304 
NATURE 
| Fuly 30, 1885 
It will be impossible for me to give you but a very briefsketch 
of the history of this industry in the time at my disposal ; any- 
thing like a complete account would fill volumes. On account 
of this I shall not be able to refer except casually to the coal-tar 
industry itself, the development of which is nearly entirely due 
to the one under consideration. Nor can I give a consecutive 
account of the coal-tar colours themselves, because the discovery 
of new series of colouring matters, and the progress of old ones, 
necessarily produce overlapping as it were, and renders such a 
course difficult and confusing. I therefore propose to take them 
according to the groups we now know them to belong to. I 
will therefore commence with that which contains the first 
colouring matter connected with this industry—mauvein and 
safranine group of compounds. 
As I already mentioned, the coal-tar colour industry dates 
from 1856, the discovery of the aniline purple or mauve dye 
being made during the Easter vacation of that year, and the 
patent for its production taken out on the 26th of the following 
August. From the accounts I have already given elsewhere, I 
have mentioned how the discovery of this colouring matter was 
made during the prosecution of scientific research, which had for 
its object the artificial production of quinine, a subject which of 
late has very much occupied the attention of chemists, though it 
has not as yet been accomplished. 
When commencing this industry, which was looked upon by 
many with considerable doubt as to its practicability, the diffi- 
culties encountered were very numerous on account of its unique 
character, but few of the processes having their representatives in 
other industries, the products were also very valuable, so that 
great care had to be employed with them. The success of the 
product tinctorially had not been proved on the large scale, so 
that it was necessary to proceed tentatively and not launch out 
too rapidly. 
Aniline, as is well known, was at this period a rare body, 
originally obtained from indigo by Unverdorben in 1826, but for 
its production from benzene we are first indebted to the discovery 
of nitrobenzenein 1834 by Mitcherlich, and then to Zineri, who 
found that this substance when submitted to certain reducing 
agents produced a base which was eventually identified as aniline. 
It was not long before the date of this industry that a method of 
producing this base from nitrobenzene, with greater ease than by 
the process of Zinin, was discovered ; and it is to Beauchaump 
we are indebted for this, who found that the reduction might be 
easily accomplished by means of iron filings and acetic acid. 
Had this discovery not been made, aniline could not have 
been produced sufficiently cheap to be used for the production of 
colouring matters. And it is interesting to note that this process 
of Beauchaump, slightly modified, is the one used to-day for the 
production not only of this base, but its homologues and 
analogous compounds. 
It was not long before the difficulties of producing nitrobenzene 
were to a great extent overcome. Messrs. Simpson, Maule & 
Nicholson also began to experiment on the production of nitro- 
benzene, and after a time were able to produce it ata sufficiently 
low cost to be able to supply us with part of our requirements. 
I mention this in passing because it was the starting point of the 
history of the connection of this firm with artificial production 
of colouring matter, which they carried on so successfully 
afterwards. 
After the mauve was discovered it was necessary to teach 
dyers how to use it. Being an organic base, it is opposite in 
properties to the vegetable colouring matter, and therefore the 
ordinary methods of application were not generally useful, and 
much time had to be spent in dyehouses and printworks in the 
early days of this product in reference to this subject, and at that 
time the question of fastness to light soap and bleaching liquor 
was much insisted on. Fortunately for the future of the coal- 
tar colour industry, although the mauve would not resist bleach- 
ing liquor well, it proved to be a very fast colour—the fastest 
purple yet produced, I believe—and thus its introduction became 
rapid. After this the love of brilliancy of colour which it had 
induced caused less attention to be given to the subject of fast- 
ness. I quite think that had this, the first coal-tar colouring 
matter, yielded colours as fugitive as some which have since been 
used, this industry would probably have been, to say the least, 
much delayed in its progress ; so that it will be seen the mauve 
had to bear all the burdens of the difficulties incident on the 
inauguration of this industry, the future products being free from 
these impediments. The importance of this colouring matter 
after its success was established was quickly recognised in France, 
and its manufacture commenced there. This soon resulted in its 
importation into this country irrespective of patent rights. As, 
however, the foreign manufacturer employed responsible agents 
in this country, the law was without difficulty put into operation 
successfully—unfortunately, however, only to teach Continental 
manufacturers the lesson not to employ responsible agents in this 
country any longer, but, by means of correspondence or travellers, 
to deal directly with the consumers, and this modus operandi 
(practically, though perhaps not theoretically) enabled them to 
ignore the existence of patents, and import their products freely 
into this country. On this point I shall have to speak again 
further on. The mauve was first employed in silk dyeing in 
London, Mr. 1Thomas Keith & Sons, of Bethnal Green, being the 
first to use it. The second application was calico printing, 
Messrs. James Black & Co., of Glasgow, being the first to em- 
ploy it largely for this purpose. It afterwards was extended to 
other trades. 
