and refrigeration systems, and in pressurizing aircraft tires. May cause asphyxiation by displacement of air. Under prolonged exposure to fire or heat containers may rupture violently and rocket.

Air & Water Reactions

Slightly soluble in water.

Reactivity Profile

These substances undergo no chemical reactions under any known circumstances except those under extreme conditions (liquid Nitrogen reacts violently in mixture with magnesium powder when a fuse is lit. Due to formation of magnesium nitride). Otherwise, they are nonflammable, noncombustible and nontoxic. They can asphyxiate.

Hazard

Nitrogen is nontoxic, but it is an asphyxiate gas that cannot, by itself, support oxidation(combustion) or support life. If you breathe pure nitrogen for any period of time, you will die—not because the nitrogen gas is a poison, but because your body will be deprived of oxygen.
Nitrogen oxides are formed under certain conditions when nitrogen combines with oxygen,thus contributing to pollution. One source is from the internal combustion engine thatproduces NO similar to lightning. Once released, it combines with more oxygen to form ,which is a very reactive polluting gas. Nitrogen dioxide NO₂ is the main cause of “brown”smog over some cities and is harmful to plants, animals, and humans. To make matter worse,if there is adequate sunlight at the time of the smog, the ultraviolet light of the sun will breakdown the N and O of the NO₂ to form free radicals of oxygen that are reactive, forming ozone(O₃), which is itself a strong oxidizing agent that adds to pollution.
Several of the oxygen, hydrogen, and halogen compounds of nitrogen are toxic wheninhaled. A common error made in using household cleaners is to mix or use together ammoniacleaning fluids (containing nitrogen) and Clorox-type cleaning fluids (containing chlorine).The combined fumes can be deadly in any confined area. NEVER mix Clorox with ammoniatypecleaning fluids.

Health Hazard

Vapors may cause dizziness or asphyxiation without warning. Vapors from liquefied gas are initially heavier than air and spread along ground.

Fire Hazard

Non-flammable gases. Containers may explode when heated. Ruptured cylinders may rocket.

Agricultural Uses

plant growth. It is a gaseous element of Group 15 (formerly VB) of the Periodic Table, having an atomic number of 7 There are two stable and four radioactive isotopes of nitrogen. Nitrogen is a part of all amino acids, proteins, chlorophylls, enzymes, alkaloids, phosphotides, vitamins, hormones, nucleic acid and other plant substances. With as much as 78% in the atmosphere and 98% in the soil organic matter, nitrogen is abundant in nature. Yet, it is most deficient in all cultivated soils because (a) nitrogen is lost in many ways, (b) both microbes and plants compete for soil nitrogen,and (c) soil has little capacity to hold nitrogen in oxidized forms. With all vital processes being associated with functionally reactive plasma in the nitrogen-containing proteins, it is obvious that life is inconceivable without nitrogen.
Nitrogen in adequate quantity often leads to the desirable thin cell walls and leads to more tender and succulent plants, resulting into a better crop yield. Nitrogen is absorbed by plants either in the cationic or the anionic form as ammonium ion (NH₄⁺ ) or nitrate ion (NO₃ ^- ). These ions are soluble in water and are, therefore, very easily leached. If fertilizer is applied when it rains, obviously a lot of it will be washed away, and in this way, the annual nitrogen loss can be as much as 50 to 80 kg/ha.
Nitrogen loss occurs through leaching, volatilization, immobilization and ammonium faation. Denitrification or conversion of nitrate to nitrogen gas by bacteria is another cause for extensive loss of gaseous nitrogen. Ammonium ions in a basic solution leads to ammonia loss by volatilization. Surface applications of any ammonium or urea fertilizer on calcareous soils cause the largest ammonia losses.
The mineralized ammonium ions have a very short life, whereas the nitrification process is rapid. So, slowing down of the oxidation of ammonium ions to the nitrate form reduces the nitrate (and nitrogen) loss by leaching or denitrification. Several nitrification inhibitors such as nitrapyrin and dicyandiamide (DCD) are used to inhibit nitrification.
Nitrogen furaton provides a major source of soil nitrogen. Nitrogen fixation involves the action of microbes that convert the relatively inert nitrogen of the soil air into such forms as are useful to plants. The natural biological and chemical processes through which inorganic and organic nitrogen are inter-converted, are collectively known as the nitrogen cycle. It includes ammonification, ammonia assimilation, nitrification, nitrate assimilation, nitrogen fixation and denitrification.
Materials supplying nitrogen are (a) anhydrous ammonia (NH₃) which is hazardous and difficult to handle, (b) urea [CO(NH₂)₂] which is a good, cheap and the most popular fertilizer, (c) ammonium nitrate (NH₄NO₃) which is a relatively cheap source of solid nitrogen fertilizer, and (d) ammonium sulphate [(NH₄)₂SO₄] which is not as popular as urea and ammonium nitrate.
Since fertilizer nitrogen efficiency is determined by the biomass yield and nitrogen uptake by the crop, all factors affecting these also affect the efficiency of nitrogen usage. These factors are classified into five groups such as the soil, crop, environment, agronomic practices and fertilizer management.
Nitrogen deficiency symptoms are most prevalent and the easiest to identify. Young plants exhibit yellowish green foliage and stunted growth while older plants show yellowing or falling of leaves.
Nitrogen deficiency impedes good yield. An effective, integrated approach employs organic manures, biofertilizers, chemical fertilizers, nitrification inhibitors, coated and long-persisting nitrogen fertilizers. Such practices hold the key to sustainable agriculture. Nitrogen is used in the production of ammonia, acrylonitrile, nitrates, cyanamide, cyanides and nitrides. It is used in the manufacture of explosives and as an inert gas for purging. It is also used in cryogenic preservation, as a source of pressure in oil wells, inflating tires and as a component of fertilizer mixtures. However, overuse of nitrogen fertilizers is responsible for increased quantities of nitrates in the soil water, posing a serious threat to the environment.

