IMPROVEMENTS IN THE DISTILLATION OF COAL-TAR AND OTHER MATERIALS, SUBSTANCES OR LIQUIDS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Edwin Drew at the Office of the
Commissioners of Patents on the 19th December 1882.
EDWIN DREW of Queen's Road, Bayswater in the County of Middlesex
"IMPROVEMENTS IN THE DISTILLATION OF COAL-TAR AND OTHER MATERIALS,
SUBSTANCES OR LIQUIDS"
The Invention has for its object improvements in the distillation of coal-tar and
other materials substances or liquids and relates. to means whereby the various
products thereof are obtained at a single distillation in a sufficiently pure state for
commercial purposes or in such a condition as to reduce considerably the operations
required to obtain products of a given quality.
It has heretofore been proposed to distil coal-tar and other materials substances
or liquids in presence of a partial vacuum but such partial vacuum has been
employed either for the purpose of quickly removing the evolved vapours from the
distilling apparatus or of getting these off at a lower temperature than would be
necessary were such partial vacuum not employed.
It has also been proposed to separate various substances or products from their
mixed vapours in a certain degree of purity by passing these vapours through a
series of condensers each of which is kept at a temperature lower than its predecessor
in the series.
The method of endeavouring to separate various substances or products from
their mixed vapours by passing these vapours through a series of condensers each
of which is kept at a temperature lower than its predecessor in the series has not
been used together with the use of a partial vacuum.
Now my Invention consists in passing the mixed vapours from coal-tar, and
other materials substances or liquids through a series of condensers each of which
is maintained at a temperature lower than its predecessor in the series and at the
temperature which in each case is adapted to the condensation of the required.
product and at the same time reducing considerably the pressure within the series
of condensers by the application of a suitable air pump or exhauster, and I use and
adapt this exhaust or partial vacuum for the purpose of increasing the differences
between the vapour tensions of the various vapours as they pass through the series
of condensers referred to and so facilitating very much their separate condensation

page_text: in the condensers under the influence of the respective temperatures at which the
condensers are maintained.
I do not confine myself to any exact degree of exhaust but I find it advantageous
to work with as high an exhaust as can be maintained economically and practically
in connection with the construction and working of the apparatus.
Nor do I confine myself to any particular form of condenser as I have found
that various forms and descriptions will answer fairly well, but I find it very
desirable to cause the vapours by slow passage or by intimate contact or, other
means to be brought as nearly as possible to the temperature of each condenser
before passing away from one condenser to the next of the series.
It is also advantageous to cause the vapours on entering into any condenser in
the series to impinge closely upon or even to bubble through any fluid which has
been already collected.