THE ANILINE DYES. 
433 
stance is formed called nitrobenzol. Nitrobenzol only differs 
from benzol by tbe latter having one of its equivalents of hydro- 
gen replaced by one equivalent of hyponitric acid, thus : — 
C 12 H 6 C 12 H 5 , NO 4 
Benzol. Nitrobenzol. 
If benzol be added to warm nitric acid by degrees, and as 
long as it dissolves in the acid, a dark red liquid is obtained, 
and when water is added, nitrobenzol falls to the bottom of 
the liquid as a heavy, yellow, oily substance, insoluble in 
water, capable of crystallising in long needles when exposed 
to a cold of 4* 3° centigr., and having a very pleasant odour 
of essence of almonds. This odour has caused it to be some- 
what largely employed in place of the more expensive essence 
for scenting* soaps, &c., .for which purpose it has been sold for 
some years under the name of “ essence of mirbane.” 
Nitrobenzol brings us another step nearer to the aniline 
dyes ; for it is from nitrobenzol that all the aniline of 
commerce is prepared. This transformation of benzol into 
nitrobenzol was also discovered by Mitscherlich, but the 
formation of aniline from nitrobenzol was first effected by 
Zinin, of St. Petersburg. This curious change is brought 
about by the substitution of 1 equivalent of amide N H 2 for 
the equivalent of hyponitric acid N O 4 , in nitrobenzol, thus : — 
C 13 H 5 , N O 4 C 12 H 5 , N H 2 or C 12 H 7 N 
Nitrobenzol. Aniline. 
Such a change is effected when nitrobenzol is acted upon by 
nascent hydrogen, when all its oxygen unites with this 
hydrogen to form water, and aniline is the result. This 
occurs best when nitrobenzol is mixed with acetic acid and 
iron-filings ; the three substances being mixed in a retort, 
and a gentle heat applied, aniline distils, and can be collected 
in a cooled recipient. It is a liquid of an oily appearance, 
falling to the bottom of a glass of water, and producing a 
vivid but evanescent purple blue colour when mixed with 
a little chloride of lime on bleaching powder. 
It should be remarked here, that aniline has been dis- 
covered by Fritsche, of St. Petersburg, in the products 
derived from indigo, when this colouring matter is acted 
upon by potash. It was met with in the products of the 
distillation of organic bodies, by Unverdorben, who described 
it under the name of crystalline ; it has also been described 
by Runge, Hofmann, and others under a host of names. We 
will not stay here to mute its biography, which would lead us 
too far. It will be sufficient to note that aniline is an organic 
base, an alkaloid, closely allied to the liquid alkaloids nicotine 
