and its compoundsAtomic weight, 355; sp. gr., 249; meltingpoint, 1015 degrees C. Chlorine is not found in nature in an uncombined state, but exists very extensively in combination with other substances, and most abundantiy in the form of common saltsodium chloride. There are large deposits of salt in Cheshire, and it forms part of the wellknown Stassfurt saline deposits. Combined with hydrogen as hydrochloric acid, it is a natural constituent of the gastric juice of men and animals. In the form of salt it is always found present in seawater; thus, the water ot the English Channel contains 2805 parts per 1,000. Common salt is mined to some extent in an impure state in the dry condition, but for the most part it is made by pumping water into the salt deposits and subsequent evaporation of the brine solution thus prepared. Chlorine in gaseous form is manufactured on a large scale, and is employed chiefly in the preparation of chloride of lime, or bleaching powder, which is used for bleaching purposes and as a sanitary reagent. For this purpose it is mostly made by the. action of hydrochloric acid upon manganese dioxide: MnOj + 4HCI = MnCl2 + aHaO + Cl2. In the Weldon process, the manganese is reprecipitated from the resulting manganese chloride liquor as manganese hydroxide by treatment with milk of lime and peroxidized by a current of air, ready for use over a sain. In the Deacon process, which is also employed on a manufacturing scale, a mixture of hydrogen chloride gas and a: l is exposed to the catalytic influence of cupric chloride distributed over a widely exposed surface at a temperature of about 400 degrees C., chlorine and water being produced as follows: 2HCI + O = HaO + Cl2. There is also an electrolytic method of manufacturing chlorine now in use, consisting in the direct electrolysis of a solution of common salt, in which the gas is evolved at the anode whilst sodium hydrate is produced at the cathode. The concentrated gaseous chlorine thus prepared and liquefied, and stored in iron cylinders, was largely used in the great war for “gassing” by reason of its corrosive and poisonous character. In the liquefied form it is of a bright goldenyellow colour, and when cooled sufficiently it freezes to a yellow crystalline mass. It immediately passes into the gaseous state when liberated in the air, and has a very violent action on the linings of the mouth, nose, throat, and lungs, causing death when nhaled in serious quantity. On account of its sterilizing value, chlorine as such, or in the form of bleaching powder, is frequently used for the purification of watersupplies.Chlorine is also employed in the manufacture of potassium chlorate, which is extensively used in matchmaking and in the preparation of certain explosives and of chloroform. Chlorine gas is of a greenishyellow colour, and nearly two and a half times heavier than air. It is somewhat soluble in water, i volume of which at io degrees C. absorbs 31 volumes of chlorine, forming a green solution. When strong chlorine water is cooled to nearly freezingpoint, it deposits a crystalline hydrate of unstable character. Metallic copper in th;n leaf form, metallic antimony in the form of a powder, and sodium, all take fire and burn readily in chlorine gas, forming chlorides, although the gas itself is not inflammable. Similarly a jet of burning hydrogen gas will burn in a vessel containing chlorine gas, thus producing hydrochloric acid in the form of white fumes: H+C1HC1. Hydrochloric Acid, or hydrogen chloride, is one of the most important compounds of chlorine. The two gases hydrogen and chlorine do not combine when mixed together in the dark, but in sunlight or electric light they combine with explosive violence. The acid can be easily prepared, amongst other methods, by the action of strong sulphuric acid upon common salt as represented by the equation aNaCl + HaS4 = NaaS04 + 2IICI; that is to say, sodium sulphate and hydrochloric acid are produced, and the hydrochloric acid can be distilled over from the mixture in the form of gas and condensed in water, thus furnishing a solution of the acid. In its gaseous form, the acid is colourless and possesses a pungent, irritating character. It is soluble in water, 1 volume of which at o degrees C. and under ordinary atmospheric pressure dissolves Hydrochloric acid finds use in the textile and chrome tanning industries, and the manufacture of dyestuffs, and is obtained as a byproduct in the manufacture of sodium carbonate from common salt and sulphuric acid, the gas being absorbed in condensers by the action of water percolating down towers or stacks pac ked with broken coke, up which it is led.

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Definition of  CHLORINE