268 CHEMICAL CONSTITUTION OF BLEACHING-POWDER. 



shaking chlorine-water with mercury, only calomel was 

 formed. From a careful perusal of Goepner's paper I was 

 unable to find the cause of his failure. 



Another argument against the existence of a hypochlo- 

 rite in bleaching-powder is, according to Goepner, the 

 following. The chlorine which is used in the manufacture 

 of bleaching-powder always contains free hydrochloric 

 acid, and thus, in bleaching-powder, more calcium chlo- 

 ride will always exist than would correspond to Gay- 

 Lussac's formula. Now, when bleaching-powder is ex- 

 hausted successively with small quantities of water, the 

 excess of calcium chloride is always found in the first 

 solutions, whilst those following contain calcium and chlo- 

 rine in the proportions corresponding to the empirical 

 formula CaOCl 2 . This fact, however, only proves that 

 bleaching-powder is not a mixture of calcium chloride 

 and hypochlorite, but that the bleaching compound con- 

 tained in it has the constitution which Prof. Odling has 

 assigned to it. 



Professor Williamson has shown that an aqueous solu- 

 tion of hypochlorous acid may also be obtained by sus- 

 pending finely divided calcium carbonate in water and 

 passing chlorine into the liquid until the carbonate is dis- 

 solved, and then distilling the solution. In this reaction 

 the compound Ca(OCl)Cl is probably also first formed 

 and acted on by an excess of chlorine in the following 

 way : — 



Ca {oci +cli=Ca {ci +clia 



