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The clown of all gases
The unique property of nitrous oxide is that when it is inhaled in a large enough quantity, it results in an outburst of uncontrollable laughter, besides hallucinations and a state of anxiety. These special characteristics became an automatic reason for its nickname — the “laughing gas”.
English scientist and clergyman Joseph Priestley (1733 — 1804), discovered nitrous oxide (N2O) in 1776. The years 1773 and 1772 are also cited as the ones in which this discovery was made. The discovery added yet another feather to Priestley’s crown, as he is also credited with the discovery of oxygen.
Priestley, who is also known as the king of serendipity, had no interest in science and this is obvious from the fact that he never took a proper science course throughout his life. Despite this, he managed to achieve many milestones in science, particularly physics.
He is also credited with the invention of soda water and the discovery of six gases besides oxygen — namely nitrous vapor (NO2), acid air (HCl), inflammable air (CO), alkaline air (NH3), vitriolic air (SO2) and flour acid air (SiF4). In short, he was one of the most influential and colourful scientists of the eighteenth century.
In the late eighteenth century, while he was in Leeds, Priestly undertook his most important scientific research study with regard with the nature and properties of gases. During that time, he learned a technique for dissolving carbon dioxide in water to create a pleasant “fizzy” taste. This technique later on led to the invention of soda water.
His experiments led to the discovery of oxygen. To boil over mercuric oxide, he used his 12-inch “burning lens” (a magnifying glass). In a succession of tests, it was witnessed that a gas was released.
He wrote in a paper which was published in 1775: “This air is of exalted nature… A candle burned in this air with an amazing strength of flame; and a bit of red hot wood crackled and burned with a prodigious rapidity, exhibiting an appearance something like that of iron glowing with a white heat, and throwing sparks in all directions. But to complete the proof of the superior quality of this air, I introduced a mouse into it; and in a quantity in which, had it been common air, it would have died in about a quarter of an hour. It lived at two different times, a whole hour, and was taken out quite vigorous.”
His work with laboratory-based scientific learning and exploration continued and during that time he discovered carbon dioxide as well. Furthermore, he practically observed the process of photosynthesis.
In his experimentation with gases, Priestley developed a new gadget, which permitted him to collect gases above mercury. During his experiment, before sealing the glass container over the top, Priestley let several material (including a mixture of iron and sulphur powders) to float on top of the mercury.
He heated up the residuals left in the container by means of a lens, by directing and focusing the sunlight. This experiment proved fruitful and Priestly invented a new gas, which was later recognised as nitrous oxide.
Nitrous oxide or nitrogen oxide is a colourless gas, with a sweet taste and it is almost odourless. At standard temperature and pressure conditions, it has a density of 1.977kg/cubic metre. And although it is not combustible, the gas does provide sustenance to burning.
The decomposition of nitrous oxide into its basic components — nitrogen and oxygen — when exposed to heat results in intensifying the combustion process. It is not only soluble in water, but also in alcohol, ether and many other solvents.
Nitrous gas is also purified after preparation. It is simultaneously compressed and cooled to achieve a liquid state and it is stored in a metal container, probably a cylinder. Nitrous oxide finds utility value in the food industry for the production of certain canned pressurised food. It would be interesting to note that Priestley described it as the diminished nitrous gas.
In the early 1840s, nitrous oxide got established as an anaesthetic in clinical dentistry and medicine. A medical school dropout Gardner Quincy Colton went around the country putting on nitrous oxide exhibitions. In 1844, he arranged for a demonstration in Hartford, Connecticut, where a local dentist named Horace Wells was also present in the audience.
Wells observed that Samuel Cooley, one of the volunteers, inhaled the gas and while still under the effect of N2O, injured his leg when he staggered into some benches. Cooley appeared to be unaware of the injury and remained in that state until the effects of the gas wore off. Dr Wells immediately realised that N2O could possess painkilling qualities.
Though concealed, but at the same time, this is an obvious advantage of nitrous oxide, which plays a key role in combustion. In view of the fact that every mole has identical volume and it is comprehensible that two moles of nitrous oxide drawn into the cylinder be converted into three moles during the combustion process. This further lifts up combustion pressures and ultimately serves to increase the power-producing potential of the engine.
The density of the atmosphere reduces with an increase in height above the Earth’s surface. Temperature also changes with variation in altitude. The International Standards Association (ISA) defines the standard temperature lapse rate of 2°C after every 1,000 feet increase in altitude and standard pressure lapse rate of one inch Hg after every 1,000 feet increase in altitude. The composition of air changes with an increase in altitude as well.
Another interesting point is that molecular oxygen is broken down into atomic oxygen due to the affect of solar ultraviolet radiations. Consequently, at about 100km altitude, atomic oxygen replaces molecular nitrogen. So, at very high altitudes, the lightest gases — hydrogen and helium, which are minor constituents of the lower atmosphere — become the primary constituents of it.
It was the German aircraft industry that discovered the use of nitrous oxide in the combustion chambers of an internal combustion engine as a means to increasing power output. At about 565 degrees F (296.1OC), nitrous oxide breaks apart into its constituting parts (nitrogen and oxygen). The gas is introduced into the intake tract of an IC or internal combustion engine (an engine in which fuel is burned within the engine rather than in an external furnace, as happens in a steam engine).
It is then drawn directly into the combustion chamber, due to the low pressure created by the downward movement of the piston. Following the action of the compressor the gas is compressed. The compression results in a reduction in volume and in a simultaneous and extreme increase in temperature and pressure.
As the temperature gets into the region of 565 degrees F, nitrous oxide breaks down into nitrogen and oxygen. This results in intensifying the oxygen share in the mixture to the desired level.
To balance the reduced air density and less oxygen at high altitudes, thousands of German fighters and reconnaissance aircraft were equipped with the “GM-1” (Gunner’s Mate First Class) system, which supplemented nitrous oxide to the intake charge. The Royal Air force also switched over to this technology.
The Luftwaffe (The German air force before and during World War II) put this technique into use during the conflict, to give boost to the performance of their aircraft at high altitudes. This system was devised in 1940 and was exclusively available for fighters, destroyers, bombers and reconnaissance aircraft.
The writer cocographer@yahoo.com is a senior instructor at a technical college
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