114 
NATURE 
[ Fane 3, 1886 
in coal-tar contains homologues of benzenes, which may be 
separated from it by fractional distillation. the 17 D 
ruary, 1856, Mansfield was occupied with the distillation of this 
hydrocarbon, which he foresaw would find further applications, 
for the Paris Exhibition, ina still. The liquid in the retort boiled 
over and took fire, burning Mansfield so severely that he died in 
a few days. 
The next step in the production of colours from benzene and 
toluene is the manufacture of nitrobenzene, CgH;NO,, and 
nitrotoluene, C;H,NO,. The former compound, discovered in 
1834 by Mitscherlich, was first introduced as a technical product 
by Collas under the name of artificial oil of bitter almonds, and 
Mansfield in 1847 patented a process for its manufacture. It is 
now used for perfuming soap, but mainly for the manufacture of 
aniline (C;H;NH,) for aniline blue and aniline black and for 
magenta. It is made ona very large scale by allowing a mixture 
of well-cooled fuming nitric acid and strong sulphuric acid to 
run into benzene contained in cast-iron vessels provided with 
stirrers. 
To prepare aniline from nitrobenzene, this compound is acted 
upon with a mixture of iron turnings and hydrochloric acid in a 
cast-iron vessel. Commercial aniline is a mixture of this com- 
pound with toluidine obtained from toluene contained in com- 
mercial benzene. Some idea of the magnitude of this industry 
may be gained from the fact that in one aniline works near 
Manchester no less than 500 tons of this material are manufac- 
tured annually. From the year 1857, after Perkin’s celebrated 
discovery ! of the aniline colours, up to the present day, the 
history of the chemistry of the tar products has been that of a 
continued series of victories, each one more remarkable than 
the last. 
Coal-tar Colours.—TYo even enumerate the different chemical 
compounds which have been prepared during the last thirty 
years from coal-tar would be a serious task, whilst to explain 
their constitution and to exhibit the endless variety of their 
coloured derivatives which are now manufactured would occupy 
far more time than is placed at my disposal. On the industrial 
importance of these discoveries the speaker reminded his audience 
of the wonderful potency of chemical research, as shown by the 
fact that the greasy material which in 1869 was burnt in the 
furnaces or sold as a cheap waggon grease at the rate of a few 
shillings a ton, received two years afterwards, when pressed into 
cakes, a price of no less than one shilling per pound, and this 
revolution was caused by Grabe and Liebermann’s synthesis of 
alizarin, the colouring matter of madder,* which is now manufac- 
tured from anthracene at a rate of more than two millions 
sterling per annum ; and it is stated that an offer was once made, 
in the earlier stages of its history, by a manufacturer of anthra- 
cene to the Paris authorities to take up the asphalt used in the 
streets for the purpose of distilling it, in order to recover the 
crude anthracene. 
Again, we have in the azo-scarlets derived from naphthalene 
a second remarkable instance of the replacement of a natural 
colouring matter, that of the cochineal insect, by artificial tar- 
products, and the naphthol-yellows are gradually driving out the 
dyes obtained from wood extracts and berries. It is, however, 
true that some of the natural dye-stuffs appear to withstand the 
action of light better than their artificial substitutes, and our 
soldiers’ red coats are still dyed with cochineal. 
The introduction of these artificial scarlets has, it is interest- 
ing to note, greatly diminished the cultivation of cochineal in 
the Canaries, where, in its place, tobacco and sugar are now 
being largely grown. 
Let us next turn to inquire as to the quantities of these various 
products obtainable by the distillation of one ton of coal in a gas- 
retort. The six most important materials found in gas-tar from 
which colours can be prepared are :— 
1. Benzene. 4. Metaxylene (from solvent naphtha). 
2. Toluene. 5. Naphthalene. 
3. Phenol. 6. Anthracene. 
The ayerage quantity of each of these six raw materials obtain- 
* See Lectures by Prof. Hofmann, F.R.S., “On Mauve and Magenta,” 
April rz, 1882, and W. H. Perkin, F.R.S., ‘‘On the Newest Colouring 
Matters,’’ May 14, 1869, Proc. Roy Just.; also President’s Address (Dr. 
Perkin, F.R.S.), Journal of Society of Chemical Industry, vol. iv., July 
1884, on Coal-Tar Colours. 
