73 A TREATISE ON THE CONNECTION OF

oxygen. The other part, called phlogisticated air, or azot, is injurious to combustion, although necessary in a certain proportion, to modify the too powerful action of pure air, in the respiration of animals. Vital air, by combining with ignited inflammable substances, pro-

duces certain gasses and new compounds.

Atmospheric air contains likewise a proportion of fix- able air, or carbonic acid gas, so called by the French chemists, from carbonaceous matter, or charcoal, form-

ing one of its constituent parts.

Atmospheric air may also contain other gasses, or airs. By far the greater part of these gasses were discovered

by Dr. PRIESTLEY.

By the term of gas is to be understood, a permanently

elastic, invisible fluid: Of these there are some which

may be considered as simple, and others as compounded.

The gasses are, empyreal air, vital air—Or—oOxygen gas;

3

Fixable air—or—carbonic acid gas;

Light inflammable air—or—hydrogenous fas;

Dense

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