270 balard's researches concerning the nature of 



deprived of its hurtful properties, while it retained only those which 

 are useful, were soon generally employed in the art of bleaching. They 

 were at first prepared with the solution, and as the first trials were made 

 in the manufactoiy of Javelle, the new liquid with which industry was 

 enriched was called eau de Javelle. But in 1798, Tennant and Knox 

 of Glasgow attempted to substitute hydrate of lime, which forms a solid 

 bleaching compound, while chlorine retains its power only when diluted 

 with a large quantity of water. This substitution was generally adopted, 

 and the new compound, which is more easily preserved and prepared, 

 and at a less price, and more easy of transport, soon became an article 

 of manufacture and considerable commerce, under the name of bleach- 

 ing powder. 



The employment of these compounds of chlorine was further ex- 

 tended in 1822. M. Labarraque, an apothecary of Paris, proved at this 

 period, by numerous trials, that these compounds, which had rendered 

 so many services to the art of bleaching, might be as successfully used 

 for disinfecting. His own trials, and the fresh proofs that his example 

 incited, placed the decolorizing compound of chlorine decidedly among 

 the most valuable resources of the art of preserving health. 



We should be at first inclined to believe that the nature of these 

 compounds, which had rendered us such various services, was perfectly 

 understood by chemists ; but it is not at all so ; and notwithstanding 

 the researches which they have occasioned, the place which they ought 

 to occupy in a classification is not clearly determined. It is, indeed, 

 true that their elementary composition and immediate analysis are well 

 known. In fact, obtained by tlie action of chlorine upon a metallic 

 oxide, they evidently must be formed merely of chlorine, oxygen, and 

 a metal ; on the other hand, the experiments of several chemists have 

 proved that in these compounds, for every two atoms of chlorine*, there 

 is one atoni each of oxj'^gen and metal. But how are these three ele- 

 ments arranged ? This is not at present known with certainty ; and 

 yet this knowledge is indispensable for determining by what reactions 

 they serve in decolorizing and disinfecting. 



§ 1 . Of the Opinions which have been entertained as to the Nature of the 

 decolorizing Compounds of Chlorine. 



The opinions of chemists on this subject are divisible into two hy- 

 potheses. According to some, these compounds are merely chlorides 

 of oxides ; according to others, they are to be considered as mixtures of 

 metallic chlorides with a salt which contains an acid of chlorine, less 

 oxygenated than the chloric, and which it has been proposed to call 

 chlorous acid. 



* Not so in England, but foreign chemists reckon the weight of chlorine only 

 half that of English chemists, hcucc the author states two atoms. — Ed. 



