coefficients of an equation sometimes disappears in its roots, as 



is the case with the equation ^iJfoq >luiifcf riadqiuq sldoloetu 



* . ii| riidJ io I'lcq laJJfil artj gniiub 



■ w,« +3/,ty + --^iy^,*iiq(^2 + t/^^y a^^e^fq oJ emh 



* I't '<"•** '/J to yiae-<fri 



which has one root symmetric with respect to yj{ srfj t^sgeao 



Birchington, near Margate, ""^ ^J'" ui-t^yv snj io moJJod odi ol 



August 29, 1845. Soa odi rnoii bgieiBqsa sd ^''^631 



__j__ ^ .i'iOiiqvc: L An I- 



XLVI. 0» M^ Action of Bleaching Powder on the Salts of 

 Copper and Lead. £^ Walter Crum, Esq., F.R.S.^ 



IN February 1843 I read to the Philosophical Society of 

 Glasgow an account of a rose-coloured oxide of copper 

 which I had obtained by the action of bleaching powder and 

 lime upon nitrate of copper. Although I had then made 

 numerous analyses of this substance, prepared under a variety 

 of circumstances, I had been unable to obtain from it the full 

 amount of oxygen which a definite compound must contain, 

 and delayed therefore to make it further known until I should 

 have the opportunity of producing it in a purer form. In 

 the mean time the rose-coloured substance was observed, and 

 correctly described, by Krxiger of Berlin, as a combination of 

 the oxide of copper, or, as he calls it, cupric acid, with lime. 

 Having completed my experiments on this subject as far as 

 my leisure will permit, I shall now state the results I have 

 obtained. 



When the hydrated oxide of copper is added to a solution 

 of bleaching powder it changes colour and becomes brown. 

 Oxygen gas is then plentifully disengaged, and the efferves- 

 cence continues till the whole of the hypochlorite of lime is 

 decomposed. The brown precipitate suffers no change during 

 this decomposition. When separated from the soluble mat- 

 ters, it is found to contain no chloiine and no excess of 

 oxygen. It is anhydrous oxide of copper. Hypochlorite of 

 soda produces the same effect. 



If we add nitrate of copper to a solution of bleaching pow- 

 der containing a considerable quantity of lime, and previously 

 cooled to below the freezing-point of water, a bluish-green 

 precipitate is formed. When the precipitate subsides, we 

 find the solution of a fine blue colour and containing copper; 

 but in what state I have not examined. As the heat advances 

 to the ordinary temperature, the copper in solution, as well as 



* Communicated by the Chemical Society; having been read April 21, 