With reference to the chemical history of this dye, although 
it had been submitted to analysis very soon after its discovery, 
its formula, or rather the formula of its principal constituent 
‘*mauvein,” was not established until some time after it had 
become a commercial product, and was prepared in a crystalline 
condition, It was then shown to have the composition 
Cy,HoyN4 (Proc. R. S. xiii. 170). 
It was found to be a very powerful base, decomposing am- 
monia salts with evolution of ammonia, and combining with 
carbonic acid to form a carbonate. Its ordinary salts are pro- 
duced by its combination with one molecule of a mono-basic 
| acid, its hydrochloride being C,,H,,N,HCl. 
In concentrated sulphuric acid it dissolves with a dirty green 
colour, changing to blue on slight dilution, and back to purple 
when thoroughly diluted ; this is a distinctive reaction of this 
class of substance. Further researches have shown (7. Chem. 
Soc. xxxv. 717-732) that in the ordinary colouring matter there 
are two other compounds, one which is remarkable for its 
solubility, and from analysis appears to have the composition 
Cy,H. N43; and the third, which has not been fully examined, 
possesses a redder shade of purple than the other. 
The first product, or mauvein, is evidently a derivative of 
paratoluidine and aniline. The third of orthotoluidine and 
aniline, and the second of pure aniline. This has been called 
pseudo-mauvein. It might perhaps be better called phenol- 
mauvein. 
When boiled with aniline mauvein yields an indigo-blue pro- 
duct, difficultly soluble in alcohol. This change takes place 
without formation of ammonia, and shows how different 
mauvein is in its character to rosaniline. 
Runge found that aniline, when treated with dilute chloride of 
lime, yielded a blue- or violet- coloured solution, which soon 
underwent change. Some experiments on this, made in 1868 
(F. Chem, Soc. xxii. 25-27), showed that the product which I 
termed ‘‘ Runge’s blue,” was a peculiar compound, the salt of 
an organic base, which itself dissolved in alcohol with a reddish 
brown colour, the salts being blue. It is quite different from 
mauvein, and of no practical value ; but what is interesting is 
that when exposed to heat, as by boiling a solution of one of its 
salts, it decomposes with formation of mauvein. 
A beautiful colouring matter was obtained from mauvein by 
treating it with ethylic iodide. It gives shades of colour of a 
very red purple tint, and it was therefore called dahlia. It was 
mostly used in calico and delaine and other kinds of printing, 
but being costly, the production was never very large. This 
substance is a mono-ethylic derivative of mauvein, and all 
attempts to further ethylate this compound have proved fruitless. 
In properties it appears to be more like an ammonium compound 
than a replacement product. 
Safranines.—In the preparation of mauvein, a colouring 
matter was obtained from the liquors, from which it was pre- 
cipitated, producing beautiful crimson-red shades of colour on 
silk. The amount produced in this way was so small, however, 
that we are even not able to introduce it as a dye. But it was 
found that it could be produced by the oxidation of the mauve dye 
itself, and was then manufactured under the name of ‘‘aniline 
pink,” but afterwards ‘“‘safranine.” This substance is evidently 
closely related to mauvein, as it gives the characteristic reaction 
with sulphuric acid I have already referred to. 
The preparation of this from the mauve dye was, however, 
too costly to allow of its being brought into general use. How- 
ever, new processes have been since discovered, by which this 
or other colouring matters of its class can be produced cheaply. 
