CHAPTER III 

 VELOCITY OF REACTION. HOMOGENEOUS SYSTEMS 



WE have already considered the velocity of the reaction 

 of the most simple kind ; namely, the spontaneous destruc- 

 tion of different antibodies in the veins of animals. If, as 

 seems to be the general case in chemistry, every molecule 

 of a substance is decomposed independently of all other 

 molecules, then the number of molecules decomposed dur- 

 ing a short interval of time is simply proportional to the 

 number of molecules present at this time. If this number 

 at a certain time, which may be regarded as the beginning- 

 time of the process, is called A, and the number of decom- 



posed molecules at a given time t is called x, then - - is 



at 



the rate of decrease of the active molecules, and we get 

 the well-known equations 





where t^ corresponds to x^ and / to x. Many such cases 

 are known in chemistry ; for example, the decomposition 

 of hydrogen arsenide (As H 3 ). They are called monomolec- 

 ular reactions. Monochloracetic acid reacts with water, 

 giving glycolic and hydrochloric acid, a so-called bimolec- 



37 



