Process and Apparatus for Obtaining Large Well Formed Crystals from Solution.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Process and Apparatus for Obtaining Large Well Formed Crystals
from Solution.
I, JOHANNES Bock, Doctor of Philosophy, of Radebeul, near Dresden, in the
Kingdom of Saxony, German Empire, do hereby declare the nature of this
invention to be as follows:-
The present invention relates to the extraction of organic or inorganic crystal-
lizable substances from solution in the form of detached crystals, and is designed
to enable such crystals to be obtained in large well formed individuals on a large
scale.
The invention is based upon the well known method of crystallisation in motion,
according to which the formation of crystal individuals is caused by the continu-
ous alteration of position or contact between crystals and a suitably concentrated
solution of the substance to be crystallised out.
The known modes of carrying out this method are not able to give satisfactory
results on the large scale for all products. The principal ground of this is the
unsuitable kind of causing the motion or change of position. If as in one of
the known modes of proceeding a stirring apparatus is caused to work in the
solution provided with the crystals, then the crystals will be subjected to
mechanical attacks during their growth, such as crushing, shivering, grinding
and the like, so that the even and undisturbed growth is prevented and neither
well formed nor large crystal individuals can be produced. This drawback is
especially experienced when the difference of the specific weights between the
crystals and the concentrated solution is considerable, because in this case the
crystals always fall quickly to the bottom of the vessel, especially when they
consist of large individuals.
Similar attacks occur in the second mode according to which the crystallisation
is effected in a large vessel revolving on its axis. In this case a considerable
proportion of the growing crystal individuals are forced continuously through
the revolving of the vessel beyond the falling angle in consequence of which a
continual falling over one another of the crystals takes place.
A second method known as the conduction from below," according to which
the solution is caused to pass upwards through a high column of crystals, causes
the said crystals to become continuously more and more pressed together by their
own weight downwards whereby they are caused to grow together in crusts and
other aggregations which inclose a good deal of solution or mother-liquor.
The above described draw-backs are obviated by the process or method here-
inafter described which constitutes the present invention.
The crystals are arranged in a long extended vessel such as gutter-like or
tubular vessel in a thin layer. This vessel is mounted horizontally or slightly
inclined. The solution for supplying those crystals with the substance required
for their growth or "feeding solution" is caused to flow through the vessel in
the direction of its long axis or transversely to the height of the layer with a

page_text: slow motion during this passage the vessel is given a see-saw or revolving
motion transversely to the direction of the flow, and the solution flowing through
is allowed to cool very gradually. The feeding solution will consequently pass
in very thin streams between the crystals. This fine division in combination
with the very slow cooling permits the surface attraction of the crystals to act
to its full extent, but causes a separation at each point only to take place in a
very small quantity, consequently at every section of the vessel uniformly.
There is obtained, moreover, a to and fro alternating washing contact between
the feeding solution and the crystals, whereby deposition in utmost thin layers
is promoted, whilst the continuous changes of position between the crystals and
the feeding solution in combination with the uniform supply of the latter at the
entrance end does not allow of any growing together. In consequence of this
combined action there is obtained a perfectly even growth of the separate crystals
without any growing together and taking up of fluid.
By aid of the above described process and suitable adjustment of the conditions
of operation such as initial saturation of the feeding solution, suitable length
of vessel, inclination of vessel, and so forth, to the peculiarities of the substance
to be crystallized, it has become possible to produce on the large scale well formed
large crystal individuals not only of sugar-candy but also of soft substances
such as fuchsine, borax, soda and the like and of brittle substances such as atum,
sulphate of copper, citric acid, and the like.
The process can also be carried out for very soft as well as for very brittle
crystals, by providing the vessel with a soft, chemically indifferent, and imper-
meable lining such as asbestos, felt, india-rubber and the like.
