Improvements in Screening or Filtering Apparatus.
Year: 1898

page_text: Date of Application, 22nd Mar., 1898-Accepted, 11th Feb., 1899
COMPLETE SPECIFICATION.
Improvements in Screening or Filtering Apparatus.
We, HERMAN EDWARD STURCKE, of No. 281, Pearl Street, in the City of New
York, County and State of New York, C.S.A., Chemist, and WILLIAM FREDERICK
JOBBINS, of Aurora, in the County of Kane and State of Illinois, United States of
America, Manufacturing Chemist, do hereby declare the nature of this invention,
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
The object of the invention is to provide an improved type of screening or filtering
apparatus which will be especially applicable for use in connection with the processes
recited in our British Patent No. 6,987 of 1898, but which also may be used in
other arts.
Our improved screening or filtering apparatus is of especial advantage in con-
nection with the processes indicated in said patent, since by its use screens of
very fine mesh may be employed, which cannot become clogged and which do not
sustain any of the weight of the material, so that the interstices of the screens
cannot become enlarged.
In order that the invention may be better understood, attention is directed to
the accompanying drawings forming a part of this specification, and in which
Figure 1 is a longitudinal section of the preferred form of screening or filtering
apparatus; Figure 2 a cross-section on the line 2-2 of Figure 1; Figure 3 a
vertical section of a modified form of screening apparatus; Figure 4 a section on
the line 44 of Figure 3; and Figures 5 and 6 further modifications of the screen-
ing or filtering apparatus.
Referring to these drawings, 1 represents a suitable receptacle or tank, having
preferably a rounded bottom and vertical ends, the said tank being conveniently
made of sheet iron. Mounted within this tank is a stationary suction pipe 2,
which leads to a suitable suction pump, or which itself may constitute a siphon to
produce the necessary suction. 3 is a sleeve mounted on the pipe 2 and passing
through a suitable packing box 4 in one wall of the tank 1. The said sleeve carries
a disk 5 within the tank 6 is a corresponding disk mounted on the suction pipe 2
near the other wall of the tank. Connecting the disks 5 and 6 are suitable stay-
rods or braces 7, which may be conveniently made of light T-irons, so that a
sufficiently strong framework will be obtained. Carried upon the braces 7 is the
screen 8 of the proper mesh. In order to provide for the desired agitation of the
material, it is preferable to make use of a plurality of paddles or wings 9, which
to the
otherwise secured
braces 7. In order to
may be bolted or
strengthen the device, suitable supports or spokes 10 may extend at
desired points between the braces 7 and collars 11, turning upon the suction

page_text: in
pipe 2. Preferably the paddles or wings 9 are curved, as shown, and extend at
an angle to the diameter of the screen, so as not only to more vigorously agitate the
liquid, but also to effectively aerate the same, it being obvious that when the
screen is rotated in the direction indicated by the arrow, a small amount of air will
be caught beneath each paddle or wing and carried down into the liquid. This
feature of aeration is important with some liquids to which a supply of air is to
be furnished. For instance, when the screening or filtering apparatus is employed
separating carbonate of lime from a milk of carbonate obtained
by adding water to the precipitate obtained in the manufacture of
caustic lime, a small quantity of caustic will appear as an impurity in
the precipitate. This caustic lime may be converted into carbonate by adding car-
bonic acid to the liquid. In practice it has been found that when a sufficient
amount of air is introduced into the liquid during the screening operation, the
carbonic acid therein will be sufficient to convert the caustic lime present into
carbonate, and therefore result in an increased capacity of the apparatus. In order
to rotate the screen, a driving pulley 12 is used, which is keyed to the sleeve 3 on
the outside of the tank 1, and to which power may be applied. The liquid carrying
the particles in solution or precipitation, is introduced into the tank through a
suitable pipe 13 having a valve 14 therein, and the heavier particles rejected by
the screen may be removed from the tank by a valved draw-off pipe 15 arranged
at the bottom of the tank or receptacle. Instead of employing a rotating screen, as
explained, a stationary screen may be used, as shown in Figures 3 to 6 inclusive.
In Figure 3, a tank or receptacle 16 substantially cylindrical in form is used, and
depended therein is a screen 17 in the shape of a truncated cone. This screen is
secured within the receptacle or tank 16 by being flanged outwardly at its upper
end and being clamped in place by an annular ring 18. In this form, a suction
pipe 19 is introduced within the screen 17, its lower end being arranged preferably
near the bottom of the screen. The liquid carrying the particles in suspension or
precipitation is introduced into the tank 16 through a pipe 13, as in Figure 1, and
the coarser particles rejected by the screen may be removed through a corresponding
valved draw-off pipe 15. In the form of device shown, provision is made for the
agitation of the liquid by means of stirring arms 20 working between the screen 17
and the interior of the tank 16 and carried on a shaft 21 to which power is applied.
Said shaft passes through a packing-box 22 in the bottom of the screen and by
which leakage will be prevented. The form of device illustrated in Figure 5 is
similar to that shown in Figures 3 and 4, except that instead of the stirring arms 20
for agitating the material, an ordinary propeller 23 is used for the purpose, and
instead of extending the suction pipe 19 downwardly within the screen, it is con-
nected to the lower end of the screen and is passed through the walls of the reeep-
tacle or tank. In Figure 6 a form of device similar to that shown in Figures 3
and is illustrated, except that the suction pipe passes from the bottom of the
screen down through the shaft of the stirring arms, as in some instances may be
desirable. In all the forms of the device shown, the suction pipe within the
screen is preferably perforated with numerous small holes, so that a very powerful
suction may be obtained. By arranging a screening or filtering apparatus as
shown, comprising in all instances a tank with a screen therein, said screen being
interposed between the suction and entrance pipes, a screening apparatus is obtained
which is especially adapted for use in the filtration of very fine particles held in
suspension or precipitation in a liquid, for the reason that the weight of such par-
ticles is in every instance removed from the screen, so that the interstices thereof
cannot be enlarged or distorted by such weight. Such construction also largely
removes the possibility of the screen becoming clogged, which objection is entirely
overcome by employing suitable means for keeping the liquid in const int agitation.
With the forms of device illustrated, and particularly with that form shown in
Figures 1 and 2, provision is made during the operation for an effective aeration

page_text: of the solution, which is of importance with materials to which a supply of air
should be added.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is:-
1. An improved screening or filtering apparatus comprising a receiving tank or
receptacle, an admission pipe for admitting a solution carrying the particles to be
screened or filtered in solution or precipitation, a suction pipe, and a screen inter-
posed between said suction pipe and the admission pipe, substantially as set forth.
2. An improved screening or filtering apparatus comprising a receiving tank or
receptacle, an admission pipe for admitting a solution carrying the particles to
be screened or filtered in solution or precipitation, a suction pipe, a screen inter-
posed between said suction pipe and the admission pipe, and a draw-off pipe for
removing the coarser particles rejected by said screen, substantially as set forth.
3. An improved screening or filtering apparatus comprising a receiving tank or
receptacle, an admission pipe for admitting a solution carrying the particles to
be screened or filtered in solution or precipitation, a suction pipe, a screen inter-
posed between said suction pipe and the admission pipe, and means for keeping
the liquid in agitation, substantially as set forth.
4. An improved screening or filtering apparatus comprising a receiving tank or
receptacle, an admission pipe for admitting a solution carrying the particles to be
screened or filtered in solution or precipitation, a suction pipe, a screen interposed
between said suction pipe and the admission pipe, and stirring arms or wings for
keeping the liquid in agitation, substantially as set forth.
5. An improved screening or filtering apparatus comprising a receiving tank or
receptacle, an admission pipe for admitting a solution carrying the particles to be
screened or filtered in solution or precipitation, a suction pipe, a screen interposed
between said suction pipe and the admission pipe, stirring arms or wings for keep-
ing the liquid in agitation, and a draw-off pipe for removing the coarser particles
rejected by the screen, substantially as set forth.
6. An improved screening or filtering apparatus comprising a receiving tank or
receptacle, an admission pipe for admitting a solution carrying the particles to be
screened or filtered in solution or precipitation, a suction pipe, a screen interposed
between said suction pipe and the admission pipe, and means for aerating the
liquid substantially as set forth.
7. An improved screening or filtering apparatus comprising a receiving tank or
receptacle, an admission pipe for admitting a solution carrying the particles to be
screened or filtered in solution or precipitation, a suction pipe, a screen interposed
between said suction pipe and the admission pipe, and means for aerating and
simultaneously agitating the liquid, substantially as set forth.
8. An improved screening or filtering apparatus comprising a tank or receptacle,
a rotating screen in said receptacle, a suction pipe opening within said screen, and
an admission pipe outside of said screen for admitting into the receptacle a liquid
carrving in suspension or precipitation the particles to be screened or filtered, sub-
stantially as set forth.
9. An improved screening or filtering apparatus comprising a tank or receptacle,
a rotating screen in said receptacle, a suction pipe opening within said screen, an
admission pipe outside of said screen for admitting into the receptacle a liquid
carrying in suspension or precipitation the particles to be screened or filtered, and
a valved draw-off pipe for removing the coarser particles rejected by the screen,
substantially as set forth.
10. An improved screening or filtering apparatus comprising a tank or receptacle,
a rotating screen in said receptacle, a suction pipe opening within said screen, an
admission pipe outside of said screen for admitting int the receptacle a liquid
carrying in suspension or precipitation the particles to be screened or filtered, and
paddles or wings carried by said screen, substantially as set forth.

