432 
POPULAR SCIENCE REVIEW. 
We are at liberty to produce as much Tyrian purple as we like ; 
but we should probably not obtain it as the ancients did from 
the whelks and other sea snails whose history, in this respect, 
I have sketched in my recent work, <( The Utilization of 
Minute Life , fyc.f but from guano. For, if the purple of the 
ancients was not derived from murexide — a substance we can 
obtain by means of the uric acid contained in Peruvian guano 
— murexide will produce the purple derived from the whelks. 
But this purple is far inferior in brilliancy to the aniline purples 
of the present day, for the art of producing colours, like every- 
thing else in nature, is subject to the law of progress ! 
To return to benzol, the history of this substance is by no 
means devoid of interest. It was first obtained in 1825, by 
Professor Faraday — who little dreamt of the future uses to which 
it would be applied — whilst studying the products derived from 
the distillation of vegetable oils, and described by him as a 
liquid hydrocarbon. In 1834 the celebrated chemist Mitscher- 
lich of Berlin obtained the same substance by distilling 
benzoic acid in presence of excess of lime or baryta, and called 
it benzol. Some French chemists afterwards called it Benzine . 
It is not difficult, on comparing Faraday’s paper with that of 
Mitscherlich, to perceive that they had both produced the same 
substance. Some time afterwards it was found that benzol 
exists in considerable quantity in coal-tar naphtha, i.e., in the 
light oils from the distillation of coal, which float on water, 
boil below 100° centigrade, and congeal to a solid mass at zero. 
The way of obtaining benzol by distilling this coal-tar naphtha 
appears to have been first pointed out by an English chemist, 
Charles Mansfeld, who died at an early age soon after publish- 
ing an ingenious pamphlet upon benzol and its economic 
applications. The idea, like so many others, was soon exploitee 
on the Continent, where, about 1850, impure benzol was sold 
about 2 francs per pint under the name of benzine- collas for 
cleaning gloves, tissues, &c., as it has the power of easily dis- 
solving grease. 
The properties of benzol are soon told. It is a hydrocarbon 
C 12 H fi , liquid at ordinary temperatures and colourless, solidifying 
into a crystalline mass at zero, boiling at 80° centigrade, 
having a specific gravity = O' 85, therefore floating upon 
water, in which it is quite insoluble, but dissolves in alcohol 
and ether. It has generally a strong odour of naphthaline 
or coal gas, but when quite pure its odour is more aromatic 
and less powerful. Pure benzol is not discoloured by strong 
sulphuric acid. But the most remarkable property of benzol 
resides in its action upon nitric acid. Other acids do not 
attack it readily ; but with concentrated nitric acid, aided at 
the commencement of the action by a slight heat, a new sub- 
