71 
REPORT OF THE 
RESULTS OF PHYSICAL AND CHEMICAL INVESTIGATIONS, 
AND OP THE 
APPLICATIONS OF PHYSICS AND CHEMISTRY IN THE ARTS. 
Aniline Blue.—This substance is produced by heating rosaniline with an excess of 
aniline; torrents of ammonia are evolved, and this magnificent blue developed. The 
process has been patented in this country by MM. De Laire and Girard, and has been 
very successfully worked by Mr. E. C. Nicholson, who has succeeded in obtaining a per¬ 
fectly pure specimen of aniline blue. This has been submitted to investigation by Dr. 
Hofmann, and the results were announced at a recent meeting of the Chemical Society. 
Dr. Hofmann finds that aniline blue is produced from rosaniline by the substitution of 
three atoms of phenyl for three atoms of hydrogen. 
It will be remembered that rosaniline, that is to say the base of magenta, has the 
composition C 20 II 19 N s , H 2 0.* 
Aniline blue therefore is represented by the formula— 
C ^H S )J W . 
and must be named triphenylated rosaniline. Its production is represented by the fol¬ 
lowing equation :— 
C 20 H 19 N3 ) H 2 O + 3(C 8 H 7 N) = C a {“‘'hjJ N ® Ha0 + 3MI ; 
liosauiline. Aniline. “Aniline Blue.” 
On the Production of Magenta.—Dr. Hofmann, who has already thrown so much 
light upon the nature and constitution of the coloured derivatives of aniline, has quite 
recently communicated to the French Academy a most startling fact in connection with 
this subject. 
Having, by analogical reasoning, been led to suspect the existence of two isomeric 
varieties of aniline, this distinguished investigator sought to compare accurately together 
specimens of aniline obtained by different processes. Aniline obtained by the distilla¬ 
tion of indigo with potash was first examined. The base thus obtained boiled at 182°, 
and possessed the general characters attributed to aniline. Upon submitting it, how¬ 
ever, to the action of chloride of mercury or chloride of tin, or arsenic acid, no reel 
colour could be obtained. The aniline obtained from benzol was next examined. 
The benzol employed was obtained by two different processes:—1st. By the distilla¬ 
tion of benzoic acid with lime. 2nd. By the fractional distillation and freezing of the 
benzol from coal-tar. The two specimens of aniline prepared from these two samples of 
benzol each boiled at 182 7 , and presented all the indications of perfect purity and iden¬ 
tity ; but when submitted to the action of arsenic acid, or the other oxidizing agents, 
they failed to yield any magenta. 
Upon communicating this curious result to Mr. Nicholson, Dr. Hofmann learnt that 
the fact was already known to the manufacturer, and received several litres of absolutely 
pure aniline, boiling at 182°, which had been obtained from coal-tar, and which was per¬ 
fectly incapable of yielding any aniline-red. 
An examination of a large number of samples of commercial aniline, obtained from 
different manufacturers, showed that, while capable of readily furnishing colour by the 
ordinary means, they all possessed a boiling point above the normal degree, ranging be¬ 
tween 180° and 220°. It became obvious therefore that commercial aniline contains some 
other substance, the co-operation of which is essential to the production of magenta. 
The fractional distillation of large quantities of this product being a long and trouble¬ 
some operation, Dr. Hofmann determined first to examine the action of the salts of mer¬ 
cury, tin, etc., upon the homologues of aniline, of which he happened happily to possess 
pure specimens. The next term in the series, namely, toluidine , first engaged his atten¬ 
tion. Of the presence of toluidine in commercial aniline there could be no doubt, and 
Mr. Nicholson was already strongly inclined to regard it as the true source of magenta. 
* C=12 ; 0 = 16. 
