92 REPORTS ON THE STATE OP SCIENCE. 



chloroamino-s-tribromobenzene), 59 per cent, of the chlorine originally 

 as chloroainine was found to be free, whilst 60 per cent, was the 

 amount calculated. For comparison in the system prepared from 

 s-tribromoacetanilide and chlorine, the free chlorine is 57 per cent., 

 whilst in that prepared from p-nitroacetanilide and chlorine, the free 

 chlorine is 89 per cent. 



In the case of p-chloroacetanilide and 2 : 4-dichloroacetanilide quoted 

 above, where the value of K (in 65 per cent, acetic acid) for the former 

 is 8'1 and for the latter 4'47, it is calculated that in the system when half 

 the chloroainine has been converted into 2 : 4-dichloroacetanilide, the 

 concentrates of the anilides and chloroamines are as follows: — 



OCl.C e H 4 .NClAc] = [2 : 4-Cl.,.C 6 tI 3 .NHAc] = 0C072, 

 [>Cl.C 6 EI 4 .NHAc] = [2 : 4-Cl.,C H 3 .NClAc]= 0053; 



that is the concentration of the chloroainine, which is changing, is 

 0-0072 instead of 0-025/2 = 0-0125. 



Chlorination of an Anilide by the Chloroamine of another Anilide. 



The chloroamine of such an anilide as 2 : 4-dichloroacetanilide is in 

 the presence of hydrochloric acid a chlorinating agent for acetanilide. 

 Thus in 65 per cent, acetic acid rapid chlorination follows the addition 

 of a gram molecular proportion of acetanilide to gram molecular pro- 

 portions of the chloroamine and hydrochloric acid (where 6 per cent, of 

 the chlorine is free). The chlorination is far more speedy, ^=0*42, 

 than in the transformation of acetylchloroaminobenzene, fc 1 = 0'0026. 



In 50 per cent, acetic acid, where a far smaller percentage of 

 chlorine is free, k' = 0-00039 for the transformation of the chloroamine, 

 and O'Ol for the action of the chloroamine on the anilide. 



Measurement of the speed of the Opposing Reactions in the Equilibrium : 

 A n [Ar.NHAc] [Cl 2 ] = k m [Ar.NClAc] [HClf. 



Since the action of chlorine on acetanilide is very rapid the chlorina- 

 tion of acetanilide by a chloroamine and hydrochloric acid gives a means 

 of determining the value of the co-efficient fc m and since Jc u /k in is 

 known also the value of Jc a . When the concentration of acetanilide 

 is so large that the velocity of the chlorination is not increased by 

 further rise in the concentration of the acetanilide, it is obvious that 

 the speed of the total change is controlled by that of the interaction of 

 the chloroamine and hydrochloric acid, the slowest step in the series. 

 That is the speed of the chlorination = Z: m [chloroamine] . [HC1] 2 . The 

 chloroamine alone varies in concentration, hence the velocity of the 

 reaction is expressed by an equation of the first order. For two deter- 

 minations of the amount of chloroamine, p and q, at times / and t , we 

 have therefore: — 



*„,[HC1P= -L- .loge^ = A; 



or 



* nl = A/[HCip. 



The values of k n and h m are shown for a number of anilides in the 

 following table (V.). 



