Gas
in chemistry, a substance possessing the condition of perfect fluid elasticity, and presenting under a constant pressure a uniform rate of expansion for equal increments of temperature, but when reaching its maximum density behaving like a vapor. All gases can be condensed into liquids by cold and pressure. Some of the elements, as oxygen, hydrogen, nitrogen, chlorine, and probably fluorine, are gases at ordinary temperatures. Atmospheric air is a mechanical mixture of 77 parts by weight of nitrogen, and 23 of GAS oxygen, or 79 volumes of nitrogen mixed with 21 volumes of oxygen. Gases are formed by the dry distillation of animal and vegetable substances, which yield carbon dioxide, carbon monoxide, ammonia, nitrogen, hydrogen, sulphur dioxide, hydrogen sulphide, and hydrocarbons.
The gas of commerce is carburetted hydrogen (CH4). Its frequent disengagerment in coal mines with resultant explosions, generally fatal to many lives, has caused the miners to give it the name of fire-damp. In parts of the world it issues from crevices or holes in the strata in so moderate and continuous a stream, as to burn with a huge jet instead of exploding. It was discovered in the United States about 1845, and is known as natural gas. Gas wells abound in Ohio, Indiana, Pennsylvania, and the West. This natural gas serves the purposes of illuminating and heating. The GAS SUPPLY PIPE GAS COCK RUBBER BAG GAS INLET PIPE INLET VALVE GAS SUPPLY OF OTTO GAS ENGINE ignition of carburetted hydrogen may be seen in any coal fire. It has been discovered that giant jets of apparently. GAS ENGINE similar gas flames exist in the sun, and are one main source of its light and heat.