Although often referred to as laughing gas, the use of nitrous oxide is a serious subject as it has a fundamental role to play in the healthcare industry and beyond.
Nitrous oxide (N2O) is one of several oxides of nitrogen. Colourless, non-toxic and very stable, on average it resides some 120 years in the atmosphere before being broken down by ultraviolet radiation in the stratosphere.
Nitrous oxide has many uses, ranging from anaesthesia and pain-killer in medicine and dentistry (where it’s known as laughing gas due to the euphoria it can induce) to high-performance racing engines, where it can be used to boost combustion. N2O should not be confused with nitrogen dioxide, which is generated during internal combustion processes and forms a toxic brown haze in many urban environments.
Nitrous oxide is produced by heating ammonium nitrate to a temperature of 250°C. Ammonium nitrate is decomposed in the process to give a mixture of nitrous oxide & super heated steam. At the same time impurities are produced including ammonium nitrate fumes, nitrogen & other oxides of nitrogen. The steam & impurities are removed by scrubbing with water, caustic soda and sulphuric acid in sequence. Nitrogen present in traces is removed by bleeding from the top of storage vessels where nitrous oxide is stored, after compression by a compressor.
Nitrous oxide can be made by heating a solution of sulfumic acid and nitric acid. A lot of gas is made this way in Eastern Europe. There is no explosive hazard in this reaction if the mixing rate is controlled, however toxic higher oxides of nitrogen are often formed too.
Properties and distribution of Nitrous Oxide
Nitrous oxide is a chemical compound of nitrogen and oxygen, and a non-flammable and nontoxic gas with a slightly sweet taste & odour. The most common way of distributing nitrous oxide is as a compressed liquid in cylinders of the same kind, as used for oxygen and nitrogen for example. The pressure in nitrous oxide cylinders is approximately 50 bar at 20°C.
Applications & Uses
Nitrous oxide gas is mainly used as anaesthetic and for its analgesic effects, administered with oxygen. With the increase in standards of living throughout third world countries, nitrous oxide consumption has been growing steadily at a rate of more than 5% annually.
The gas is used as a propellant in food, perfumes and cosmetics and can be used for cryosurgery, as well as acting as an oxide gas for atomic absorption in spectrophotometry. The oxidizing property of N2O is helpful for etching microchips, while nitrous oxide is occasionally injected into the fuel of racing cars to give them exceptional or enhanced acceleration.
At present there is no mismatch between demand and supply, with nitrous oxide readily available in most regions. One critical factor is that nitrous oxide production plants are not too capital intensive and besides the big players, there are numerous small domestic players who are engaged in the production of this versatile gas at medium and small level.
Prices of nitrous oxide have shown an upwards trends like most other industrial gases, but the rise is less so when compared to other gases - over the last year prices have increased in the range of 5-7% worldwide.
Health and Safety
Nitrous oxide is a simple asphyxiant and a weak narcotic. Air hunger, dizziness, confusion, headaches, nausea, vomiting and loss of consciousness or death may occur if nitrous oxide is present in quantities sufficient to dilute the oxygen concentration in air. Overexposure creates an altered (euphoric or excited) mental state, while neurobehavioral impairment is usually evident when nitrous oxide exposure levels are several hundred to several thousand ppm. Exposure to the liquid can cause frostbite.
The Serious side of Laughing Gas
Harmless enough when your dentist uses it for anesthesia, N2O shows its darker side as a major component of global greenhouse-gas emissions and accounts for 9% of all greenhouse gases, yet is 300 times more potent than carbon dioxide (CO2). As a result its longevity in the atmosphere provides a potentially more damaging legacy than CO2.
Agriculture accounts for around 70% of N2O emissions. The sources are mainly from soil micro-organisms that make N2O from nitrogen-rich fertilizers added to soils to maximise crop yields. Other significant biological sources of N2O come from the wastewater treatment industries where the greenhouse gas is again produced from micro-organisms.
Long-term exposure to nitrous oxide has been associated with neuropathy, while increased rates of spontaneous abortion (dentist’s wives and female dental assistants) and congenital anomalies in offspring (female dental assistants) have been reported.
Epidemiological studies have not firmly established a cause-and-effect relationship and it should probably be noted that no scientific evidence has proved a concrete link, but exposure to the gas should be minimised.