118 REPORTS ON THE STATE OF SCIENCE.—1912. 
be regarded as an intramolecular change. But the possibility that under 
certain conditions a cleavage into aniline and a nitrating substance 
occurs, at least partly, cannot be excluded. Thus as an instance s-tri- 
chloronitroaminobenzene in an environment when transformation is 
generally rapid, yields largely s-trichloroaniline. 
In the substances which we have closely investigated, one ortho- 
position only is vacant, into which the nitro group can migrate. The 
migration of the nitro group into the para-position is observed in the 
conversion of 2: 6-dibromonitroaminobenzene into 2: 6-dibromo-4- 
nitroaniline; this change is, however, accompanied by the formation of 
about an equal amount of the isomeric 2: 4-dibromo-6-nitroaniline, the 
bromine atom in the ortho-position being displaced. From a considera- 
tion of the relative proportions of o- and p-nitro-anilines and -anilides 
produced under various conditions, in the transformation of nitro- 
amines, nitration by acetyl nitrate, &c., Holleman* has concluded that 
the ortho-compound is generally formed by way of the nitroamine, whilst 
the para-compound is formed by some other process. In the case above 
cited, however, the p-nitroaniline is undoubtedly obtained from the 
nitroamine, although perhaps not by a simple intramolecular re-arrange- 
ment. Comparison of the two changes shows at least that the con- 
version to the o-nitroaniline is a far more rapid and easy process. 
Formation. of Nitroaminobenzenes.—Owing to the difficulties of 
following further the conversion of nitroamines into nitroanilines, we 
have been led to study the conditions and mechanism of the formation 
‘of nitroamines. An excellent way of converting anilines into nitro- 
amines is by treatment in acetic acid solution with a mixture of nitric 
acid and acetic anhydride. (Orton* and Orton and Edwards.*) The 
behaviour of nitric acid offers in this respect a marked contrast to that 
of other strong acids; they are powerful accelerators of the direct 
reaction between the anhydride and anilines (Orton and Smith).* In 
order to investigate these highly distinctive reactions more closely a 
means of determining acetic anhydride in such systems was required. 
A good method was finally devised (Edwards and Orton’) which is 
based on the following reactions; certain anilines, for example, 2: 4- 
di-chloroaniline, react with acetic anhydride in acetic acid solution, even 
containing a certain proportion of water, very rapidly and quantitatively ; 
the anilide is extracted from the diluted medium with chloroform and the 
excess of aniline removed by treatment with an acid; finally the anilide 
is converted into a chloroamine which can be estimated by titration. In 
this manner very small quantities of acetic anhydride can be estimated 
in the presence of acetic acid. 
With the aid of this method of analysis, the hydrolysis of acetic 
anhydride has been studied and remarkable differences between nitric 
and other acids, in their effect on this process, discovered. 
2 Orton and Pearson, T'rans. Chem. Soc., 1908, 98, 725. 
8 Ber. d. deutsch. Chem. Gesel., 1911, 44, 704. 
4 Trans. Chem. Soc., 1902, 81, 806. 
5 Reports, 1911. 
y ® Trans. Chem. Soc., 1908, 98, 1242; 1909, 95, 1060. 
= 7 Tbid., 1911, 99, 1181. 
