1835.] Decolourizing Combinations of Chlorine, 263 



the manufactory of Javelle, the new liquid was termed 

 Javelle water. But in 1798, Knox, Mackintosh and Ten- . 

 nant, * of Glasgow, substituted lime for the potash, and 

 thus introduced a solid substance, which came speedily into 

 general use, under the name of bleaching powdei'. 



In 1822 the employment of chlorine was farther extended 

 by M. Labarraque, who shewed that these bleaching sub- 

 stances might also be used for disinfecting purposes. 



It might be supposed that the nature of such important 

 compounds would be well understood by chemists. This is, 

 however, not the fact. Their elementary composition, and 

 immediate analysis, it is true, are known ; that is to say, 

 they consist of chlorine, oxygen, and a metal ; but the 

 experiments of different chemists have proved that, for two 

 atoms of the first of these bodies, they contain an atom of 

 each of the others. The question, then is, how are these 

 three elements combined ? 



1. Opinions respecting the nature of the Bleaching Com- 

 pounds of Chlorine. — Two hypotheses have been broached 

 by chemists on this subject. According to one opinion, 

 these compounds are nothing else than chlorides of oxides. 

 According to another hypothesis, they are regarded as 

 mixtures of metallic chlorides, with a salt containing a 

 chlorine acid, possessing less oxygen, in its composition, 

 than chloric acid, and, therefore, denominated chlorous 

 acid. By the first supposition, it is conceived that the 

 chlorine, in acting upon some metallic oxides, combines 

 with them without decomposing them, so as produce weak 

 compounds. The gas being thus feebly retained, acts upon 

 vegetable colours as if it were free ; that is to say, it destroys 

 them, either by directly combining with their hydrogen, or 

 by exciting their oxidation by means of the oxygen of the 

 water. The chlorine, in combining with the hydrogen, 

 either from the water or colouring matter itself, is converted 

 into muriatic acid, and, consequently, into a muriate. 



In the second opinion, it is supposed that the chlorine 

 re-acts upon the metallic oxide employed, so as to decom- 

 pose a portion of it ; that one part of the chlorine unites 

 with the metal, to form a chloride, and another to its oxy- 



* M. £alard terms the lirm erroneously, Georges, Tennant and Knox. — Edit. 



