CHLORINE. (FE., Morino ; GER., Chlor.) Symbol, Cl; combining weight, 35.5.
This important element was discovered, in 1771, by Scheele, a Swedish chemist. Its elementary character was first established by Sir Humphry Davy, in 1810. At ordinary temperatures, chlorine is a gas, having a yellowish-green colour (Gr. xiewpris, green), and an extremely pungent, irritating odour. It does not support respiration, unless abundantly diluted with air. Under a pressure of four atmo spheres, at 15°, chlorine condenses to a mobile, yellow liquid, having a density of 1.33. It has never yet been solidified. In the ordinary gaseous condition, it is two and a half times heavier than atmospheric air. Water dissolves twice its volume of chlorine gas, at ordinary temperatures, and a still larger proportion if the temperature is lowered ; at 0°, a hydrate may be obtained in crystals. The aqueous solution possesses the colour, odour, and other general characteristics of the gas. Chlorine is a powerful bleaching agent, and is largely used for this purpose in the form of bleaching powder, or chloride of lime ; it is also very effective as a disinfectant.
Chlorine is found widely distributed in nature, in the form of common salt, or chloride of sodium. This salt exists in enormous quantities in sea water, and in inland deposits, when it is termed " rock-salt." It also exists abundantly in combination with potassium, calcium, magnesium,
and other metals. It may be obtained either by the action of sulphuric acid upon a, mixture of common salt and peroxide of manganese, or of strong hydrochloric acid upon the peroxide alone. The former method is preferable when the gas is required in small quantity ; tte proportions used are four parts of common salt, three parts of the peroxide of manganese, and seven parts of concen trated sulphuric acid previously diluted with an equal volume of water. These are intimately mixed, and the mixture is placed in a flask and heated gently. Owing to its extreme solubility, the gas cannot be collected under water ; it is best collected by downward displacement.
In' the method employed in alkali works for the generation of chlorine gas on a large scale, for the manufacture of bleaching powder, hydrochloric acid, having a specific gravity of 1.15, is gently heated with the powdered peroxide, chlorine gas, chloride of manganese, and water being formed. The details of the manufacture of chlorine, on a commercial scale, by this method have been set forth in the article ou Bleaching Powder, to which the reader is referred.