page_text: 11. An improved screening or filtering apparatus comprising a tank or receptacle,
a rotating screen in said receptacle, a suction pipe opening within said screen, an
admission pipe outside of said screen for admitting into the receptacle a liquid
carrying in suspension or precipitation the particles to be screened or filtered, and
curved paddles or wings carried by said screen, substantially as set forth.
Dated this 25th day of November
1808 מ
HERMAN EDWARD STURCKE,
WILLIAM FREDERICK JOBBINS.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicants.
HERMAN EDWARD STURCKE,
WILLIAM FREDERICK JOBBINS.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicants.

page_text: Date of Application, 22nd Mar., 1898-Accepted, 11th Feb., 1899
Improved Processes of and Apparatus for Obtaining Amorphous Car-
bonate of Lime from Caustic Soda or Caustic Potash Residues and
for Obtaining Sulphate of Lime from such Residues.
We, HERMAN EDWARD STURCKE, of No. 284, Pearl Street, in the City of New
York, County and State of New York, United States of America, Chemist, and
WILLIAM FREDERICK JOBBINS, of Aurora, in the County of Kane and State of
Illinois, United States of America, Manufacturing Chemist, do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:-
In the manufacture of caustic soda or caustic potash by treating soda ash or
potash solutions with caustic lime, a worthless residue is obtained which is a
source of annoyance to the manufacturers. This residue consists principally of
carbonate of lime, caustic or hydrated lime and impurities. The prime object of
the invention is to obtain from these residues a novel article of commerce, namely,
substantially pure carbonate of lime of microscopically small, extremely finely
divided, substantially uniform particles or loose aggregates thereof capable when
dried of being reduced to an impalpable powder. A further object is to provide a
process by which this product will be obtained.
A further object of the invention is the production of a process by which the
said carbonate of lime obtained from caustic soda or caustic potash residues may
be treated for obtaining a substantially pure sulphate of lime, suitable for use as a
paper filler, and for other purposes to which sulphate of lime is now applied.
A further object of the invention is to provide a process by which chemically
pure sulphate of lime may be obtained from such residues, and which will be
capable of many industrial uses, such, for instance, as a paper filler.
A further object of the invention is to provide suitable apparatus for carrying
out the processes of treating the caustic soda or caustic potash residues for obtaining
carbonate of lime and for treating the carbonate of lime for obtaining sulphate of
lime therefrom, as stated.
The essential discovery which has been made in connection with the invention
is that the carbonate of lime obtained in the caustic soda or caustic potash residues
referred to is capable of being practically entirely separated from all insoluble
impurities contained in such residues, such as coal, sand, dirt, etc., by mechanical
means, such as by screening, floating, jigging, or bolting, either in the dry form
or when mixed with water to form a milk of carbonate. In this way the carbonate
of lime is separated from such insoluble impurities, but it generally contains
varying quantities of caustic lime, which may be converted into carbonate of lime,
either before or after the mechanical separation, by treatment with carbonic
acid, or else which may be dissolved by a suitable acid, as will be explained. If
however, the caustic lime contained in the carbonate is of small quantity, it will
he dissolved in the relatively large excess of water used, and it will be removed in
the subsequent separation of the water or liquid from the solid insoluble carbonate
of lime, as will be explained; so that in the latter case, treatment with carbonic

page_text: acid or any other suitable acid will not be necessary. It has been found, moreover,
that even if relatively large traces of caustic lime remain with the carbonate
of lime, the final drying and exposure of the carbonate of lime to atmospheric air
will transform the caustic lime into carbonate of lime; so that it will be under-
stood that the chemical treatment of the carbonate of lime after its mechanical
separation from the impurities, or of the caustic soda or caustic
potash residue prior to such mechanical separation, is not an absolute
essential to the success of the process, the essence of which consists,
as stated, in the separation of carbonate of limo from the several
insoluble impurities found in caustic soda or caustic potash residues by mechanical
means, such as by screening, floating, jigging, or bolting, either in dry form or
in the presence of an excess of water.
In carrying out the improved process, the preferable procedure is substantially
as follows: The lime residue obtained from the manufacture of caustic soda or
caustic potash, when such residue is in the form of more or less dried cakes, or in
a more or less consistent paste or mush, is mixed with a large excess of water
and stirred up therewith until a relatively thin milk of carbonate of lime results.
During this mixing or stirring, there is preferably added either a sufficient quantity
of a liquid acid (such as hydrochloric acid, acetic acid, sulphuric acid. or sulphurous
acid) to dissolve the intermixed caustic or hydrated lime, or else sufficient carbonic
acid (in gas form or otherwise, such as that found in atmospheric air) is injected
into or added with the milk of carbonate of lime to transform such caustic or
hydrated lime into carbonate of lime. It is, however, not absolutely necessary
to remove all the caustic or hydrated lime by a liquid acid, or to transform such
caustic lime by carbonic acid into carbonate, because when the process of manu-
facturing caustic soda from soda ash with caustic lime is properly carried out, the
lime residue contains but relatively little caustic lime, and if such is the case,
the small amount is readily dissolved in the large excess of water and removed in
the subsequent separation of the water or liquid from the insoluble carbonate of
lime. It is, therefore, frequently only necessary to mix the lime residue with
water in order to dissolve the caustic lime; and even, as stated in the introductory
part of this specification, if relatively large traces of caustic lime remain with the
carbonate of lime, the final drying and exposure of the carbonate to the atmo-
spheric air will transform the caustic into carbonate. Hence, as stated, it is not
necessary to remove the caustic lime or to transform it by the chemical means
indicated. The thin milk of carbonate of lime, whether the same has been treated
for the dissolution or transformation of caustic as explained or not, is now sub-
jected to a mechanical treatment to effect the separation of the carbonate from
practically all other insoluble solid impurities, and in this mechanical separation lies
the essentially novel feature of this part of the invention.
The mechanical treatment of the milk of carbonate of lime may be effected by
screening and sitting, or by floating, or by a combination of both, or by jigging,
or by bolting, or by any other of the mechanical manipulations by which sub-
stances of different degrees of fineness or of different specific gravities are separated
one from the other. Preferably, however, this separation is effected by screening,
since it has been found that the carbonate of lime obtained from the residue
resulting from the manufacture of caustic soda when intimately mixed with
water is in the form of extremely fine particles which are much finer than the
greater portion of the solid impurities usually accompanying the carbonate of
lime in the residue. This carbonate of lime can readily be passed through a wire
screen or gauze of 100, 150 and even 200 meshes to the linear inch. It is, there-
fore, only necessary to pass the thin milk of carbonate of lime through a very fine
screen in order to retain and separate the larger portion of the solid impurities.
In practice, it has been found that it is advantageous to pass the thin milk of
carbonate of lime through two or more screens of successively increasing fineness
of mesh, the first screen being relatively coarse, for instance 10 meshes to the linear
inch, the next screen being somewhat finer, for instance 100 meshes to the

