August 6, 1885] 
tility. It has, however, since become useful for the manufacture 
of induline. 
The first really successfull azo colour was Manchester and Bis- 
inark brown (triamidoazobenzene), which is produced by the 
action of nitrous acid on metadiaminobenzene. 
The next important step took place in 1876, by the discovery 
of chrysoidine, by Caro and Witt. Independently this product 
is prepared by the action of diazobenzene on metadiamidoben- 
zene. 
About this time the subject began to be worked out on a 
scientific basis, and since then the number of diazo dyes pro- 
duced is marvellous, and it will be useless for me to do more 
than to refer to one or two of the most important. About this 
period also the value of the sulpho group, began to be realised, 
and this has greatly added to the value of these dyes. 
The first use of the sulpho group in relation to azo colours 
was in connection with amidoazonaphthalene, patented by 
myself in 1863. 
During the early history of coal-tar colours, innumerable ex- 
periments were made with naphthalene derivatives to produce 
colouring matters, but no results of any value were obtained ; 
the experiments were mostly made with naphthalamine. The 
first colouring matter that was obtained from it that was of value 
was Martin’s yellow, a dinitronaphthol. After this came the 
Magdala red, which was not much used. The principal develop- 
ment of the coal-tar colours of late years has, however, been in 
connection with diazo reaction. In these reactions naphthol is 
much used, and this product, which a few years ago was un- 
knewn, is now manufactured by tons by fixing the naph- 
thalene sulphonic acid with alkali, and is produced at a few 
pence per pound. Most of the azo colours produced from ben- 
zene derivatives are of a yellow or brown colour, but, by taking 
products of a higher molecular weight, colours of different 
shades of red are produced. The one which has commanded the 
greatest success is the scarlet, first known as Meister scarlet, pro- 
duced by the acting of diazoxylene chloride on the disulphonic 
acid of B-naphthol ; its constitution may be represented thus :— 
CoHs(CH,)_ — Ny — Cy) Hy(OH)(HSO,),. 
And in the formation of bluer shades, diazocumene chloride is 
used. The cumedene used is now made from xylidene, by the 
beautiful reaction of Hofmann’s, in which an alcohol radical as- 
sociated with the nitrogen becomes that element, and enters 
with the hydrocarbon radical. These scarlets have had a very 
injurious influence on the cochineal market, and have in many 
cases displaced it. 
If a-diazonaphthalene chloride be used instead of the xylene 
or cumene compounds, the colour known as Bordeaux is pro- 
duced. Then, again, where derivatives of a-naphthol are used, 
different results are also obtained, so that great varieties of pro- 
ducts can be produced. The preparation of these azo colours is. 
a matter of much simplicity, and (colouring matter being pre- 
cipitated in bringing the products together, and, moreover, they 
can be produced in many theoretical quantities ; hence they are 
remarkably cheap dyeing agents. The following are the formule 
of some of these azo dyers :— 
Manchester Brown, Vesuvius or Bismarck Brown.— 
(Qn) 
NH,C,H, — N,C,H;(NH.),HCL. 
(72) 
Chrysoidine C,H;.N,.C,H3(NH,).HCI. 
Fast yellow KSO,.C,Hy.N,.CgHN Hy. 
Metaucher yellow NaSO2N HN). C,H,NHCH,. 
Orange NaSOy-CoH Ny CyyHq(OH). 
Fast red NaSO3.C,)H,. No.Cy)H,(OH). 
Ponceau G, CH,.N.C,H,OH(NaSO). 
Ponceau 2R (CH),CsHs-Nz-CigH,OH(NaS0,)5 
(B) 
Bordeaux C, )H,.a-N,.C,,H,OH(NaSO,),. 
From which it will be seen that the colour changes from yellow 
to red and claret by the increase of the molecular weight of the 
radicals introduced, and also by the relative position occupied 
by the group, &c. 
