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Nitrogen

This gas is, as its name implies, the producer of nitre, or at least forms a portion of the nitric acid contained in nitre. It is rather lighter than atmospheric air, colourless, transparent, incapable of supporting animal life, on which account it is sometimes called azote--an objectionable name, as it is not a poison like many other gases, but destroys life only in the absence of oxygen. This gas extinguishes all burning bodies plunged into it, and does not itself burn. It exists largely in nature, for four-fifths of the atmosphere consists of nitrogen gas. It is also an important constituent of animal bodies, and is found in the vegetable world.

Nitrogen may be most easily obtained for experiment by setting fire to some phosphorus contained in a porcelain or metallic cup, placed under a gas jar full of air, and resting on the shelf of the pneumatic trough, or in a soup-plate filled with water.

Nitrogen combines in five different proportions with oxygen, producing five distinct chemical compounds, named respectively nitrous oxide, nitric oxide, nitric tri-oxide, nitric tetr-oxide, nitric pent-oxide, which last, united with water, forms nitric acid, now called hydric nitrate, as nitrous acid is termed hydric nitrite.

Nitrous oxide gas is generally known by the name of "laughing gas," from the jolly sensations experienced on inhaling it. It may be procured by distilling in a glass retort a salt called nitrate of ammonia, which yields the gas in considerable quantities, and it should be kept standing in jars over water for some hours before it is used. It should be transferred into a silk air-tight bag, furnished with a stopcock and mouthpiece, from which the gas may be breathed; a little practice is required to do this easily, and more resolution to desist when the gas begins to produce its effects, as it appears to fascinate the experimenter, and actual force is often necessary to remove the bag from the mouth. The effects produced vary according to the temperament of the person inhaling it; they are, however, always of a highly pleasurable nature, muscular action being generally greatly exalted, compelling the individual to race round the apartment and execute leaps and pirouettes perfectly astounding. Some persons shout and sing, and I have seen one expend his superfluous animation in twisting his features into such ludicrous grimaces as would be the envy of the candidates at a grinning match, and beat them all out of the field. Sir H. Davy was the discoverer of this gas, and of its peculiar effects on the nervous system, and a full account of it may be found in his "Researches on Nitrous Oxide Gas."

This gas is heavier than air, and supports combustion nearly as energetically as oxygen, as may be shown by introducing a piece of ignited phosphorus into a jar of this gas. It will not, however, support the life of small animals, such as mice, which introduced into it die very quickly.

The next compound of nitrogen with oxygen, when one proportion of nitrogen unites with two of oxygen, is termed nitric oxide gas. It may be easily procured by heating in a retort some copper turnings in dilute nitric acid. It is colourless and transparent, and has the property of combining with oxygen to form other compounds.