page_text: linear inch, and the last screen being very fine, for instance 150 to 200 meshes to
the linear inch. When a plurality of screens is used, the first screens will retain
the bulk of the coarser particles, thereby avoiding clogging up of the last or finest
screen. By employing a special form of screen, which will be subsequently
described herein, the possibility of clogging thereof is reduced to a minimum,
while at the same time the weight of the material is removed from the screen, so
that the interstices thereof cannot be distorted by such weight. When the carbonate
of lime is passed through screens of the proper mesh, 95% or more of the im-
purities are separated from the carbonate. While it is considered preferable
to employ screens of the novel type in carrying out the invention, the form of
screen is not absolutely essential to the success of the operation, it being possible
to use stationary or rocking, flat, horizontal, or slightly inclined screens, with or
without brushes cooperating with the same, or they may be horizontal or vertical
revolving cylinders, with or without such brushes.
The thin milk of carbonate of lime, after passing the screens, holds in suspen-
sion practically only pure carbonate, and it is run into a reservoir if necessary,
from which, or directly from the screens, it passes into settling tanks or onto a
vacuum filter or through a filter press by means of which the solid carbonate of
lime will be separated from the bulk of the water and the impurities dissolved
therein. Washing with water will remove the last traces of soluble impurities
in the carbonate. It is preferable to run the milk of carbonate of lime from the
screen or other mechanical separators into a reservoir provided with a mechanical
stirrer, and from there into a vacuum filter of ordinary form, from which the
carbonate of lime as a more or less dry cake is removed and dried, either by ex-
posure to the air or in a suitable dryer. The resulting dried material will be
substantially
carbonate of lime in
pure
a
of either
white powder, or in the form of extremely friable lumps. The carbonate
of lime which will be obtained by this process will, as stated, be adapted
for use as whiting, Paris white, gilders' white, etc. Moreover, it forms a basis
for the manufacture of numerous lime salts. For instance, by dissolving the pure
carbonate of lime in the proper acid, solutions of pure lime acetate, lime sulphite,
or bisulphite are formed, which require only concentration and crystallization to
obtain the pure lime salts in dry form. To obtain these lime salts, it is not neces-
sary that the carbonate of lime be in dry form, since the thin milk of carbonate
of lime coming from the screens may be directly treated with acetic or sulphurous
acid, the resulting solution being concentrated as stated.
the form
fine
The carbonate of lime which is obtained by the process previously outlined may
be subjected to a further treatment for obtaining substantially pure sulphate of
lime therefrom, and this constitutes a further or supplemental part of the present
invention. Preferably, however, the carbonate is subjected, not in the form of
a dry powder or friable lumps, but in the form of the thin milk of carbonate
after the same has passed the mechanical separators, such, for instance, as the
screens referred to. In this form, the milk is treated with a dilute solution of
sulphuric acid, which converts the carbonate of lime into pure sulphate of lime,
which latter is filtered off and subsequently dried. In the manufacture of sulphate
of lime, there is no necessity of removing any caustic lime which may be present,
since the addition of the sulphuric acid solution converts both the carbonate and
the caustic of lime into sulphate. This addition of sulphuric acid is preferably
effected in a tank, into which the milk of carbonate is passed after leaving the
screens or other mechanical separators. The sulphate of lime is preferably
separated from the liquid in a vacuum filter or in a filter press, and the resulting
cakes are either suitably dried or are sold in the moist or paste form. This sulphate
of lime is well adapted for use as a paper filler or for other purposes to which lime
sulphate is now applied.
Instead of subjecting the carbonate of lime obtained as a precipitate in the
manufacture of caustic soda or caustic potash to a mechanical separation after the
addition thereto of an excess of water to form a suitable milk of carbonate of lime,

page_text: it will be possible to effect a sufficiently thorough purification of the raw materials
before the same are brought together in the converting kettle as to result in the
production of a practically pure carbonate of lime as a precipitate. In order to
purify the alkali carbonate, it is preferably used in the form of a clarified, filtered
solution. Frequently when very pure alkali carbonate is employed, it is not
necessary to clarify and filter the solution thereof, but when inferior grades are
used, and especially such as form a waste or recovered product, as, for instance,
the black ash liquor of soda fibre (paper pulp) factories, the alkali carbonate solu-
tion is clarified by careful filtration, with or without the previous addition of such
clarifying materials as clay or alum solutions or calcium salt solutions etc. The
caustic lime is preferably purified by reducing the same to a thin milk of lime,
in which condition the lime is reduced to extremely fine particles, which by screen-
ing, floating or jigging can readily be separated from all accidental impurities,
thus obtaining the caustic lime in a purified condition. Instead of screening the
caustic lime in the form of milk of lime, the lime can also be purified by slacking
the lime with sufficient water only to reduce it to a fine dry powder. This powder
is then screened and bolted, to remove foreign coarser particles; or the lime, as
quick lime, may be mechanically powdered, screened and bolted. While the
mechanical purification of the lime in the form of a thin milk of lime is preferable
as more economical (if the preliminary purification of the raw materials is carried
out), the other methods indicated may be employed. It is, however, not always
necessary to purify the lime in this manner, as it is possible to obtain the caustic
lime on the market having so little impurities that the subsequent purification
of the carbonate of lime is sufficient to remove all of such impurities. The pure or
purified materials are allowed to react upon each other in the presence of water,
preferably at an increased temperature. If the alkali carbonate and the lime
are relatively pure, they may be mixed by throwing the alkali carbonate into water
and by then slacking the quick lime in this alkali carbonate solution, or the alkali
carbonate may be dissolved in the thin milk of lime obtained by slacking the quick
lime in an excess of water. In whatever manner the mixture may be made, it
is preferable that it shall consist of 100 to 120 parts of water, 10 parts of carbonate
of potash, and 4 to 5 parts of caustic lime, or of 80 to 100 parts of water, 10 parts
of carbonate of soda, and 6 to 7 parts of caustic lime. While these proportions
may be greatly varied without materially changing the results, it is preferable to
follow the same as resulting in a quick and fairly complete reaction when the
temperature of the mixture is raised by steam or otherwise. The reaction results
in a solution of caustic soda or caustic potash, with probably a small amount of
caustic lime in solution, and an insoluble sediment of calcium carbonate or carbon-
ate of lime containing possibly an excess of caustic hydrated lime and other
impurities. The solution is separated from the calcium carbonate by decantation
or filtration. The calcium carbonate is washed to remove as far as possible the
caustic alkali. The remaining calcium carbonate may still contain an excess
of caustic lime and soluble and insoluble impurities which must be removed. The
caustic lime and soluble impurities may be removed by washing with an excess
of water, or the caustic lime may be converted into carbonate of lime by an 4
additional treatment with a new quantity of alkali carbonate, or by treating with
carbonic acid in aqueous solution or in gas form; or it may be converted into a
more or less soluble solution of lime salt by treatment with a suitable acid, such
as muriatic acid, sulphurous acid or sulphuric acid. Whatever the treatment may
be to convert or remove the caustic lime contained in the lime carbonate, the treat- 5
ment is preferably applied to the lime carbonate suspended in an excess of water.
This thin milk of carbonate of lime, which consists of extremely fine amorphous
particles of carbonate of lime, of soluble impurities and of insoluble impurities,
is separated from the insoluble impurities by screening, floating or jigging, and
from the soluble impurities by filtration and lixiviation. The previous screening, 5
floating or jigging of the caustic milk of lime will, however, frequently make it
unnecessary to apply a corresponding operation to the milk of carbonate of lime.

