202 



CHLORINE. 



colour. Of all the eases, it is the most insupportable 

 in its action on the lungs. When pure, it occasions 

 immediate death if an animal is immersed in it; and 

 even when largely diluted with common air, it can- 

 not be respired with safety. It occasions a severe 

 sense of stricture at the breast, which renders it im- 

 possible to make a full inspiration. This continues 

 for a considerable tune after it has been inspired, and 

 has often produced a permanently injurious effect. 

 When thoroughly drieu, by exposure to fused chlo- 

 ride of calcium, it suffers no cliange, though cooled 

 to 4O>. When prepared over water, however, so as 

 to contain a quantity of aqueous vapour, it condenses 

 on the sides of the vessel even at a temperature of 

 40 ; and, if surrounded by snow or ice, it shoots in- 

 to acicular crystals of a bright yellow colour, and 

 sometimes two indies in length, which remain attached 

 to the sides of the vessel. This solid is a hydrate of 

 chlorine, and, when heated to 5CX>, it melts into a yel- 

 lowish oily fluid. Chlorine is absorbed by water, in 

 a quantity which increases as the temperature dimi- 

 nishes. At 50, the water takes up about twice its 

 volume. The solution lias a yellowish-green colour, 

 and its odour is that of the gas itself. Its taste is 

 rather styptic than sour, and the liquid, like the gas, 

 has the property of destroying the vegetable colours. 

 Hence it may be employed in bleaching. It is not 

 changed by a boiling temperature. Solution of chlo- 

 rine is decomposed, however, by exposure to the 

 solar light ; the chlorine attracts hydrogen from the 

 water, forming muriatic acid, which remains dissolved, 

 and pure oxygen is disengaged. Chlorine gas sup- 

 ports the combustion ot a number of inflammable 

 substances. A lighted taper burns in it, though fee- 

 bly, with a red flame ; phosphorus takes fire when im- 

 mersed in it ; and a number of the metals, as antimo- 

 ny, arsenic, copper, and others, if introduced into it 

 in leaves or filings, burn spontaneously. Potassium 

 and sodium burn vividly in it. In these cases, the 

 inflammable or metallic substances are believed sim- 

 ply to unite with the chlorine: Chlorine combines with 

 many of these bases in more than one proportion. 