Products of the quinoline series have of late been claiming 
attention in relation to colouring matters. It will perhaps be 
remembered that, in the early days of the coal-tar colour 
NATURE 
222 
VII 
industry, a beautiful blue colour belonging to this series, dis- 
covered by Greville Williams (Chem. News, Oct. 11, 1860, 219), 
was introduced. This substance was called cyanine. The em- 
ployment as a dye for silk at first produced quite a sensation, 
on account of the beauty of the colour; but unfortunately it 
was too fugitive to be of any practical value. Recent researches 
haye shown that chryaniline is also to be regarded as a body of 
the chinoline class. Alizarin blue, and also the beautiful yellow 
dye obtained from acetonilide by Fischer, and known as 
flavanilin, are found also to belong to this class of substance. 
Other colouring matters which have long been prepared from 
quinoline direct might be referred to did time permit. The 
peculiar green which is produced by the condensation of 
tetramethyldiphenylketone with quinoline is of interest, because 
the introduction of this quinoline has a very different influence 
on the resulting colouring matter to that of other groups con- 
taining amidogen—in fact, it appears to act more like the phenyl, 
as the green is very analogous to benzaldehyde green. 
There is a very interesting new manufacture growing out of 
the coal-tar colour industry, and that is, the preparation of 
derivatives of quinoline as substitutes for quinine. I have 
mentioned that much work has of late been directed to the 
study of quinine itself, and although the artificial formation of 
this substance has not yet been discovered, new bodies have 
been obtained during these investigations which are thought to 
possess valuable medical properties, This is rather a remark- 
able development from this industry, seeing that it was owing to 
experiments made on the artificial formation of quinine that it 
owes its foundation. 
There is another’ peculiar colouring matter I have not yet 
referred to, peculiar—as it contains sulphur. I refer to methy- 
line blue, a very valuable dye, the constitution of which has 
been so well worked out by Bernthsen, but I feel I must be 
content with this slight reference to it. 
As I have shown, the coal-tar colour industry originated in 
this country, where for some time it was solely carried on. The 
second impulse was from France in the discovery of magenta 
and its blue and purple phenylic derivatives, which were soon 
brought toa state of great purity in this country. The Hofmann 
violets were then discovered and produced also in this country, 
several other colours being perfected and largely used. By this 
time the manufacture of coal-tar colouring matter had made 
some progress in Germany and Switzerland; crude products 
in a cheap form were first made, but improvements soon 
followed. 
The subject of these colouring matters was taken up with 
great earnestness in the German laboratories, so much so that it 
was stated at one time that this industry was acting injuriously 
to science, as it had diverted an undue amount of attention 
from other subjects. Time has, however, proved the ground- 
lessness of this statement. This laboratory work, as well as 
research work generally, fitted a number of highly-trained 
chemists to enter the works, when they soon improved the 
processes, and thus they were able to produce products of a 
quality to compete with those of English manufacture, which 
had, owing to their purity, given superior and more reliable 
shades of colour in the hands of the dyer; and the result of 
the application of this scientific labour to this industry is that 
Germany produces products of the highest class and at the lowest 
price. The fact that Germany is now the head-quarters of this 
industry, raises the important question, Why has England 
allowed this state of things to come about ? All the raw materials 
are produced in this country, both the products from coal and 
the other chemicals required, and, as we have seen, the industry 
originated and was first carried on here, and, in addition, we 
are the greatest consumers of the colouring matters. This fact 
is well worth considering, and it is many-sided. In my opinion, 
the Patent Laws, and the difficulty of preventing infringements 
from abroad, was one cause which may have prevented this 
country from maintaining its first position. 
When speaking of the early history of the first coal-tar colour, 
mauvein, I referred to this class of infringement and how it was 
first met by the proceedings taken against the agents employed 
in this country, and this course wus so far successful, but only 
pointed out how easily the law could be evaded if foreign manu- 
facturers gave up responsible agents and sold direct to the con- 
sumers. Having no duties on such articles, no assistance could 
be obtained at the Customs, and the colouring matters were 
generally declared under the name of vegetable dyes or extracts, 
so that it was impossible to stop them entering the country, and 
