ON THE TRANSFORMATION OF AROMATIC NITROAMINES. 117 



(iii) Concentration of the Acid. — The effect of the concentration of 

 the acid catalyst on the rate of change has been carefully tested with 

 several acids both in aqueous and acetic acid solution. 



In aqueous solution the rate is proportional to the square of the 

 concentration of the acid — that is, on doubling the concentration of 

 the acid the velocity is quadrupled. 



In acetic acid solution this proportionality does not hold, the increase 

 of velocity being less for given increases of concentration of acid. For 

 example, the ratio of the velocity coefficients for IST/IO and N/20 H2SO4 

 in glacial acetic acid at 25° is k^^ ^ : A;n,.2o= 2'14 instead of 4. 



(iv) Effect of Temi}erature. — Within a range of temperature of 0-35" 

 the products of the transformation of the nitroamine were not moditied. 

 When the nitroamine was melted under water or other solvents, a more 

 profound decomposition was observed accompanied by oxidation of the 

 benzene nucleus. 



In aqueous solution the rate of the transformation was greatly 

 increased by a rise of temperature. At 25^ the rate of change is 

 approximately thirty times as great as at 0° ; the ratio of the velocity 

 coefficients, when 2N HCl is the catalyst, at 25° and 35° C. is 

 ^35° : /c:6°=0-002488/0-00108 = 2-3. 



Exp&riments on Hitroaminobenzene, C5H5.NH.NO2. 



A number of preliminary experiments have been made with the 

 unsubstituted nitroaminobenzene. In its main features the molecular 

 rearrangement of this nitroamine resembles that of its dichloro- 

 derivative, but it is complicated by the simultaneous formation of 

 both 0- and ^^-nitroaniline — 



Nil, 



Experiment has shown that the latter is only formed to the extent of 

 some 10 per cent., but the difference in the intensity of the colours 

 of the solutions of the nitroanilines has so far m.ade any accurate 

 measurement of the rate of change impossible by the method above 

 described. Under like conditions (temperature and concentration of 

 catalyst) the velocity is about one and a half times greater in the case 

 of the unsubstituted than with the dichloro-compound ; in glacial 

 acetic acid, however, the change was roughly ten times as rapid. 



Reduction to the diazo-compound also takes place, and since in this 

 case the diazo-compound is unstable, the subsequent decomposition intro- 

 duces another factor, which prevents quantitative measurements of the 

 velocity. 



