IMPROVEMENTS IN THE PROCESS OF PURIFYING ANTHRACHINONE AND ALIZARINES, AND IN APPARATUS FOR EFFECTING THE SAME, SAID PROCESS AND APPARATUS BEING ALSO APPLICABLE TO THE PURIFICATION OR CRYS- TALLIZATION OF OTHER SUBSTANCES
Year: 1882

page_text: LETTERS PATENT to Joseph Anthony Dixon, of 151, St. Vincent Street,
Glasgow, in the County of Lanark, North Britain, Solicitor, for an Invention
of "IMPROVEMENTS IN THE PROCESS OF PURIFYING ANTHRACHINONE AND
ALIZARINES, AND IN APPARATUS FOR EFFECTING THE SAME, SAID PROCESS
AND APPARATUS BEING ALSO APPLICABLE TO THE PURIFICATION OR CRYS-
TALLIZATION OF OTHER SUBSTANCES." A communication from abroad by
Julius Brönner, of Frankfort on-the-Main, in the Empire of Germany,
Manufacturing Chemist.
PROVISIONAL SPECIFICATION left by the said Joseph Anthony Dixon
at the Office of the Commissioners of Patents on the 16th February 1882.
JOSEPH ANTHONY DIXON, of 151 St. Vincent Street, Glasgow, in the County of
Lanark, North Britain, Solicitor. "IMPROVEMENTS IN THE PROCESS OF PURIFYING
ANTHRACHINONE AND ALIZARINES AND IN APPARATUS FOR EFFECTING THE SAME,
SAID PROCESS AND APPARATUS BEING ALSO APPLICABLE TO THE PURIFICATION
OR CRYSTALLIZATION OF OTHER SUBSTANCES." [A communication from abroad by
Julius Brönner, of Frankfort-on-the-Main, in the Empire of Germany, Manufacturing
Chemist.]
The nature of this Invention consists (1.) in a process for purifying impure
anthrachinone, impure alizarines, and other analogous substances hereinafter
described, by dissolution of their soluble parts by means of and recrystallization of
the substance to be purified from volatile solvent media so applied that only such a
limited proportion of solvent requires to be used as makes purification by means of
such solvents now for the first time industrially practicable and workable to
profit; while at the same time, the insoluble impurities are, without any loss of the
solvent by evaporation, filtered out from the hot solutions from which the purified
crystals are afterwards to be obtained; and (2.) in the construction or arrange-
ment of an apparatus suitable for carrying out the said process.
Alizarine, as is well known, is prepared from anthrachinone and anthrachinone
from anthracene.-Crude anthracene is a body which, according as it is derived

page_text: from one coal or another, exhibits very varying qualities and properties, and
contains impurities which are more or less injurious as regards the manufacture of
alizarine. There are very many anthracenes the injurious impurities of which are
such that they can be rendered pure enough for the purposes of manufacture only
with great difficulty and expense, or not at all. This is especially the case where
the impurities consist of higher homologues of anthracene such as methyl
anthracene and the other alkyl compounds of anthracene.-These in the oxidation
of the crude anthracene become converted into homologous anthrachinones, as
methyl-anthrachinone and so forth, which as regards the processes of purification
in common use, (such as for example purification by means of concentrated
sulphuric acid or by means of sublimation) oppose the same amount of resistance
or are as refractory to the treatment as anthrachinone itself, and these impurities
cannot consequently be separated from the anthrachinone by such processes of
purification.
An impure anthrachinone is moreover in the highest degree injurious in the
manufacture of alizarine, not only as respects the quality but also as respects the
yield or outcome of the alizarine produced on which account it has become with
many alizarine makers a rule to employ only anthracenes of the most select quality
although these are much the more expensive. As anthracenes of this quality,
apart altogether from their higher price, can only be obtained in limited quantity,
it has been a constant aim in the alizarine factories to discover a process
which would make it possible to prepare, on the industrial scale and for manu-
facturing purposes, from anthracene of any quality, anthrachinone of sufficient
purity, if not also of absolute chemical purity.-The single property in which the
most mischievious of the impurities ordinarily associated with anthrachinone differ
from anthrachinone itself, and which can be taken advantage of for the purpose of
purifying the anthrachinone, is their greater solubility in volatile organic solvent
media belonging to the fatty or the aromatic series, such as acetic acid, spirit,
ether, petroleum, petroleum-naphtha, benzol, toluol, xylol, phenol and the like, or
mixtures of two or more of these solvents. In the commion process of dissolving
an impure anthrachinone in a quantity of any one of these solvents in the liquid
form sufficient to dissolve, and to hold in solution at once, the whole quantity of
antrachinone to be operated upon, and of then allowing it to crystallize out from
the solvent, it is well known that these impurities above mentioned and more
especially the homologues of anthrachinone remain dissolved in the solvent while
the anthrachinone itself, which is more difficultly soluble in the solvent media
mentioned, crystallizes therefrom in a state of almost chemical purity-But
although this difference in the behaviour of anthrachinone and of its principal
impurities towards the solvents mentioned is not a newly discovered fact, yet a
process of purifying anthrachinone by crystallization in the manner just mentioned
has for technical reasons never been applied hitherto on an industrial scale.
Anthrachinone is so very difficult to dissolve in the solvents mentioned that a
manufacturer applying them as they have hitherto been applied would be obliged
to employ an enormous quantity of the solvent. The solvent which acts most
favourably is the so-called "solvent naphtha," a rectified coal tar oil which boils at
from 120° to 160° centigrade. Of this solvent we are in the habit of applying
about 16 parts to effect the solution of one part of anthrachinone at boiling point.
