VELOCITY OF REACTION. HETEROGENEOUS SYSTEMS 1 19 



Rather similar to these haemolytic and agglutinating 

 processes in which the chemical attack is directed against 

 cells suspended in the acting medium, are some other 

 processes in heterogeneous systems, namely, the decom- 

 position of coagulated protein, or of small emulsified 

 fat drops by so-called Upases. These processes are not 

 very different from those in homogeneous systems. The 

 coagulated proteins are introduced in the state of a fine 

 powder and the suspension held in uniform concentration 

 in all its parts by shaking. In this manner the digestion 

 of coagulated egg-white by means of pepsin (Sjoqvist) 

 or for the digestion of casein by means of trypsin (Madsen 

 and Walbum) have been examined. 



Perhaps the most important of the processes is the diges- 

 tion of coagulated albumen by pepsin (in the presence of 

 acids). Regarding this process Schutz * had found the 

 rule, that the digested quantity of albumen hydrolysed in 

 a given time is proportional to the square root of the time 

 and of the concentration of pepsin. Against the figures 

 of Schutz, which, according to a criticism of Sawjalow, 2 

 give no very accurate results, he quotes the experiment 

 of Sjoqvist 3 as indicating that the reaction is proportional 

 to the time, i.e. follows the laws for a monomolecular 

 reaction. In Sjoqvist's experiment the protein was coagu- 

 lated egg-albumen in the state of a powder, which was 

 brought in 100 c.c. of a solution at 37 C. containing 

 50 c.c. of o.i n. hydrochloric acid, 2.5, 5, 10, or 20 c.c. 

 of a 0.067 per cent solution of pepsin and water to con- 



1 Schiitz: Zeitschr.f. ph. ch. v. Hoppe-Scyler, 9. 557 (1885). 

 2 Sawjalow: Zeitschr. / ph. ch. v. Ifoppe-Seyler,$Q. 307 (1905). 

 3 Sjoqvist: Skand. Archiv. f. Physiologic, 5. (1895). 



