CATALYSIS AND ENZYMES 303 



in that a substance may effect chemical changes without itself taking part in 

 them. Berzelius is careful, however, to guard himself from the supposition 

 that this force is other than a special manifestation of known properties of 

 matter. We shall see later that, in certain cases, explanation on the lines 

 of known chemical and physical laws is actually possible. To return to our 

 author, we find a definition of the process given as follows : " I will call it 

 the catalytic power of substances and the decomposition effected thereby, catalysis ; 

 just as we understand by analysis the separation of the constituents of substances 

 by means of ordinary chemical affinity. Catalytic power appears to consist 

 essentially in the fact that substances are able to set into activity affinities which 

 are dormant at this particular temperature, and this, not by their own affinity, 

 but by their presence alone." 



Turning to living nature, it is pointed out that " we have justifiable reasons to 

 suppose that, in living plants and animals, thousands of catalytic processes take 

 place between the tissues and the liquids and result in the formation of the great 

 number of dissimilar chemical compounds, for whose formation out of the common 

 raw material, plant juice or blood, no probable cause could be assigned. The 

 cause will perhaps in the future be discovered in the catalytic power of the organic 

 tissues of which the organs of the living body consist." 



With respect to the name itself, it must be admitted that " catalysis " suggests 

 an opposite kind of process to that of " analysis " ; so that, since this latter implies 

 the separation of a process or compound into its constituents, catalysis might be 

 taken to mean a synthetic process. The word has come into general use, however, 

 to denote such processes as those referred to by Berzelius. It is also convenient 

 to have a word for the agent itself : " catalyst " is most frequently used, sometimes 

 "catalyser." Both have the same meaning, but the former seems to me to be 

 more euphonious and to correspond better to the Greek form of the word, although 

 it may have the suggestion of human personality. 



If now we turn back to the examples given at the beginning of this chapter, 

 we see at once that they belong to those called catalytic, in that the agent 

 concerned, acid or tissue extract, does not itself form a part of the final chemical 

 system in equilibrium. Again, considering the first of these, the ester system, we 

 note that the catalyst does not actually set into action a new process, but merely 

 hastens one that was already in progress. Ostwald ([1903, II., 1., p. 515 ; 2nd 

 edition) therefore defines a catalyst a's a substance that increases the rate at which 

 equilibrium is reached, but at the same time he points out that the reaction, 

 without the catalyst, may be so slow that it appears not to take place at all. 



A simple experiment will assist us in understanding the essential properties 

 of a catalyst and avoid confusion with some other processes, which have a 

 superficial resemblance to those of catalysis. 



Take a piece of carefully-cleaned, polished plate glass about a metre long and some 20 c. 

 broad. Rest one end on the table and raise the other end on an adjustable support. Now 

 take a brass weight of about one kilogram, polish the bottom and place it on the top of the 

 glass plate, which forms an inclined plane. By delicate adjustment of the angle of the plane, 

 it will be found possible to find such a position that the weight slides down very slowly. This 

 is the most difficult part of the experiment, since a speck of gritty dust will stop the descent, 

 so that it is well to polish the surface with a little talc and a chamois leather immediately 

 before the weight is placed thereon. This part of the experiment represents a reaction taking 

 place of itself very slowly. Apply, next, a little oil to the bottom of the weight and again 

 place it at the top of the plane. It will slide down with great rapidity. The oil represents 

 the catalyst. 



There are several instructive points about this scheme. Notice first that the 

 energy available in the " reaction " is simply that due to the fall of the weight 

 from the vertical height of the top of the plane to that of the lower end, and that 

 this is unaffected by the addition of the catalyst, which therefore takes no part 

 in the final state. A point of importance in relation to the catalytic reactions in 

 the living organism is, however, that the form of the energy may be different in 

 the two cases. Without the oil, the weight arrives at the bottom with very little 

 kinetic energy, most of its potential energy having been lost as heat, due to 

 friction along the glass. With oil, very little energy is lost as heat and the 