Pharmaceutical Applications

Nitrogen and other compressed gases such as carbon dioxide and nitrous oxide are used as propellants for topical pharmaceutical aerosols. They are also used in other aerosol products that work satisfactorily with the coarse aerosol spray produced with compressed gases, e.g. furniture polish and window cleaner. Nitrogen is insoluble in water and other solvents, and therefore remains separated from the actual pharmaceutical formulation.
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. Most of the propellant is contained in the vapor phase and therefore 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 been used for pharmaceuticals and cosmetic aerosol sprays and foams utilizing nitrogen as the propellant.
Nitrogen is also used to displace air from solutions subject to oxidation, by sparging, and to replace air in the headspace above products in their final packaging, e.g. in parenteral products packaged in glass ampoules. Nitrogen is also used for the same purpose in many food products.

Industrial uses

Nitrogen is often called an inert gas, and is used for some inert atmospheres for metal treating and in lightbulbs to prevent arcing, but it is not chemically inert. It is a necessary element in animal and plant life, and is a constituent of many useful compounds. Nitrogen combines with many metals to form hard nitrides useful as wear-resistant metals. Small amounts of nitrogen in steels inhibit grain growth at high temperatures, and also increase the strength of some steels. It is also used to produce a hard surface on steels.
Because of the importance of nitrogen compounds in agriculture and chemical industry, much of the industrial interest in elementary nitrogen has been in processes for converting elemental nitrogen into nitrogen compounds. The principal methods for doing this are the direct synthesis of ammonia from nitrogen and hydrogen, the electric arc process, which involves the direct combination ofN₂ and O₂ to nitric oxide, and the cyanamide process.

Materials Uses

Gaseous nitrogen is noncorrosive and inert, and may consequently be contained in systems constructed of any common metals and designed to safely withstand the pressures involved. At the temperature of liquid nitrogen, ordinary carbon steels and most alloy steels lose their ductility and are considered unsafe for liquid nitrogen service. Satisfactory materials for use with liquid nitrogen include austenitic stainless steel (for example, types 304 and 316) and other nickel-chromium alloys, copper, Monel, brass, and aluminum.

Pharmacology

Atropine does not reactivate the phosphorylated AChE but competes with acetylcholine for binding with the muscarinic acetylcholine receptor acting as an antagonist.

Safety Profile

Low toxicity. In high concentrations it is a simple as-p~h yxiant. The release of nitrogen from solution in the blood, with formation of small bubbles, is the cause of most of the symptoms and changes found in compressed air illness (caisson disease). It is a narcotic at hgh concentration and hgh pressure. Both the narcotic effects and the bends are hazards of compressed air atmospheres such as found in underwater dving. Nonflammable gas. Can react violently with lithium, neodymium, titanium under the proper condtions. See also ARGON.