The process of crystallizing from this solvent, when conducted in the ordinary way
above described, is therefore suited only for laboratory purposes, and not at all for
industrial application on the large scale, and that not only on account of the
quantity and size of the apparatus which would be required, but also, and chiefly,
on account of the immense losses which are inseparable from the handling of such
large quantities of a volatile solvent in the heat; and, in point of fact, all attempts
to apply this process on the large scale have, for the reasons assigned, remained
without success.
The new process which I am about to describe has solved the problem of effecting
the crystallization of anthrachinono with a much smaller quantity of solvent viz :

page_text: with from 2, to 3, times, instead of with 16 times, the quantity of solvent naphtha,
and with similarly diminished proportions of the other solvents. In other words
the new process permits the crystallization to be effected with only from an eighth
to a fifth of the quantity of solvent medium which is necessary for dissolving and
holding in solution at once the whole material which is to be crystallized. The
losses on solvent medium are thus reduced to the minimum, so that the new process
is practicable and workable to profit on the large scale.
The new process has also solved the further problem of rendering it possible, while
the process of dissolving and crystallizing is going on, to carry on simultaneously
the filtration of the hot solution, in order to separate out, and that without any loss
of the solvent by evaporation, the insoluble impurities, so that the pure anthrachinone
to be obtained shall crystallize from a clear filtered solution, whilst the soluble
impurities remain behind in the solution and the insoluble on the filter.
Both the objects described are conveniently attained by the employment of a new
continuously working filtering and crystallizing apparatus constructed and described
as follows:-
The apparatus, in the form which I prefer to give to it, consists of three main
parts. First, A caldron or boiler open at the top and steam jacketed.-In this
vessel the solvent liquid to be used is raised to the boiling point so that the vapours
shall ascend therefrom into the upper parts of the apparatus, and, being condensed,
there, shall fall back again into the boiler, traversing both in ascending and descending
the material to be dissolved, which is placed, as aftermentioned, on a perforated floor
between the boiler, where the vapours are generated, and the upper parts of the
apparatus, where they are condensed into hot liquid. In the centre of the convex
bottom of the boiler there is provided an outlet or passage for the escape of liquids
through an outside escape cock connected therewith, and this passage is closed from
within by a conical valve or plug, provided with a handle by which the plug can
when required be withdrawn to be replaced by a filtering plug, through which the
liquors, can filter into the passage, where they are to be drawn off through the escape
cock. Near the upper rim of the boiler, and inside it there is an angle-iron ledge
intended to support another vessel, which I call the receiver, or holder.-This is a
vessel with a perforated filtering floor, or bottom, on which the anthrachinone, or
other substance, to be purified by dissolution in the volatile solvent and by
recrystallization therefrom, is to be placed in the first instance.-It is made of such
diameter that it may be readily set upon, or removed from, the angle-iron ledge
before mentioned.-The receiver is provided with a stirrer, agitator, or distributor,
carried on a central perpendicular shaft, which can move up or down through a gland
in the upper part of the apparatus.-The receiver being set on the angle-iron ledge,
is covered above and all round with a third vessel, which I call the hood, the lower
edges of which are, when it is in situ, sunk in a hydraulic seal, with which the
upper edges of the caldron, or boiler, are provided, so as to prevent any escape of the
vapours from the apparatus.-The upper part of the hood above the receiver contains
cooling spaces, and it is provided with a coil of pipes through which cold water or
any other refrigerating substance can be kept flowing, in order to condense the
vapours of the solvent as they rise from the boiler, through the perforated bottom
of the receiver up into the upper part of the apparatus, and to cause them to drop
or flow down again on to, and percolate in the form of a hot liquid, through the
substance to be purified lying on the filter floor of the receiver.-The hood is
made so that when necessary it can be readily lifted up out of the hydraulic seal
and off the receiver.
Although the arrangement and putting together of the parts of the apparatus
which I have described is that which I prefer, yet the parts need not be so
arranged relatively to each other. The apparatus may be arranged in two or three
separate parts. Thus, for example, the hood with a fixed bottom and the boiler
with a close fitting cover or top may be arranged side by side and connected with
a pipe. So also the cooling or condensation of the vapours instead of being carried
on inside the hood, may be effected separately or outside of it.-Again the heating

page_text: of the solvent may be effected, instead of by high pressure steam, by superheated
steam, by direct fireheat, by oil baths, metal baths, and other contrivances.-It is
obvious that the principle of the process may be carried out under various inodi-
fications which will readily occur to a practical chemist, and, especially with the
aid of these variations on the process, there may be many different modifications of
the apparatus and rearrangements of its essential parts. But I prefer the mode of
manipulating the materials which I am about to describe, and I prefer for that
purpose the construction and arrangement of the apparatus which I have described.
In order to crystallize anthrachinone I proceed as follows:-The impure
anthrachinone which has been treated with sulphuric acid is thoroughly inter-
mixed and stirred up with from 1% to 2% of dissolved calcined soda.—It
is then perfectly dried and then brought into the receiver, over whose filter
bottom a filtering cloth is stretched.-Into the under part of the apparatus
(the boiler or caldron) there is introduced the quantity already mentioned of
the solvent medium. If for instance solvent naphtha be used a weight of
naphtha twice or three times the weight of the anthrachinone is introduced into
the boiler. The receiver is placed on the angle-iron ledge, and the hood is sunk in
the hydraulic seal.-The solvent medium is heated up to its boiling point.-The
vapours ascend up to the cooling surfaces in the uppermost part of the apparatus
and fall in the form of a condensed hot liquid on the anthrachinone, dissolve it
along with its impurities, and finally get back again in the form of a filtered
saturated solution into the lower part of the apparatus (the boiler).-On account of
the evaporation of the solvent medium which is in this way continually going on
from the boiler, the dissolved anthrachinone, which is much more difficult of
solution than its impurities, finds too little of the solvent in the boiler to hold it in
solution there, and it therefore crystallizes out in the boiler, while the soluble
impurities, which require much less of the solvent, remain dissolved and the
insoluble impurities have been retained on the filter.
