AN IMPROVED METHOD OF EXTRACTING ANTHRACENE CONTAINED IN COAL TAR AND THE PITCH ACCRUING THEREFROM WITHOUT EITHER CARBONIZING OR DECOMPOSING THE PITCH
Year: 1872

page_text: LETTERS PATENT to William Clark, of 53, Ohancery Lane, in the
County of Middlesex, for the Invention of "AN IMPROVED METHOD OF
EXTRACTING ANTHRACENE CONTAINED IN COAL TAR AND THE PITCH ACCRUING
THEREFROM WITHOUT EITHER CARBONIZING OR DECOMPOSING THE PITCH."-A
communication from abroad by Paul Audouin, of Paris, France,
Engineer.
Sealed the 1st November 1872, and dated the 13th May 1872.
PROVISIONAL SPECIFICATION left by the said William Clark at the
Office of the Commissioners of Patents, with his Petition, on the
13th May 1872.
I, WILLIAM CLARK, of 53, Chancery Lane, in the County of
Middlesex, do hereby declare the nature of the said Invention for "As
IMPROVED METHOD OF EXTRACTING ANTHRACENE CONTAINED IN COAL TAR AND THE
PITCH ACCRUING THEREFROM WITHOUT EITHER CARBONIZING OR DECOMPOSING THE
PITCH," to be as follows:
-
When distilling coal tar with the view of obtaining anthracene it is
necessary to carry the distillation as far as possible, that is to say, to
extract from the tar the utmost quantity of heavy oils it contains, as it
is only in the last distilled oils that anthracene is to be found.

page_text: Heretofore the ordinary methods of distilling tar did not allow of the
extraction from such tar of a sufficient amount of heavy oils to obtain
any considerable quantity of anthracene as compared to the whole
amount thereof which exists in tar. In fact when by this distillation
there has been extracted besides tho oils lighter than water an i
equivalent amount of heavy oils according to the nature of the coal tar
used, say about 25 per cent. of the weight of the tar in the distilling
apparatus, it is necessary to discontinue the operation as the remaining
matter in the apparatus becomes viscous, and being a bad conductor of
heat it tends to decompose and become carbonized to the great detriment 1
of the apparatus, which would be rapidly destroyed were the operation
prolonged under such conditions. The operation has thus heretofore
been compulsorily stopped after extracting about 25 per cent. of heavy
oils as above alluded to, the viscous matter remaining in the distilling
apparatus becoming after cooling what is termed pitch. This still
contains a large amount of anthracene, and the method used heretofore
for extracting it was to completely carbonize and destroy the pitch, so
as to form coke.
.
.
°
This Invention has for its object to avoid such destruction and
carbonization of the pitch, and to extract from tar the whole amount or :
nearly so of the anthracene it contains while still producing the matter
or substance so called "pitch," and it is this process it is desired to
protect by the present application for Letters Patent.
In distilling coal tar it was heretofore necessary as above-mentioned
to stop distilling after extracting besides the lighter oils than water about
25 per cent. of heavier oils than water, generally known by the name of
Heavy oils or creosote, or to incur the risk of decomposing part of the
pitch left in the apparatus, which still contains a considerable amount
of anthracene, and also of quickly destroying the distilling apparatus.
The process of this Invention consists in carrying this distillation a
further and heating without decomposing the pitch, which result is
attained by a continuous stirring of the viscous matter left in the
distilling apparatus, viz., the pitch. In fact by such stirring the
surfaces of the viscous material become constantly renewed, so as to
enable large quantities of oils and of course of anthracene to be again a
extracted therefrom without decomposing the pitch. Instead of about
25 per cent. of heavy oils which were up to this day obtained from the
distillation of coal tar by the old processes, I extract without any more