Safety

Nitrogen is generally regarded as a nontoxic and nonirritant material. However, it is an asphyxiant and inhalation of large quantities is therefore hazardous.

Potential Exposure

Nitrogen is present in the air we breathe. Health effects may occur at concentrations above 80%. It has many medical and industrial uses including the quick freezing of food. The gas is used for purging, heat treating; food freezing; annealing, cooling, oil recovery; in the inert blanketing of sensitive materials and as a reactant in chemical synthesis of ammonia.

Physiological effects

Nitrogen is nontoxic and largely inert. It can act as a simple asphyxiant by diluting the concentration of oxygen in air below levels necessary to support life. Inhalation of nitrogen in excessive concentrations can result in dizziness, nausea, vomiting, loss of consciousness, and death.
Death may result from errors in judgment, confusion, or loss of consciousness, which prevents self-rescue. At low-oxygen concentrations, unconsciousness and death may occur in seconds without warning.
Gaseous nitrogen must be handled with all the precautions necessary for safety with any nonflammable, nontoxic compressed gas.
All precautions necessary for the safe handling of any gas liquefied at very low temperatures must be observed with liquid nitrogen. Extensive tissue damage or burns can result from exposure to liquid nitrogen or cold nitrogen vapors.

storage

Nitrogen is stable and chemically unreactive. It should be stored in tightly sealed metal cylinders in a cool, dry place.

Shipping

UN1066 Nitrogen, compressed, Hazard Class:, Hazard Class: 2.2; Labels: 2.2-Nonflammable compressed gas; UN1977 Nitrogen, refrigerated liquid cryogenic liquid, Hazard Class:, Hazard Class: 2.2; Labels: 2.2- Nonflammable compressed gas. 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

Cylinder N2 can be freed from oxygen by passage through Fieser's solution [which comprises 2g sodium anthraquinone-2-sulfonate and 15g sodium hydrosulfite dissolved in 100mL of 20% KOH; see Fieser, J Am Chem Soc 46 2639 1924] followed by scrubbing with saturated lead acetate solution (to remove any H2S generated by the Fieser solution), conc H2SO4 (to remove moisture), then soda-lime (to remove any H2SO4 and CO2). Alternatively, after passage through Fieser's solution, N2 can be dried by washing with a solution of the metal ketyl from benzophenone and Na wire in absolute diethyl ether. [If ether vapour in N2 is undesirable, the ketyl from liquid Na-K alloy under xylene can be used.] Another method for removing O2 is to pass the nitrogen through a long, tightly packed column of Cu turnings, the surface of which is constantly renewed by scrubbing it with ammonia (sg 0.880) solution. The gas is then passed through a column packed with glass beads moistened with conc H2SO4 (to remove ammonia), through a column of packed KOH pellets (to remove H2SO4 and to dry the N2), and finally through a glass trap packed with chemically clean glass wool immersed in liquid N2. Nitrogen has also been purified by passage over Cu wool at 723oK and Cu(II) oxide [prepared by heating Cu(NO3)2.6H2O at 903oK for 24hours] and then into a cold trap at 77oK. A typical dry purification method consists of a mercury bubbler (as trap), followed by a small column of silver and gold turnings to remove any mercury vapour, towers containing anhydrous CaSO4, dry molecular sieves or Mg(ClO4)2, a tube filled with fine Cu turnings and heated to 400o by an electric furnace, a tower containing soda-lime, and finally a plug of glass wool as filter. Variations include tubes of silica gel, traps containing activated charcoal cooled in a Dry-ice bath, copper on Kieselguhr heated to 250o, and Cu and Fe filings at 400o. [Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I pp 458-460 1963.]

Incompatibilities

Containers may explode when heated. Liquid nitrogen is very unreactive, nonflammable, noncombustible and nontoxic. Contact with water may result in vigorous or violent boiling and extremely rapid vaporization. If the water is hot, there is the possibility that a liquid “superheat” explosion may occur. Pressures may build to dangerous levels if the liquid contacts water in a closed container.

Waste Disposal

Return refillable compressed gas cylinders to supplier. Vent to atmosphere.

Regulatory Status

GRAS listed. Included in the FDA Inactive Ingredients Database (injections; dental preparations; nasal sprays; oral solutions; rectal gels). Accepted for use as a food additive in Europe. Included in parenteral and nonparenteral medicines licensed in the UK and USA. Included in the Canadian List of Acceptable Non-medicinal Ingredients.