Let it be supposed, for the sake of illustration, that I have a certain quantity of
anthrachinone, say 20 lbs, to purify-Instead of throwing the whole 20 lbs into
320 lbs of solvent naphtha and applying heat, and then allowing the liquor to cool,
and crystallization of the anthrachinone to go on partly by reason of the cooling
and partly by reason of evaporation of part of the solvent, I employ only a small
quantity of the solvent quito insufficient to dissolve, even at the boiling point, the
whole 20 lbs. at once.-1 make the solvent pass in vapour through the 20 lbs. and
return as hot liquor through it.-One molecule, or portion of the solvent takes up
a charge of, say, methyl-anthrachinone or any other impurity, another molecule of
the solvent saturates itself with anthrachinone.-Both molecules return to the
boiler, where, from the limited quantity of solvent originally employed and the
continuous process of volatilization kept up, the anthrachinone is readily deposited
as a crystal, while the much more soluble impurity still finds solvent enough to
keep it from crystallizing.-The molecule of solvent, which has deposited its
anthrachinone is again volatilized, and repeats its work, it may be many times over.―
If we suppose, for sake of illustration, that it always charges itself with anthra-
chinone, ou each of its journeys up and down the apparatus, it is obvious that it will
in this way continue to travel round its cycle, carrying down repeated charges of
anthrachinone each time depositing its charge, and returning for a further charge,
until the whole anthrachinone has been carried down in infinitesimal instalments.-
The molecule which has taken up inethyl-anthrachinone may, on the contrary, be
supposed to hold it without ever afterwards depositing it in the apparatus.-This
appears to me to be the correct theory of my process, and it suggests the observation
that the quantity of solvent required in my process, will vary, to a considerable
extent, with the proportion of soluble impurities in the anthrachinone, seeing there
must always be such an amount of solvent present as will hold the whole soluble
impurities in solution at once.-It is not necessary nor desirable that there should
be, besides, a quantity of solvent sufficient to retain in solution the whole anthrachi-
none which has gone into solution.-The crystallization of the anthrachinone

page_text: depends on the fact that there is always a deficiency of solvent present in the boiler
in proportion to the amount of anthrachinone which has been carried down into it.—
I give this theory of my process as what I believe to be its true theory, but I do
not commit myself to it, my. Invention being the process itself, whatever be the
proper explanation of how it attains its results.
When all the anthrachinone on the filter has been dissolved (a point which may
be ascertained by the sinking down of the shaft of the agitator, which is turned
round from time to time) the hood is drawn up out of the hydraulic seal, the
receiver is then lifted out from its resting place on the angle-iron ledgo, the conical
plug, or bung, in the bottom of the boiler is replaced by a filtering plug perforated
with holes, and the liquid which is found in the lower part of the apparatus (the
boiler) is allowed to run out through the escape cock into a reservoir, and that at
the temperature at which the impurities still remain in solution (say about 80°
centegrade). The crystals of anthrachinone which are left behind in the boiler are
then freed by evaporation, from the remains of the solvent which adhere to them,
and are dried, and they are then very nearly pure anthrachinone.
The liquid which has been allowed to flow down into the reservoir is, after
cooling, (during which crystals of inferior purity separate out), again applied in
the apparatus for a new operation.-The crystals which separate out in the
reservoir are collected, till they amount to a large enough charge, and are treated
over again in the apparatus as herein before described.—The crystals which separate
out in the boiler in the course of this second operation are also nearly chemically
pure anthrachinone.
The liquor which has been allowed to flow out into a reservoir may, after cooling,
be applied for the third time as a solvent medium.-The crystals which have
separated out in the reservoir after the second operation, and of which the
quantity is of course much smaller than in the working of the original anthrachi-
none, are collected and treated again in the apparatus as hereinbefore described.―
The crystals which separate out in the apparatus in this third operation are, as a
rule, also nearly chemically pure anthrachinone.-If not they are reserved for and
added to another charge and then give almost chemically pure anthrachinone.
The solvent medium which has been used three times, is subjected, along with
the crystalline mass which has separated out from the third charge in the reservoir,
to distillation, in order to recover the solvent medium in a state of purity. The
residue left by the distillation process is run off, filtered on cooling, and subjected
to hydraulic pressure.-The filtrate is distilled, and, from the solid cakes from
which the liquor has been expressed, there may still be recovered, by treatment in
the apparatus, a small quantity of anthrachinone.
The insoluble residues, which remain on the filter in the apparatus, are subjected
to hydraulic pressure and sublimed with steam.-The sublimate, treated in the
apparatus, also yields authrachinone, almost chemically pure.
If one prefers it, the crude anthrachinone, before its treatment with sulphuric
acid, may be submitted to the continuous crystallization process in the apparatus,
and afterwards treated with sulphuric acid, whereby there will be an important
saving in the latter.-Or, again, the crude anthrachinone may, without the
sulphuric acid treatment, be submitted to continuous crystallization, in which case
the non-oxidized anthracene may be recovered again from the mother liquors.—I
do not however prefer this method of treatment to that first described, because
the method first described is surer in its operation.
A further application of this Invention deals with the purification of impure
alizarine, and purpurine, and all such dyestuffs or colouring matters, comprehended
under the general commercial designation of alizarine, as may have miscarried or
turned out failures, in the process of manufacture, and which are not to be freed
from their injurious impurities by any other paying method.-If these colouring
matters, well dried, are subjected, in the same apparatus as is hereinbefore
described, to a continuous crystallization from solvent naptha, or other suitable

page_text: solvent medium, they may be recovered in extraordinary purity, all the injurious
impurities being perfectly separated out.