page_text: The remaining pure carbonate of lime of amorphous, finely divided form, may be
suitably dried and used in the place of precipitated chalk or in place of whiting,
or it may be utilized in paste or fluid form to form the basis of other pure lime
salts, such as sulphate of lime and others, by treating the milk of carbonate of
lime with a suitable acid, as already explained.
Instead of mixing the carbonate of lime obtained as a residue in the converting
kettle during the manufacture of caustic soda or caustic potash with an excess of
water and passing the resulting milk of carbonate of lime through a mechanical
separating apparatus, as first described, or of first purifying the raw materials
previous to their introduction into the converting kettle, with or without the
subsequent mechanical treatment of the carbonate of lime, as next described, it
is possible to provide for the mechanical purification of the carbonate of lime in
the dry form. This may be done by mixing the calcium oxide, whether the same
is employed as quick lime or in the hydrated form as slacked lime, with an alkali
carbonate solution, and allowing the materials to act upon each other under proper
conditions. The products obtained are then separated, the solution of caustic lye
being decanted off, and the precipitated calcium carbonate being passed through a
filter press to remove the soluble impurities, or without such treatment being
immediately removed to a suitable drying apparatus, by which the moisture con-
tained in the same is driven off. The dry product, whether that obtained as the
precipitate in the first instance or the filter-cake, is then reduced to the form
of a fine powder, such as by being passed through grinding rolls. This powder is
then passed through a mechanical separating apparatus, such as an ordinary
bolting mill, and in this way the fine particles of the calcium carbonate will be
separated from the coarser particles of impurities, which are rejected as tailings.
If desired, the raw materials may be properly purified before they are brought
together in the converting kettle, as has already been described, although this
preliminary purification is not strictly necessary.
Instead of either of the mechanical manipulations above indicated, a chemical
process for the treatment of the caustic soda or caustic potash residues may be
carried out, and which will result in the production of a chemically pure sulphate
of lime which will be capable of many industrial uses, such, for instance, as a
paper filler. This chemical process will also be adapted for use in the treatment
of residues resulting from ammonia soda processes, wherein both the caustic and
carbonate processes are carried out, and by which are obtained as waste products
a lime residue and calcium chloride, said waste products being at the present time
valueless and difficult of disposal.
The lime residue, which consists largely of carbonate of lime with some inter-
mixed hydrated or caustic lime therewith, together with impurities such as coal sand,
dirt, etc., is dissolved in muriatic acid. The resulting solution of muriate of lime
or calcium chloride is filtered through the finest possible mesh, so as to reject all
ot the insoluble impurities. This filtration may be carried out in a suitable filter
press or in any other way. The clear calcium chloride solution, after this filtra-
tion, is treated with sulphuric acid, the reaction precip ituting pure sulphate of lime,
which sulphate is filtered off, carefully washed to remove all traces of muriatic
acid and suitably dried and sold in paste or moist form. The filtrate from the
sulphate of lime, which consists of a solution of muriatic acid with a small amount
either of free sulphuric acid or of undecomposed calcium chloride and some sulphate
of lime, is neutralized with new quantities of the lime residue. If a sufficient
excess of lime residue is employed and the solution again filtered, all impurities,
such as iron and alumina salts, are precipitated and removed from the solution,
which contains calcium chloride and a small amount of sulphate of lime. This
calcium chloride solution is again precipitated with sulphuric acid, the sulphate
of lime filtered off, and the filtrate again neutralized with an excess of the lime
residue.
The improved apparatus comprises suitably arranged receptacles combined with

page_text: suitable mechanical separating devices conveniently disposed so that the processes
above indicated may be conveniently and effectively carried out therein.
In order that the invention may be better understood, attention is directed to
the accompanying drawings forming a part of this specification, and in which
Figure 1 represents a diagrammatic view of a suitable apparatus intended for
carrying out the process first indicated, wherein the carbonate of lime obtained
as a residue in the converting kettle is mixed with an excess of water to form a
milk of carbonate, which latter is passed through a suitable separating apparatus
before the drying thereof; Figure 2 a detailed section on the line 2-2 of Figure 1;
Figure 3 a diagrammatic view of a convenient form of apparatus for use in carry-
ing out the process for the production of sulphate of lime from the carbonate after
the latter has been mechanically purified; Figure 4 a similar view of a convenient
form of apparatus for effecting the preliminary purification of the raw materials
before the same are brought together in the converting kettle, and showing
apparatus also for subsequently mechanically purifying the carbonate of lime in
the form of a milk of carbonate and for producing sulphate therefrom; Figure 5
a similar view of a convenient form of apparatus suitable for use in effecting the
purification of the carbonate of lime in the dry form after the same has been
removed from the converting kettle.
Referring to Figure 1, 1 represents the mixing or receiving tank, into which
the residues are placed and to which water is added for converting said residues into
a thin milk, as stated. When it is desired to subject the residue in this mixer
to chemical treatment for dissolving out the caustic lime or for converting said
caustic lime into carbonate of lime, the necessary appliances are to be employed.
For example, a perforated injection coil 2 is employed, as shown in dotted lines,
for injecting carbonic acid into the mixer so as to convert said caustic lime into
carbonate of lime. As stated, however, this treatment is not absolutely necessary,
and it may equally well be carried out after the mechanical separation of the
carbonate of lime from its impurities as before such separation. The water may
be admitted through a suitable pipe 3. The mixer 1 is provided with suitable
stirring arms 4, 4, operated from the vertical shaft 5, by which the material will
be thoroughly agitated and the necessary thin milk produced. Power to the
shaft 5 may be communicated from a line shaft 6 or in any other suitable way.
From the mixing tank the thin milk of carbonate of lime is pumped by a pump 7
(preferably a rotary pump) to the mechanical separating apparatus, which in the
drawing comprises two revolving screens and 9. The first mentioned screen
may be of a relatively coarse mesh, for instance 80 meshes to the linear inch, but
the screen 9 should be of a very fine mesh, say 150 or 200 meshes to the linear
inch, so as to allow only for the passage through the same of the minute particles
of carbonate. These screens are operated from suitable shafts 10, 10, as is
common, and the tailings pass off through suitable chutes 11, 11. These chutes
may be separate or he connected to a common duct or pipe 12, as shown in Figure 1.
The filtrate passing from the screen 9 and which consists almost entirely of
earbonate of lime and water, may be passed to a suitable receiving reservoir or
directly into a vacuum filter 14, as shown in Figure 1. By preference, the screen 15
of said filter is made inclined and is connected to a portion 16 of one end of the
filter, which portion is hinged at 17, so that it may be moved down to the position
shown in dotted lines, and constitutes a chute for effecting the easy removal of
the filtered carbonate. The vacuum pipe 18 connects with the vacuum filter
preferably above the screen 15, as shown in Figure 2, but a hood 19 is provided
so as to direct the vacuum or suction beneath said screen. The object of con-
necting the suction end of the vacuum pipe 18 to the filter above the screen 15,
is to overcome the danger of the fluids entering said vacuum pipe. The said
vacuum pipe 18 connects with a vacuum pump 20, which pump also is connected
by a pipe 21 to a vacuum tank 22, in which a vacuum may be maintained.
3-way valve 24 is provided to cut off the vacuum pump 20 from or to connect
said vacuum pump directly with the tank 22, it being possible therefore to operate
A

page_text: the filter from the pump or to allow the pump to effect the desired vacuum in the
tank 22 during the time that the material is being removed from the screen 15,
the pipe 18 being provided with a valve 25 so as to cut off the filter. The discharge
pipe 26 from the vacuum filter connects with the vacuum tank 22, a 3-way valve 27
being placed in said pipe so that the tank may be connected with the atmosphere
when it is to be discharged. The tank is provided with the valved draw-off pipe 28.
After the carbonate in the vacuum filter 14 has been freed from the water in which
it was suspended, it is allowed to dry, either naturally in the air, or is removed
down the inclined screen 15 and section 16 into a suitable dryer 29 of any
convenient type, by which it will be dried, the resulting carbonate being in the
form of a very fine dry powder or in friable lumps, as explained.
In the drawing the vacuum filter is shown as being provided with an overflow
pipe 31, which preferably connects with the mixing tank 1, and the purpose of
which is two-fold, said overflow pipe serving not only to prevent the liquid from
overflowing the filter, but also acting to give notice to the attendant on the
apparatus when a sufficient amount of the carbonate has been introduced into the
filter, it being understood that until the carbonate has formed a very considerable
layer upon the screen 15, any water which may overflow through the pipe 31 will
be comparatively clear, but that as soon as such water presents a milky appear-
ance, an ample indication will be given that a sufficient amount of the carbonate
has accumulated upon the screen 15 to be subjected to the effect of the vacuum.
When it is desired to obtain sulphate of lime from the carbonate, the apparatus
illustrated in Figure 3 may be conveniently employed. Referring to this figure,
1 represents the mixer or receiving tank, into which the residues are placed and
to which water is added for converting said residues into a thin milk, as stated.
If it is desired to subject the residue in this mixer to chemical treatment for dis-
solving out the caustic lime or for converting said caustic lime into carbonate of
lime, the necessary appliances are to be employed. For instance, a perforated
injection coil 2 may be used, as shown, for injecting carbonic acid into the mixer
so as to convert said caustic lime into carbonate of lime. As stated, however, this
treatment is not necessary, since the caustic will be converted into carbonate by
the action of sulphuric acid. The water may be admitted through a suitable
pipe 3. The mixer 1 is provided with suitable stirring arms 4, 4, operated from
the vertical shaft 5, by which the material will be thoroughly agitated and the
necessary thin milk produced. Power to the shaft 5 may be communicated from
a line shaft 6 or in any other suitable way. From the mixing tank the thin milk
of carbonate of lime is pumped by a pump 7 (preferably a rotary pump) to the
mechanical separating apparatus, which in the drawing comprises two revolving
screens 8 and 9, arranged as in Figure 1. These screens are operated from suit-
able shafts 10, 10, and the tailings pass off through suitable chutes 11, 11. The
filtrate passing from the screen 9 and which consists almost entirely of carbonate
of lime and water, is preferably passed to a suitable reservoir 12, having stirring
arms 13 therein. Said reservoir is large enough to enable a considerable supply
of the thin milk of carbonate of lime to be maintained on hand. From the reser-
voir 12 the milk of carbonate of lime passes by a pipe 14 to a mixing tank 15
having stirring arms 16 therein. This mixing tank 15 contains a sufficient amount
of dilute sulphuric acid by which the carbonate will be immediately converted
into a practically pure sulphate of lime. This sulphate of lime in the form of a
precipitate is drawn off with the water from the tank 15 through a draw-off
Dipe 17, and is passed into a suitable vacuum filter 18 or other equivalent apparatus
by which the water will be drawn off from the sulphate. The vacuum filter 18 is
of any suitable type, and comprises a receptacle 19 having a screen 20 therein and
with a pipe 21 which connects with a vacuum pump or tank having a vacuum
supply. A valve 22 cuts off the vacuum supply. 23 is a pipe leading from the
receptacle 19 into the sewer or elsewhere, provided with a valve 24 therein, and
25 is a pipe connecting the pipe 23 with the mixing tank, the latter pipe having
a valve 26 therein, whereby water from the vacuum filter may be conducted back