page_text: detriment to the distilling apparatus and without any partial de-
'composition of the pitch as much as 35 and even 40 per cent. of heavy
oilsaccording to the nature of the coal tar used, say, from 10 to 15 per
cent. more, and it is precisely in these last oils that is to be found the
largest amount of anthracene contained in tar. Moreover the matter
remaining in the apparatus after such distillation is an unaltered pitch.
This process is therefore based on the principle of stirring the material
to be distilled whatever may be the means employed for effecting this
object.
I will however indicato the following methods :-First, stirring produced
by any mechanical device, such as a pallet or agitator driven by hand
or by steam, or in a word any instrument or device that may be applied
to produce the same result; secondly, introducing into the distilling
apparatus, and under any conditions suitable for effecting a thorough
stirring of the matter, any inert gas under pressure by means of a
pipe projecting jets of gas in all directions, and so that the surfaces of
the pitch in contact with the heated sheet iron casing may be constantly
renewed. This conveying apparatus may be located permanently within
the distilling apparatus, or be arranged so as to be set in motion either
by the gas itself or by any suitable motor. Among the inert gases I
will instance lighting gas, carbonic acid gas, atmospheric gas, and pro-
ferably such gases as proceed from the combustion of coal or coke or
other fuel in fire-places, water, steam, or any gases and vapors. These
being introduced in jets projected in all directions, preferably downwards
and near to the bottom and sides of the distilling apparatus, will act like
a mechanical agitator so as to stir the material, renew the surfaces, and
prevent the solid particles which might be the product of a partial
decomposition from adhering to the sheet iron casing, and forming an
incrustation injurious to the proservation of the apparatus and to tho
conductibility of the heat. These gases or vapors have been before
employed for distilling volatile products by acting as heating agents in
distilling alcohols, for instance, and benzine, or as mechanical carrying
agents of vapors as these are formed as in the case of distilling nitra-
benzine; but the above indications will suffice to show that theso
properties of the gases and vapors are not the same as I make use of to
attain the result which I contemplate.
The process which constitutes the present Invention is applicable
not only for distilling coal tar, but also for distilling pitch, as this last.

page_text: product which is extracted from tar is itself nothing but the result of
the cooling of the viscous matter above mentioned as remaining in the
apparatus at the very time when manufacturers are accustomed to
discontinue the distillation to this day. The pitch resulting from this
process.is more distilled than the common trade pitch, but it may be
made when desired (by an addition of heavy oil or other residue from
the same in a heated state by operating either in the distilling apparatus
.or.in any special apparatus or otherwise) to acquire the required con-
sistency for any use it is intended for, but such addition is merely
indicated here and constitutes no part of the Invention.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Clark in the Great Seal Patent Office on
the 12th November 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CLARK, of 53, Chancery Lane, in the County of Middlesex, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirteenth day of May, in the year of
our Lord One thousand eight hundred and seventy-two, in the thirty-
fifth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said William Clark, Her special licence that
I, the said William Clark, my executors, administrators, and assigns,
or such others as I, the said William Clark, my executors, -adminis-
trators, and assigns, should at any time agree with, and no others,
from time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exerciso, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "AN IMPROVED METHOD OF
EXTRACTING ANTHRACENE CONTAINED IN COAL TAR AND THE PITCH ACCRUING THERE-
FROM WITHOUT EITHER CARBONIZING OR DECOMPOSING THE PITCH," a communication
to me from abroad by Paul Audouin, of Paris, France, Engineer, upon
the condition (amongst others) that I, the said William Clark, my
executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe and
ascertain the nature of the said Invention, and in what manner the
same was to be performed, and cause the same to be filed in the Great

page_text: ..
Seal Patent Office within six calendar months next and immediately
after the date of the said Letters Patent.
NOW KNOW YE, that I, the said William Clark, do hereby declare
the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by
the following statement, (that is to say) :-
When distilling coal tar with the view of obtaining anthracene it is
necessary to carry the distillation as far as possible, that is to say, to
extract from the tar the utmost quantity of the heavy oil it contains,
as it is only in the oils which distil last that anthracene is to be found.
:.
The ordinary methods of distilling tar do not allow of the extraction
from such tar of a sufficient amount of heavy oil to obtain any con-
siderable quantity of anthracene as compared with the whole amount
thereof which exists in tar. In fact when by distillation there has been
extracted besides the oils lighter than water an equivalent amount of
oil heavier than water, generally known by the name of heavy oil or
creosote, according to the nature of the tar used (say about 25 per
cent. of the weight of the tar in the distilling apparatus), it is necessary
to discontinue the operation, as the remaining matter in the apparatus
has become viscous, and being a bad conductor of heat it tends to
decompose and carbonize to the great detriment of the apparatus,
which would be rapidly destroyed were the operation prolonged under
such conditions. The operation has thus heretofore been compulsorily
arrested after extracting about 25 per cent. of heavy oil as above alluded
to, the viscous matter remaining in the distilling apparatus becoming
after cooling what is termed pitch. The pitch still contains a large
amount of anthracene, and the method used heretofore for extracting
it consists in completely carbonizing and destroying the pitch so as to
form coke.
This Invention has for its object to avoid such destruction and
carbonization of the pitch, and to extract from tar the whole amount
or nearly so of the anthracene it contains while still producing the
matter or substance so called "pitch," and it is this process that it is
desired to protect by the present Letters Patent.
The process of this Invention consists in carrying this distillation
further by heating without decomposing the pitch, which result is
attained by a continuous stirring of the viscous matter left in the

