nzene and nitro-benzene made from it at the British Association
meeting held at Manchester in 1842, but the report of the meeting says
nothing about it, and the world in general learned the presence of
benzene in coal-tar only from the independent discovery of A. W.
Hofmann, published in 1845. And it was most assuredly in Hofmann's
London laboratory that Charles Mansfield worked out that method of
fractional distillation of the coal-tar and of isolating the single
hydrocarbons which laid the foundation of that industry. His patent,
numbered 11,960 and dated November 11th, 1847, is the classical
land-mark of it. About the same time, in 1846, Bronner, at Frankfort,
brought his "grease-remover" into the trade, which consisted of the most
volatile coal-tar oils, of course not separated into the pure
hydrocarbons; he also sold water-white "creosote" and heavy tar-oils for
pickling railway timbers, and used the remainder of the tar for the
manufacture of roofing-felt. The employment of heavy oils for pickling
timber had already been patented in 1838 by John Bethell, and from this
time onward the distillation of coal-tar seems to have been developed in
Great Britain on a larger scale, but the utilization of the light oils
in the present manner naturally took place only after Sir W. H. Perkin,
in 1856, discovered the first aniline colour which suddenly created a
demand for benzene and its homologues. The isolation of carbolic acid
from the heavier oils followed soon after; that of naphthalene, which
takes place almost automatically, went on simultaneously, although the
uses of this hydrocarbon for a long time remained much behind the
quantities which are producible from coal-tar, until the manufacture of
synthetic indigo opened out a wide field for it. The last of the great
discoveries in that line was the preparation of alizarine from
anthracene by C. Graebe and C. T. Liebermann, in 1868, soon followed by
patents for its practical manufacture by Sir W. H. Perkin in England,
and by Graebe, Liebermann and H. Caro in Germany.

The present extension of the industry of coal-tar distilling can be only
very roughly estimated from the quantity of coal-tar produced in various
countries. Decidedly at the head is Great Britain, where about 700,000
tons are produced per annum, most of which probably finds its way into
the tar-distilleries, whilst in Germany and the United States much less
gas-tar is produced and a very large proportion of