AND ITS DERIVATIVE COLOURS. 
G51 
The action of numerous bodies upon aniline and its homologues was found to be pro¬ 
ductive of colour. Nitrate of silver, nitrate of mercury, chloride of mercury, chloride of 
tin, arsenic acid, iodine, and many others, when heated with the base, gave a rich crim¬ 
son colour in more or less abundance ; and although it would be impossible for me to 
enter into a disquisition on the comparative merits of these various methods for the 
production of colour, I trust to be able to produce magenta, although in a somewhat 
crude form, at this lecture table, and also to dye this tassel of silk from a solution of its 
salt. The reagent I will employ is iodine. A few crystals of this element are placed 
in a tube with about twice their weight of aniline. Heat is at once developed, and with 
the assistance of a higher temperature from the spirit-lamp, you will observe that in a 
few moments intense colour is developed. If a few drops are now poured into spirit, 
and this solution added to w r ater, a fine rose-coloured tint will appear. 
3 It may seem strange to those who have read Dr. Hofmann’s beautiful researches upon 
the aniline substitution products, his chloraniline, hromaniline, iodaniline, and a multi¬ 
tude of others, that he had not observed this curious reaction ; and this leads me to tell 
you enpassant, for time will not allow me to dwell upon this interesting topic to-night, 
that aniline, when perfect^ pure, does not yield any amount of colour with most of the 
reagents mentioned above,—a most important fact discovered by Mr. Nicholson and Dr. 
Hofmann, and which has given rise to one of the most difficult questions which yet 
remain to be answered. I will simply say that it appears there must be a homologue 
of aniline present with that base to produce the colour you see before you, although that 
homologue/;<?r se will give no colour whatever. 
The tinctorial power of the salts of magenta is something marvellous. No dye that I 
have examined, whether from the animal, vegetable, or mineral world, can bear com¬ 
parison for one moment with this crimson colour obtained from aniline. One grain in a 
million times its weight of water gives a pure red; in ten millions, a rose pink; in 
twenty millions, a decided blush ; and even in fifty millions, with a white screen behind 
the vessel in which it is dissolved, an evident glow. Perhaps the most startling and 
graphic incident of this wonderful power is found in an account, which I presume to be 
authentic, of one of the passages of the 1 Great Eastern’ from Liverpool to New York, 
some few years ago, when a hurricane swept over the Atlantic, rendering the mighty 
vessel powerless amid the mightier sea. After one terrific night, it was observed that 
far around the vessel the waves seemed tinged as though with blood, faint and diluted 
in the distance, but deep, and crimson, and terrible in the immediate vicinity, while 
after every roll of the giant ship gushed forth anew a deep ensanguined flood. YYhen 
the storm had somewhat abated, and search was made for the origin of this startling 
phenomenon, it was discovered that some tremendous billow had staved in part of the 
hold, and at the same time shattered some vessels containing magenta in a most con¬ 
centrated form, which, sweeping over hatches and through port-holes, did more truly 
than Banquo’s blood on Macbeth’s hand, “ the multitudinous sea incarnardine.” 
Although the salts of magenta are possessed of such wonderful colouring power, the 
base itself is colourless; and it is remarkable that the union of base and acid for the 
formation of a salt does not appear to take place, in dilute solutions, in the cold. We 
have here two vessels, one of hot, the other of cold water; an equal quantity of magenta 
base is added to each, and also an equal amount of dilute sulphuric acid. You will 
observe that in the hot solution colour is instantaneously developed, while in the cold there 
is no change ; but if hot water be added to the latter, so as to raise the temperature, the 
colour at once becomes apparent. You may judge, therefore, that, having free acid in a 
solution of base without production of colour, it is possible to have free alkali in a coloured 
solution of a salt of the base without destroying its tint. Such is the case: to these two 
solutions of acetate of magenta, one hot and the other cold, are added equal quantities of 
caustic soda; the hot liquid is rendered colourless, the cold retains its original hue. 
Ethyl-rosaniline, a substitution product of rosauiline, discovered by Dr. Hofmann, and 
which gives a most beautiful shade of violet when in solution, is capable of affording 
most remarkable manifestations. This dark, violet liquid, on the addition of sulphuric 
acid, becomes colourless; on adding ammonia the purple is restored. If hydrochloric acid 
is employed in small quantities, the liquid changes to blue; if in larger quantities, to a 
brilliant green ; but if this green liquid be thrown into water, you will observe that the 
original violet x - eturns. 
When aniline is heated with salts of rosaniline, purple and blue compounds are prc- 
