Improvements in and connected with the Production of Pure Salt and Glauber's Salt from Brine.
Year: 1899

page_text: Date of Application, 3rd Oct., 1899
Complete Specification Left, 29th June, 1900-Accepted, 18th Aug., 1900
PROVISIONAL SPECIFICATION.
Improvements in and connected with the Production of Pure Salt and
Glauber's Salt from Brine.
We, HARRY BAKER and EDWARD HAWORTHI, both of The Castner Kellner
Alkali Company Limited, Weston Point, Runcorn, Cheshire, Chemists, do
hereby declare the nature of this invention to be as follows:-
It is well known that all natural brines, and also artificial brines made by
dissolving rock salt, that are suitable for making salt for culinary and manu-
facturing processes, contain as principal impurity calcium sulphate, and in
smaller quantities the sulphates or chlorides of magnesium, chloride of calcium
sulphate of soda and bicarbonate of iron and of lime. Many processes have
been devised for more or less completely purifying the brine to be used in salt
making, or the salt after it has been made but where such processes are
cheap (adding but little to the cost of producing salt without such purifica-
tion, they are also exceedingly inefficient and where they are efficient and
yield a chemically pure salt they are also so expensive as to have prohibited
hitherto the manufacture of chemically pure salt for general purposes. Thus
the removal of iron magnesia and lime by the well known chemical reagents
lime and sodium carbonate, and of sulphates by the well known
chemical reagent barium chloride is complete but the cost of the brine is
increased ten fold and the cost of the salt is at least doubled, and this mainly
because of the expensiveness of barium chloride.
Recently in the progress of electro chemical and other chemical, manufactures it
has become important to obtain chemically pure salt as cheap as possible and in
large quantities, hence the present invention. The iron, magnesia and lime
are removed by the well known chemical reagents lime, and carbonate of
sodium, and the rapid settling is assisted by a gentle heat in the first case and
by a heat of say 50-70° C. in the last case. There is thus obtained a salt
solution which contains as only impurity sodium sulphate, and a very small
quantity of excess of sodium carbonate. It is known as a laboratory
operation for the preparation of small quantities of pure salt that as such
brine is gradually evaporated the salt which first separates is after removal of
the mother liquor by draining and pressing between blotting paper chemically
pure; but this can only be carried on for a short time as the salt becomes
gradually more impure until the method becomes useless and there then
remains a quantity of brine containing the major part of the sulphate of soda
and this is entirely useless and waste.
Castner in Specification 21284 of 1898 has described how the sodium
sulphate may be removed from the solid salt by fractional washing of such
salt with a brine saturated as to sodium chloride and containing little or no
sodium sulphate and the present invention consists largely of improvements on
that described by Castner and gives a continuous method of preparing a salt
of any desired degree of purity and recovers all the salt and also all the

page_text: sodium sulphate (each of them in a state of purity), from the above named
waste liquor.
According to this invention the brine is first to be purified by means of
lime and soda ash in the ordinary way so as to produce a brine containing only
sodium chloride and sodium sulphate in solution. Instead of feeding this
brine into one evaporating pan as described by Castner it is proposed to use
a series of evaporating pans. All the brine required for all the pans being fed
into the first one and the brine not evaporated in that pan being passed on by
means of a pipe, conduit, pump or any suitable method to the next pan in the
series. Similarly the brine not evaporated in the second pan will be passed
to the third pan and so on. As the brine which is fed to the pans will not be
saturated with sodium sulphate, the salt deposited in the first pan will be pure
sodium chloride wetted with a brine containing more sodium sulphate relative
to sodium chloride than the original brine. The deposition of pure sodium
chloride will continue in succeeding pans until a. pan is reached in which the
brine becomes saturated with sodium sulphate at the temperature at which the
evaporation takes place. When this stage is reached the salt deposited in the
evaporating vessel will contain a new constituent viz.: solid sodium sulphate
and in all succeeding pans the feed brine being saturated with sodium sulphate
the condition of the pans will be uniform and constant and the salt fished
contain a maximum of solid sodium sulphate. It has been found by experi-
ment that if the evaporation is carried out at about 190° F. the brine becomes
saturated with sodium sulphate when the proportion of sodium chloride to
sodium sulphate in the brine becomes 100-19 and this proportion varies with
the temperature at which the evaporation takes place. Ordinary brine purified
as above described contains about 100 parts of sodium chloride to 1.6 parts
of sodium sulphate and therefore it is possible to obtain 91.6 parts of sodium
chloride free from solid sodium sulphate and 10 parts of a salt containing
8.4 parts of sodium chloride and 1.6 parts of solid sodium sulphate. In practice
these figures will probably only be approximately obtained owing to losses in
working and the removal from the pans of sodium sulphate not solid but dis-
solved in the brine which wets the salt even after draining as long as con-
venient. The number of pans in series may be varied according to circum-
stances and requirements but generally the best results will probably be obtained
with the most pans. It is obvious that by stopping the number of pans in
series at a suitable point a solid salt may be obtained from the last pan con-
taining sodium chloride, and solid sodium sulphate in any proportions between
10019 and 100-mil if the evaporation is carried out at about 190° F. If
the evaporation is carried out at any other temperature the ratio 100-19 will
change as the solubility of sodium sulphate in the brine changes with the
temperature.
