Liquid nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere. The element nitrogen was discovered as a separable component of air, by Scottish physician Daniel Rutherford, in 1772.

Many industrially important compounds, such as ammonia, nitric acid, organic nitrates (propellants and explosives), and cyanides, contain nitrogen. The extremely strong bond in elemental nitrogen dominates nitrogen chemistry, causing difficulty for both organisms and industry in breaking the bond to convert the N2 into useful compounds, but at the same time causing release of large amounts of often useful energy when the compounds burn, explode, or decay back into nitrogen gas.

Nitrogen occurs in all living organisms, and the nitrogen cycle describes movement of the element from the air into the biosphere and organic compounds, then back into the atmosphere. Synthetically produced nitrates are key ingredients of industrial fertilizers, and also key pollutants in causing the eutrophication of water systems. Nitrogen is a constituent element of amino acids and thus of proteins and nucleic acids (DNA and RNA). It resides in the chemical structure of almost all neurotransmitters, and is a defining component of alkaloids, biological molecules produced by many organisms. The human body contains about 3% by weight of nitrogen, a larger fraction than all elements save oxygen, carbon, and hydrogen.

Nitrogen is formally considered to have been discovered by Daniel Rutherford in 1772, who called it noxious air or fixed air. The fact that there was an element of air that does not support combustion was clear to Rutherford. Nitrogen was also studied at about the same time by Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley, who referred to it as burnt air or phlogisticated air. Nitrogen gas was inert enough that Antoine Lavoisier referred to it as "mephitic air" or azote, from the Greek word ἄζωτος (azotos) meaning "lifeless". In it, animals died and flames were extinguished. Lavoisier's name for nitrogen is used in many languages (French, Polish, Russian, etc.) and still remains in English in the common names of many compounds, such as hydrazine and compounds of the azide ion.

The English word nitrogen (1794) entered the language from the French nitrogène, coined in 1790 by French chemist Jean-Antoine Chaptal (1756–1832), from "nitre" + Fr. gène "producing" (from Gk. -γενής means "forming" or "giving birth to."). The gas had been found in nitric acid. Chaptal's meaning was that nitrogen gas is the essential part of nitric acid, in turn formed from saltpetre (potassium nitrate), then known as nitre. This word in the more ancient world originally described sodium salts that did not contain nitrate, and is a cognate of natron.

Nitrogen compounds were well known during the Middle Ages. Alchemists knew nitric acid as aqua fortis (strong water). The mixture of nitric and hydrochloric acids was known as aqua regia (royal water), celebrated for its ability to dissolve gold (the king of metals). The earliest military, industrial, and agricultural applications of nitrogen compounds used saltpetre (sodium nitrate or potassium nitrate), most notably in gunpowder, and later as fertilizer. In 1910, Lord Rayleigh discovered that an electrical discharge in nitrogen gas produced "active nitrogen", an allotrope considered to be monatomic. The "whirling cloud of brilliant yellow light" produced by his apparatus reacted with quicksilver to produce explosive mercury nitride.

The Industrial Gas Business is the supply of technical gases by one of three supply modes;

• On-site and pipeline,
• Bulk - (liquids and tube-trailer compressed gases)
• Cylinder or packaged gases.

It excludes gases used primarily for heating, such as natural gas and LPG, except where these are used for cutting and welding or supplied at very high purity for chemical or other use.

The defining characteristic of the Industrial Gas business is that whilst the cost of such gases in the final product is often small, the absence of the gas generally inhibits production.

The Industrial Gas Business is thus a service industry focused on the reliability and availability of the supply to end-users.

Cost Management

However, Industrial Gas Companies realise that costs can really only be managed by production and distribution expertise for any supply mode. Therefore, a successful Industrial Gas Company manages its costs by supply mode or product line but manages its customers and applications technologies by market sector.

In the case of larger volume users there is also an option to own an industrial gas plant and "make" their own gases, rather than the "buy" option of onsite or pipeline supply.

Most of the major Industrial Gas Companies will sell such plant to an end-user as will a large number of independent equipment suppliers.

The "make" versus "buy" decision is often at the heart of most new large volume industrial gas requirements. Plants owned by end-users are generally referred to as "captive".

Industrial Gas Companies view the conversion of "captive" capacity to "onsite" as a low risk opportunity to increase market penetration or market share.

There are six broad categories of gas

Industrial

The basic gases used in "industrial" applications, often in large quantities:

• Oxygen, nitrogen and argon - the "air gases"
• Acetylene and acetylene substitutes
• Carbon dioxide
• Hydrogen
• Carbon monoxide
• Air and "artificial" air

Medical

Gases intended for use in the medical field:

• Special grades of oxygen or breathing air
• Nitrous oxide
• Special grade carbon dioxide
• Breathing mixtures
• Blood analysis mixtures

Special

Rare, uncommon or speciality gases used in small quantities and delivered with strict quality assurance:

• Helium
• Xenon, Krypton, Neon - the noble gases
• Lighting mixtures
• Ultra-pure electronics gases
• Electronics dopants such as silane and arsine
• Calibration gas mixtures
• Research grade gas mixtures
• Sterilisation and fumigation gases

Fuel Gases

Gases such as LPG or its components from some companies but generally not considered when used for heating

• Butane
• Propane
• Cutting mixtures

Refrigerants

Gases used in the refrigeration cycle in cooling technologies are supplied by some companies.

Fire fighting gases are supplied by some companies

• Carbon dioxide
• Halon substitutes