It is obvious that the apparatus and mode of purification and of crystallization
herein before described are susceptible of being applied to other substances than
authrachinone or impure alizarines; in short, that they are applicable wherever
the substance to be purified is soluble in, and crystallizable from, a volatile solvent
medium, which either does not dissolve the impurities or dissolves them more
readily (by a practicably appreciable degree of difference) than it dissolves the
substance to be purified.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Joseph Anthony Dixon in the Great Seal Patent Office on the
16th August 1882.
JOSEPH ANTHONY DIXON, of 151 St. Vincent Street, Glasgow, in the County of
Lanark, North Britain, Solicitor. "IMPROVEMENTS IN THE PROCESS OF PURIFYING
ANTHRACHINONE AND ALIZARINES AND IN APPARATUS FOR EFFECTING THE SAME,
SAID PROCESS AND APPARATUS BEING ALSO APPLICABLE TO THE PURIFICATION
OR CRYSTALLIZATION OF OTHER SUBSTANCES." A communication from abroad by
Julius Brönner of Frankfort-on-the-Main, in the Empire of Germany, Manufacturing
Chemist.
The nature of this Invention consists (First), In a process for the purification of
impure anthrachinone and impure alizarines by solution of their soluble constituents
in hot volatile solvents and crystallization of the substance to be purified from the
hot and filtered solution in such a manner that there is required only a very
limited proportion, say about one fifth, of that quantity of solvent which must be
applied according to the method hitherto known and practised in order to attain
the same end; and (Second) In a crystallizing apparatus which has been especially
constructed and arranged for effecting the said purification by crystallizing as
aforesaid and which at the same time permits the insoluble impurities to be
separated by filtration from the hot solution without any loss by evaporation; by
means of which process of combined simultaneous solution, filtration, and crystal-
lization in one and the same apparatus with only a very limited proportion of the
hitherto requisite quantity of solvent the way is now for the first time shewn to
effect the purification of the substances above mentioned by crystallization froin
volatile solvents in an industrial, practical, economical mannor, workable to profit
on the large scale, a result hitherto often attempted but never with success.
Alizarine as is well known, is prepared from anthrachinone and anthrachinone
from anthracene. Crude anthracene is a body which according as it is derived
from one coal or another exhibits very varying qualities and properties, and contains
impurities which are more or less injurious as regards the manufacture of alizarine.
There are very many anthracenes the injurious impurities of which are such that
they can be rendered pure enough for the purposes of alizarine manufacture only

page_text: with great difficulty and expense or not at all. This is especially the case where
the impurities consist of higher homologues of anthracene such as methyl anthracene
and the other alkyl compounds of anthracene. Such impurities in the oxidation
of the crude anthracene become converted into homologous anthrachinones, as methyl-
anthrachinone and so forth, and there are other similar impurities which in the
oxidation undergo corresponding changes, and all or most of these resulting
impurities of the anthrachinone, as regards the processes of purification in common
use (such as for example purification by means of concentrated sulphuric acid or by
means of sublimation) oppose the same amount of resistance to, or are as refractory
under the treatment as anthrachinone itself and these impurities cannot consequently
be separated from the anthrachinone by such processes of purification.
An impure anthrachinone is moreover in the highest degree injurious in the
manufacture of alizarine, not only as respects the quality, but also as respects the
yield or outcome of the alizarine produced, on which account it has become with
many alizarine makers a rule to employ only anthracenes of the most select quality
although these are much the more expensive. As anthracenes of this quality, apart
altogether from their higher price, can only be obtained in limited quantity, it has been
a constant aim in the alizarine factories to discover or make economically applicable
a process which would make it possible to prepare, on the industrial scale, and for
manufacturing purposes, from anthracene of any quality, anthrachinone of sufficient
purity, if not also of absolute chemical purity. The single property in which the
said impurities ordinarily associated with anthrachinone differ from anthrachinone
itself, and which can be taken advantage of for the purpose of purifying the
anthrachinone, is their greater solubility in volatile organic solvent media belonging
to the fatty, or the auromatic series, such as acetic acid, spirit, ether, petroleum,
petroleum-naphtha, benzol, toluol, xylol, phenol, and the like or mixtures of two
or more of these solvents. The common process of purifying anthrachinone by
crystallization from a volatile solvent consists in dissolving the impure anthrachinone
in such a quantity of any one of these solvents, at boiling point, as is necessary to
dissolve and to hold in solution at boiling point at once the whole quantity of
anthrachinone with its soluble impurities, which is to be operated on and in then
allowing the anthrachinone to crystallize out from the solvent on cooling. It is
well known that in this process the impurities above mentioned and more especially
the homologues of anthrachinone, remain dissolved in the solvent while the
anthrachinone itself, which is more difficultly soluble in the solvent media
mentioned, crystallizes therefrom in a state of almost chemical purity. The
technical difficulties in the way of such a process are very great. Anthrachinoue is
so very difficult to dissolve in the solvents mentioned that a manufacturer, applying
them as they have hitherto been applied that is in the way above described,
would be obliged to employ an enormous quantity of solvent. The solvent which
acts most favourably is the so called "solvent naphtha," a rectified coal tar oil
which boils at from 120° to 160° centigrade. Of this solvent it is necessary working
in the way above described to apply about 16 parts to effect the solution of one
part of anthrachinone at boiling point. The process of crystallizing from this
solvent, when conducted in the ordinary way above described is therefore suited
only for laboratory purposes, and not at all for industrial application on the large
scale, and that not only on account of the quantity of solvent, and size of the
apparatus which, would bo required in treating such quantities of impure anthira-
chinone as are usually treated at once in manufacturing establishments, but also
and chiefly on account of the large working losses in solvent which are inseparable
from the handling of such large quantities of a volatile solvent in the heat, so
that in point of fact all attempts to apply this process on the large scale have, for
the reasons assigned remained without success.
