he small fraction that comes over up to
this temperature constitutes what the tar-distiller calls "first
runnings." From 110 deg. C. to 210 deg. C. there comes over a limpid inflammable
liquid known as "light oil," and this is succeeded by a fraction which
shows a tendency to solidify on cooling, owing to the separation of a
solid crystalline hydrocarbon known as naphthalene. This last fraction,
boiling between 210 deg. C. and 240 deg. C., is known as "carbolic oil," because
it contains, in addition to the naphthalene, the chief portion of the
carbolic acid present in the tar. From 240 deg. C. to 270 deg. C. there comes over
another fraction which shows but little tendency to solidify in the
condensing coil, and which is known as "heavy oil," or "creosote oil."
From 270 deg. C. up to the end of the distillation there distils a fraction
which is viscid in consistency, and has a tendency to solidify on cooling
owing to the separation of another crystalline hydrocarbon known as
anthracene, and which gives the name of "anthracene oil" to this last
fraction. When the latter has been collected there remains in the still
the black viscid substance known as pitch, which is obtained of any
desired consistency by leaving more or less of the anthracene oil mixed
with it, or by afterwards mixing it with the heavy oil from previous
distillations. The process carried out in the tar-still thus separates the
tar into--(1) First runnings, up to 110 deg. C. (2) Light oil, from 110 deg. to
210 deg. C. (3) Carbolic oil, from 210 deg. to 240 deg. C. (4) Creosote oil, from 240 deg.
to 270 deg. C. (5) Anthracene oil, from 270 deg. to pitch. (6) Pitch, left in
still.

It has already been said that coal-tar is a complex mixture of various
distinct chemical compounds. Included among the gases, ammoniacal liquor,
and tar, the compounds which are known to be formed by the destructive
distillation of coal already reach to nearly one hundred and fifty in
number. Of the substances present in the tar, about a dozen are utilized
as raw materials by the manufacturer, and these are contained in the
fractions described above. The first runnings and light oil contain a
series of important hydrocarbons, of which the three first members are
known to chemists as benzene, toluene, and xylene, the latter being
present in three different modifications. The carbolic oil furnishes
carbolic acid and naphthalene, and the anthracene oil the hydrocarbon
which gives its