In view of the increased output of bleach from electrolytic processes a salt
containing 19 parts of sodium sulphate to 100 parts sodium chloride would be
useful in the manufacture of salt cake. Having described how to produce
salts containing any amount of solid sodium sulphate from nothing to a maxi-
mum, it remains to describe how to obtain from these pure salt and also
Glaubers salt.
PREPARATION OF PURE SALT FROM PORTIONS CONTAINING NO SOLID SODIUM
SULPHATE.
To obtain salt from those portions containing no solid sodium sulphate the
brine which wets the salt must be removed by some means. Simple drainage
will not be sufficient to effect this if a pure salt is required nor would any of
the well known methods of separating liquids from solids give a very satis-
factory result. A pure salt may however be obtained by replacing the brine
containing sodium sulphate with a brine free from sodium sulphate or nearly
The salt may be drawn in to watertight carts, allowed to drain a con-
80.

page_text: venient length of time and the drainage returned to the pan.
A brine con-
taining less sodium sulphate than the brine in the pan would then be pumped
on to the salt, this in its turn drained off and replaced by a still purer brine
and so on until finally pure brine containing no sodium sulphate would be
pumped on to the salt. In this way a salt free from all impurities may be
obtained. The pure brine for washing may be obtained from the original
brine by precipitating the sulphate with barium chloride or other reagent or
by dissolving pure salt, (as the salt obtained by the purification process) in
water. It is obvious that a salt containing small quantities of sodium sul-
phate may be obtained by stopping the washing at any desired point; in this
case the original brine only may be used in the washing or it may be required
to be supplemented by a quantity of pure brine. The number of washings
will vary with the amount of sodium sulphate in the brine wetting the salt
originally, and the degree of purity required in the finished salt, and may be
from 1 to as many as 12. Some of the brine strongest in sodium sulphate
having been removed to treat the salt containing solid sodium sulphate as
described in the next paragraph, the wash brines may all be thrown forward
and the series completed by the addition of the required quantity of new.
washing brine. The amount of new brine required will be about 5 gallons per
300 lbs. of salt but will of course vary with the composition of the raw brine.
and the purity of the salt to be produced.
PREPARATION OF GLAUBERS SALT AND PURE SALT FROM PORTIONS CONTAINING
SOLID SODIUM SULPHATE.
To prepare Glaubers salt from the portions containing solid sodium sul-
phate, the wash brine containing most sodium sulphate in solution may be
pumped into the carts, and the temperature brought to about 33° C. The brine
will dissolve out the solid sodium sulphate until it is saturated and this point
is reached, when it contains approximately 6.5%, sodium sulphate (or 28 to 30
parts sodium sulphate to 100 parts salt). The salt is to be treated with brine
at 33° C. in such a manner that almost all the solid sodium sulphate is dis-
solved, and the wash brine is brought up to saturation. A second washing
with another portion of similar brine will remove all the solid sodium
sulphate, and the salt may then be washed pure as described in the previous
section. The wash brine containing 6% sodium sulphate on cooling, will
deposit Glaubers salt along with small quantities of sodium chloride. If a
purer form of Glaubers salt is required it may be obtained by recrystallising.