The process which I am about to describo has solved the problem of effecting not
merely the solution of the anthrachinone, and its soluble impurities with a
smaller quantity of solvent (for which if this were all that is needed, existing
processes of a similar kind might suffice) but of effecting, as the final purpose of

page_text: the process, the crystallization of the anthrachinone free from those soluble
impurities, with (and indeed by reason of) the smaller quantity of solvent, viz:
with, in the case of anthrachinones of average or ordinary impurity, from two to
three times (instead of with sixteen times) the quantity of solvent naphtha, and
with similarly diminished proportions of the other solvents. In other words this
process permits and indeed as will be explained afterwards, requires the crystal-
lization of the anthrachinone to be effected (while the soluble impurities dissolved
along with it do not crystallize) with, and by means of an adjusted quantity
amounting to no more in ordinary cases than from an eighth to a fifth of the
quantity of solvent medium which is necessary for dissolving and holding in
solution at once the whole anthrachinone which is to be crystallized, and the
whole soluble impurities from which it is to be separated by its crystallization.
The quantum of solvent employed is so adjusted to the proportion of soluble
impurities in the crude anthrachinone that while there is enough of solvent always
present to keep the impurities in solution there is not enough of solvent besides to
keep the dissolved anthrachinone in solution and the latter necessarily crystallizes,
free from the impurities. The losses in solvent medium are thus reduced to the
minimum so that the process of purifying by crystallization is practicable and
workable to profit on the large scale.
The process further, while the operations of dissolving and crystallizing are
going on, carries on simultaneously the filtration of the hot solution, so as to
separate therefrom, and that without any loss of the solvent by evaporation, the
insoluble impurities, so that the pure anthrachinone to be obtained crystallizes
from a clear filtered solution, whilst the soluble impurities remain behind in the
solution, and the insoluble on the filter. The nere filtration from insoluble
impurities might however be effected by existing processes and arrangements, but,
for the purpose of purifying anthrachinono or alizarines, such filtration is of no
technical importance per se, or except as adminicular to the obtaining of a clear
mother liquor from which crystallization may take place.
All the objects described may be conveniently attained by the employment of a
continuously working, dissolving, filtering, and crystallizing apparatus constructed
especially for the purpose which I call my anthrachinone- (or alizarine-) crystal-
lizing apparatus, and which I now proceed to describe as follows:-
:―
My said crystallizing apparatus in that form and arrangement which I prefer to
give it, consists of three principal parts, which, according to the requirements of
the operations to be carried on by means of it, can be put together into one entire
whole, or can be taken asunder into the said parts.
Figure 1, represents in transverse section an apparatus constructed according to
my present Invention.
Figures 2, 3, 4, and 5, represent in transverse section detail views of parts of an
apparatus constructed according to my present Invention.
The apparatus consists of three parts, a boiler A, surrounded by the steam
jacket D, with its inlet h, and outlet i, a filter C, and a hood or cover B, also
surrounded by a jacket m, the space between which and the cover is filled with
any suitable non-conducting material I. These three parts are so formed as to be
easily taken apart, and put together again. At the bottom of the boiler A, there
is an opening to which is attached an outlet pipe E, into which is fitted the stop-
cock c, by which it may be opened or closed. In order that this outlet should not
get blocked or choked up, during the crystallization it is provided with a conical
plug or stopper v, which is fitted to the end of a handle whose upper end extends
above the liquid with which the boiler A, may be charged. Around the inside and
at the upper part of the boiler A, are fitted at intervals the angle iron brackets b,
upon which the filter C, rests when placed in position. The filter C, consists of a
holder or receiver formed with cylindrical sides and at its bottom with a perforated
disc s, which is covered with the filter cloth 7. The hood or cover B, when placed
in position fits loosely over the filter C, so as to leave a space between the two,
which allows the vapours passing in between the angle iron brackets b, a free

page_text: passage therethrough to the top of the filter C. Around the outside of the upper
part of the boiler A, there is a channel a, into which the lower edge of the hood or
cover B, when placed in position is dropped. This channel is filled with a suitable
liquid to form a hydraulic seal or lute between the boiler A, and the hood or
cover B. At the upper part, and at the inside of the hood or cover B, there is the
coil of pipe k, through which the refrigerating water flows, passing in at g, and out
nt f, into the tank d, which is formed by the sides of the hood or cover B, extending
up beyond its roof. The water from this tank d, flows away through the spout or
outlet f¹.
In the centre of the tank d, and to the top of the roof of the hood or cover B, is
fitted the cast iron framing S, in which is formed a gland through which the
handle 2, of the distributor passes and the necessary holes for the passage of the
pipes g, and f, therethrough, and outlets e, for the escape of any superfluous steam
having corresponding holes formed in the roof of the hood or covor B. The
distributor consists of a perforated disc G, to the underside of which is fastened &
strong wire or scraper o, both of which are fixed to the lower end of the handles,
which passes to the outside through the gland herein before mentioned, and is
terminated with a lever handle and swivel attachment. This distributor is at
periods moved so as to spread the mass lying in the filter, and prevents the con-
densed solvent dropping from the cooling coil k, from dissolving channels through
the mass to be treated through which it might run directly back into the boiler A,
without having effected that which it was intended to perform. The distributor
also provides the means of ascertaining the height of the contents of the filter C.
The sides of the hood or cover B, being formed (as hereinbefore mentioned) sur-
rounded by the non-conducting material I, prevents the condensation of the
ascending vapours of the solvent medium thereon.
