August 6, 1885] 
was not prepared by the tar distillers, as it had no application, 
and very little was known about it. It was discovered in 1832 
by Dumas and Laurent. In 1854-55, when studying under Dr. 
Hofmann, I worked with it for some time, but my results were 
never published, because, owing to the erroneous formula given 
for it by Dumas and Laurent, which was accepted, my results 
would not fit in; nevertheless the information obtained after- 
wards proved of great value to me, although at the time the 
labour spent appeared to be lost labour, showing the value of 
research even when not successful. The formula of this hydro- 
carbon was not established until 1862, when it was studied by 
Dr. Anderson. This was only six years before the discovery of 
Graebe and Liebermann, and, had not the formula of anthracene 
been established before these chemists commenced their work, 
the relationship of alizarin to it would not have been discovered, 
and up this day it is possible that this artificial alizarin industry 
would not have been in existence. Researches like that of Dr. 
Anderson I have often heard spoken of slightingly, because 
they don’t bear much on their surface ; but who knows what 
such work may lead to? Earnest workers cannot be too much 
encouraged. 
Asanthracene was not a commercial product, it was necessary 
to experiment on its production before alizarin could be manu- 
factured, and not only on the best methods of getting it, but 
also to get a rough idea of how much could be produced, 
because unless the hydrocarbon could be obtained in large 
quantities, artificial alizarin could not compete with madder. 
In our works at Greenford Green we commenced by distilling 
pitch ; but afterwards tar distillers were induced to try to 
separate it from the last runnings of their stills by cooling and 
then filtering off the crystalline products which separated out, and 
in fact visits were paid. to most of the tar distillers of the 
United Kingdom, others being corresponded with on the subject, 
and the result was that in a short time such quantities came 
in that the distillation of pitch was abandoned. And although 
much doubt and anxiety prevailed at first as to the possibility of 
getting a sufficient supply of this raw material, at the present 
day there are about 1000 tons of commercial product (about 
30 per cent.) produced in excess of the requirements, the 
annual production in the United Kingdom being estimated at 
about 6000 tons 30 per cent., or nearly 2000 tons pure 
anthracene. 
Although the colouring matter obtained from anthraquinone 
or dechloranthracene was at first simply considered as alizarin 
more or less pure, yet on investigating the matter it was soon 
found that it contained other colouring matter. To this I drew 
attention in 1870 (¥. Chem. Soc. xxiii. 143, footnote), and in 
1872 gave the analysis of a product which I named anthrapur- 
purin, followed by a more extended account a year afterwards 
(F. Chem Soc. xxv. 659, and xxvi. 425). This was called an- 
thrapurpurin ; because it is an anthracene derivative having the 
formula of purpurin, with which it is isomeric. In the latter 
paper I also referred to another colouring matter dyeing alumina 
mordants of an orange colour (¥. Chem. Soc. xxvi. 425). It was 
also shown that anthrafluoric acid when fused with alkali gave a 
colouring matter behaving with mordants in the same way (¥. 
Chem. Soc. xxvi. 20), and which has proved to be the’same body. 
This latter reaction was afterwards more fully studied by Schunck 
and Roemer, and the colouring matter produced by it was shown 
also to Lave the formula of purpurin; they therefore called it 
flavopurpurin (Ber. ix. 678), so that the colouring matters 
formed have proved to be three in number—alizarin, anthrapur- 
purin, and flavopurpurin, all of which are valuable dyes, whereas 
in madder root there is only alizarin and purpurin, the latter 
being of only secondary value. This can now also be produced 
from anthracene. The researches which have been reached on 
the subject of the conditions under which these different colour- 
ing matters are formed, have led to the discovery of methods for 
their separate production, so that in artificial alizarine, which 
name commercially embraces all these colouring matters, both 
mixed and separate, we have more than a simple replacer of 
madder root, and as these colouring matters just referred to can 
be applied with the same mordants, varieties of styles of work can 
be produced by the calico printer and dyer which before were un- 
known, Anthrapurpurin is, I believe, of as great importance as 
alizarin itself, and used with it increases its brilliancy, and alone 
gives very brilliant scarlet shades. 
