CHLO'RINE (from Ck.x2wpbc,chloros, green ish-yellow). A gaseous element discovered by Scheele in 1774. It was supposed by its dis coverer to he hydrochloric acid deprived of phlogiston, and was called by him dephlogisti cated marine acid gas. In 1785 BerthoBet ad \ :wed the view that this gas should be regard ed as a compound of hydrochloric acid with oxygen. and this view was universally main tained for nearly a quarter of a century. The error was first pointed out by Gay-Lussac and in 1809, and in the following year Davy demonstrated elearly the elementary na ture of the gas. which he named chlorine. It is never found free, but occurs extensively in the form of chlorides, as in the mineral halite, or rock salt, and in sea-water; in sylvitc (potas sium chloride) ; in cernrgyritc (silver chloride) ; also as alkaline chlorides in plants and animals. It may be readily prepared by the action of hy drochloric acid on manganese dioxide, the chlo rine gas thus produced being washed by passing through a small quantity of water and drying with sulphuric acid. Commercially it is ob tained by passing over heated bricks a mixture of air and hydrochloric acid, the oxidation of the latter giving rise to the formation of free chlorine, which is then utilized for the manufac ture of bleaching-powder (q.v.).
Chlorine (symbol, Cl; atomic weight, 35.45) is a greenish-yellow gas with an irritating odor.
It is liquefied at 15° C. (59° F.), under a pres sure of four atmospheres, yielding a dark-yellow liquid heavier than and not miscible with water. Chlorine is a non-conductor of electricity, and is exceedingly poisonous; it attacks the mucous membranes, causing much irritation, and if in haled is eapable of causing death. It dissolves in half its volume of cold water, yielding a solu tion that resembles the gas in color, odor, and other properties. It finds important applica tion in the arts as a bleaching agent. and is very extensively used in cotton and paper indus tries. Its bleaching action is due to the readi ness with which it combines, in the presence of water, with the hydrogen of the coloring mat ter. This avidity for the hydrogen of organic matter may lie demonstrated by introducing a lighted taper into an atmosphere of chlorine— the taper will continue to burn, its hydrogen combining with the chlorine, while its carbon is liberated in the form of soot. Chlorine is also a powerful disinfectant and deodorant, and is much used for the destruction of the poisonous germs of infectious diseases. In chemical proc esses chlorine is frequently used as an oxidizer. Chlorine combines readily with basic radicals to form chlorides. Its most important com pounds are described under SALT; BLEACHING