page_text: to the mixing tank 1, when economy is desired. With the apparatus shown,
there is a pipe 27 leading from the pipe 14 into the vacuum filter, the purpose
of which is to conduct the thin milk of carbonate into said vacuum filter when
it is not desired to form the sulphate, as explained, whereby the apparatus illus-
trated will be capable of use for carrying out the process of producing a dry
carbonate of lime. After the said sulphate of lime has been dried in the filter 18,
it may be desiccated by exposure to the air or by being introduced into a dryer 27¹
artificially heated and of any suitable type.
When, however, it is desired to obtain the carbonate of lime or sulphate by the
process before indicated wherein the purification of the raw materials is effected,
the apparatus illustrated in Figure 4 may be employed. Referring to this
figure, A represents a tank, in which a solution of alkali carbonate is contained.
Connected with this tank is a filter press B, or other filtering device, by means of
which the solution will be clarified. C is a tank for receiving from said filter
press the filtered solution. D represents a tank or other storage device for con-
taining the thin milk of caustic or crude lime, and which, if the same is not
sufficiently pure, is passed through a separating device E by means of which the
very fine lime particles are separated from the heavier and coarser impurities.
The particular form of separating device shown comprises a receiving tank or
vessel a having a very fine screen b therein, depending from the cover or top
downwards in the form of a truncated cone. Working on the outside of this
screen are a plurality of stirring arms c driven from a shaft & through the beveled
gears e. Extending from a point within the screen b is a siphon f provided with
a valve g therein. Instead of said siphon, a suction pipe may be employed. The
tank D connects with the interior of the vessel E outside of the screen 6 by a
valved pipe h. The siphon f and a valved exit pipe i from the tank C lead to a
reaction tank F. This tank is preferably provided with a steam coil j by which
the contents of the reaction tank can be heated to the desired temperature. In
order to draw off the clear caustic alkali solution, a draw-off pipe k is employed,
having a pivoted inner end 7 by means of which the liquid may be drawn off at
different levels, as will be understood. The calcium carbonate precipitate formed
by the reaction in the tank F is removed through a valved pipe m and passes into
a mixing tank (, in which tank the carbonate of lime from the reaction tank Fis
mixed with a sufficient amount of water to form a very thin milk of carbonate of
lime. Either in tank G or in the screening apparatus H, the milk of lime may
be treated with a small amount of carbonic acid or muriatic acid, sulphurous acid
or sulphuric acid to convert the possibly present caustic lime into
carbonate, or to make the caustic lime and other impurities more
soluble. Instead of applying this treatment to the carbonate of lime before
another possible screening operation, it may be applied after the screening before
or during the separation of the carbonate of lime from the water which carries it in
suspension. From the tank G the milk of carbonate may, if desired, pass to a
second separating apparatus by which the very finely divided amorphous carbonate
may be mechanically separated from any impurities which may still be contained
therewith. This mechanical separation may be effected by screening, floating or
jigging, but it is preferably effected by a screening operation owing to the economy
and effectiveness of such character of separation. The screening apparatus illus-
trated is represented generally by H. Said screening apparatus in this instance
may comprise a containing vessel n having a hollow shaft o mounted horizontally
therein. Carried on said shaft is a very fine cylindrical screen 2, on the outer
periphery of which are a plurality of stirring paddles or arms q. The hollow
shaft is provided within the screen with one or more short suction pipes or
openings therein. The shaft is rotated from a pulleys, so as to rotate the
screen and the paddles or stirring arms r. A suction pipe t communicates by a
suitably packed joint u with the hollow shaft o and extends downwardly to consti-
tute a siphon, the lower end thereof leading preferably to a filter press J. The
suction pipe is provided above and below, as shown, with valves e and respec-

page_text: tively. By closing the valve w and opening the valve , a supply of fresh water
may be ejected through the hollow shaft o to wash out the screen p in the event
of the same becoming clogged. K represents any suitable form of drying device
for desiccating the filter-cake obtained in the press J. If it is desired to convert
the carbonate into a sulphate of lime or any other pure lime salt, a tank L may be
used, to which the carbonate from the screening or mechanical separating device H
may be conducted and subsequently treated with a suitable acid, such as sulphuric
acid and others, to produce the desired lime salt.
With this apparatus, the operation will be substantially as follows:
The solu-
tion of alkali carbonate in the tank A is passed into the filter press B and is
thereby clarified, the pure solution flowing into the tank C, in which it will be
stored for use. The crude milk of caustic lime contained in the tank D is allowed
to flow into the mechanical separator E, the stirring arms c keeping the liquid
in agitation, and the siphon f drawing off the liquid and the finer particles of lime
which pass through the mesh of the screen. b. The heavier impurities will be
rejected by the screen and may be removed from the separator E in any suitable
way. From the siphon f the purified crude milk of lime passes into the reaction
tank, and when a sufficient amount thereof has accumulated in said tank, the
valve 9 is closed. The proper proportion of the clarified alkali carbonate solution
from the tank C is now allowed to enter the reaction tank, and the mixture is
heated by the steam coil j. It is preferable that the mixture thus accumulated
in the reaction tank shall consist of from 300 to 120 parts of
water, 10 parts of carbonate of potash, and 4 to 5 parts of caustic
lime, or of from 80 to 100 parts of water, 10 parts of carbonate of
soda, and 6 to 7 parts of caustic lime. It will be understood, however,
that these proportions may be greatly varied without materially changing the
results, and hence without departing from the essential spirit of the invention.
The proportions given, however, result in a quick and fairly complete reaction
under the increase of temperature. The reaction in the tank F results in the
formation of a solution of caustic soda or causfic potash containing probably a
small amount of caustic lime and an insoluble sediment of calcium carbonate
containing possibly some hydrated lime. The caustic soda or caustic potash
solution is drawn off from the reaction tank through the pipe k, and is used for
any purpose desired. The insoluble sediment consists, as stated, of carbonate of
lime, which will be in a comparatively pure state if the crude materials have been
subjected to the purifying operations referred to. In some cases therefore, and
particularly when relatively pure raw materials in the first instance have been
used, the carbonate of lime from the reaction tank F may be mixed with water
and passed directly to the filter press J and the filter-cake subsequently dried in
the dryer K, or instead thereof the milk of carbonate from the reaction tank F may
be passed directly to the tank L and be subsequently treated with a suitable acid,
such as sulphuric acid and others, for obtaining the more or less soluble lime salt
desired. Ordinarily, however, it is desirable to subject the carbonate of lime
resulting from the reaction in the tank F to a further chemical or mechanical
separating action, or both. Hence it is preferable to remove the carbonate of lime
from the tank into the tank G and to add thereto a sufficient quantity of water
to form a relatively thin milk of carbonate of lime. Eventually carbonic acid, or
alkali carbonate, muriatic acid or sulphuric acid, or other suitable acids, are added.
From this mixing tank, the mixture is allowed to flow through the mechanical
separating device H. When the form of device illustrated is employed, the mix-
ture enters the tank n, and is kept in constant agitation by the stirring arms or
paddles q. By reason of the siphon t, the water carrying the fine particles of
carbonate of lime will pass through the screen p, entering the opening or open-
ings r in the shaft o and passing thence to the filter press J. By reason of the
screen, the coarser impurities which may be still present will be rejected, and
a very pure carbonate of lime in finely divided amorphous form will thereby be
produced as a filter-cake in the press J. This cake is then dried in the dryer K,