Artificial alizarin was first produced commercially in this coun- 
try by my firm at Greenford Green in 1869 ; when one ton was 
produced in 1870, forty tons were made in 1871, 227 tons, and 
NATURE 
331 
so on increasingly. It was not produced on the Continent until 
1871, when, according to Graebe and Liebermann, 125-150 tons 
were made. These weights do not apply to dry colour, but to 
paste. 
I cannot go into any lengthened account of the chemistry of 
this industry here ; its development, however, has kept pace with 
theoretical investigations, in some cases it may be said to have 
forestalled it. For example, in the old methods of working, more 
anthrapurpurin than alizarin was produced ; the conditions re- 
quired to modify this were found out by experiment. According 
to all our previous knowledge as to the introduction of hydroxyl 
into a body by the fusion of its sulphonic acid with alkali, a 
monosulphonic acid should give a monohydroxyl compound, and 
a disulphonic acid a dihydroxyl compound. Therefore to pro- 
duce alizarin, which is a dihydroxy] compound, an anthraqui- 
none disulphonic acid was thought to be the proper thing to use. 
By experience this was gradually found to be incorrect, a 
monosulphonic acid being required to produce alizarin, a disul- 
phonic giving anthra or flayopurpurin, the colouring matter not 
being due to the primary but to a secondary reaction as was 
afterwards shown by research—the mono and dioxyanthraqui- 
nones (the latter known as anthraflavic and isoanthraflavic acids) 
being the first products of the reaction, and then undergoing 
oxidation by the caustic alkali employed, and then yielding the 
corresponding colouring matter, a portion of the products, how- 
ever, being at the same reduced back to anthraquinone. 
A very important improvement preventing this loss by reduc- 
tion was discovered by J. J. Koch, who found it might be avoided 
by the use of a small quantity of potassium chlorate with the 
alkali used in the fusion. 
The amount of caustic soda used in this industry is very large 
at the Badische Aniline and Soda Fabrik—and, I believe, else- 
where—it is made on the spot; and I must say the cleanly way 
in which alkali is made in the above works contrasts very favour- 
ably with what I have seen in some of the alkali works in this 
country. 
Like rosaniline, alizarin has now become a material for pre- 
paring other colouring matters. Of these there are two in use, 
viz., nitroalizarin, which gives orange-yellow shades with alumina 
mordants, and alizarin blue, a remarkable compound prepared 
from nitroalizarin by treating it with sulphuric acid and glycerine. 
This gives shades of colour like indigo. When first discovered, 
considerable difficulty was found in its application, on account of 
its insolubility ; it has since been found to form a soluble com- 
pound with sodium bisulphite, and by this means its application 
has become much easier. The constitution of the colouring 
matter derived from anthracene may be represented as fol- 
lows :-— 
Alizarin. 
co 
CHK De Eno 
Purpurin. 
co OHA) 
CH. SCH’ OHO 
\co% * NoH® 
Anthrapurpurine. 
OHQ) 
6 
CO OH) 
(@HO—C,H,~ CHC 
= *\co”% * Nowe) 
Flavopurpurin. 
CO. 
co” 
Alizarin Blue. 
Joon JOM 
c OH) 
\co”% | \N@) 
a \ 
CH=CH-CH 
1 
por ) 
C,H» 
v0) 3(2) 
(HOCH, 
C,H, 
These colouring matters under the name of artificial alizarin 
are the most important of the coal-tar colours, their money value 
amounting to more than a third of the entire value of all the 
colours produced in the industry, and at present the price of 
artificial alizarin compound tinctorially is not more than one-fourth 
of that which madder or garancium ordinarily were before their 
production. There are now three works producing it in this 
country, but the bulk of that used still comes from Germany. 
