TRANSACTIONS OF SECTION B. 685 
Apparently the ortho- acid is formed from the sulphamic acid if the sulpho- 
group be, as it were, let down gently ; otherwise the para- acid is produced. 
When the ortho- is converted into the para- acid by heating it with sulphuric 
acid, probably it is first hydrolysed, and sulphamie acid is then formed, and this in 
turn undergoes conversion into para- acid. 
9. Whatever the changes invclved in the production of ortho- and para- com- 
pounds, the nitrogen in amino- compounds clearly exercises both an attractive and 
a directive influence. 
The nature, and more particularly the degree, of its influence depends, in a 
remarkable manner, on the nature of its immediate associates ; hydrogen especially 
exercises an altogether peculiar influence on the course of substitution. 
Nitrogen per se has little attractive or directive power, compounds such as 
azobenzene and diazobenzene bromide manifesting a singular inertness in presence 
of substituting agents; and it would seem that the more the influence of the 
hydrogen in amines is counteracted and the basic properties of the nitrogen 
neutralised, the more nearly do aminoid compounds generally approximate in 
their behaviour to simple azo- derivatives. 
10. But not only does nitrogen cease to be attractive and directive when 
deprived of hydrogen and neutralised; it apparently even acquires inhibiting powers. 
Thus dimethylanilinepara-sulphonic acid exchanges only a single atom of 
hydrogen for bromine, and the SO,H group is displaced with difficulty by the 
further action of bromine. This behaviour is in striking contrast with that of sul- 
phanilic acid, which is very readily converted into tribromaniline by the mere 
addition of bromine to its aqueous solution. | 
The effect of acid radicles is even more striking, and somewhat different in 
character from that exercised by alkyls: thus when a single molecular propurtion 
of bromine is added to a solution of acetylsulphanilic acid, less than half the acid is 
converted into the monobrominated acid; a major proportion simply exchanges the 
sulphonic group for bromine. Benzoylsulphanilic acid in like manner yields a 
mixture of monobrominated acid and parabromobenzanilid. 
The stability of the brominated acid from dimethylanilinesulphonic acid is 
perhaps accounted for—on the assumption that the attack proceeds from the 
nitrogen atom—by the fact that it forms a relatively stable dibromide. In the case 
of the mon-acetylated acid, on the other hand, it may be supposed that the hydro- 
gen in the amino- group is initially displaced, and that the bromine ‘ wanders out’ 
from this position partly into the ortho- and partly into the para- position. 
11. When the conditions under which meta- derivatives are formed from amines 
are considered, it is clear that they are such as to favour the neutralisation of the 
basic properties of the amines, and to prevent the displacement of aminoid 
hydrogen. 
The nitration of aniline in presence of excess of sulphuric acid may be taken as 
an example. A major proportion of the molecules being present as sulphate, the 
access of nitric acid to the azo-radicle, and therefore to the system, is prevented : 
consequently no nitramine is formed, and a necessary stage in the formation of both 
o- and p-nitro- derivative is eliminated and their production prevented. On the 
other hand, as the action takes place at a low temperature, and nitric acid is 
present in its most concentrated form—perhaps, to some extent, as anhydride— 
the conditions are such as to favour the attack of the benzenoid portion of the 
molecule, but only in the meta- position, the ortho- and para- positions being in a 
measure protected, owing to the inhibitive influence exercised by the fully saturated 
azo-radicle, 
Although the basic properties of aniline are much reduced by the introduction 
of acetyl, acetanilid is still sufficiently basic to be attractive of nitric acid, and 
it therefore undergoes conversion into nitramine, and subsequently into ortho- and 
para-nitro- derivative. 
Benzanilid, being far less basic, is only very partially acted upon in this 
manner; the benzenoid portion of the molecule is therefore preferred for attack, 
and consequently a considerable number of molecules become meta-nitrated. 
Dimethylaniline is converted entirely into para- acid when sulphonated by 