page_text: distilling apparatus, viz., the pitch. In fact by such stirring the
surfaces of the viscous material become constantly renewed, so as to
enable large quantities of oil and consequently of anthracene to be still
extracted therefrom without decomposing the pitch. Instead of about
25 per cent. only of heavy oils which have hitherto been obtained
from the distillation of coal tar by the old processes, 1 extract without
any detriment to the distilling apparatus and without any partial
decomposition of the pitch as much as 35 and even 40 per cent. of
heavy oils according to the nature of the coal tar used, say from 10 to
15 per cent. more, and it is precisely in these last oils that is to be
found the largest amount of anthracene contained in tar. Moreover
the matter remaining in the apparatus after such distillation consists
of pitch, the properties of which remain unaltered. The process is
therefore based on the principle of stirring the material to be distilled
whatever may be the means employed for effecting this object.
I will however indicate the following methods:-First, stirring pro-
duced by a pallet or agitator or other mechanical device driven by
hand, steam, or other power; secondly, introducing into the distilling
apparatus and under any conditions suitable for effecting a thorough
stirring of the matters any inert gas under pressure by means of a
pipe projecting jets of gas in all directions, and so that the surfaces
of the pitch in contact with the heated sheet iron casing may be
constantly renewed. This conveying apparatus may be located perma-
nently within the distilling apparatus, or be arranged so as to be set
in motion either by the gas itself or by any suitable motor. Among 5
the inert gases I will instance illuminating gas, carbonic acid gas,
atmospheric air, and preferably such gases as proceed from the com-
bustion of coal, coke, or other fuel in fire-places, steam, or any gases or
vapors. These being introduced in jets projected in all directions,
preferably downwards and near to the bottom and sides of the distilling :
apparatus, will act like a mechanical agitator, and stir the material so
as to renew the surfaces and prevent any solid particles which might
result from partial decomposition adhering to the sheet iron casing and
forming an incrustation injurious to the preservation of the apparatus
and to the conductibility of the heat.
I am aware that these gases or vapors have been before employed for
distilling volatile products by acting as heating agents in distilling
alcohols, for instance, and benzine, or as a means of carrying off vapors

page_text: as they are formed, as in the distillation of nitro-benzine; but the above
indications will suffice to show that these properties of the gases and
vapors are not the same as I make use of to attain the result which I
contemplate.
The process which constitutes the present Invention is applicable not
only for distilling coal tar but also for distilling pitch, as this last
product which is extracted from tar is itself, but the result of the
cooling of the viscous matter above mentioned as remaining in the
apparatus at the time when manufacturers have been hitherto accus-
tomed to discontinue the distillation. The pitch resulting from this
process is more highly distilled than the common trade pitch, but it
may be made when desired (by an addition of heavy oil or other residue
from the same in a heated state, either in the distilling apparatus or
in any special apparatus or otherwise) to acquire the required con-
sistency for any use it is intended for, but such addition is merely
indicated here, and constitutes no part of the Invention..
Having described the nature of the Invention, and in what manner the
same is to be performed, I declare that what I claim as the Invention
to be protected by the herein-before in part recited Letters Patent is,
obtaining the whole of the anthracene (or nearly so) contained in
coal tar without decomposing the pitch whose properties are preserved
(a result hitherto unattainable) by the process heroin described, which
process is designed to counteract the slight conductibility of the tar
and its ready decomposition on contact with the sides of the distillatory
apparatus, and consists in the stirring of the matters to be distilled
whatever may be the means employed for effecting this object, so that
by constantly renewing the surfaces in contact with the heated sheet
iron casing of the apparatus all damage thereto or decomposition of the
pitch is avoided.
In witness whereof, I, the said William Clark, have hereunto set
my hand and seal, this Twelfth day of November, in the year