“On the Artificial Production of Alizarine, the Colouring Matter of 
Madder,” by Prof. H. E. Roscoe, Proc. Roy. Znst., April 1, 1870; also Dr. 
Perkin, F.R-S., ‘On the History of Alizarine,’’ Journal Society of Arts, 
May 30, 1879. 
On the 17th of Feb- | 
able by the destructive distillation of one ton of Lancashire coal 
is seen in Table I. Moreover, this table shows the average 
amount of certain colours which each of these raw materials 
yields, viz. :— 
| ae 4. (Xylidine 0°07 |b.) 
2.9) esate ONES INs 5. Vermilline scarlet 7°11 lbs. 
3. Aurin 1°2 Ib. 6. Alizarin 2°25 lbs. (20 per cent.) 
Further, it shows the dyeing power of the above quantities of 
each of these colours, all obtained from one ton of coal, viz.:— 
1 and 2. Magenta, 500 yards of flannel. 
3. Aurin, 120 yards of flannel 27 in. wide. 
4and 5. Vermilline scarlet, 2560 yards of flannel. 
6. Alizarin, 255 yards Turkey red cloth. 
Lastly, to point out still more clearly these relationships, the 
dyeing power of one pound of coal is seen in the lowest hori- 
zontal column, and here we have a party-coloured flag, which 
exhibits the exact amount of colour obtainable from one pound 
of Lancashire coal. 
Let us moreover remember, in this context, that no less than 
ten million tons of coal are used for gas-making every year in 
this country, and then let us form a notion of the vast colouring 
power which this quantity of coal represents. 
The several colours here chosen as examples are only a few 
amongst a very numerous list of varied colour derivatives of each 
group. Thus we are at present acquainted with about sixteen 
distinct yellow colours ; about twelve orange ; more than thirty 
red colours ; about fifteen blues, seven greens, and nine violets ; 
also a number of browns and blacks, not to speak of mixtures of 
these several chemical compounds, giving rise to an almost 
infinite number of shades and tones of colour. These colours 
are capable of a rough arrangement according as they are origin- 
ally derived from one or other of the hydrocarbons contained in 
the coal-tar. The fifty specimens of different colours exhibited 
may thus be classified, but in Table II., for the sake of brevity, 
only the commercial names and not the chemical formule of 
these compounds is given. 
(Zo be continued.) 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE 
CAMBRIDGE.—Prof. Liveing has been appointed Chairman of 
the Examiners for the Natural Sciences Tripos, and Mr. James 
Ward of those for the Moral Sciences Tripos. There were 106 
candidates for the first part of the Natural Sciences Tripos 
recently held. 
Attention has recently been given to the preservation of Uni- 
versity buildings from fire, and serious defects have been, or are 
being, remedied. Such matters should be carefully thought out 
in regard to every museum and library, and it is to be hoped 
that attention will be constantly given to the efficiency of means 
of prevention and extinction of fires. The report on this sub- 
ject in No. 636 of the Cambridge University Reporter is well 
worthy of the study of officials concerned in guarding precious 
scientific collections. 
Prof. Darwin will lecture in the Long Vacation on the 
Theory of the Potential, Attractions, and the Figure of the 
Earth, the first lecture being on Tuesday, July 13. 
A recent discussion of a report by the Special Board on Medi- 
cine emphasised the desirability of teaching elementary physics 
as part of general education to those intending to become 
medical students, and showed that the new “‘ extra subjects ” of 
the Previous Examination do not satisfactorily secure this, 
dynamics and a mathematical treatment being required, rather 
than experimental acquaintance with the physical forces. Mr. 
Oscar Browning said the interests of education were suffering 
terribly from the want of agreement as to what schoolboys ought 
to be taught. Mr. Shaw remarkéd on the importance of a 
training in inductive reasoning for medical students, for their 
whole practice would consist in drawing inductions. 
The grants from the Worts Fund to Messrs, Bateson, Seward, 
Gadow, and Potter, to which we recently referred, have been 
voted by the Senate. 
Prof. Alfred Marshall is giving a prize of 15/. annually for 
Political Economy, to be open to all members of the University 
under the M.A. degree. The examination is to consist of the 
papers on Political Economy in Part I., and on Advanced Poli- 
a 
