produced by Catalytic Bodies. 195 



disposition to pass into the state of peroxide, aids the oxalic 

 acid to decompose the nitric acid, the united affinities of 

 both being able to accomplish what neither by itself could do. 

 The protoxide remains unaffected at the end of the experi- 

 ment, because, under the circumstances (the presence of acid), 

 it cannot gratify its desire to become peroxide, and, therefore, 

 it passes over its oxygen to the carbon, which escapes as 

 carbonic acid. Mercer cited, as further examples, the action 

 of protoxide of copper in eliminating oxygen from a solution 

 of hypochlorite of lime, and of peroxide or binoxide of nitro- 

 gen in commencing the oxidation of a mixture of protochlo- 

 ride of tin and nitric acid. Mercer implied by these instances, 

 that catalysis is an affinity of the catalytic agent for an ele- 

 ment in the body acted upon, that affinity being feeble and 

 incapable of gratification under the circumstances. 



It would be advantageous to science if we could arrange 

 under a known power the cases of decomposition which ap- 

 peared so mysterious as to induce the great Berzelius to 

 ascribe them to the action of a new force. It may not be 

 possible in the present state of our knowledge to comprehend 

 the whole of the instances observed, but, if most are included 

 in one category, we have a right to suppose that the others 

 may be embraced as our knowledge progresses. I shall there- 

 fore endeavour to show that many catalytic decompositions are 

 merely cases of chemical affinity exerted under peculiar con- 

 ditions. 



In no instance of chemical union does there seem to be 

 such a complete gratification of affinity as to suppress the at- 

 tractions of the elements. The inherent affinities still remain 

 more or less powerful, for, if it were not so, the compound 

 would be permanent under all circumstances and not liable 

 to further change by the action of external agents. When 

 manganese unites with 1 atom of oxygen, the affinity of the 

 metal for oxygen is not wholly merged, but is still strong 

 enough to attach to itself 1, 2 or 3 atoms more oxygen. 

 When the oxide is one of the lowest of the series, this affinity 

 exhibits itself in a basic power by attaching itself to any com- 

 plex highly oxygenized molecule, such as the oxygen acids, 

 or of radicals playing the part of oxygen. When, on the 

 other hand, the manganese or other radical becomes highly 

 oxygenized, we find it possessing acid properties, that is, the 



1-30 sp. gr. No action ensues on this mixture, but it immediately com- 

 mences on the addition of a protosalt of manganese, which for simplicity 

 may be the oxalate or nitrate. The action is also strikingly shown by heat- 

 ing a mixture of oxalic acid until tlie action commences, then diluting it 

 till all action ceases. A little protosalt of manganese now added to the 

 solution causes an immediate renewal of the oxidation. 



02 