When the apparatus above described is put in order and put together and the
solvent is heated up to the boiling point by the steam in the jacket of the boiler
the vapours of the solvent ascend through the eight openings, or interspaces
between the eight brackets, on which the receiver rests and through the interspaces
between the receiver, the boiler and the hood, and find their way upwards to the
refrigerating surfaces in the upper part of the hood condense there and fall as hot
liquid on the contents of the receiver. The hot liquid charges itself with soluble
constituents of the substance, with which the receiver has been filled, passes
through the filter, and gets back again into the lower part of the boiler, in order to
commence its work over again, and so on until the crystallization which is taking
place in the lower part of the boiler and which will be explained more fully
afterwards, is finished. When this is the case and when we have got the length of
emptying the boiler, the hood is lifted up and the receiver with the filter and filter-
residues is lifted from its position on the brackets in the upper part of the boiler
to the side. This can be done with the greatest case without the filtered substances
in the lower part of the boiler being contaminated in doing so by smearing about
or spilling the filter residues over or upon them, a result which of course would
defeat the aim of the whole operation. This ready handling of all parts of the
apparatus is due to the circumstance that the connection between the boiler and
hood is arranged so as to be just about the middle of the apparatus when it is all put
together. When the hood is lifted up, the receiver stands quite free and accessible
and the handle of the solid plug in the bottom of the boiler is also accessible, which
under a different arrangement could not be withdrawn and replaced with the
filter plug. This arrangement also permits the easy removal of the crystals from
the boiler even in an apparatus of large size, while an arrangement which had the
lute higher, would make their removal inconvenient or impossible.
The heating of the solvent may be effected instead of by high pressure steam, by
superheated steam, by direct fire heat, by oil baths, metal baths, baths of various salts
and other contrivances, and the apparatus may be arranged to suit these variations.
In order to crystallize anthrachinone (and substantially the same procedure is
followed as aftermentioned in order to crystallize alizarines), I proceed as follows:-

page_text: The impure anthrachinone which has been treated with concentrated sulphuric
acid is thoroughly intermixed and stirred up with from 1% to 2% of dissolved
calcined soda. It is then perfectly dried and then brought into the receiver, over
whose filter bottom a filtering cloth is stretched. Into the under part of the
apparatus (the boiler or caldron) there is introduced the properly adjusted quantity
of the solvent medium. If for instance solvent naphtha be used, a weight of
naphtha twice or three times the weight of the quantity of ordinarily impure
anthrachinone to be prepared is introduced into the boiler. The receiver is placed
on the eight angle-iron ledges in the upper part of the boiler, and the hood is sunk
in the hydraulic seal. The solvent medium is heated up to its boiling point. The
vapours ascend up to the cooling surfaces in the upperinost part of the apparatus,
and fall in the form of a condensed hot liquid on the anthrachinone, dissolve it
along with its soluble impurities and finally get back again in the form of a filtered
saturated solution into the lower part of the apparatus (the boiler). On account
of the evaporation of the solvent medium which is in this way continually going
on from the boiler, the dissolved anthrachinone, which is much more difficult of
solution than its impurities, finds too little of the solvent in the boiler to hold it in
solution there and it therefore crystallizes out in the boiler, while the soluble
impurities which, because they are much more soluble than anthrachinone and
therefore require much less of the solvent, remain dissolved, and the insolublo
impurities have been retained by the filter.
Let it be supposed for the sake of illustration that I have a certain quantity of
ordinarily impure anthrachinone, say 20 lbs. to purify (although this is only a very
small quantity in comparison with the quantities which will ordinarily be treated
in a single charge in actual practice). Instead of throwing the whole
20 lbs. into 320 lbs. of solvent naphtha, and applying heat, and then allowing
the liquor to cool, and crystallization of the anthrachinone to go on partly by reason
of the cooling, and partly by reason of evaporation of part of the solvent, I
employ only a small quantity of the solvent (for instance 50 lbs.) quite insulficient to
dissolve even at the boiling point the whole 20 lbs. of anthrachinone and its soluble
impurities at once. I make the solvent ascend in vapours to the cooling flat of
the apparatus, and return as hot liquor through the 20 lbs. of impure
anthrachinone. One molecule, or portion of the solvent takes up a charge of say
methyl-anthrachinone or any other soluble impurity, while another molecule of
the solvent saturates itself with anthrachinone. Both molecules return to the
boiler, where, from the limited and adjusted quantity of solvent originally
employed and the continuous process of volatilization kept up, the anthrachinoue
is readily deposited as a crystal, while the much more soluble impurity still finds
solvent enough to remain in solution. The molecule of solvent which has
deposited its anthrachinone is again volatilized and repeats its work, it may be
many times over. If we suppose for sake of illustration that this moleculo of
solvent always charges itself with anthrachinone in each of its journeys up and
down the apparatus, it is obvious that it will in this way continue to travel round
its cycle, carrying down repeated charges of anthrachinone, each time depositing
its charge, and returning for a further charge until the whole anthrachinone has
been finally carried down. On the other hand a molecule of solvent which has
taken up (let me say) methyl-anthrachinone, may be supposed to hold it without
ever afterwards depositing it in the apparatus. This appears to me to be the
correct theory of my process and it suggests the observation that the quantity of
solvent required in my process may vary with the proportion of soluble impurities
in the anthrachinone, seeing there must always, in order to prevent the soluble
impurities from crystallizing out along with the anthrachinone, be such an amount of
solvent present as will not fail to hold the whole soluble impurities in solution at
But it is necessary to avoid having in the apparatus, besides that quantity
of solvent required to hold in solution at once the whole soluble impurities, also
such a further quantity of solvent as would be sufficient to retain in solution also
the anthrachinone which at any given monent has gone into solution. The
once.