The brine from which the Glaubers salt has deposited is returned either to the
washing tanks or to the evaporating vessels as desired, so that nothing is lost.
Dated this 3rd day of October 1899.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London,
Chartered Patent Agent,
For the Applicants.
5 Improvements in and connected with the Production of Pure Salt and
Glauber's Salt from Brine.
We, HARRY BAKER and EDWARD HAWORTII, both of The Castner Kellner
Alkali Company Limited, Weston Point, Runcorn, Cheshire, Chemists, do
hereby declare the nature of this invention and in what manner the same is

page_text: to be performed, to be particularly described and ascertained in and by the.
following statement:-
It is well known that all natural brines and also artificial brines made by
dissolving rock salt, that are suitable for making salt for culinary and manu-
facturing processes, contain as principal impurity calcium sulphate, and in
smaller quantities the sulphates or chlorides of magnesium, chloride of calcium.
sulphate of soda and bicarbonate of iron and of lime. Many processes have
been devised for more or less completely purifying the brine to be used in salt
making, or the salt after it has been made but where such processes are
cheap adding but little to the cost of producing salt without such purifica-
tion, they are also exceedingly inefficient and where they are efficient and
yield a chemically pure salt they are also so expensive as to have prohibited
hitherto the manufacture of chemically pure salt for general purposes. Thus
the removal of iron magnesia and lime by the well known chemical reagents
lime and sodium carbonate and of sulphates by the well known,
chemical reagent barium chloride is complete but the cost of the brine is
increased ten fold and the cost of the salt is at least doubled, and this mainly
because of the expensiveness of barium chloride.
Recently in the progress of electro chemical and other chemical manufactures
it has become important to obtain chemically pure salt as cheap as possible and
in large quantities-hence the present invention. The iron, magnesia and lime
are removed by the well known chemical reagents lime, and carbonate of
sodium, and the rapid settling is assisted by a gentle heat in the first case and
by a heat of say 50-70° C. in the last case. There is thus obtained a salt
solution which contains as its only impurity_sodium sulphate and a very small
quantity of excess of sodium carbonate. It is well known as a laboratory
operation for the preparation of small quantities of pure salt that as such
brine is gradually evaporated the salt which first separates is after removal of
the mother liquor by draining and passing between blotting paper chemically
pure, but this can only be carried on for a short time as the salt becomes
gradually more impure until the method becomes useless and there then
remains a quantity of brine containing the major part of the sulphate of soda
and this is entirely useless and waste.
Castner in British Specification 21284 of 1898 lias described how the sodium
sulphate may be removed from the solid salt by fractional washing of such
salt with a brine saturated as to sodium chloride and containing little or no
sodium sulphate and the present invention consists largely of improvements on
that described by Castner and gives a continuous method of preparing a salt
of any desired degree of purity and recovers all the salt and also all the
sodium sulphate (each of them in a state of purity), from the above named
waste liquor.
According to this invention the brine is first to be purified by means of
lime and soda ash in the ordinary way so as to produce a brine containing only
sodium chloride and sodium sulphate in solution. Instead of feeding this
brine into one evaporating pan as described by Castner it is proposed to use
a series of evaporating pans, all the brine required for all the pans being fed
into the first one and the brine not evaporated in that pan being passed on by
means of a pipe, conduit, pump or any suitable method to the next pan in the
series. Similarly the brine not evaporated in the second pan will be passed
to the third pan and so on. As the brine which is fed to the pans will not be
saturated with sodium sulphate, the salt deposited in the first pan will be purc
sodium chloride wetted with a brine containing more sodium sulphate relative
to sodium chloride than the original brine. The deposition of pure sodium
chloride will continue in succeeding pans until a pan is reached in which the
brine becomes saturated with sodium sulphate at the temperature at which the
evaporation takes place. When this stage is reached the salt deposited in the
evaporating vessel will contain a new constituent viz.: solid sodium sulphate

page_text: and in all succeeding pans the feed brine being saturated with sodium sulphate
the condition of the pans will be uniform and constant and the salt fished.
