650 
ON MAGENTA 
ON MAGENTA AND ITS DERIVATIVE COLOURS. 
BY FREDERICK FIELD, F.R.S. 
Three years ago, in this theatre, Dr. Hofmann delivered his celebrated lecture on 
mauve and magenta ; and it might seem temerity in me to trespass upon the premises of 
so great and distinguished a master, were it not remembered that during that interval 
rapid strides had been made in organic chemistry, and especially, perhaps, in the direc¬ 
tion of the aniline colours. 
Although I will endeavour to confine myself as much as possible to the immediate 
subject of the lecture, it will be necessary to glance for a few moments at the history 
of aniline, the progenitor of nearly all the beautiful compounds you see around the 
table. 
Aniline was discovered in the year 182G, by Unverdorben, who obtained it from the 
destructive distillation of indigo. A short time afterwards, Runge and Fritsche observed 
that by the action of strong hydrate of potash upon the dye, aniline was eliminated in 
far greater quantity. Indigo in small fragments is heated in a retort with a strong solu¬ 
tion of caustic potash, and in the distillate, which consists of many products, there is 
found a thin and nearly colourless fluid, having a specific gravity of T028, a peculiar 
but not disagreeable odour, and a pungent, biting taste. When kept for some time, even 
in the dark and in stoppered bottles, it assumes a darker tint, and becomes ultimately a 
very dark brown. Unverdorben called it crystalline,” Runge Ci kyonal,” and Fritsche 
“ aniline.” 
This substance is a nitrogenized base, and is capable, when combined with acids, of 
forming most beautiful crystallized salts, nearly all of which have been carefully exa¬ 
mined by Dr. Hofmann and other chemists. 
There are many other sources besides indigo, from which aniline may be obtained. 
For commercial purposes it is always prepared from nitro-benzol, a substance derived 
from the action of nitric acid upon benzol,— 
C 6 H 6 + NHN0 3 = C c H.NO -f- II 2 0. 
Nitrobenzol, when agitated with water, acetic acid, and iron, yields aniline,— 
C fi H,NO, + GII — C g H 7 N + 2H 2 0. 
Benzol, originally discovered by Mr. Faraday in 1825, in his investigations upon the 
gaseous products from oils, was subsequently obtained by the decomposition of benzoic 
acid by means of caustic lime. Mr. Mansfield, however, succeeded in producing it in 
much larger quantities from coal-tar naphtha. When the lighter portions of this com¬ 
pound are distilled fractionally, until a constant boiling-point of 180° F. is arrived at, 
the product consists of pure benzol, identical with the carbo-hydrogen obtained by Mr. 
Faraday. 
From the earliest discovery of aniline, it was noticed that certain oxidizing agents, 
when mixed with a solution of its salts, produced a fine violet tint. Even in minute 
quantities, a few drops of hypochlorate of lime render it purple. There is another 
test for aniline, which I will show you, and which, as far as I am aware, has not been 
observed previously. If the red gases obtained by the decomposition of nitric acid by 
starch or sugar be passed into an aqueous solution of aniline, the liquid speedily 
assumes a yellow colour, owing to the formation of a new base—azophenylamine—which 
is gradually precipitated as a bright yellow powder. It was not, however, until the 
year 185G that aniline was applied to any great practical purpose, although from the 
beauty of its compounds and from its comparative accessibility, it had, from the time of 
its discovery, become a great favourite with chemists. 
Mr. Perkin was the first who produced colour on an extensive scale from this base. He 
added a solution of bichromate of potash to a salt of aniline, and from the precipitate 
thereby produced, he isolated a magnificent purple dye he termed “ mauve,” which at 
once became popular, and, indeed, at the time, almost universal. It may truly be said 
that this discovery has identified Mr. Perkin with the aniline colours, and that he will be 
always associated with one of the most striking and brilliant passages in the history of 
chemistry as applied to the industrial arts. 
It cannot be supposed that such a discovery would be allowed to rest. A mine had 
been opened which chemists began to explore, and in such numbers and with such 
avidity and zeal as almost to lead us to anticipate that its riches will soon be exhausted. 
