THE ANILINE DYES. 
437 
W e have a yellow aniline dye called chrysaniline, the com- 
position of which is represented by C 40 H 17 N 3 . It is obtained 
from the residue which remains after the extraction of rosani- 
line. This residue is submitted to a current of steam, which 
carries off the yellow dye. When nitric acid is added to the 
condensed liquid, the chrysaniline is precipitated as nitrate of 
chrysaniline. This salt is so insoluble in water, that nitric 
acid may be precipitated from a weak solution, by adding a 
little hydrochlorate of chrysaniline, a more soluble salt. 
The beautiful blue aniline dye is obtained by heating for 
some time a salt of rosaniline with an excess of aniline, at a 
temperature ranging from 150° to 160° C. The rough colour 
thus produced is purified by washing with boiling water, &c. 
It is soluble in spirit, and may be obtained in crystals of a 
copper-metallic appearance. We have also a green aniline 
dye, called emeraldine, yet little known and not very fine; 
also various shades of red and purple, and a black aniline dye, 
which we have not space to notice here. 
Specimens of the principal aniline colours at present pro- 
duced, and in use, have been kindly furnished to me by 
Messrs. Simpson, Maule, & Nicholson, to illustrate this 
paper. Their superior brilliancy over all other dyes will be 
easily seen by approaching near to them a similar piece of 
silk dyed with any other colouring matter. Almost all dyes 
are more or less affected by sunlight : some are more brilliant 
when prepared in the sunshine than when prepared at night ; 
others quickly fade by the action of the sun's rays. The ani- 
line dyes are not exempt from this actinic action (so useful to 
the photographer, so prejudicial to the dyer) ; some specimens 
fade quicker than others, demonstrating the necessity of pro- 
ducing these dyes as pure as possible. The composition of 
the beautiful aniline blue has been established by Messrs. 
Nicholson and Hofmann : it is very remarkable. Its formula 
is C 7<3 H 31 N 3 ; it is rosaniline in which 3 equivalents of 
hydrogen are simply replaced by 3 equivalents of phenyle, 
C 12 H 5 . It has since been found that the other radicals — 
ethyle, methyle, amyle — may be substituted for phenyle, and 
give the same splendid blue colour. This is effected by acting 
upon rosaniline by the iodides of these radicals ; and as a 
demand has suddenly arisen for iodine for this purpose, the 
price of that metalloid has risen considerably of late. 
I think enough has now been said to show, in a general 
manner, how the aniline dyes were discovered, how they are 
produced, what is their chemical composition, and how a con- 
siderable commercial value may, sooner or later, attach to 
what was, in the origin, a purely scientific curiosity . 