page_text: or it may be sold in its relatively moist form. If desired, the purified carbonate
from the mechanical separator H may be passed to the tank L and be subjected to
the treatment of a suitable acid, as explained. The pure carbonate of lime in
amorphous, finely divided form which is obtained by the process above indicated,
may be used in place of precipitated chalk or as whiting, and for both of these
uses it is commercially well adapted. At the same time, it is obtained with the
greatest economy of manufacture.
If, on the other hand, the mechanical purification of the carbonate of lime is
to be effected in the dry form rather than in the form of milk of carbonate, the
form of apparatus illustrated in Figure may be employed. Referring to this
figure, A represents a tank, in which a solution of alkali carbonate is contained.
Connected with this tank is a filter press B, or other filtering device, by which
the solution may be clarified. C is a tank for receiving from said filter press the
filtered solution. D represents a tank or other storage device for containing the
thin milk of caustic or crude lime, and which, if the same is not sufficiently pure,
is passed through a separating device E, by means of which the very fine lime
particles are separated from the heavier and coarser impurities. The particular
form of separating device shown comprises a receiving tank or vessel a, having a
very fine screen & therein, depending from the cover or top downwards in the form
of a truncated cone, as shown in Figure 4. Extending from a point within the
screen is a siphon f provided with a valve g therein. The tank I connects with
the interior of the vessel E outside of the screen b by a valved pipe h. The siphon f
and a valved exit pipe i from the tank C lead to a reaction tank F. When the
preliminary purification of the raw materials is not carried out in connection with
the invention, the elements above referred to, with the exception of the reaction
tank, may be dispensed with, and the raw materials directly introduced into said
tank without any preliminary treatment. The tank F is preferably provided
with a steam coil j, by which the contents of the reaction tank can be heated to
the desired temperature. In order to draw off the clear caustic alkali solution,
a draw-off pipe k is employed, having a pivoted inner end 1. The calcium
carbonate precipitate formed by the reaction in the tank F is removed through a
valved pipe m and passes into a mixing tank G, in which tank the carbonate of
lime from the reaction tank F is mixed with a sufficient amount of water to form
a very thin milk of carbonate of lime. In this tank the milk of lime may be
treated with a small amount of carbonic acid or muriatic acid, sulphurous acid or
sulphuric acid, to convert the possibly present caustic lime into carbonate, or to
make the caustic lime and other impurities more soluble. From the tank the
milk of carbonate of lime is passed through a suitable filter press H, by which the
soluble impurities will be removed.
The filter-cake from this press is removed therefrom after filtration and is dried
in a suitable dryer I, atter which the dry carbonate of lime, together with any
coarser impurities, is removed from said dryer and reduced to powdered form.
This grinding of the dry material may be effected by a suitable set of grinding
rolls J, arranged in any suitable way, and by means of which the products will
be reduced to a fine powder. From the grinding mill or other device, the
ground materials are passed through suitable bolting apparatus K, by means of
which the fine amorphous particles of carbonate of lime will be separated from
the coarser insoluble impurities, which pass out of the bolting apparatus in the
form of tailings.
The bolting apparatus illustrated comprises three inclined screens arranged in
the well known manner, but it will be understood that any other apparatus for
the purpose may be employed. When such screens are used, they will be of very
fine mesh, so as to allow for the passage through the same of the amorphous particles
of carbonate ot lime, but rejecting the heavier and coarser impurities.
With this apparatus, the operation will be substantially as follows: The solu-
tion of alkali carbonate in the tank A is passed into the filter press B and is thereby

page_text: clarified, the pure solution flowing into the tank C, in which it will be stored
for use.
The crude milk of caustic lime contained in the tank D is allowed to flow
into the mechanical separator E, the stirring arms e keeping the liquid in agitation,
and the siphon f drawing off the liquid and the finer particles of lime which pass
through the mesh of the screen b. The heavier impurities will be rejected by this
screen and may be removed from the separator E in any suitable way. From
the siphon the purified crude milk of lime passes into the reaction tank if, and
when a sufficient amount thereof has accumulated in said tank, the valve g is
closed. The proper proportion of the clarified alkali carbonate solution in the
tank C is now allowed to enter the reaction tank, and the mixture is heated by the
steam coil j. When the preliminary purification of the raw materials is not
necessary, the operations above described are dispensed with.
The reaction in the tank F results in the formation of a solution of caustic soda
or caustic potash, containing probably a small amount of caustic lime and an in-
soluble sediment of calcium carbonate containing possibly some hydrated lime.
The caustic soda or caustic potash solution is drawn off from the reaction tank
through the pipe k, and is used for any purpose desired. The insoluble sediment
consists, as stated, of carbonate of lime, which will be in a comparatively pure
state if the crude materials have been subjected to the purifying operations referred
to. In some cases, therefore, and particularly when relatively pure raw materials
in the first instance have been used, the carbonate of lime from the reaction tank F
may be passed directly to the dryer, and after being dried, subjected to the subse-
quent mechanical separation referred to. Ordinarily, however, it is desirable
to subject the carbonate of lime resulting from the reaction in the tank F to a
treatment in the tank G, and by which any possible excess of caustic lime and
soluble impurities may be removed. From the tank G the thin milk of carbonate
of lime, together with its contained soluble and insoluble impurities, is passed
through the filter press H, by which the soluble impurities will be removed. The
filter-cake obtained in the press is now dried in the dryer I, after which it is passed
through the grinding apparatus J, by which the dry cake will be ground or reduced
to a fine powder. This dry, fine powder is now passed through the bolting appar-
atus K, by which the fine amorphous particles of carbonate of lime will be separated
from the coarser and heavier particles of the insoluble impurities contained therein.
The fine dry amorphous carbonate of lime thus obtained may be sold in its
powdered form, or it may be subjected to pressure and converted into bricks or
into other forms.
When it is desired to subject the residues resulting from the manufacture of
caustic soda to a purely chemical process, in order to obtain chemically pure sulphate
of lime, the procedure is as follows; The lime residue, which consists largely of
carbonate of lime with some intermixed hydrated or caustic lime therewith,
together with impurities such as coal, sand, dirt, etc., is dissolved in muriatic
acid. The resulting solution of muriate of lime or calcium chloride is filtered
through the finest possible mesh so as to reject all of the insoluble impurities.
This filtration may be carried out in a suitable filter press or in any other way.
The clear calcium chloride solution, after this filtration, is treated with sulphuric
acid, the reaction precipitating pure sulphate of lime, which sulphate is filtered off.
carefully washed to remove all traces of muriatic acid, and suitably dried or sold
in moist or paste form. The filtrate from the sulphate of lime, which consists of
a solution of muriatic acid with a small amount either of free sulphuric acid or of
undecomposed calcium chloride and some sulphate of lime, is neutralized with new
quantities of the lime residue. If a sufficient excess of lime residue is employed
and the solution again filtered, all impurities, such as iron and alumina salts, are
precipitated and removed from the solution, which contains calcium chloride and
a small amount of sulphate of lime. This calcium chloride solution is again
precipitated with sulphuric acid, the sulphate of lime filtered off, and the filtrate
again neutralized with an excess of the lime residue.

