Mil Crum on the Action of Bleaching Powder, frc. 71 



When a clear solution of bleaching powder is mixed with nitrate of 

 copper, a light bluish green powder precipitates, the bulkiness of which 

 renders it somewhat difficult to wash. This powder is very slightly 

 soluble in water, and scarcely changes colour in boiling. Heated in 

 a glass tube over a spirit-lamp, chloride of copper sublimes into 

 a cooler part of the tube, and water escapes. Tho residue consists of 

 black oxide of copper, mixed with a quantity of chloride, which may be 

 separated from the oxide by washing. Professor Graham, who sug- 

 gested to me this experiment, remarked on the analogous effect of 

 boiling water in separating water from a hydrate. It proved to be a 

 hydrated oxichloride of copper — the substance known by the name of 

 Brunswick green, and found in a variety of other circumstances. 

 Analysis gave me a result approaching more nearly to 3 CuO, Cu CI 

 than to 4 CuO, Cu CI ; but the presence of carbonate in the specimen 

 left me in doubt upon this point, and I could not resume the inquiry. 

 In this reaction tho whole of tho hypochlorous acid is set free. 



4 (CuO No 5 ) + 3(CaO CIO, Ca CI) = 



4 (CaO N0 5 ) + 3 CuO, Cu CI, + 2 Ca CI + 3 CIO. 



Peroxide of lead is often produced by passing a stream of chlorine 

 through a solution of sugar of lead. The chloride which accompanies 

 it in this way may be also converted into peroxide, by employing a 

 solution of bleaching powder instead of chlorine. By adding free 

 lime to the bleaching powder, and applying heat, we obtain a com- 

 pound, nearly colourless, of the peroxide of lead with lime: — Dis- 

 solve in water 1 lb. of nitrate of lead, and add it, along with three 

 equivalents of lime, to 16 lbs. of a solution of bleaching powder, 

 sp. gr. 1-08. Heat the mixture gradually to 160° Fahr., and stir 

 it frequently during five hours. Pour off the clear liquid, add 16 lbs. 

 more of the same solution, and continue the heat three hours longer. 

 The combination is obtained with only a slight brown tinge. 

 It is quite insoluble in water, and, when dried, does not alter in the 

 air. Nitric acid, by dissolving the lime, leaves the peroxide of a jet 

 black colour ; and, therefore, much deeper than that obtained by any 

 of the processes usually employed. I have had no means of determin- 

 ing the proportion of lime contained in this plumbate. With less than 

 two equivalents to one of oxide the compound is not white. An 

 excess of lime cannot afterwards be dissolved away by an acid without 

 discolouring the salt 



I found it convenient in these experiments to prepare a quantity of 

 cream of lime, by dropping newly burnt lime into boiling water, stirring 

 up, allowing the sand and the grosser parts to subside, and pouring 

 off tho superstratum. When this again had subsided for some time, 