contain a maximum of solid sodium sulphate. It has been found by experi-
ment that if the evaporation is carried out at about 190° F. the brine becomes
saturated with sodium sulphate when the proportion of sodium chloride to
sodium sulphate in the brine becomes as 100 to 19 and this proportion varies with
the temperature at which the evaporation takes place. Ordinary brine purified
as above described contains about 100 parts of sodium chloride to 1.6 parts
of sodium sulphate and therefore it is possible to obtain 91.6 parts of sodium
chloride free from solid sodium sulphate and 10 parts of a salt containing
8.4 parts of sodium chloride and 1.6 parts of solid sodium sulphate. In practice
these figures will probably only be approximately obtained owing to losses in
working and the removal from the pans of sodium sulphate not solid but dis-
solved in the brine which wets the salt even after draining as long as con-
venient. The number of pans in series may be varied according to circum-
stances and requirements but generally the best results will probably be obtained
with the most pans. It is obvious that by stopping the number of pans in
series at a suitable point a solid salt may be obtained from the last pan con-
taining sodium chloride, and solid sodium sulphate in any proportions between.
100-19 and 100-mil if the evaporation is carried out at about 190° F. If
the evaporation is carried out at any other temperature the ratio 100-19 will
change as the solubility of sodium sulphate in the brine changes with the
temperature.
In view of the increased output of bleach from electrolytic processes a salt.
containing 19 parts of sodium sulphate to 100 parts sodium chloride would be
useful in the manufacture of salt cake. Having described how to produce
salts containing any amount of solid sodium sulphate from nothing to a maxi-
mum, it remains to describe how to obtain from these pure salt and also
Glaubers salt.
PREPARATION OF PURE SALT FROM PORTIONS CONTAINING NO SOLID SODIUM
SULPHATE.
To obtain salt from those portions containing no solid sodium sulphate the
brine which wets the salt must be removed by some means. Simple drainage
will not be sufficient to effect this if a pure salt is required nor would any of
the well known methods of separating liquids from solids give a very satis-
factory result. A pure salt may however be obtained by replacing the brine
containing sodium sulphate with a brine free from sodium sulphate or nearly
SO.
The salt may be drawn in to watertight carts, allowed to drain a con-
venient length of time and the drainage returned to the pan.
A brine con-
taining less sodium sulphate than the brine in the pan would then be pumped
on to the salt, this in its turn drained off and replaced by a still purer brine
and so
on until finally pure brine containing no sodium sulphate would be
pumped on to the salt. In this way a salt free from all impurities may be
obtained. The pure brine for washing may be obtained from the original
brine by precipitating the sulphate with barium chloride or other reagent or
by dissolving pure salt, (as the salt obtained by the purification process) in
water. It is obvious that a salt containing small quantities of sodium sul-
phate may be obtained by stopping the washing at any desired point; in this.
case the original brine only may be used in the washing or it may be required"
to be supplemented by a quantity of pure brine. The number of washings
will vary with the amount of sodium sulphate in the brine wetting the salt
originally, and the degree of purity required in the finished salt, and may be
from one to as many as 12. Some of the brine strongest in sodium sulphate
having been removed to treat the salt containing solid sodium sulphate as
described in the next paragraph, the wash brines may all be thrown forward,
and the series completed by the addition of the required quantity of new.
washing brine. The amount of new brine required will be about 5 gallons per

page_text: 300 lbs. of salt but will of course vary with the composition of the raw brine
and the purity of the salt to be produced.
PREPARATION OF GLAUBERS SALT AND PURE SALT FROM PORTIONS CONTAINING
SOLID SODIUM SULPHATE.
To prepare Glaubers salt from the portions containing solid sodium sul-
phate, the wash brine containing most sodium sulphate in solution may be
pumped into the carts and the temperature brought to about 33° C. The brine
will dissolve out the solid sodium sulphate until it is saturated and this point
is reached, when it contains approximately 6.5% sodium sulphate (or 28 to 30
parts sodium sulphate to 100 parts salt). The salt is to be treated with brine
at 33° C. in such a manner that almost all the solid sodium sulphate is dis-
solved, and the wash brine is brought up to saturation. A second washing with
another portion of similar brine will remove all the solid sodium
sulphate, and the salt may then be washed pure as described in the previous
section.