page_text: The operations thus referred to are repeated indefinitely, and the reactions
are represented by the following equations;-
CaSO + 2HCI
CaCO + 2HCI
CaCl2 + H2SO
2HCI + CaCO,
=
Cat
H2O + CO₂
==
=
CaCl2 + H₂SO
======
2
CaCl2 + H2O + CO₂
CaSO +2ĤCI
These equations show that theoretically a given amount of muriatic acid is
sufficient to make an infinite amount of sulphate of lime in the manner indicated,
but in practice it has been found that about ten per cent. of the muriatic acid is
wasted, which must be supplied as the several operations are repeated.
Instead of starting with muriatic acid and dissolving lime residue therein,
as will be the case in the treatment of residues obtained from the manufacture
of caustic soda, a chloride of calcium solution may be used, precipitated with
sulphuric acid, forming sulphate of lime and muriatic acid. In the manufacture
of carbonate of soda by treating chloride of soda with caustic ammonia and carbonic
acid, the resulting ammonia chloride being treated with caustic lime so as to again
produce caustic ammonia, calcium chloride as a residue is formed, which at the
present time is not only valueless, but a source of inconvenience to the manu-
iacturers. If, in connection with the same carbonate process, the manufacturer
carries on a caustic process for producing caustic soda by treating carbonate of
soda with caustic lime, a lime residue such as referred to will be produced. These
two residues can be commercially utilized for the production of chemically pure
sulphate of lime, in accordance with the process which has been above outlined,
the calcium chloride solution and the lime residue of the two processes being
combined and being treated with sulphuric acid to produce the sulphate of lime,
as has been indicated.
The
The carbonate of lime obtained by any of the processes above outlined is essen-
tially a new article of commerce. It consists of microscopically small, extremely
finely divided, substantially uniform amorphous particles or loose aggregates
thereof, capable when dried of being reduced to an impalpable powder.
amorphous particles have no crystalline structure, nor do they show in themselves
the presence of any organic forms or residues thereof. The specific weight of my
new carbonate of lime, when dried and powdered, ranges from 78 to 94 grams
per 100 cubic centimeters, when the drying temperature does not materially exceed
212 degrees F. If, however, my new carbonate of lime is dried at a temperature
greatly exceeding 212 degrees F., the specific weight will be higher. The car-
bonate may show traces of causticity, especially when the residues are not sub-
jected, preliminary to the mechanical separation, to the action of carbonic acid, to
convert the caustic into carbonate, or to other acid to dissolve the caustic. My
new carbonate when dried and powdered does not form into aggregates or balls and
hence passes readily through screens of from 20 to 60 mesh per linear inch, and
slowly through screens of from 80 to 100 mesh per linear inch.
Of the numerous forms of more or less finely divided carbonate
of lime at present on the market, those which, superficially con-
sidered, most closely resemble my new carbonate, are "precipitated chalk"
so-called, and chalk whiting. Precipitated chalk is readily distinguishable
from my new carbonate, in having a much lower specific weight, namely, from
50 to 75 grams per 100 cubic centimeters. Precipitated chalk also tends to ball"
or form into relatively large cohesive aggregates, and hence does not readily pass
through a 20 or 40 mesh screen, and extremely slowly through a 60 or 80 mesh
screen. Chalk whiting like precipitated chalk tends to ball," and therefore
does not readily pass through sereens of the indicated mesh. The specific weight
of chalk whiting ranges between 105 and 110 grams per 100 cubic centimeters,
and is therefore considerably higher than the specific weight of my new carbonate
when the drying temperature does not materially exceed 212 degrees F. Chalk
whiting under the microscope invariably presents particles, which in their forms

page_text: show the origin of the raw material, the chalk being the decayed residue of micro-
organisms. While a great many of the chalk particles resemble amorphous forms,
there are always present hooklike, or ringlike, or scalelike particles, not formed
by loose aggregates of smaller particles of the chalk.
The new carbonate of lime will, as stated, be adapted for use as whiting, Paris
white, gilders' white, etc.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is:-
1. Separating carbonate of lime from its contained impurities by screening and
sifting, or by floating, or by a combination of both, or by jigging, or by bolting,
or by any other of the mechanical manipulations by which substances of different
degrees of fineness or of different specific gravities are separated one from the other.
2. The process of utilizing residues obtained in the manufacture of caustic soda
and caustic potash, comprising essentially carbonate of lime with insoluble im-
purities, which consists in mixing the residues with water so as to form a thin
milk, and in subjecting said milk to the action of mechanical separating devices,
substantially as set forth.
3. The process of utilizing residues obtained in the manufacture of caustic soda
and caustic potash, comprising essentially carbonate of lime with insoluble
impurities, which consists in mixing the residues with water so as to form a
thin milk, and in passing said milk through a screen of very fine mesh so as to
effect the separation of the carbonate from such impurities, substantially as set
forth.
4. The process of utilizing residues obtained in the manufacture of caustic soda
and caustic potash, comprising essentially carbonate of lime with insoluble
impurities, which consists in mixing the residues with water so as to form a thin
milk, and in passing said milk through a series of screens of progressively finer
mesh by which the carbonate will be separated from said impurities, substantially
as set forth.
5. The process of utilizing residues obtained in the manufacture of caustic
soda and caustic potash, comprising essentially carbonate of lime with insoluble
impurities, which consists in adding water to the residues to form a thin milk, in
subjecting said milk to the action of the mechanical separator so as to separate
the carbonate from the insoluble impurities and in removing the carbonate from
the water by the action of a vacuum filter, substantially as set forth.
6. The process of utilizing the residues from the manufacture of caustic soda
and caustic potash which comprise carbonate of lime with insoluble impurities,
which consists in adding water to the residues to form a thin milk, in subjecting
said milk to the action of a mechanical separator so as to separate the carbonate
from the insoluble impurities, in subjecting the separated carbonate and water to
the action of a vacuum filter so as to remove the water, and in drying the carbonate,
substantially as set forth.
7. An apparatus for treating residues obtained in the manufacture of caustic
soda and caustic potash, comprising a mixing tank in which the residues are
subjected to the action of water, mechanical separating devices for separating the
carbonate of lime from the insoluble impurities, and a vacuum filter, substantially
as set forth.
8. An apparatus for treating residues obtained in the manufacture of caustic
soda, comprising a mixing tank in which the residues are mixed with water, a
screen of very fine mesh to which the material is passed and by which the carbonate
of lime will be separated from the insoluble impurities, and a vacuum filter,
substantially as set forth.
9. An apparatus for treating residues obtained in the manufacture of caustic
soda, comprising a mixing tank in which the residues are mixed with water, a
plurality of screens of progressively finer mesh to which the material is passed and

page_text: by which the carbonate of lime will be separated from the insoluble impurities,
and a vacuum filter, substantially as set forth.
10. In an apparatus for treating residues obtained in the manufacture of caustic
soda, and caustic potash, an improved vacuum filter comprising a receptacle, a
screen therein, a vacuum pump connected to said receptacle, and a vacuum tank
connected to said receptacle, substantially as set forth.
11. In an apparatus for treating residues obtained in the manufacture of caustic
soad, and caustic potash, an improved vacuum filter comprising a receptacle, an
inclined screen mounted in said receptacle, a vacuum pipe connected to said recep-
tacle above said screen, a sleeve surrounding the suction end of said vacuum pipe,
and a vacuum pump connected to said pipe, substantially as set forth.
12. In an apparatus for treating residues obtained in the manufacture of caustic
soda, and caustic potash, an improved vacuum filter comprising a receptacle, an
inclined screen mounted in said receptacle, a hinged section 16 for said receptacle,
and a vacuum pump connected to said receptacle, substantially as set forth.
13. In an apparatus for treating residues obtained in the manufacture of caustic
soda, and caustic potash an improved vacuum filter comprising a receptacle, a
screen in said receptacle, a vacuum pump connected to said receptacle, and an
overflow pipe for said receptacle, substantially as set forth.
14. The process of treating residues obtained from the manufacture of caustic
soda or caustic potash, comprising essentially carbonate of lime with insoluble
impurities, which consists in adding water to the residues so as to form a thin
milk, in passing said milk through mechanical separators so as to separate the
carbonate of lime from the insoluble impurities, and in subjecting the milk of
carbonate to the action of sulphuric acid so as to convert the carbonate into sulphate
of lime, substantially as set forth.
15. The process of treating residues obtained from the manufacture of caustic
soda or caustic potash, comprising essentially carbonate of lime with insoluble
impurities, which consists in adding water to the residues so as to form a thin
milk, in passing said milk through mechanical separators so as to separate the
carbonate of lime from the insoluble impurities, in subjecting the milk of carbonate
to the action of sulphuric acid so as to convert the carbonate into sulphate of lime,
and in separating said sulphate of lime from the water, substantially as set forth.
16. The process of treating residues obtained from the manufacture of caustic
soda or caustic potash, comprising essentially carbonate of lime with insoluble
impurities, which consists in adding water to the residues so as to form a thin milk,
in passing said milk through mechanical separators so as to separate the carbonate
of lime from the insoluble impurities, in subjecting the milk of carbonate to the
action of sulphuric acid so as to convert the carbonate into sulphate of lime, in
separating said sulphate of lime from the water, and in finally drying said sulphate,
substantially as set forth.
17. An apparatus for treating residues obtained from the manufacture of caustic
soda or caustic potash, comprising a mixing tank in which the residues are sub-
jected to the action of water, mechanical separating devices for separating the
carbonate of lime from the insoluble impurities, a second mixing tank in which
the milk of carbonate is subjected to the action of sulphuric acid, and a vacuum
filter for drying the sulphate of lime produced in said second tank, substantially
as set forth.
18. An apparatus for treating residues obtained from the manufacture of caustic
soda or caustic potash, comprising a mixing tank in which the residues are mixed
with water, a plurality of screens of progressively finer mesh to which the material
is passed and by which the carbonate of lime will be separated from the insoluble
impurities, a second mixing tank in which the milk of carbonate will be subjected
to sulphuric acid, and a vacuum filter, substantially as set forth.
19. The process of treating residues resulting in the manufacture of caustic
seda and which comprise essentially carbonate of lime, said process consisting
in dissolving the residues in muriatic acid to form a calcium chloride solution,

