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Royal Institution of Great Britain. 461 



infection, and by the proofs he had brought forward of their very 

 efficacious nature. The application of these compounds, and their 

 medical uses, havinj^ been spoken of by Mr. Alcock, on February 

 2nd*, Mr. Faraday confined himself to considerations purely che- 

 mical. Free chlorine acts upon putrid or infectious miasmata, 

 sometimes by the abstraction of hydroi^en, with which it forms 

 muriatic acid ; sometimes by combining with and forming triple 

 compounds with the carbon and hydrogen of the vapours; and 

 sometimes, perhaps, by evolving oxygen, which, in its nascent 

 state, acts upon the effluvia : but in all cases it acts chemically, and 

 converts tjiat which is noxious into inoffensive substances ; and this 

 t does by mere contact at common or even very low temperatures. 



Free chlorine is often inconveniently applicable, because it is 

 itself offensive and injurious to the lungs ; but, when combined 

 with hydrated lime, or with a carbonated alkali, it forms compounds 

 which may be obtained in the solid state, or sometimes more con- 

 veniently in a state of solution, and in which, although none of the 

 offensive qualities of the chlorine remain, its power of destroying 

 odorous and infectious matter is still singularly eminent. The first 

 of them is usually known by the name of chloride of lime, or 

 bleaching powder, and is prepared in enormous quantities in this 

 and other countries, for the use of the bleacher. In it the chlorine 

 is held by so weak an affinity, that even carbonic acid evolves it, 

 and it is by such an action that the powder, or its solution, acts as 

 a disinfectant upon the air to which it is exposed ; for, according 

 to the good experiments of M. Gaultier de Claubryt, the carbonic 

 acid in the air first evolves a small portion of chlorine, and then 

 the free chlorine acts upon the putrid or infectious matter. 



The compound of chlorine with carbonate of soda, which has 

 been distinguished by several very unphilosophical names, is not 

 so well understood. Mr. Faraday inclined to think it the result of 

 a simple union between the two substances, unattended by any 

 decomposition of the alkaline carbonate. He stated, as the 

 result of his own experience, that no carbonic acid gas was given 

 out when prepared according to M. Labarraque's prescription ; and 

 as the result of Mr. Phillips's experience, that a peculiar crystalline 

 mass was obtained by evaporating the solution to dryness, which, 

 when dissolved, although it possessed no bleaching power, acquired 

 that property by passing a current of carbonic acid gas through it. 

 He also mentioned an experiment made by Mr. Phillips, at which 

 he was present, in which a portion of the compound which had 

 * See page 211 of this volume, t See page 237. 



