269 



Ariicle XII. 



Researches concerning the Nature of the Bleaching Compounds 

 of Chlorine ; by J. A. B a lard. 



From the Annales de Cliimie et de Physique, vol. Ivii. p. 225. 



xxMONG the remarkable properties which chlorine pof3sesses, there 

 is one which became advantageous to manufactures verj^ shortly after 

 its discovery, viz. its energetic action on colouring matter. The illus- 

 trious Swede to whom we owe the knowledge of this body, mentioned 

 the facility with which it destroys vegetable colours ; but that which to 

 Scheele was merely an interesting experiment, became to BerthoUet 

 the basis of a new art. BerthoUet conceived the happy idea of apply- 

 ing the decolorizing property of chlorine to the purjjose of bleaching, 

 and the success which he obtained even in his first attempts exceeded 

 his hopes. Up to this period, cotton and linen manufactures were 

 spread in meadows, and by exposing them alternately moist and dry to 

 heat and cold, light and shade, they were indeed, after a very long 

 time, perfectly bleached. 



The eagerness Avith which a new process was welcomed will be con- 

 ceived, when manufacturers could produce by it in a few hours what 

 previously occupied several months. The new process of bleaching, to 

 which public gratitude gave the name of the Berthollean method, was 

 generally adopted, and chlorine thus proceeded from the laboratory 

 of the chemist to the workshop of the arts. Manufactures were first 

 bleached Avith chlorine gas, and after^vards with the aqueous solution ; 

 but it was soon found that its penetrating smell, and its powerful action 

 on the lungs, were very prejudicial to the Avorkmen employed. In his 

 endeavours to free them from these dangerous exhalations, BerthoUet 

 perceived that by the addition of a little quicklime, and even carbon- 

 ate of lime or of magnesia, the penetrating smell of the chlorine was 

 removed from the aqueous solution, without diminishing its bleaching 

 power. This important observation conducted him to another still 

 more important. He stated that if, instead of dissolving the alkali in 

 aqueous solution of chlorine, a current of the gas was made to pass 

 into the alkaline solution, it would dissolve a much larger quantity than 

 mere water, and the liquid possessed decolorizing power in a much 

 higher degree. 



These new compounds, in which the chlorine seemed in some degree 