As the remaining solution leaves the vessel at a certain concentration i.e. a
concentration corresponding to the temperature of exit, it affords a very advan-
tageous means for supplying the vessel with fresh quantities of substance by
simply heating it up to the entrance temperature and saturating it with the
substance to be supplied to the crystals, or by evaporating or otherwise concen-
trating it to the original saturation point, and causing the thus re-established
solution to return into the vessel as the feeding-solution. The dissolving medium
can thus be allowed to move in a circuit, and it is only necessary in order to
make the process continuous, to replace the finished crystals removed from the
vessel by the introduction of small crystals or by the new formation of crystals
from the solution, and to compensate the loss of dissolving medium.
Th
1
Gaul
1
Process and Apparatus for Obtaining Large Well Formed Crystals
from Solution.
I, JOHANNES Bock, Doctor of Philosophy, of Radebeul, near Dresden, German
Empire, 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 present invention relates to the extraction of organic or inorganic crystal-
lisable substances from solution in the form of detached crystals, and is designed
to enable such crystals to be obtained in well formed large individual crystals
on a large scale.

page_text: The invention is based upon the well known method of crystallisation from
liquids in motion, according to which the formation of individual crystals is
caused by the continuous alteration of position or contact between crystals and a
suitably concentrated solution of the substance to le crystallised out.
The known modes of carrying out this method are not able to give satisfactory
results on the large scale for all products. The principal ground of this is the
unsuitable kind of motion or change of position. If as in one of the known modes
of proceeding a stirring apparatus is caused to work in the solution provided with
crystals, then the crystals will be subjected to mechanical attacks during their
growth, such as crushing, shaking, grinding and the like, so that the even and
undisturbed growth is prevented and neither well formed nor large individual,
crystals can be produced. This drawback is especially experienced when the differ-
ence of the specific weights between the crystals and the concentrated solution is
considerable, because in this case the crystals always fall quickly to the bottom of
the vessel, especially when they consist of large specimens.
Similar drawbacks occur in the second method according to which the crystal-
lisation is effected in a large vessel revolving on its axis. In this case owing to
the revolving of the vessel a considerable proportion of the growing individual
crystals is forced continuously beyond the falling angle in consequence of which
a continual falling over one another of the crystals takes place.
Another method known as the upward conduction," according to which the
solution is caused to pass upwards through a high column of crystals, causes the
said crystals to become continuously more and more pressed together downwards
by their own weight whereby they are caused to grow together in crusts and
olher aggregations which enclose a good deal of solution or mother-liquor.
The above described drawbacks are obviated by the process or method here-
inafter described which constitutes the present invention.
The crystals are arranged in a thin layer in a long-extended vessel such as
gutter-like or tubular vessel. This vessel is mounted horizontally or slightly
inclined. The solution for supplying those crystals with the substance required
for their growth, or "feeding solution," is caused to flow through the vessel in
the direction of its long axis or transversely to the height of the layer with a
slow motion; during this passage the vessel is given a see-saw or revolving
motion transversely to the direction of the flow, and the solution flowing through
is allowed to cool very gradually. The feeding solution will consequently pass
in very thin streams between the crystals. This fine division in combination
with the very slow cooling permits the surface attraction of the crystals to act
to its full extent but causes a separation at each point only to take place in a
very small quantity, consequently at every section of the vessel uniformly.
There is obtained, moreover, a to and fro alternating washing contact between
the feeding solution and the crystals, and the feeding solution in combination
with the uniform supply of the latter at the entrance end does not allow of any
growing together. In consequence of this combined action there is obtained a
perfectly even growth of the separate crystals without any growing together and
taking up of fluid.
By the aid of the above described process and suitable adjustment of the condi-
tions of operation such as initial saturation of the feeding solution, suitable length
and inclination of vessel, and so forth, to the peculiarities of the substance to be
crystallised, it has become possible to produce on the large scale well formed
large individual crystals not only of sugar candy but also of soft substances such
as fuchsine, borax, soda and the like, and of brittle substances such as alum,
sulphate of copper, citric acid and the like.
The process can also be carried out for very soft as well as for very brittle
crystals, by providing the vessel with a soft chemically unaffected, and imper-
meable lining such as asbestos, felt, india-rubber and the like.