page_text: in filtering said solution, in precipitating the clear filtrate with sulphuric acid to
form sulphate of lime, in filtering off said sulphate, and in using the filtrate from
the second filtration for treating fresh quantities of the lime residues, substantially
as set forth.
20. The process of treating residues resulting in the manufacture of caustic soda
and which comprise essentially carbonate of lime, said process consisting in dis-
solving the residues in muriatic acid to form a calcium chloride solution, in
filtering said solution, in precipitating the clear filtrate with sulphuric acid to form
sulphate of lime, in filtering off said sulphate, in using the filtrate from the second
filtration for treating fresh quantities of the lime residues, and in finally washing
the sulphate of lime to remove traces of muriatic acid, substantially as set forth.
21. The process of treating residues resulting in the manufacture of caustic
soda and which comprise essentially carbonate of lime, said process consisting in
dissolving the residues in muriatic acid to form a calcium chloride solution, in
filtering said solution, in precipitating the clear filtrate with sulphuric acid to
form sulphate of lime, in filtering off said sulphate, in using the filtrate from the
second filtration for treating fresh quantities of the lime residues, in washing
the sulphate of lime to remove traces of muriatic acid, and finally drying said
sulphate, substantially as set forth.
22. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and extremely divided carbonate of lime, which consists in purifying
the calcium oxide and alkali carbonate, in allowing these materials to react upon
each other in the presence of water, and in separating the calcium carbonate
formed by the reaction, substantially as set forth.
23. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and extremely divided carbonate of lime, which consists in mechanically
purifying the calcium oxide and alkali carbonate, in allowing these materials to
react upon each other in the presence of water, and in separating the calcium
carbonate formed by the reaction, substantially as set forth.
24. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and extremely divided carbonate of lime, which consists in first filtering
the alkali carbonate and in screening the calcium oxide, then in allowing these
materials to react upon each other in the presence of water, in separating the
calcium carbonate formed by the reaction, and in subsequently drying said calcium
carbonate, substantially as set forth.
25. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and extremely divided carbonate of lime, which consists in purifying the
calcium oxide and alkali carbonate, in allowing these materials to react upon
each other in the presence of water, in separating the calcium carbonate formed
by the reaction, and in subsequently subjecting the resulting carbonate of lime
to the action of a mechanical separator, substantially as set forth.-
26. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and extremely divided carbonate of lime, which consists in purifying
the calcium oxide and alkali carbonate, in allowing these materials to react upon
cach other in the presence of water, in separating the calcium carbonate formed
by the reaction, in subjecting the resulting carbonate of lime to the action of a
niechanical separator, and finally in drying the same, substantially as set forth.
27. A process for producing from calcium oxide and alkali carbonate, a pure,
amorphous and extremely divided carbonate of lime, which consists in purifying
the calcium oxide and alkali carbonate, in allowing these materials to react upon
each other in the presence of water, in separating the calcium carbonate formed
by the reaction, in mixing the resulting carbonate of lime with water, and finally
in passing said mixture through a mechanical separating apparatus, substantially
as set forth.
28. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and extremely divided carbonate of lime, which consists in purifying
the calcium oxide and alkali carbonate, in allowing these materials to react upon

page_text: each other in the presence of water, in separating the calcium carbonate formed
by the reaction, in mixing the resulting carbonate of lime with water, in passing
said mixture through a mechanical separating apparatus, and finally in filtering
the mixture, substantially as set forth.
29. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and extremely divided carbonate of lime, which consists in purifying
the calcium oxide and alkali carbonate, in allowing these materials to react upon
each other in the presence of water, in separating the calcium carbonate formed
by the reaction, in mixing the resulting carbonate of lime with water, in passing
said mixture through a mechanical separating apparatus, in filtering the mixture,
and finally in drying the filter-cake, substantially as set forth.
30. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and finely divided carbonate of lime, which consists in allowing the
raw materials to react upon each other in the presence of water, in separating the
calcium carbonate formed by the reaction, in drying such calcium carbonate, in
reducing the dry calcium carbonate to powdered form, and in subjecting such dry
powder to a mechanical separating action, substantially as set forth.
31. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and extremely divided carbonate of lime, which consists in allowing
the raw materials to react upon each other in the presence of water, in separating
the calcium carbonate formed by the reaction, in mixing said calcium carbonate
with water, in passing the milk of carbonate of lime thus obtained through a
filter press, in drying the filter-cake, in grinding the dry cake, and in subjecting
the powder thus obtained to a mechanical separating action, substantially as set
forth.
32. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and extremely divided carbonate of lime, which consists in allowing
the raw materials to react upon each other in the presence of water, in separating
the calcium carbonate formed by the reaction, in mixing said calcium carbonate
with water, in passing the milk of carbonate of lime thus obtained through a filter
press, in drying the filter-cake, in grinding the dry cake, and in bolting the fine
powder thus obtained, substantially as set forth.
33. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and extremely divided carbonate of lime, which consists in purifying
the calcium oxide and alkali carbonate and allowing these materials to react upon
each other in the presence of water, in separating the calcium carbonate formed
by the reaction, in mixing said calcium carbonate with water, in passing the milk
of carbonate of lime thus obtained through a filter press, in drying the filter-cake,
in grinding the dry cake, and in subjecting the powder thus obtained to a
mechanical separating action, substantially as set forth.
34. A process for producing from calcium oxide and alkali carbonate a pure,
amorphous and extremely divided carbonate of lime, which consists in purifying
the calcium oxide and alkali carbonate and allowing these materials to react upon
each other in the presence of water, in separating the calcium carbonate forined
by the reaction, in mixing said calcium carbonate with water, in passing the milk
of carbonate of lime thus obtained through a filter press, in drying the filter-cake,
in grinding the dry cake, and in bolting the fine powder thus obtained, substan-
tially as set forth.
35. As a new article of manufacture, carbonate of lime in the form of micro-
scopically small, extremely finely divided amorphous particles or loose aggregates
thereof, having when dried and powdered a specific weight of from 78 to 94 grams
per 100 cubic centimeters when the drying temperature does not materially exceed
212 degrees F., substantially as set forth.
36. As a new article of manufacture, carbonate of lime in the form of micro-
scopically small, extremely finely divided amorphous particles or loose aggregates
thereof, having when dried and powdered a specific weight of from 78 to 94 grams

page_text: per 100 cubic centimeters when the drying temperature does not materially exceed
212 degrees F. and having a slight caustic reaction substantially as set forth.
37. As a new article of manufacture, carbonate of lime in the form of micro-
scopically small, extremely finely divided amorphous particles or loose aggregates
thereof, having when dried and powdered a specific weight of from 78 to 94 grams
per 100 cubic centimeters when the drying temperature does not materially exceed
212 degrees F. and having a slight caustic reaction caused by the presence of
traces of hydrated lime, substantially as set forth.
38. As a new article of manufacture, carbonate of lime in the form of micro-
scopically small, extremely finely divided amorphous particles or loose aggregates
thereof, having when dried and powdered a specific weight of from 78 to 94 grams
per 100 cubic centimeters when the drying temperature does not materially exceed
212 degrees F. and capable when dried and powdered of passing easily through a
screen of from 40 to 60 meshes per linear inch, substantially as set forth.
39. As a new article of manufacture, dry carbonate of lime in the form of micro-
scopically small, extremely finely divided amorphous particles or loose aggregates
thereof, having when powdered a specific weight of from 78 to 94 grams per
100 cubic centimeters when the drying temperature does not materially exceed
212 degrees F., substantially as set forth.
40. As a new article of manufacture, dry, powdered carbonate of lime in the
form of microscopically small, extremely finely divided amorphous particles or
loose aggregates thereof, having a specific weight of from 78 to 94 grams per
100 cubic centimeters when the drying temperature does not materially exceed
212 degrees F., substantially as set forth.
41. As a new article of manufacture, dry, powdered carbonate of lime in the form
of microscopically small, extremely finely divided amorphous particles or loose
aggregates thereof, having a specific weight of from 78 to 94 grams per 100 cubic
centimeters when the drying temperature does not materially exceed 212 degrees F.,
and capable of passing easily through a screen of from 40 to 60 meshes per linear
inch, substantially as set forth.
Dateu
this fun day or Anaren A.D. 1000.
HERMAN EDWARD STURCKE.
WILLIAM FREDERICK JOBBINS.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicants.