70 Mil. Ckum on the Action of Bleaching Powder, #*c. 



atoms to three of copper yielded 1*295. I conceive the rose-coloured 

 powder, then, to be a compound of an oxide of copper with limo, in 

 which the copper exists in the state of sesquioxide, Cu 2 3 . 



I have not succeeded in producing this oxide by means of tho 

 hypochlorites of potash or soda, even with the alkali in great excess ; 

 but by adding caustic soda to a solution of hypochlorite of lime, and 

 afterwards nitrate of copper, we obtain tho calcareous compound (lime 

 being precipitated along with the copper) in a state of division so fine 

 as to show the rose colour as soon as it is formed. This method, how- 

 ever, does not serve for the purposes of analysis, for the powder never 

 becomes granular, and remains therefore too bulky to be washed. 



It will now be observed that the dehydrating action of tho hypo- 

 chlorites upon oxide of copper depends upon the momentary forma- 

 tion of a sesquioxide, in which the oxygen has replaced the previously 

 combined water. 



The solution of bleaching powder in which the sesquioxide has 

 been formed is of a fine, but very pale pink colour ; and contains so 

 small a proportion of its colouring ingredient, that the nature of that 

 body can scarcely be discovered by analytical means. The second 

 washing of the oxide is colourless ; but if a very minute portion of 

 sulphate of manganese be added, the pink colour is restored. When 

 manganate of potash is dropped into nitric acid, the well-known red 

 colour of hypermanganic acid is produced. Dropped into lime-water 

 its colour is bluish green ; but in bleaching liquor, even with excess of 

 lime, the manganate yields the peculiar amethystine colour of the 

 solution in which the sesquioxide of copper has been produced. 

 Bleaching powder has long been said to contain manganese, which is 

 believed to pass over, during its formation, along with the chlorine, in 

 the state of the gaseous hyperchloride of Dumas ; and to this I at first 

 attributed the pink colour of the original solution, but I afterwards 

 found that it could be reproduced from the Irish limestone which I 

 employed. 



The vessel in which the sesquioxide has been produced, is lined 

 with a beautiful rose-coloured deposit, which remains attached to tho 

 glass when the other matters are washed out; but it fades away in a 

 few hours, particularly when exposed to light, and cannot even be long 

 preserved in the solution which forms it. Dissolved in dilute nitric 

 acid, copper is found in the solution, and no manganese. There can 

 be no doubt, that, like the precipitate, it is the sesquioxide of copper 

 in combination with lime. 



The red oxide of iron has also the power of decomposing the hypo- 

 chlorites. This fact, as well as the formation of a superoxide of 

 copper, was observed many years ago by Mr. Mercer of Oakenshaw, 

 and stated by him to the British Association in 1842, in a paper con- 

 taining some interesting speculations on these and other weak affinities, 

 which give riso to many of the phenomena of catalysis. 



