CHAP, i.] LIEBIG'S VIEWS OF * CATALYSIS.' 7 



contact action of the catalysing body operated. In the case of the most 

 striking catalytic actions to which Berzelius drew attention, the progress 

 of research "has utterly disproved the passive part of the catalysing agent. 

 The occlusion of gases by metals, for instance, is a process in which un- 

 stable molecular compounds are formed, and it plays, no doubt, a most 

 important part in the cases where finely divided metals bring about the 

 combination of gases. In these cases easily dissociated compounds are 

 doubtless formed, and both the heat generated at the time of combination 

 and the ease with which the newly-formed compound splits up with 

 variations in temperature furnish the conditions which are necessary for 

 the so-called catalytic processes. 



There are obviously a variety of types of so-called catalytic processes. 

 Essentially they are all processes in which are concerned, as the principal 

 factors, bodies of which the constituent atoms and molecules are in a state 

 of virtually unstable equilibrium. An apparently insignificant variation 

 in the conditions under which they exist is sufficient to lead to a rearrange- 

 ment of the molecules of which they are composed and to chemical trans- 

 formations of the most striking characters, often associated with transfor- 

 mations of energy which are even more startling. To conclude, however, 

 that the catalytic agent, which has furnished the energy which has as it 

 were exploded the mine, remains actually passive, is to embrace a hypo- 

 thesis which is opposed to all analogy. 



The conception of a catalytic force absolutely indefinite in nature, and 

 displayed by a body whose function is active but whose transformations 

 are none, is, as suggested by Hiifner 1 , nearly akin to the adoption of the 

 conception of a vital force to explain obscure phenomena beyond the 

 reach of actual knowledge. The doctrine of catalysis embodied, however, 

 conceptions which are opposed to great and immutable principles. The 

 true and, as it appears to the author, the really philosophical conception of 

 the processes of catalysis was admirably set forth by the great J. R. Mayer. 



'We call a force catalytic,' says the philosopher of Heilbron, 'when 

 it holds no commensurable proportion to the assumed results of its action. 



An avalanche is hurled into the valley a puff of wind or the fluttering 



of a bird's wings is the catalytic force which has given the signal for, 

 and which is the cause of, the widespread disaster 2 .' 



The theory of catalysis of Berzelius possessed the sole merit of calling 

 attention to a previously unstudied group of phenomena, which however 

 it attempted to explain in a manner which did not tend to throw any 

 light upon them. 



Liebig's mo- Liebig 3 modified the Berzelian theory, especially in 



dificatlon of reference to the ferments, by supposing that a ferment is 



the theory of invariably a body in a state analogous to, if not identical 



' Catalysis.' with, decomposition, and that in virtue of the changes which 



it is itself undergoing it is able to bring about changes 



1 Hiifner, ' Zur Lehre von den katalytisehen Wirkungen. Erste Abtheilung, 1. 

 Ueber die geschichtliche Entwickelung des Begriffs.' Journal f. prakt. Chemie, Vol. 10, 

 1874, p. 148. 



2 J. K. Mayer, Mechanik der Warme, 1867, p. 91, quoted by Hiifner. The author 

 has been unable to verify this reference. 



3 Liebig, J. v. ' Eechtfertigung der Contact-Theorie.' Annalen, Vol. 36, (1840), pp. 

 161171. 16. 'Ueber die Gahrung und die Quelle der Muskelkraft. ' 