 When in one proportion, the compound is called a 

 chloride ; when in two, a bi-chloride, or a deuto-chlo- 

 ride, &c. Whenever a metallic chloride, winch is 

 soluble in water, is thrown into that fluid, it is con- 

 ceived to be instantly converted into a muriate ; the 

 water present is decomposed, its oxygen goes to the 

 metallic base, and its hydrogen to the chlorine, and 

 a muriate of an alkali, earth, or metallic oxide, is 

 formed. Thus common salt, when dry, is a chloride 

 of sodium : it is no salt, containing neither acid nor 

 alkali, but, whenever it is dissolved in water, it is 

 immediately transformed into a salt : the sodium at- 

 tracts oxygen and becomes soda, and the chlorine 

 takes hydrogen and becomes muriatic acid, and mu- 

 riate of soda exists in the solution. When any of the 

 compounds of chlorine, with inflammable substances 

 or metals, are subjected to the action of a galvanic 

 apparatus sufficiently powerful to decompose them, 

 the chlorine is always evolved at the positive pole of 

 the battery, and the base at the negative pole. In 

 this respect, and in its power of supporting combus- 

 tion, chlorine is analogous to oxygen. One of the 

 most important chemical properties of chlorine is dis- 

 played in its action on the vegetable colours. Many 

 of them it entirely destroys ; and even those which 

 are the most deep and permanent, such as the colour 

 of indigo, it renders fault, and changes to a light yel- 

 low or orown. This agency is exerted by it, both in 

 its gaseous and its liquid form. The presence of 

 water is, however, necessary to this. Hence, when 

 the gas destroys colour, it must, probably, be enabled 

 so to do by the hygrometric water it contains. It is 

 accordingly found, that, when freed from this, it does 



not destroy the colour of dry litmus paper. The de- 

 struction of colour appears to be owing to the com- 

 munication of the oxygen of the water present to the 

 colouring matter : the chlorine attracts the hydrogen 

 of the water to form muriatic acid, and the evolved 

 oxygen unites with the colouring matter, and, by 

 changing its constitution, alters its relation to light, 

 so that the tint disappears. Berthollet applied this 

 agency of clilorine to the process of bleaching, and 

 with such success as to have entirely clianged the 

 manipulations of that art. The method of using it 

 has been successively improved. It consisted, at 

 first, in subjecting the thread or cloth to the action of 

 the gas itself; but the effect, in this way, was un- 

 equally produced, and the strength and texture were 

 sometimes injured. It was then applied, condensed 

 by water, and in a certain state ot dilution. The 

 thread, or cloth, was prepared as in the old method 

 ofbleaching, by boiling first in water, and then in al- 

 kaline lye ; it was then immersed in the diluted chlo- 

 rine : this alternate application of alkali and chlorine 

 was continued until the colour was discharged. The 

 offensive, suffocating odour of the gas rendered this 

 mode of using it, however, scarcely practicable ; the 

 odour was found to be removed by condensing the 

 chlorine by a weak solution of potash : lime, diffused 

 in water, being more economical, was afterwards 

 substituted. Under all these forms, the chlorine, by 

 decomposing water, and causing oxygen to be im- 

 parted to the colouring matter, weakens or discharges 

 the colour, and the colouring matter appears to be 

 rendered more soluble in the alkaline solution, alter- 

 nately applied, and of course more easily extracted 

 by its action. More lately, a compound of chlorine 

 and lime has been employed, prepared by exposing 

 slacked lime to clilorine gas : the gas is quickly ab- 

 sorbed, and the chloride of lime, as it is called, being 

 dissolved in water, forms the bleaching liquor now 

 commonly employed, and which possesses many advan- 

 tages. In using it, the coloured cloth is first steeped 

 in warm water to clean it, and is then repeatedly 

 washed with a solution of caustic potash, so diluted 

 that it cannot injure the texture of the cloth, and 

 which is thrown upon it by a pump ; the cloth is 

 then washed and steeped in a very weak solution of 

 chloride of lime, again washed, acted on by a boiling 

 lye as before, and again steeped in the solution ; and 

 these operations are performed alternately several 

 times. The cloth is lastly immersed in very dilute 

 sulphuric acid, which gives it a pure white colour ; 

 after which it is washed and dried. Chloride of 

 magnesia has been substituted, with great advantage, 

 for that of lime, in whitening cloth for calico print- 

 ing ; the cloth, when lime is used, retaining a little 

 of it, which, in the subsequent operation of clearing 

 by immersion in weak sulphuric acid, forms sulphate 

 of lime, which remains, and affects the colours when 

 it is dyed ; while the sulphate of magnesia is so solu- 

 ble, that it is entirely removed. Chloride of alumine 

 has been employed to discharge the colour of the 

 Turkey-red dye, which resists the action of other 

 chlorides, and is only discharged by chlorine gas, by 

 an operation very injurious to the workmen. An- 

 other important application of chlorine gas is that of 

 destroying or neutralizing contagion. Acid vapours, 

 sulphurous acid in particular, under the form of the 

 fumes of burning sulphur, had often been employed 

 for that purpose ; but chlorine, from the facility witii 

 which it decomposes the different compound gases 

 that contain the elements of vegetable and animal 

 matter, and which may be supposed to constitute 

 noxious effluvia, is superior to any other agent, and 

 is now universally employed for the purposes of fu- 

 migation. It is the only agent which can admiuisti r 

 1 relief in cases of asphyxia from sulphuretted liydro- 



