INERT GAS

:''Inert gases and noble gases are not exactly synonyms although some of the objects they describe overlap. "Noble gas" refers to inert elemental gases only whereas "inert gas" refers to molecular as well as elemental gases which are inert. Also "inert gas" is an archaic term for noble gas.''
An 'inert gas' is any gas that is not reactive under normal circumstances. Unlike the noble gases an inert gas is not necessarily elemental and are often molecular gases. Like the noble gases the tendency for non-reactivity is due to the valence, the outermost electron shell, being complete in all the inert gases. This is a tendency, not a rule, as noble gases and other "inert" gases can react to form compounds.
Although the term "rare gases" is sometimes used as a synonym for the elemental inert gases, i.e. noble gases—they are only rare relative to other gases found in Earth's atmosphere (i.e. air) with the exception of argon which makes up a significant portion of air, around %0.934; hardly rare at all. Because of their unreactivity, and perhaps their relative scarcity, the inert gases were not discovered until helium was discovered to exist in the Sun, where it is abundant, before it was discovered to exist in Earth's atmosphere. This is possible through the analysis of spectral lines.
Helium and neon are the only true elemental inert gases, because they do not form any (known) true chemical compounds, unlike the heavier noble gases (argon, krypton, xenon and radon).
In marine applications, inert gas refers to gases with a low content of oxygen that are used to fill void spaces in and around tanks for explosion protection. There are two types of inert gas which are either based on nitrogen or on flue gas.

Contents

Production

Applications

See also

Production

The elemental inert gases are usually obtained by evaporating them off from condensed air at their respective vapor pressures.
Nitrogen based inert gas is produced on board of chemical tankers and product carrieres (smaller vessels) with compressors and a Nitrogen specific membrane.
Flue gas based inert gas is produced on board of crude oil carriers (larger vessels) in a dedicated IGG (Inert Gas Generator) or in an inert gas system that takes the flue gas from the boilers and washes it.

Applications

Because of the non-reactive properties of inert gases they are often useful to prevent undesirable chemical reactions from taking place. For example molecular nitrogen, a molecular inert gas, is often used in food packaging to ensure that food does not spoil in transit since no bacteria or fungi can flourish without the reactive gases oxygen or carbon dioxide, which the molecular nitrogen displaces, since most extant cells on Earth require the reactions which these gases are involved in to function. Most importantly since molecular nitrogen is inert it will not cause any reactions to take place in the food, possibly changing the intrinsic taste or smell, nor will it cause any chemical reactions in the human body. Thus the inert gas is used as a passive preservative, preventing biological decay, while being undetectable to the consumer since taste and olfactory senses require a chemical reaction to take place in order to send a signal to the brain. This is in contrast to active preservatives which react with the biological material of bacteria, fungi, and possibly the food itself changing the food's intrinsic taste or smell, or may even act directly on the consumer's taste and olfactory mechanisms.
In gas metal arc welding inert gases are used to shield the heated metal from the reactive gases in air which can cause undesirable reactions in the metal. Some gases which are not usually considered inert but which behave like inert gases in all the circumstances likely to be encountered in some use can often be used as a substitute for an inert gas. This is useful when an appropriate pseudo-inert gas can be found which is inexpensive and common. For example carbon dioxide is sometimes used in gas mixtures for gas metal arc welding because it is not reactive in the circumstances encountered in arc welding even though it is often reactive in other circumstances. Carbon dioxide is usually used as a 25% mix with argon because pure carbon dioxide is too reactive.
On board of tankers, inert gas is used as explosion protection. Especially when discharging the cargo, the emptying tanks must not be filled with normal air. The oxygen content could rise to a critical level.

See also

★ inerting system