The name given by Sir Humphrey Davy to a gas which long went, and even still commonly goes, by the name of oxymuriatic acid gas, as being imagined to be a compound of oxygen and muriatic acid, but which he showed to be a simple substance, which, when combined with hydrogen, formed muriatic acid. Chlorine is commonly, in the small way, obtained by distilling in a glass retort, at a gentle heat, 3 parts of common salt, 1 part of black oxide of manganese, and 2 parts of sulphuric acid. The gas which comes over is of a greenish yellow colour, and its odour and taste are disagreeable, strong, and so characteristic, that it is impossible to mistake it for any other gas. Like oxygen, it is a supporter of combustion, the products of which are termed chlorides. It has two remarkable properties: 1st, Its affinity for hydrogen is superior to that of any other substance, whence it is extremely useful in destroying contagious miasmata; and 2dly, its destructive action upon vegetable colours, with the aid of a little moisture. Scheele first remarked this property, Berthollett applied it to the art of bleaching in France, and Mr. Watt introduced its use into Great Britain.

The alkaline metals, as well as copper, tin, arsenic, zinc, antimony, in fine laminae or filings, spontaneously burn in chlorine: metallic chlorides result. Phosphorus also takes fire at ordinary temperatures, and is converted into a chloride. Sulphur may be melted in the gas without taking fire. See Bleaching.