25,^o t..,, -\ u,..^ ^^'' Crum o?i the Action oJ^<\ xyiK\ks^'^^ 



By calculation 20 grains CuO changed into Cu2 O3 ought 

 to yield, by Berzelius's numbers, 1*98 grain of oxygen. A 

 nearer approximation than in the foregoing results is scarcely 

 to be expected; for although there was no perceptible disn! 

 engagement of gas during the washing of the precipitate i^j 

 these experiments, it is certain that oxygen always escapesij 

 during the time so employed. ijuuot 



The quantity of lime necessary to the production andi(^f^3fj) 

 bility of this oxide is not more than 1 equivalent after saturafvi 

 tion of the nitric acid : 1 atom of lin)e to 3 of copper gave 

 only 0558 gr. of oxygen gas instead of the mean quantity 

 of r828 ; 2 atoms to 3 of copper yielded 1*295. 1 conceive^ 

 the rose-coloured powder then to be a compound of an oxid^ 

 of copper with lime, in which the copper exists in the state o^^ 

 sesquioxide, Cu2 Og. ,, 



I have not succeeded in producing this oxide by means of 

 the hypochlorites of potash or soda, even with the alkali in 

 great excess ; but by adding caustic soda to a solution of hyto 

 pochlorite of lime, and afterwards nitrate of copper, we obtain,) 

 the calcareous compound (lime being precipitated along witHj 

 the copper) in a state of division so fine as to show the rosQj 

 colour as soon as it is formed. This method, however, docii?;) 

 not serve for the purposes of analysis, for the powder neveiV 

 becomes granular^^ aj?^dj rem^^i||i,,^lje^-§f(^^,;fl^_, l?u||^y,,tfl„A)^n 



washed. \r^ -^ovio]f>*''l ->m']^^^u vrlybixo oHi inml 



It will now be doservea that the dehydratmg action of then 

 hypochlorites upon oxide of copper must depend upon th^o 

 momentary formation of a sesquioxide in which the oxygen q 

 has replaced the previously combined water. ,ij{ 



The solution of bleaching powder in which the sesquioxid/^y 

 has been formed is of a fine but very pale pink colour, andg 

 contains so small a proportion of the colouring ingredient^cJ 

 that the nature of that body can scarcely be discovered by I 

 analytical means. The second washing of the oxide is colour-to 

 less; 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. In lime water the colour 

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

 lime, we have the peculiar amethystine colour of the solution f, 

 in which the sesquioxide of copper has been produced.^ 

 Bleaching powder has long been said to contain manganese,lo 

 and to this I at first attributed the pink colour of the originaLil 

 solution ; but I afterwards found that it could be reproducedu; 

 from pure Irish limestone which I employed. Even marblejjt 

 gives a pink solution in the same circumstances. -\^) 