The wash brine containing 61% sodium sulphate, on cooling, will deposit
Glaubers salt along with small quantities of sodium chloride. If a purer form
of Glaubers salt is required it may be obtained by washing the salt with cold
water and recrystallising. The brine from which the Glaubers salt has deposited
is returned either to the washing tanks or to the evaporating vessels as desired,
so that nothing is lost.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is:
1. The process of producing pure salts from brine consisting in first remov-
ing from said brine all its salts except sodium chloride and sodium sulphate
and then passing such purified brine through a series of evaporating pans so
heated as to cause practically pure sodium chloride wetted with a solution
containing a proportion of sodium sulphate to be deposited in the first pan while
in each subsequent pan the proportion of sodium sulphate to sodium chloride
in the brine wetting the salt deposited increases and continuing the feeding
from pan to pan and evaporation until the brine approaches or becomes saturated
with sodium sulphate.
2. The process of producing pure salts from brine consisting in first remov-
ing from said brine all its salts except sodium chloride and sodium sulpliate
and then passing such purified brine through a series of evaporating pans so
heated as to cause practically pure sodium chloride wetted with a solution con-
taining a proportion of sodium sulphate to be deposited in the first pan while
in each subsequent pan the proportion of sodium sulphate to sodium chloride in
the brine wetting the salt deposited increases and continuing the feeding from
pan to pan and evaporation until the brine becomes saturated with sodium
sulphate and causing a mixed salt of sodium chloride and sodium sulphate to
be deposited and continuing the feed from pan to pan so as to produce in all
such pans a salt containing the maximum proportion of solid sodium sulphate.
3. The process of producing pure salt from brine consisting in first removing
from said brine all its salts except sodium chloride and sodium sulphate and
then passing such purified brine through a series of evaporating pans so heated
as to cause practically pure sodium chloride wetted with a solution containing
a proportion of sodium sulphate to be first deposited, draining such salt and
submitting it to a series of washings with solutions containing a continuously
less proportion of sodium sulphate and a continuously greater proportion of
sodium chloride until the desired purity is attained.
4. The process of producing pure salts from brine consisting in first removing
from said brine all its salts except sodium chloride and sodium sulphate and
then passing such purified brine through a series of evaporating pans so heated

page_text: as to cause practically pure sodium chloride wetted with a solution containing
a proportion of sodium sulphate to be deposited in the first pan while in each
subsequent pan the proportion of sodium sulphate to sodium chloride in the
brine wetting the salt deposited increases and continuing the feeding from pan
to pan and evaporation until the brine becomes saturated with sodium sulphate
and causing a mixed salt of sodium chloride and sodium sulphate to be deposited
and continuing the feed from pan to pan so as to produce in all such pans
a salt containing the maximum proportion of solid sodium sulphate then treat-
ing at a temperature of about 33° C such salts with a wash brine containing
sodium sulphate in solution yet below the maximum amount until the solid
sodium sulphate has been dissolved out and a solution is obtained saturated
with sodium sulphate and then cooling the wash liquors containing the sodium
sulphate and depositing the sodium sulphate in a solid form.
5. The process of producing pure salts from brine consisting in first removing
from said brine all its salts except sodium chloride and sodium sulphate and
then passing such purified brine through a series of evaporating pans so heated
as to cause practically pure sodium chloride wetted with a solution containing
a proportion of sodium sulphate to be deposited in the first pan while in each
subsequent pan the proportion of sodium sulphate to sodium chloride in the
brine wetting the salt deposited increases and continuing the feeding
from pan to pan and evaporation until the brine becomes satu-
rated with sodium sulphate and causing a mixed salt of sodium
chloride and sodium sulphate to be deposited and continuing the feed from pan
to pan so as to produce in all such pans a salt containing the maximum pro-
portion of solid sodium sulphate then treating at a temperature of about 33° C.
such salts with a wash brine containing sodium sulphate in solution until the
solid sulphate has been dissolved out then removing the solution so formed
and washing the remaining salt with solutions of sodium chloride containing
continuously less proportions of sodium sulphate so as to remove any remaining
sodium sulphate and leave pure sodium chloride as a solid salt.
Dated this 29th day of June 1900.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London,
Chartered Patent Agent,
For the Applicants.