page_text: crystallization of the anthrachinone depends on the fact that there is always
such a deficiency of solvent in the boiler as will, as far as can be adjusted,
prevent the amount of anthrachinone which has been carried down into it
from being retained in solution in the boiler, while there is enough to keep
the impurities in solution. I give this theory of my process as what
believe to
be its true theory, but I observe that this part of my Invention is the process itself,
as applied to anthrachinone and alizarines, whatever be the proper explanation of
how it attains its result. With anthrachinones of average or ordinary impurity and
of which the nature of the impurities is known, the proportions of solvent given will
be very near the mark of what is required. If we have to deal with exceptional
specimens, a rough preliminary analysis of the anthrachinone will readily indicato to
what extent it may be necessary to increase (or it may be to diminish) the allowance
of solvent to what is required to hold in solution the whole soluble impurities
without having such an excess as would also retain in solution the anthrachinone
which has been brought down into the boiler. Two points are to be attended to
in the adjustment of the quantity of solvent, first and mainly, that there shall be
such an amount employed that the soluble impurities shall remain constantly in
solution and never crystallize, and secondly, that the surplus solvent beyond this
amount shall be kept at a minimum point, so that there shall be a constant
depositation of anthrachinone crystals going on, and that the quantity of
anthrachinone from time to time, retained in solution shall always be as little as
possible.
When all the soluble contents of the mass on the filter have been dissolved (a
point which may be ascertained by the sinking down of the shaft of the distributor
which is turned round from time to time), the hood is drawn up out of the
hydraulic seal, the receiver is then lifted out from its resting place on the angle
iron ledge, the conical plug, or bung in the bottom of the boiler is replaced by a
hollow filtering plug perforated with holes, and the liquid which is found in the
lower part of the apparatus (the boiler) is allowed to run out through the escape
cock into a reservoir and that at the temperature at which the impurities still
remain in solution (say about 80° centigrade). The crystals of anthrachinone
which are left behind in the boiler are taken out, and then freed, by evaporation,
from the remains of the solvent which adhere to them, and are dried, and they are
then very nearly chemically pure anthrachinone.
The liquid which has been allowed to flow down into the reservoir may, after
cooling (during which crystals of inferior purity separate out) be again applied in
the apparatus for a new operation.
The crystals, which have separated out as the liquor cooled in the reservoir, aro
collected till they amount to a large enough charge, and they are then treated over
again in the apparatus as herein before described, and the crystals which separate out
in the boiler in the course of this second crystallization are found to be nearly
chemically pure anthrachinone.
The crystals which have separated out from the liquor run off into the reservoir
after the second crystallization above mentioned, and of which the quantity is of
course much smaller than in the working of the original anthrachinone, are collected
and treated again in the apparatus as herein before described. The crystals which
separate out in the apparatus in this third crystallization are as a rule also nearly
chemically pure anthrachinone. If not, they are reserved for and added to another
charge, and then give almost chemically pure anthrachinone.
The liquor which has been allowed to flow out after the first crystallization, or
into the reservoir as above mentioned may, as I have stated, be applied without
any special treatment a second time as a solvent medium. But the liquor which
has been used twice is subjected to distillation in order to recover the solvent
medium in a state of purity and the crystalline mass, which has separated out in
the reservoir from any third charge, may also be distilled along with it. The
residue left by the distillation process is run off, filtered on cooling, and subjected
o hydraulic pressure. The filtrate is distilled and from the solid cakes from which

page_text: the liquor has been expressed there may still be recovered by treatment in the
apparatus a small quantity of anthrachinone.
The insoluble residues which remain on the filter in the apparatus are subjected
to hydraulic pressure and sublimed with steam. The sublimate, treated in the
apparatus also yields anthrachinone, alinost chemically pure.
If one prefers it, the crude anthrachinone, before its treatment with sulphuric
acid, may be submitted to the continuous crystallization process in the apparatus
and afterwards treated with sulphuric acid, whereby there will be an important
saving in the latter. Or again, the crude anthrachinone may, without the sulphuric
acid treatment be submitted to continuous crystallization, in which case the non-
oxidized anthrachinone may be recovered again from the mother liquors. I do not
however prefer this method of treatment to that first described, because the method
first described is surer in its operation.
A further application of this Invention deals with the purification of impure
alizarines, impure purpurines, and all impure dyestuffs or colouring matters com-
prehended under the general commercial designation of "alizarines" and particularly
such as may have miscarried or turned out failures in the process of manufacture
and which are not to be freed from their injurious impurities by any other paying
method. If these colouring matters, well dried, are subjected in the same apparatus
as is herein before described to a crystallization from solvent naphtha or other
suitable solvent medium, they may be recovered in extraordinary purity, all the
injurious impurities being perfectly separated out.
Extraction processes and arrangements of apparatus somewhat similar to those
herein before described have been previously applied to the extraction, by means of
volatile solvents, of the soluble contents of various bodies, as for example the
extraction of oil from seeds by sulphide of carbon, of the fats and oils from dirty
wool and the like.-I wish to point out that my process differs from such extraction
processes in this, that, although in common with other processes I avail myself of
the continuous or cyclical evaporation and liquefaction, and re-evaporation and re-
liquefaction of volatile solvents, and do so partly with that which is their sole
object, viz-the reduction of the quantum and the expense of solvent required.-
My process is one which, while it dissolves and filters, is characteristically a process
of purification by crystallization, a process for purifying anthrachinone and
alizarines by causing them to crystallize out from a quantity of solvent so
diminished and so adjusted in its diminution, that while the soluble impurities are
kept in solution the anthrachinone and alizarine crystallizes out, the anthrachinone
and alizarine being further chemical substances to which notwithstanding many
attempts, no process of purification by crystallizing from volatile solvents has ever
been successfully applied on the industrial scale before. In the ordinary processes
of extraction, although as in my process, all the soluble matter is, or may be,
dissolved and filtered from the insolubles, there is not, as there is in my process,
any separation of one part of the dissolved matter from another and without this
last result my process would be practically of no use.-It is however not merely
that in my process such a separation is effected, but that it is effected by the
diminution in the quantity of solvent being so adjusted to the relative proportions
of anthrachinone or alizarine and of soluble impurities in the impure substance to
be treated that while the anthrachinone or alizarine must crystallize, the soluble
impurities shall be retained in solution and so separated from the crystals; and the
separation of the filtered solution by means of this adjustment into the pure
substance and the impurities is the most important differentia of my process.
