produced by Catalytic Bodies. 209 



phuretted hydrogen of its spontaneous inflammability*. The 

 very conception of a catalytic agent, on the view adopted, 

 implies the exertion of an affinity, which is passed over or 

 added to that of the body acted upon. If, therefore, a third 

 body claim this added affinity, the increase of power being 

 divided, may be insufficient to exert the force which it did 

 when wholly applied to aid the affinity of one body. It may 

 be this balancing of affinities which prevents the action of 

 platinum on a mixture of oxygen and hydrogen. The plati- 

 num by its surface affinity condenses oxygen, and presenting 

 it to hydrogen in a condensed form produces union. But in 

 the presence of small quantities of certain oxidizable gases, 

 such as sulphuretted hydrogen, carbonic oxide, and defiant 

 gases f , it ceases to exert this action, the assumption in this 

 case being that the affinity of the added gases for oxygen 

 balances that of hydrogen for the same gas. 



This balancing of affinities may account for several phaeno- 

 mena otherwise inexplicable. On the decay of vegetable 

 mould we find the hydrogen constantly diminishing in quan- 

 tity until a certain period of decomposition, when the affinity 

 of the carbon of the humus for its hydrogen balances the 

 affinity of the surrounding oxygen. It seems to be the same 

 balancing of affinities which renders corrosive sublimate so 

 antiseptic in its properties ; but, in this case, the balance re- 

 sults from the affinity of the second atom of chlorine in the 

 bichloride of mercury for the hydrogen of the organic sub- 

 stance, thus preventing its union with oxygen. It is probable 

 that the same affinity of chlorine for hydrogen causes turpen- 

 tine and the volatile oils to act cataly tically in exploding chlo- 

 ride of nitrogen. The chlorine attracted by the hydrogen of 

 these substances is drawn without the sphere of its attraction 

 for nitrogen, and a disruption of the elements consequently 

 ensues, compounds such as this resting on the very verge of 

 separation between physical and chemical attraction. The 

 antiseptic action of corrosive sublimate is very different from 

 that exerted by sulphurous acid and sulphate of iron, these 

 bodies acting by their superior affinity for oxygen, and neu- 

 tralizing the power of the ferments or accessory oxidizers 

 present in the organic body. 



There is no difficulty in applying these notions of catalysis 

 to organic compounds, which from the complexity of their 



• The influence which the vapours of turpentine exert in jjreventing 

 the oxidation of phosphorus in the air is probably another instance of this 

 balancing of affinities. 



t Faraday, Phil. Mag., Third Series, vol. v. p. 405 ; Turner, Jameson's 

 Journal, xi. 99 and 311. 



Phil. Mag. S. 3. Vol. 31. No. 207. Sept, 184.7. P 



