ENZYMES. 37 



with the real chemical reaction it can be neglected. In these cases 

 the reaction velocity behaves similarly to a homogeneous system. 1 



2. The chemical reaction occurs at a rate which in comparison with 

 the time necessary for the accumulation can be neglected. In this 

 case the time necessary can be generally compared with a diffusion 

 process. 2 



The catalytic processes in heterogeneous systems have excited 

 interest since BREDIG 3 showed that the colloidal metals prepared by 

 him showed catalytic properties. The best-studied process is the decom- 

 position of H202 by colloidal platinum, gold, and other metals or oxides 

 (MnC>2, PbO2). Attention must be called to the small quantity of 

 catalyst sufficient to decompose H 2 02. The action of 1 gram atom 

 platinum in 70 million liters of reaction mixture has been detected. The 

 decomposition of H2C>2 by platinum catalyst in nearly neutral or faintly 

 acid solution has been shown to be a monomolecular reaction. 



Still certain differences occur from the conditions formed in the 

 homogeneous catalysis. At one time in certain experiments the value 

 for k rises considerably during the catalysis, and secondly, k is not 

 proportional to the ferment concentration, but rises more quickly than 

 this. 



In connection with these experiments BREDIG has expressed the 

 view that an analogy exists between the catalytic processes of the inor- 

 ganic world and the enzyme action of the organic. 



The following important facts give support to BREDIG' s view: 



1. In both cases we are dealing with catalytic processes; the metallic sol and 

 the enzyme are active in very small quantities and during the reaction they do 

 not undergo any appreciable change. 



2. In the decomposition of H 2 2 by platinum sols or by the enzyme haemase, 

 the reaction is monomolecular. . 



3. The action of metallic sols as well as enzymes is paralyzed by certain 

 poisons (HCN, H 2 S). 



4. Both classes of bodies are colloid substances and possess an enormous 

 surface upon which their catalytic action depends. 



According to NEiLSON, 4 ethyl butyrate, salicin and amygdalin are decom- 

 posed by platinum black as well as by enzymes. 



IV. ENZYMES. 



Chemical Processes in Plants and Animals. It follows from the law 

 of the conservation of matter and of energy that living beings, plants 

 and animals, can produce neither new matter nor new energy. They 



1 Goldschmidt, Zeitschr. f. physik. Chem., 31, 235 (1899). 



2 Nernst and Brunner, ibid., 47, 52 and 56 (1904). 



3 Anorganische Fermente, Leipzig, 42 (1901). 



4 Amer. Journ. of Physiol., 10, 191 (1904); 15, 148 (1906). 



