VELOCITY OF REACTION. HOMOGENEOUS SYSTEMS 49 



Tammann investigated also the slow destruction of emul- 

 sin in 0.5 per cent solution and in the form of dry powder. 

 Even in this case the reaction was monomolecular. The 

 content of emulsin in the solution or in the powder at 

 different times was determined by estimating its decom- 

 posing influence on salicin. He found for the solution 

 (between 60 and 75) /* = 45,000, corresponding to an in- 



DESTRUCTION OF A 0.5 PER CENT EMULSIN 



/x = 45,000 



crease in the proportion 7:1 in an interval of 10 degrees. 

 For the solid powder /x was only 26,300; that is, 60 per 

 cent of that for the solution (the determination is rather 

 uncertain). Furthermore, the decomposition of the powder 

 at 80.5 C. proceeds about 500 times more slowly than 

 that of the 0.5 per cent solution. As will be seen in the 

 following, rennet behaves in a similar manner, and it 

 seems to be a very common observation that the sub- 

 stances with which we are dealing are much more resist- 

 ing to heat in dried form than in solution. This reminds 



