produced by Catalytic Bodies. 201 



be elevated, the oxygen resumes its elastic state and refuses to 

 form this higher oxide, as in fact we know is the case in Mer- 

 cer's experiment Avith oxalic acid and nitric acid, where the 

 presence of hot NO5 is an unfavourable chemical condition 

 to the existence of Mug Og, and therefore it is not formed, 

 but in its stead the oxygen is passed over to the organic mat- 

 ter, which is able to unite with it under the circumstances. 

 A similar instance of the effect of such conditions is seen 

 when the peroxides of copper, manganese or lead, are thrown 

 into a solution of bleaching powder. The affinity of these 

 oxides for an additional quantity of oxygen enables them to 

 decompose the hypochlorite of lime, converting it into chlo- 

 ride of calcium. When the protoxides are used, this liberated 

 oxygen unites and converts them to peroxides. The latter 

 themselves have sufficiently strong affinity for oxygen to cause 

 the decomposition to proceed ; but not uniting with it, pure 

 oxygen is given off in the gaseous state. Here elasticity has 

 come into play, and being more powerful than the feeble che- 

 mical affinity, causes the oxygen to escape as a gas. When 

 the solution is cool the gas goes off in a succession of small 

 bubbles ; but when hot, the escape is tumultuous, the heat 

 aiding the oxygen to enter into the elastic state*. A solution 

 of chloride of lime evolves oxygen slowly at the boiling-point ; 

 but the decomposition is much accelerated by the accessory 

 agents referred to. 



The action of certain oxides upon peroxide of hydrogen is 

 exactly similar to that on a solution of hypochlorite of lime. 

 Thus peroxide of manganese, the protoxides of cobalt and 

 lead, minium, peroxide of iron, and the protoxides of nickel, 

 copper and bismuth, all exert this action on peroxide of hy- 

 drogen with a force indicated by their orderf. In none of 

 these cases does the oxide unite with a further proportion of 

 oxygen. The violence of the action is however in proportion 

 to their power of uniting with more oxygen. The first five 

 oxides in the list have higher oxides of definite composition 

 and of a certain degree of stability, with the exception of ferric 

 acid; while the protoxides of copper and bismuth, although 

 possessing the power of uniting with more oxygen, do not 

 present superior oxides of a marked character. We should have 



* The best mode of instituting the experiment is to make a mixture of 

 chloride of soda and caustic soda, lieat this to a temperature near ebuUition, 

 and add sulphate of copper. The oxide of copper precipitated in the fine 

 state of division causes such a copious evolution of oxygen gas that the con- 

 tents are apt to be thrown out of the vessel : a mixture of chloride of lime 

 and lime, or the ordinary unfiltered bleaching-powder of commerce, are 

 also well-fitted to show the action. 



f Thenard's Traite de Chetnie, 6th edit. vol. i. p. 216. 



