392 CHEMICAL DYNAMICS 



conceptions of catalysis based upon insufficiently extended inves- 

 tigation. 



A phenomenon which at a very early date greatly impressed 

 the investigators in this field was the extraordinarily small quan- 

 tity of a catalytic agent which, in " typical" instances of catalysis, 

 was found sufficient to bring about the chemical alteration of 

 enormous quantities of material. Thus T % of a milligram of 

 colloidal platinum will bring about the combination of the hydro- 

 gen and oxygen in no less than 10 litres of gas, without the least 

 reduction in its efficiency as a catalysor (25); 0.000001 grams of 

 potassium permanganate in 10 cc. of solution notably accelerates 

 the reduction of mercuric chloride by oxalic acid (64); the rate 

 of oxidation of an aqueous solution of sodium sulphite is per- 

 ceptibly accelerated by the presence of 0.0000000000001 N CuSO 4 , 

 or even by merely dipping a strip of clean metallic copper in 

 the water for less than a minute (136). Were any appreciable 

 proportion of the catalyst used up during the process of catalysis 

 it is obvious that quantities so minute as these would be incapable 

 of bringing about the conversion of such enormous quantities of 

 material, and, in fact, we find in many cases, even when relatively 

 large quantities of catalysor are employed, the catalysor is not 

 appreciably used up during the progress of the reaction; thus 

 a solution of cane sugar contains the same amount of acid after 

 hydrolysis as it did before (19) (67). But if the catalysor is 

 unaltered at the end of the reaction which it accelerates then it 

 must have accomplished this acceleration without adding any energy 

 to or subtracting any energy from the reacting system, in other 

 words it cannot in any way have affected the final equilibrium 

 of the system, but only hastened the attainment of that equi- 

 librium, since any shift in equilibrium must in general be ac- 

 companied either by an expenditure or an absorption of energy. 

 This theoretical deduction has been confirmed in a great variety 

 of instances in the field of non-fermentative catalysis*; in the 

 field of fermentations data bearing upon this deduction are either 

 lacking or fail to establish its validity (27) (14). 



If, however, the station of equilibrium in any reaction is un- 

 affected by the presence of a given catalysor, then that catalysor 



* Cf. especially Turbuba (137) (138), who has shown that the equilibrium 

 between aldehyde and paraldehyde is the same whether sulphur dioxide, zinc 

 sulphate, hydrochloric acid, oxalic acid or phosphoric acid is used as catalysor. 



