CATALYSIS. 57 



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

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

 case the time necessary can be generally compared with a diffusion 

 process. 1 



The catalytic processes in heterogeneous systems have excited 

 interest since BREDIG 2 showed that the colloidal metals prepared by 

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

 decomposition of H 2 O 2 by colloidal platinum, gold, and other metals 

 or oxides (MnO 2 , PbO 2 ). Attention must be called to the small quan- 

 tity of catalyst sufficient to decompose H 2 O 2 . The action of 1 gram 

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

 The decomposition of H 2 O 2 by platinum catalyst in nearly neutral or 

 faintly acid solution has been shown to be a monomolecular reaction. 



In this connection we will give one experiment of BREDIG and v. BERNECK: 3 



Time. Cone, of H 2 O2. 0.4343A;. 



47.4 



10 37.9 0.0097 



20 30.0 0.0099 



30 23.6 0.0101 



40 18.2 0.0104 



60 11.0 0.0106 



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 O 2 by platinum sols or by the enzyme hasmase, 

 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, ethyl butyrate, 4 salicin and amygdalin 5 are decom- 

 posed by platinum black as well as by enzymes. 



1 Nernst and Brunner, ibid., 47, 52 and 56, 1904. 



2 Anorganische Fermente, Leipzig, 42, 1901. 



3 Zeitschr. f. physik. Chem., 31, 288, 1899. 



4 Amer. Journ. of Physiol., 10, 191, 1904. 



5 Ibid., 15, 148, 1906. 



