CHLORINE 791 



which on exposure to heat yields chlorine, magnesia, and chloride of manganese. The 

 chloride of magnesium used in this process may be obtained from carnallite, a mineral 

 largely -worked in the salt mines of Stassfurt and Kalucz. According to Longmaid's 

 methods, chlorine is prepared by passing dry air over a mixture of common salt and 

 iron-pyrites, roasted together ; or a mixture of salt and some metallic sulphate, such 

 as sulphate of iron. In Mac Dougal and Kawson's process any chromate or bichromate 

 is acted on by hydrochloric acid. Shank's method is very similiar, chromato of lime 

 being decomposed by hydrochloric acid ; but the mode of reproducing the chromate is 

 different. By Lauren's method protochloride of copper (cupric chloride), mixed -with 

 sand, is heated, and free chlorine evolved, -while the residue of subchloride (cuprous 

 chloride) is reconverted into the higher chloride by exposure to air in contact -with 

 hydrochloric acid. Mallet directs a current of air over subchloride of copper, 

 thus forming an oxychloride, from which chlorine may bo eliminated by hydrochloric 

 acid. 



Mr. Dunlop has also obtained a patent for the production of chlorine by a very 

 elegant method, which dispenses with the use of manganese altogether. It consists in 

 mixing common salt with nitrate of soda, and submitting the mixture to the action of 

 sulphuric acid. Chlorine and nitrous gas are evolved, and are caused to traverse a 

 vessel containing strong sulphuric acid, by which the nitrous gas is readily absorbed, 

 and the chlorine passes off. A current of atmospheric air is now passed through the 

 nitrous sulphuric acid, until the nitrous is converted into nitric acid. These mixed 

 acids are then made to act upon common salt without any addition of nitrate of soda, 

 and the same gaseous products are obtained as before. 



A description of Mr. Weldon's process by which the refuse liquors left in the 

 ordinary mode of preparing chlorine are utilized and the spent manganese re-oxidised, 

 will be found under CHLORIDE OF LIME (p. 785). 



Chlorine has a peculiar smell and irritates the nostrils and other air-passages most 

 violently when inhaled. It is eminently noxious to animal life, and if breathed in its 

 undiluted state, would prove instantly fatal. It supports the combustion of many 

 bodies, and, indeed, several substances, such as antimony and phosphorus, spon- 

 taneously burn in chlorine without being previously kindled. The resulting combina- 

 tions are called chlorides, and act most important parts in many manufacturing pro- 

 cesses. 



Water absorbs, at the ordinary temperature of the atmosphere, about 2J times its 

 volume of chlorine, and acquires the colour, taste, and smell of the gas, as well as its 

 power of destroying or bleaching vegetable colours. When this aqueous solution of 

 chlorine is cooled down to 36 R, dark yellow crystalline plates appear in it of the 

 hydrate of chlorine, which are composed in 100 parts of 27'7 chlorine and 72 - 3 water. 

 If these crystals be heated to about 45, they liquefy, and the gas is evolved. 



Chlorine has a powerful affinity for hydrogen, not only combining with it rapidly 

 in the gaseous state, but seizing it in many of its liquid and solid combinations : as in 

 certain volatile hydrocarbons, which it inflames. The compound of chlorine and 

 hydrogen gases is hydrochloric or muriatic acid gas. Binoxide of manganese, when 

 mixed with liquid hydrochloric acid, as in the above process, abstracts the hydrogen 

 and eliminates the chlorine. When chlorine is passed into water, it decomposes some 

 of it, seizes its hydrogen to form a little hydrochloric acid, and enables its oxygen to 

 unite, either with the chlorine into chlorous acid, or with the remaining water, and to 

 constitute oxygenated water. Hence an aqueous solution of chlorine, exposed to the 

 sunbeam, continually evolves oxygen, and ere long becomes hydrochloric acid. 



In the presence of moisture, chlorine acts powerfully upon vegetable colouring 

 matters ; water is decomposed, its hydrogen combining with the chloride to form 

 hydrochloric acid, whilst its oxygen is liberated, and in its nascent state, or at the 

 moment of its liberation when most active, oxidises the colouring principles, and thus 

 bleaches them. Bleaching by means of chlorine is therefore a true process of oxida- 

 tion ; in some cases, however, it appears that colourless substitution-products con- 

 taining chlorine are produced. The value of chlorine as a deodorizer and disinfectant 

 consists also in its power of decomposing water, and setting free oxygen, which thus 

 oxidises the poisonous miasmatic exhalations, and converts them into more or less 

 innocuous products. For such purposes, chlorine is usually best employed in the form 

 of bleaching powder, or chloride of lime ; but in some cases the pure gas may be 

 conveniently employed : it requires, however, from its poisonous nature to be used 

 with the greatest care. In fumigating the Millbank Penitentiary, Dr. Faraday found 

 that a mixture of 1 part of common salt and 1 part of binoxide of manganese, when 

 acted upon by two parts of oil of vitriol previously mixed with one part of water (all 

 by weight), and left till cold, produce the best results. Such a mixture, at 60, in 

 shallow pans of rod earthenware, liberated its chlorine gradually, but perfectly, for 

 four days. The salt and manganese were well mixed, and used in charges of 3 pounds 



