VELOCITY OF REACTION. HOMOGENEOUS SYSTEMS 95 



Evidently the reaction follows very nearly the law for 

 a bimolecular reaction, in regard to the quantity of free 

 toxin (q), so that : 



and: 



The observed and calculated values agree within the 

 errors of observation. An exception is evidently displayed 

 by the first value (t = o). Just as in similar chemical 

 processes it is difficult to determine the time zero, since 

 the reaction does not end instantaneously when the mix- 

 ture is removed from the water-bath. We therefore em- 

 ploy the same method that has been applied to similar 

 cases studied before, namely, to reduce the time to that 

 of the first experimental determination of the toxicity, 

 which was made after the mixture had been held at 

 36.1 C. for half an hour. 



The constant (K) increases very rapidly with the con- 

 centration of the pepton, as the following table shows : 



Concentration of pepton, C . 0.15 0.20 0.25 



Constant, K, obs. . . . 0.0062 0.0147 0.0285 



Constant, A", calc. = 1.833 C 3 0.0062 0.0147 0.0286 



The velocity of reaction is proportional to g*C 3 , which 

 may be explained by supposing that at first there is 

 formed a compound of two molecules of tetanoysin 

 with three molecules of peptone, which is decom- 

 posed very rapidly with the destruction of the tetano- 

 lysin. 



