CHLORINATION 787 



with gum. The colour is discharged in those places where the acid was present, but 

 elsewhere untouched. Sulphate of zinc or chloride of zinc may be employed, instead 

 of acids, for liberating chlorine from bleaching powder. 



On acting upon cotton-cloth with a concentrated solution of chloride of lime, at from 

 110 to 120 F., pure carbonic acid is disengaged, and the texture of the cloth is injured. 

 Here the hydrogen of the water, and of the cotton, being seized by the chlorine, the 

 liberated oxygen combines with the carbon to form carbonic acid. In the discharge- 

 troughs, where printed calicoes are passed through strong solutions of chloride of lime, 

 stalactitic crusts of carbonate of lime come to be formed in this way. 



When chloride of lime is heated, it evolves oxygen gas, and sometimes chlorine, 

 and it becomes converted into a mixture of chlorate of lime and chloride of calcium, 

 which has no bleaching properties. Half an ounce of chloride of lime boiled in two 

 ounces of water yields, according to Keller, 165 cubic inches of oxygen contaminated 

 with chlorine. 



The property of chlorine, to destroy offensive odours and to prevent putrefaction, 

 gives to the chlorides of lime and soda a high value. On this important subject 

 Pereira, has the following remarks (Mat. Med. vol. i.) with reference to medical 

 police : ' If air be blown through putrid blood, and then through a solution of chlo- 

 ride of lime, carbonate of lime is precipitated, and the air is disinfected ; but if the air 

 be first passed through putrid blood, then through caustic potash, or milk of lime, to 

 abstract the carbonic acid, and afterwards through the solution of chloride of lime, it 

 retains its stinking quality. Chloride of lime may be employed to prevent the putre- 

 faction of corpses previous to interment ; to destroy the odour of exhumed bodies 

 during medico-legal investigations ; to destroy bad smells and prevent putrefaction 

 in dissecting-rooms and workshops in which animals substances are employed (as cat- 

 gut manufactories) ; to destroy unpleasant odours from privies, sewers, drains, wells, 

 docks, &c. ; to disinfect ships, hospitals, prisons, stables, &c. The various modes 

 of applying it will readily suggest themselves. For disinfecting corpses, a sheet 

 should be soaked in a pailful of water containing a pound of chloride, and then 

 wrapped round the body. For destroying the smell of dissecting rooms, &c., a solu- 

 tion of the chloride may be applied by means of a gardening pot.' Of equal impor- 

 tance is this substance to the medical practitioner. The poisonous exhalations from 

 foul sewers may be counteracted by a slight inhalation of chlorine gas, as obtained 

 from a little chloride of lime placed in the folds of a towel wetted with acetic acid. 

 The importance of chlorine as a disinfecting agent appears to have been fully 

 proved during the period of the cattle plague. Both Dr. Augus Smith and Mr. 

 Crookes, in their reports, give several very striking examples of the power of this 

 agent in cleansing sheds and houses which had been occupied by cattle suffering 

 under and dying from the disease. Carbolic acid, however, appears to be preferred 

 by one of these chemists. Both these preparations may, it is clear, be used with 

 satisfaction when required. 



For estimating the amount of chlorine in bleaching powder, and thus determining 

 the commercial value of a given sample, see CHLOBOMETBY. 



CHLORIDE OF POTASSIUM. See POTASSIUM. 



CHLORIDES OF POTASH AND SODA. When a weak solution of caustic 

 potash or soda is saturated with chlorine, it affords a bleaching liquor, still used by 

 eorne bleachers and calico-printers for delicate processes ; but the price of the alkalis 

 has led to the disuse of these chlorides as a general means, and has occasioned an 

 extensive employment of chloride of lime. The chloride of potash is known as 

 Water of Jai-ellc, and the chloride of soda as Labarraguds Liquor. They may be pre- 

 pared by transmitting chlorine gas through a solution of caustic alkali or alkaline 

 carbonate, or by decomposing chloride of lime with an alkaline sulphate or carbonate. 

 These so-called chlorides are now generally considered to be mixtures or compounds 

 of chlorides and hypochlorites. See CHLORIDE OF LIME. 



CHXiORXNATIOXfT. The method of extracting gold and silver from certain ores 

 by means of chlorine. This process is especially employed for separating gold from 

 sulphides and arsenides which cannot be treated by the ordinary methods of amalga- 

 mation. By the aid of chlorine gas, the gold is converted into a chloride, and from a 

 solution of this salt the metal may be precipitated as a sulphide by sulphuretted 

 hydrogen, or reduced at once to the metallic state by means of sulphate of iron. The 

 process enables a very small percentage of gold to be extracted with advantage from 

 an ore ; indeed, according to Mr. Allain, it is possible to extract gold from pyrites by 

 means of chlorine, when the metal is present to the extent of only one part in 10,000 

 parts of roasted ore. 



The chlorination-process was originally proposed by Professor Plattner, and was 

 applied, as far back as 1851, to the extraction of gold from the arsenical pyrites of 

 Eeichensloin in Silesia an ore containing .about 200 grains of gold to the ton. In 



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