My apparatus is characteristically a crystallizing apparatus although for the
purpose of leading up to the crystallization, it also dissolves and filters.—The
general arrangement and details of my apparatus are specially devised partly with
a view to the requirements of a process for treating on an industrial scale the
special substances which I treat, and partly with a view to the removal of the
crystallized substances in a clean and easy way and without danger to workmen.-—
Thus, I provide for the ascent of the vapours by lateral passages as described, and

page_text: not through the filter floor of the receiver, because in the treatment of anthra-
chinone and alizarines on the industrial scale, the floor would require to be heaped
too high with dense materials for the vapours to penetrate the mass, nor could
they be made to ascend through between the filter floor and the side walls of the
receiver because the filter cloth, which is a very essential addition to the perforated
floor, must be tightly packed to the walls otherwise it would be no adequate filter
for anthrachinone or alizarines, nor could the vapours in my apparatus be made to
ascend through a central pipe, such as that in Hänig's extraction apparatus,-such
central pipe being replaced in my apparatus by the distributor, or scraper, the
necessity of which has been already explained.-To carry the vapours up through
some kind of central pipe might be possible but it would create serious if not
insuperable difficulties in those stages of my process which require to be gone
through after the crystallization is finished since the operations which the presence
of such a pipe would involve in emptying the apparatus would create serious risk
of contaminating the crystals with the residue of filtration.-The arrangements for
having an outlet pipe and cock and a solid plug, and for replacing the solid plug
at the proper time by a hollow perforated filter plug, aro naturally not found in
the ordinary extraction apparatus which do not contemplate any separation of
the dissolved substance into further sub-divisions.-But it is highly convenient in
my apparatus to have an easy arrangement for such separation of the crystals, from
the mother liquors, and the plugs are respectively necessary to prevent the exit
passage and outlet cock from being stopped up with crystals during the crystal-
lization, and to separate the crystals from their mother liquors afterwards.-In
such an apparatus again, as that of Hänig for example it would be practically
impossible on account of the depth of the apparatus to have and manage such
plugs without risk of danger to the workmen from the naphtha vapours.-These
difficulties of detail in the apparatus which are incidental to my process as one for
crystallizing the particular substances which I treat I have obviated by making
the vapours pass up through said lateral spaces, by the providing of the exit
passage and the stop cock and plugs, and by arranging the apparatus in parts and
so that it can be taken asunder readily in or near the middle so that the filter and
receiver can be easily removed, and the insoluble impurities taken out without
danger of contaminating the crystals thereby, while the boiler and its interior and
contents at the same tino become accessible for changing the plugs and removing
the crystals readily and without danger to the workmen.-It would be possible,
although inconvenient, to dispense with these plugs, and with the outlet passage
and cock, in which case however the liquid contents of the boiler must be separated
from the crystals in some less direct and ready manner as by filtration and
pressure. It would be possible to dispense with steam jacketing of the boiler
by substituting other arrangements for heating-The novelty of my apparatus
consists firstly in the separate parts or sub-combinations following, viz: (a) The
arrangement of the boiler in connection with the receiver and filter and the hood,
the hood and the receiver being both seated in manner described with their lower
rim on the upper rim of the boiler about the middle of the whole apparatus, so
that the hood and received can be easily and without danger removed along with
the filter and filter residues from above the boiler, and the boiler and its contents
made easily and without danger accessible; and (b) the arrangement of the boiler
filter, receiver, and hood, in connection with the distributor and consequent
arrangements of lateral passages necessitated by the distributor and that with or
without the outlet passage, cock, and plugs and also finally (c) in the entire
combination or whole formed by the union of the said separate parts or sub-
combinations.―
Having now described and particularly ascertained the nature of my said
Invention and the system, mode, or manner, in or under which the same is, or may
be carried into practice, I wish it to be understood that 1 do not confine myself to
the process in combination with the apparatus herein before described as the process
may be effectually carried out with other apparatus without departure froin the

page_text: nature of my Invention, but on the other hand, I disclaim so called extracting
apparatus in general, as I am well aware that similar apparatus have already been
in use, and publicly described previous to my application, but what I consider to
be novel and original and therefore claim as the Invention secured to me by the
herein before in part recited Letters Patent is :-
First. The process and method of purifying anthrachinone and alizarines, and
other substances by crystallization from volatile solvent media effected in the
manner as hereinbefore described.
Second. An extracting or crystallizing apparatus consisting in boiler A, in
combination with the filter C, and the hood or cover B, the two last mentioned
parts being both seated with their lower rim on the upper rim of the boiler A, so
that they can be easily and without danger removed with the filter residues,
whereby the boiler A, and its contents become accessible, substantially as, and for
the purpose set forth.
Third.— In extracting and crystallizing apparatus, the distributor, with or without
the conical plug or stopper v, substantially as and for the purpose set forth.
Fourth. The entire combination or whole consisting of the union of the separato
parts or sub-combinations claimed in the preceding second and third claiming
clauses.