136 
PROCEEDINGS OF THE PERTHSHIRE SOCIETY OF NAT0RAL SCIENCE. 
which were produced through the agency of the natural 
processes of plant or animal life ; and 2nd, the artificial 
colouring matters, or those which could be produced by 
various chemical processes without the aid of vital force. 
Having exhibited numerous samples of natural colouring 
mattera, and of extracts prepared from them, Mr Pullar 
proceeded to explain more particularly artificial colouring 
matters, or, as they were commonly called, the coal-tar or 
auiline colours. It was in the year 1856, he said, that Mr, 
now Dr Perkin, first introduced his mauve dye—a colour 
derived from aniline. His discovery resulted from experi¬ 
ments of a purely theoretical nature. His own account of 
it was interesting. He said—“ Chemists have always 
been desirous of producing natural organic bodies arti¬ 
ficially, and have in many instances been successful. It 
was while trying to solve one of these questions that I dis¬ 
covered the mauve dye. I was endeavouring to convert an 
artificial base into the natural alkaloid quinine, but my ex¬ 
periment, instead of yielding the colourless quinine, gave 
a reddish powder. With a desire to understand this pecu¬ 
liar result, adifferent base of more simple construction— 
viz., aniline, was selected, and repeating my experiments 
in this case, I obtained a perfectly black product. This, 
when purified, and digested with spirits-of-wine, gave the 
mauve dye.” (Mr Pullar here poured a few drops of ani¬ 
line and hypochlorite of sodium into a vessel containing 
water, when a splendid violet liquid—the mauve dye—was 
produced.) Proceeding, Mr Pullar said Mr Perkin was ad¬ 
vised to attempt the manufacture of his colouring matter 
on a large scale, but he did so with considerable fear of 
the result. He had many difficulties to overcome. At 
that time, aniline, the source of the mauve, was not an 
article of commerce, but a mere laboratory prepara¬ 
tion. It was known that it could be prepared from nitro- 
benzol, but then nitro-benzol was a rare product—only ob¬ 
tainable from benzol by treatment with nitric acid, 
then a difficult and dangerous operation. Benzol itself, 
however, was readily obtainable from coal tar—an oily 
black fluid, one of the products of coal, when heated 
in gas work retorts. It was once a great nuisance to 
gas manufacturers, but now, he need hardly say, a 
source of immense profit. It was a mixture of a great 
number of substances, but he should only trouble them 
with the names of those which were used as sources of the 
coal tar colours—namely, benzol, carbolic acid, naphthalin, 
and anthracen. These, and many other substances, could 
be separated from coal tar by appropriate means, and each 
of them was the starting polfet in the manufacture of a 
series of colours. In order to manufacture mauve, the 
clear liquid benzol was first obtained from coal tar by 
distillation; it was then converted into the oily liquid 
nitro-benzol, by treatment with nitric acid, and then 
finally into aniline, from which the mauve dye w»s ob¬ 
tained, as he had already shown them. He (Mr Pullar) 
hoped he had made it clear to them how black coal 
tar came to be the raw material from which, by a series 
of processes, beautiful colours were obtained. They 
would, therefore, understand that, by the designation 
coal tar, it was not meant to imply that colouring mattera 
actually existed in coal tar, and might therefore be ex¬ 
tracted from it, but that coal tar was the source of certain 
products which, when changed by various chemical pro¬ 
cesses, were capable of yielding coloured derivatives. It 
was interesting to know the amount of colour obtained 
thus directly from coal. Prom 100 lbs. of coal they 
got a little more than 10 lbs. of coal tar, and from that 
only about a quarter of an ounce of mauve. Although 
the amount of colouring matter was very small, it was 
fortunately very intense, as he would try to show them. 
(Mr Pullar here took one or two small crystals, of the 
aniline colour eosine, and dissolving them in a little hot 
water, mixed them in a large vessel of water, which at 
once was tinged a deep shade, although the proportion 
was by weight one part of eosine to a quarter of a million 
parts of water.) Mr Pullar also showed the intensity of 
aniline dyes in another way. Taking a bouquet of 
flowers, which appeared to be white (but which had previ¬ 
ously been dusted with various aniline dyes), Mr Pullar 
damped them with spirits of win6 for the purpose of dis¬ 
solving the colours, when a remarkable effect was produced 
—the flowers composing the bouquet being instantly 
changed into brilliant colours. Proceeding, Mr Pullar 
said be had already told them that aniline colours had 
superseded the natural colouring matters to a large extent, 
but there was also another way in which the natural 
colouring matters had been replaced by the manufactured 
article. It had been found possible to make, by chemical 
means, the identical colouring matters contained in those 
animals and plants which had hitherto been the only 
source of these products. Many of these processes were 
at present difficult and expensive, but artificial indigo was 
beginning to be made on a commercial scale, and for more 
than 10 years now that artificial alizarine—which was 
identical with natural alizarine—the colouring matter con¬ 
tained in madder, had been an article of commerce. It 
could be prepared from the coal tar derivative anthracen, 
by a series of processes into which they could not now 
enter, and brought into the market cheaper than the mad¬ 
der plant could be grown and prepared for use. Not onl 
was it cheaper than natural madder, but it was free from 
