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It was formerly in great demand by perfumers, but its poisonous properties render it a dangerous substance to deal with. In practice a given quantity of benzene will yield about 150 per cent of nitrobenzene. Stated chemically, the reaction is shown by the following equation:
We saw that water may be formulated HOH, and that benzene is C H . Well, carbolic acid or phenol is a derivative of water, or a derivative of benzene, just as you like, and it is formulated C H OH. You can easily prove this by dropping carbolic acid or phenol down a red-hot tube filled with iron-borings.
In addition to dyestuffs, it is a starting-product for the manufacture of many drugs, such as antipyrine, antifebrin, &c. Aniline is manufactured by reducing nitrobenzene with iron and hydrochloric acid and steam-distilling the product. The purity of the product depends upon the quality of the benzene from which the nitrobenzene was prepared.
By this means nearly all the volatile matters pass over in the form of condensible vapours, and the crude oils are at once formed, from whence are obtained at different temperatures various volatile ethers, benzene, and artificial turpentine oil or petroleum spirit.
"By combining the hyper-sulphate of iridium with the fumes arising from oxide of copper heated to 1000 C. and combining with picric acid in the proportions described in formula x 18, a reaction, the nature of which I have not fully determined, follows. This must be performed with extreme care owing to the unstable nature of the benzene compounds." "Picric acid? Benzene compounds?
It is sometimes known and sold as benzene collas, and is used for removing grease from clothing, cleaning kid gloves, &c. If pure it is in reality a most dangerous spirit, being very inflammable; it is also extremely volatile, so much so that, if an uncorked bottle be left in a warm room where there is a fire or other light near, its vapour will probably ignite.
Generally, too, with signal success. The discovery of benzene in 1825 by Faraday was followed in the course of a few years by its discovery in coal-tar by Hofmann. Toluene, which was discovered in 1837 by Pelletier, was recognised in the fractional distillation of crude naphtha by Mansfield in 1848.
Benzene, which is only a compound of carbon and hydrogen, was first discovered by Faraday in 1825; it is now obtained in large quantities from coal-tar, not so much for use as benzene; is for its conversion, in the first place, by the action of nitric acid, into nitro-benzole, a liquid having an odour like the oil of bitter almonds, and which is much used by perfumers under the name of essence de mirbane; and, in the second place, for the production from this nitro-benzole of the far-famed aniline.
There were thus two methods of obtaining aniline from tar, the experimental and the practical. The mixture is gradually introduced into the large cast-iron cylinder into which the benzene has been poured.
The water which is thus formed in the process, by the freeing of one of the atoms of hydrogen in the benzene, is absorbed by the sulphuric acid present, although the latter takes no actual part in the reaction. From the nitrobenzene thus obtained, the aniline which is now used so extensively is prepared.
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