As the remaining solution leaves the vessel at a certain concentration i.e. a
concentration corresponding to the temperature of exit, it affords a very advan-

page_text: tageous means for supplying the vessel with fresh quantities of substance by
simply heating it up to the initial temperature and saturating it with the
substance to be supplied to the crystals, or by evaporating or otherwise concen-
trating it to the original saturation point, and causing the re-saturated solution
to return into the vessel to serve anew as feeding solution. The solvent can thus
be allowed to move in a circuit, and it is only necessary in order to make the
process continuous, to replace the finished crystals removed from the vessel by
small crystals or by the new formation of crystals from the solution, and to
compensate the loss of solvent.
The accompanying drawing shews an apparatus for carrying out the invention
Figure 1 is a perspective front elevation and
Figure 2 the right hand end view, the crystallisation vessel being shewn in
cross section.
The apparatus shewn is one for continuous operation with a see-saw motion
of the crystallizing vessel. The crystallisation vessel is in the form of a gutter
of semicircular section, the lid of which, where such is required, consists most
suitably of covering plates a folding on one another so that local observations
may be taken. The said gutter is provided with an inlet b and an outlet e both
of which may be adjustable.
"
To effect the oscillating movement the gutter is suspended by means of links 2
from the cross arms of a shaft supported above revolubly in a bearing,
which shaft is coupled by means of an arm in the usual manner with the
The rotation of the said
rod of the eccentric of the driving shaft a”.
shaft will consequently cause the shaft a to oscillate, whereby the gutter a
is given a see-saw motion. The exit is attached by means of a Hexible tube d
to the pump which forces the exit liquor through the pipe
apparatus or re-saturator provided with heating apparatus h.
the re-saturator is connected by a flexible pipe with the inlet
Figure 2 shows the gutter provided with a soft lining f.
If it be desired to carry out the process in a crystallising vessel with slow
revolving motion, the said vessel is formed tubular with inlet and outlet through
the trunnions thereof, and the apparatus may be revolved by worm gearing as
is well known in many constructions for other branches of technics.
to the dissolving
The outlet 7 of
of the gutter a.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. The process for producing well formed large individual crystals which
consists in preparing from the substance to be transformed into individual
crystals a saturated solution, causing this solution to pass slowly through a long
extended thin layer of crystals of like substance in the direction of the longi-
tudinal axis of said layer, causing a relative motion to take place between the
crystals and the solution transversely to the direction of flow of the latter,
and allowing the solution to cool gradually during its passage, substantially as
and for the purpose specified.
2. The process for producing well formed large individual crystals which
consists in preparing from the substance to be transformed into individual
crystals, a saturated solution, causing the solution to pass slowly through a long
extended thin layer of crystals of like substance in the direction of the longi
tudinal axis of said layer, causing a relative motion to take place between the
crystals and the solution transversely to the direction of flow of the latter,
allowing the solution to cool gradually during its passage, re-saturating the
solution, and returning the re-saturated solution to the entrance end of the
crystal-layer, substantially as and for the purpose specified.
8. In apparatus for producing well-formed large individual crystals, the com-
bination with a device for imparting swinging or rotary motion, of a long

page_text: extended narrow crystallizing vessel having an inlet at one end and an outlet
at the other end, substantially as and for the purpose specified.
4. In apparatus for producing well formed large individual crystals the com-
bination, with a device for imparting swinging or rotary motion, of a long
extended narrow crystallizing vessel having an inlet at one end and an outlet
at the other end, and a soft lining applied to the interior of said vessel, substan-
tially as and for the purpose specified.
5. In apparatus for producing well formed large individual crystals from
solutions the combination of a long extended narrow crystallizing vessel having
an inlet at one end and an outlet at the other end, a re-saturating vessel con-
nected to said inlet, a pump connected to the outlet of the crystallizing vessel
and the inlet of the re-saturating vessel, and a device for imparting to the
crystallizing vessel an oscillating or rotary motion, substantially as and for the
purpose specified.
Dated the 2nd day of August 1998
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.