CHLORINE. 



CHLORINE. 



already noticed, is evolved in the gaseous state. When three equiva- 

 lents of chlorate of potash are acted upon by sulphuric acid, there are 

 produced two equivalents of peroxide of chlorine and one equivalent of 

 perchloric acid. 



By substituting oxalic acid for sulphuric acid, Messrs. Grace Calvert 

 and E. Davis assert, that peroxide of chlorine may be prepared with 

 far greater facility and much less danger. One equivalent of chlorate 

 of potash (122'5 parts) and nine equivalents of crystallised oxalic acid 

 (567 parts), well powdered and intimately mixed, furnish, when heated 

 in a water-bath to a temperature of 158, a steady stream of the gas, 

 chloride of potassium and an acid oxalate of potash being left in the 

 vessel. The peroxide of chlorine thus produced, however, always con- 

 tains carbonic acid. 



Chlorous Acid (CIO,) is a dangerously explosive yellowish green gas, 

 evolved when chlorate of potash, arsenious acid, and nitric acid are 

 K-ntly heated together. It possesses considerable bleaching powers, 

 and forms definite salts, chlorite*, with bases. 



lltijioctdwoua Add (CIO). This acid is thus obtained : add finely- 

 powdered peroxide of mercury, mixed with twelve times its weight of 

 distilled water, to chlorine gas in a bottle, and shake it well ; the oxide 

 of mercury should be slightly in excess, so that when the absorption 

 of the chlorine, which goes on rapidly, is over, the residue should have 

 a reddish rather than a white colour. The whole contents of the bottle 

 are to be put in a filter, upon which there remains oxychloride of 

 mercury, while the filtered liquor, when distilled in vacuo, yields weak 

 hypochlorous acid, which may be concentrated by redistillation. 



Hypochlorous acid thus procured is a transparent slightly yellow- 

 coloured fluid ; its smell is penetrating and very distinct from that of 

 chlorine or the peroxide ; its taste is extremely strong but not acid. 

 When prepared by passing dry chlorine over dried precipitated peroxide 

 of mercury, and condensing the gaseous product by aid of a freezing 

 mixture, it presents the appearance of a deep red liquid, which boils at 

 68. It attacks the epidermis with great activity, even more so than 

 strong nitric acid, and imparts a brown stain to the skin. It is a very 

 unstable compound, decomposing probably even at common tempera- 

 tures. In hot weather it can be preserved for a few days only, without 

 immersion in ice ; when weaker and kept from the light, it may be 

 preserved for a longer time. During decomposition it gives out small 

 bubbles of chlorine gas, and some chloric acid is formed, and this 

 decomposition is accelerated by agitation with angular bodies : it is 

 decomposed by the action of light as well as by that of heat. 



When to a concentrated solution of hypochlorous acid an equal bulk 

 of solid dry nitrate of lime is added, a brisk effervescence is produced, 

 which is owing to the' separation of pure hypochlorous acid gas, which 

 lias the following properties : its colour is very little deeper than that 

 of chlorine ; its smell is penetrating like that of the solution ; it is 

 rmiipletely absorbed by mercury, which is transformed into a red 

 oxychloride. It is best prepared by passing up a little of the gas at a 

 tirne'into ajar filled with and inverted in mercury; the nitrate of lime 

 which is dissolved prevents the action of the liberated gas upon the 

 metal: water dissolves nearly 100 times its volume of this gas; it is 

 decomposed by heat with explosion. The fixed alkalies and the 

 alkaline earths combine with hypochlorous acid. 



The hypochlorite of lime, usually called chloride of lime, or bleaching 

 potvder, is a compound of great importance, both in the arts and as a 

 disinfectant. [CALCIUM.] The exact composition of this compound is 

 a subject still under discussion. Another compound, the nature of 

 which is perhaps more problematical, is that formed by passing 

 rhlorine gas into a solution of carbonate of soda ; the gas is plentifully 

 absorbed without evolving any carbonic acid. This compound, like the 

 hypochlorite of lime, is used as a disinfectant, under the name of 

 Labarraque's soda liquor. With regard to the composition of the 

 substances formed when chlorine is absorbed by the bases, chemists 

 usually hold one of two opinions. First, that a double salt is formed, 

 consisting of a chloride of the metal and a hypochlorite of the oxide of 

 the metal, thug, 



2MO + CT, = MCI + MO, CIO 



Oxide of a Chlorine, 

 metal. 



Double salt. 



Second, that the chlorine unites directly and simply with the oxide 

 of the metal, and that the so-called double salt merely consists of two 

 a body, thus, 



MCI + MO, CIO = 2(MO, Cl) 



Double salt. 



Chloride of 

 metallic oxide. 



The second view is the more probable one. 

 Nitrogen and chlorine combine to form the 



C'/Uoride of \ltnnjui. This compound was discovered by Duloug in 



1811. These gases do not combine by direct action, but when chlorine 



gas meets nitrogen gas in the nascent state they unite. It may be 



prepared by dissolving an ounce of chloride of ammonium in twelve to 



sixteen times it* weight of water, and then inverting a bottle of 



me gas in the solution. The clJorine is gradually absorbed, and 



nrc formed small drops of an oil-like fluid which sink in the 



solution: these are -the chloride of nitrogen, derived from the com- 

 bination of the chlorine with the nitrogen of the ammonia. 



The properties of this substance are that it is extremely explosive, 

 sometimes detonating spontaneously, but always on the contact of 

 fatty matter, phosphorus, and various other bodies. Its specific 

 gravity is 1'653. It is not solidified by the most intense artificial cold. 

 At 160 it may be distilled, but at 200 to 212 it explodes. 



Chlorine and hydrogen combine to form the 



Ifi/droMaric Acid (HC1), sometimes called muriatic, acid and 

 spirit of salt. When equal volumes of these gases are mixed and kept 

 in the dark, they do not unite, but if exposed to daylight they combine 

 slowly, and by the direct rays of the sun, the electric spark, or a taper, 

 they unite with explosion, and there is formed a quantity of hydro- 

 chloric acid equal in volume to that of the two gases employed. As 

 50 cubic inches of hydrogen weigh 1-07 grain and 50 of chlorine 3S-57 

 grams, their combined weight gives that of 100 cubic inches of the 

 gas = 39-64 grains, or its specific gravity is V2474. This gas is 

 colourless, has a very pungent odour, and an acid and acrid taste. It 

 excites coughing, unless largely diluted with air; extinguishes burning 

 bodies when they are immersed in it; and reddens vegetable blue 

 colours strongly. By heat it is merely expanded, but by electricity it 

 is decomposed. Under a pressure of forty atmospheres at 50, it con- 

 denses to a colourless liquid, which the most intense cold does not 

 solidify. The affinity of this gas for water is so great, that when it 

 escapes into the air, it forms a white vapour by combining with 

 atmospheric moisture ; water absorbs 400 times its bulk of this gas, 

 and the result is liquid hydrochloric acid, usually called hydrochloric 

 acid. 



As this acid is largely employed, it is prepared in a more economical 

 manner than the direct formation of the gas, by decomposing common 

 salt with sulphuric acid. For this purpose, 24 parts of common salt, 

 termed chemically chloride of sodium, are mixed in a retort with 20 

 parts of sulphuric acid, and 12 of water, and into the receiver an equal 

 quantity of water is put ; by distillation to dryness, a colourless acid is 

 obtained, which has a specific gravity of about V16. 



For manufacturing purposes this process is usually conducted in iron 

 vessels, and the product condensed in a series of stoneware (Woulfe's) 

 bottles, or by conducting the gas through tall columns or towers filled 

 with coke, down which a small current of water is made to trickle. 

 The acid thus produced, though very strong, always contains a con- 

 siderable quantity of iron and other impurities in solution, and is, 

 therefore, always more or less coloured. 



During the mutual action of the salt, acid, and water, a portion of 

 the water is decomposed, which yields hydrogen to the chlorine, and 

 these form hydrochloric acid, while its oxygen unites with the sodium, 

 to form soda, which with the sulphuric acid constitutes sulphate of 

 soda, which remains in the retort. This solution of hydrochloric acid 

 has the smell and acid properties of the gas itself ; it emits white 

 fumes, and reddens litmus paper. It dissolves many metals, such as 

 iron, zinc, and tin, and forms with them chlorides, the acid being 

 decomposed and yielding hydrogen gas during their solution. These 

 compounds will be treated of as chlorides, under the respective metals. 

 Hydrochloric acid is largely employed in the arts connected with, or 

 dependent upon, chemical operations, as in dyeing and calico printing, 

 and in making chloride of ammonium or sal ammoniac [AMMONIA] ; 

 it unites also with the vegetable alkalies, as morphia, quinine, &c., to 

 form hydrochlorates ; but with metallic oxides, it forms chlorides, and 

 not hydrochlorates, on account of the decomposition which it suffers, 

 as just explained. When mixed with the nitric acid also, it is decom- 

 posed, and a solution is obtained, which is used under the name of 

 aqua-regia, or nitro-rtiuriatic acid, or nitro-hydroehloric acid, for dis- 

 solving gold and platinum. 



The strength of commercial hydrochloric acid is most readily ascer- 

 tained by taking its specific gravity. The following table, slightly 

 abridged from one drawn up by Dr. A. Ure, shows the per pentago of 

 hydrochloric acid gas in aqueous hydrochloric acid : 



