Known to some as laughing gas and to some as \\$quot;˜hippy crack\\$quot; the gas nitrous oxide - N2O, also known as dinitrogen oxide or dinitrogen monoxide, is a colourless gas and one of the gas industry\\$quot;s major product lines. Commercially it is used extensively in the food sector as an aerosol propellant and by surgeons and dentists for its anesthetic effects. To the man on the street, however, it is most commonly known as \\$quot;˜laughing gas\\$quot;- due to it\\$quot;s ability to produce euphoria to those inhaling it.

Nitrous oxide was first discovered in 1793 by pioneering British scientist and clergyman Joseph Priestley. He is also credited with being the first to isolate other important gases such as oxygen, carbon monoxide, carbon dioxide, ammonia and sulphur dioxide. Priestley was able to make N2O by heating ammonium nitrate in the presence of iron fillings, filtering the gas emitted through water to remove toxic by-products. Initially Priestley was unsure as to how his discovery might be applied to practical use; at first he hoped that it may be a preserving agent. However, this was quickly disproved and it was Sir Humphrey Davy of the Pneumatic Institute in Bristol, England who learnt the full extent of N2O\\$quot;s physical properties.

Davy learnt of its affects on human respiration when he administered purified N2O to himself, visitors and friends (including the poets Samuel Taylor Coleridge and Robert Southey). Davy was the first to note its euphoric and anaesthetic properties and coined the term \\$quot;˜laughing gas\\$quot;. Ironically it was the inhalation of N2O as well as other gases that Davy made his name exploring that eventually led to Davy\\$quot;s premature death.

Despite Davy\\$quot;s observations of N2O\\$quot;s potential medical benefits for the next 40 years its use was largely restricted to recreational purposes. In fact N2O became the 19th century\\$quot;s drug of choice for social gatherings of the wealthy classes, particularly amongst the dignitaries and elite of Bristol, England. The public were also able to buy a minute\\$quot;s worth of nitrous oxide from travelling medicine shows and carnivals known as \\$quot;˜nitrous oxide capers\\$quot;. Upon inhaling the gas people would become relaxed, have laughing fits and behave uncontrollably until the drug suddenly wore off. People would then be abruptly left standing around in confusion.

The 19th century philosopher William James and many contemporaries found that inhalation of N2O resulted in a powerful, spiritual and even mystical experience for users. James even claimed that N2O led him to experience the fusing of dichotomies into a unity and a revelation of ultimate truth during the inhalation of nitrous oxide. Predictably, however, memories of these so called \\$quot;˜experiences\\$quot; faded quickly and any attempt to describe or communicate the \\$quot;˜discoveries\\$quot; were near to impossible.

The development of applications
Surprisingly it wasn\\$quot;t until 1844 that an American dentist, Dr Wells attempted to explore N2O\\$quot;s anaesthetic qualities. After witnessing a public demonstration of N2O Wells administered it to himself and had a fellow dentist remove a tooth. He experienced no significant pain and seized on the gas as a newfound anaesthetic - the dawn of N2O as a medical anaesthetic had arrived.

Use of N2O has continued to modern times, despite being illegal in many countries to inhale for the purpose of becoming intoxicated. In fact, the drug is still popular for recreational purposes, especially among \\$quot;˜psychedelic\\$quot; communities as an inhalant. This has led to the newest, somewhat pejorative, slang term for N2O - \\$quot;˜hippie crack\\$quot;.

However, N2O inhalation is not without its dangers. While the gas itself is pure if it is not inhaled with a sufficient percentage of oxygen, death can result. Longterm use in large quantities has been associated with dangerous symptoms similar to vitamin B12 deficiency: anaemia due to reduced hemopoiesis, neuropathy, tinnitus and numbness in extremities. It can be habitforming, primarily because of its short lived effects (1 to 5 minutes) users are prone to repeated doses.

In modern medicine N2O is quite a weak general anaesthetic and is generally used in tandem with other more powerful anaesthesia. Pharmacologically it is still useful as it has a very low short-term toxicity; therefore a 50 / 50 mix with oxygen known as Entanox is widely used for dental procedures obstetrics and emergency medicine.

N2O has been used in food production both as a food additive and as a propellant in aerosol products. N2O\\$quot;s worth as an inert gas means it is used to displace
staleness-inducing oxygen in packages of potato snacks and other similar products. N2O is uniquely soluble in fatty compounds like whipped cream, dissolved N2O is mixed into cream contained in a spray can until it leaves, becomes gaseous and creates a foaming effect.

Mechanical engineers have also favoured N2O\\$quot;s unique properties as a propellant, it is comparably nontoxic and, because of its stability at room temperature,
relatively safe to work with at altitude. The German Luftwaffe was among the first to use N2O to boost the power output of aircraft\\$quot;s engines, by injecting N2O into the engine they were able to propel aircraft to high altitude operations.

Car racing has also used N2O extensively to boost performance. Subsequently N2O was banned from mainstream racing after its use became controversial due to dangerous performance enhancement. Indeed harnessing the raw power of N2O as a propellant was the main difficulty facing engineers. The stresses that power increases of 100-300% place on engine require extensive re-enforcement necessary to prevent their destruction.

The harmful effects of N2O
The darker consequences of N2O production in industrial use and, more significantly, agricultural fertilizers; is only now becoming evident. N2O emissions attack the ozonosphere, after carbon and methane, it is the world\\$quot;s third most significant contributor to greenhouse gases and global warming. N2O is naturally emitted from soils and oceans but human activity especially in
cultivation of soils and the use of nitrogen fertilizers in agriculture, nylon production, the burning of fossil fuels and other matter combine to produce dangerously large N2O emissions. Governments are only now taking steps to combat the levels of N2O in the atmosphere and are helping our industry to achieve
emission targets.

Philip Urner, Manager
Helison Marketing Ltd

Q. gasworld: Who are the biggest N20 suppliers?
"In Europe it would have to be Strombeek in Belgium, they\\$quot;re situated north of Brussels. Worldwide it would have to be Puritan Bennett, based in California."
Q. gasworld: What types of N2O are commercially produced?
"There are two grades, for food and medical grade there is 99.7% purity,
but also six 9\\$quot;s purity for electronic applications in manufacturing in the far east, where N20 is used in fairly large amounts for electronic gas."
Q.gasworld: What new applications are we seeing for N2O?
"N2O is being used to produce nitride; we are seeing this in the far east where nitride is for metal binding in micro chips."
Q. gasworld: Any new products in the N2O market?
"I don\\$quot;t see any new applications in the near future. I think that we are
seeing a decline in the use of N2O as an anaesthetic, it is being replaced by injectable drugs that are more expensive but far more convenient for use."
Q. gasworld: Future developments for N2O?
"There could be in the not too distant future developments in applications
N20 in line items refrigeration units requiring -50oC & -60oC cooling temperature."

Jatind Sanghi, Manager
Sanghi, India

Q. gasworld: What role do you have in N20 production?
"We only produce N2O for medical use at the moment."
Q. gasworld: New applications for the future of N2O?
"Currently we are producing N2O mostly for medical purposes although we study developments."