IMPROVEMENTS IN THE MANUFACTURE OR PRODUCTION OF CAUSTIC ALKALIES, CAUSTIC BARYTA AND CAUSTIC STRONTIA
Year: 1882

page_text: This Specification was, upon the 25th day of March, 1887, amended under
Sections 18 to 21 of the Patents, Designs, and Trade Marks Act, 1883.
LETTERS PATENT to William Lloyd Wise of 7 Whitehall Place, in the City
of Westminster for an Invention of IMPROVEMENTS IN THE MANUFACTURE
OR PRODUCTION OF CAUSTIC ALKALIES, CAUSTIC BARYTA AND CAUSTIC
STRONTIA A communication to him from abroad by Professor Dr. Carl
PROVISIONAL SPECIFICATION left by the said William Lloyd Wise at the
Office of the Commissioners of Patents on the 14th September 1882.
WILLIAM LLOYD WISE of 7 Whitehall Place in the City of Westminster
"IMPROVEMENTS IN THE MANUFACTURE OR PRODUCTION OF CAUSTIC ALKALIES,
CAUSTIC BARYTA AND CAUSTIC STRONTIA (a communication to me from abroad
by Professor Dr. Carl Löwig of Breslau Kingdom of Prussia German Empire)
"
If a mixture of carbonate of soda or carbonate of potash with oxide of iron is
exposed to a very high temperature, a chemical compound or combination is
obtained of oxide of iron with soda and potash and carbonic acid is evolved, this
compound or combination if treated with water is decomposed into caustic soda
or caustic potash (which is dissolved in the water) and into oxide of iron.
The same reaction will take place if carbonate of baryta or carbonate of strontia
and oxide of iron are exposed to heat; a chemical compound or combination of
baryta or strontia with oxide of iron is obtained, and carbonic acid is evolved.
This compound or combination if treated with boiling water is decomposed into
caustic baryta or caustic strontia (which dissolves in the water) and into oxide
of iron. On these facts the improved process is based for manufacturing on a large
scale and for industrial purposes caustic alkalies as well as caustic baryta and
caustic strontia.
The process is characterised by the simplicity and facility of its working
inasmuch as the lyes obtained by it, are ready for immediate evaporation without
any intermediate operation and the oxide of iron recovered may be used for the
next process.
For the success of the process it is necessary to have pure oxide of iron either
artificial or natural. The same must not contain either alumina or silica; a small
percentage of chalk or magnesia however is not injurious.
Numerous experiments shew that for the manufacture of caustic alkalies according

page_text: to this invention a mixture of one molecule of carbonate of potash or soda with
two molecules of oxide of iron will give the best result.
In manufacturing caustic baryta or caustic strontia it is preferred to employ a
mixture containing an equal number of molecules of each substance. The oxide
of iron may be employed either finely granulated, like sand, or as a finely ground
powder. In either case the mixture must be made as thoroughly as possible.
The process of heating the above mixture is by preference effected in iron
cylinders or retorts, similar to those which are used in gasworks, and the firing is
performed in a similar manner.
The temperature must be raised up to strong cherry heat. In manufacturing
pure caustic alkalies it is advisable to heat the mixture twice and to regrind and
sift it after the first heating. In manufacturing caustic baryta and caustic strontia
one heating will be sufficient. The heating must be continued for about one hour
or until on trial with diluted acid no effervescence is produced. Heating in
cylinders is preferable to heating in an open oven or in a bauxite oven; but care
must be taken that the cylinder is perfectly filled with the mixture and is brought
uniformly in its entire length up to a cherry heat.
If the oxide of iron is pure, the mixture will stand a very high temperature
without becoming soft or agglutinating.
This will not be the case if the oxide of iron contains 10% to 12% of silica.
The lixiviation of the heated mass is preferably effected in a vessel provided with
a stirring or agitating apraratus with iron blades and with pipes for the admission
of steam. In manufacturing on a large scale it is preferable to employ two such
vessels for alternate use. The vessel is first of all two thirds or three quarters filled
with hot water or diluted lye and the above named mixture after it has undergone
the heating process, is introduced into it. During the addition of the mass to the
water or lye the agitator or stirring apparatus must be continuously and rapidly
worked and steam must be admitted. The addition of the compound is stopped
when the lye has arrived at the desired strength shown by a hydrometer. Stirring
must be continued for say half or three quarters of an hour and the temperature
90° Celsius
must be kept up to 194° Fahrenheit*
quarter or half an hour the clear lye is drawn off into an iron vessel remaining
there until the lye has become quite clear. It is advisable to determine before
evaporation of the lye, whether any iron is contained in it, this is ascertained by
adding to a small quantity of it a few drops of a solution of sulphide of ammonium ;
the presence of iron will be shown by a dark color and in this case the lye must
remain warm for some time longer. In manufacturing caustic baryta and caustic
strontia clear solutions or lyes are obtained at once.
The agitator is then stopped and after a
If the solutions of caustic alkalies still contain small quantities of carbonic acid,
it may be removed by carefully adding caustic baryta.
The oxide of iron remaining and recovered after the lixiviation is more or less
of a dark colour and will always contain a small portion of protoxide and several
per cent of soda, because the lixiviation must not be carried on for too long a
period or the lyes will be too much diluted. Therefore in reusing the oxide of iron
its quantity must be increased or added to in proportion.
As a rule it is desirable to have the oxide of iron in excess as too much will do
no harm and is not lost. It is therefore advisable to ascertain by a sample trial
whether a product free from carbonic acid can be obtained. If this is not the case
after repeatedly strongly heating the mixture the quantity of oxide of iron must
be increased.
It is obvious that in the production of caustic alkalies a loss of alkali (strictly
speaking) cannot take place as the small quantity of soda remaining with the
oxide of iron after lixiviation, will be recovered when re-employing the latter, but
still as a matter of practice it is found that a loss of say 4 to 6% can hardly be
avoided.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Lloyd Wise in the Great Seal Patent Office on the
14th March 1883.
WILLIAM LLOYD WISE late of 7 Whitehall Place in the City of Westminster,
now of 46 Lincoln's Inn Fields in the County of Middlesex, IMPROVEMENTS IN
THE MANUFACTURE OR PRODUCTION OF CAUSTIC ALKALIES, CAUSTIC BARYTA AND
GAUSTIC STRONTIA " (a communication to me from abroad by Professor Dr. Carl
Löwig, of Breslau, Kingdom of Prussia, German Empire.)
If a perfect mixture of carbonate of soda with oxide of iron is exposed to a
very high temperature (high red heat) "ferrid" (ferrate) of soda is forined, being
a chemical compound or combination of soda with oxide of iron, which, if treated
with hot water will be rapidly decomposed into caustic soda and oxide of iron. If
instead of carbonate of soda, carbonate of potash is used, "ferrid" of potash is
produced in the same manner and which if treated with hot water will decompose
into caustic potash and oxide of iron; the " ferrids are however decomposed only
slowly in cold water.
"
Upon these facts the following method is based for producing caustic alkalies on
a large scale and for industrial and commercial purposes; it is remarkable for its
simplicity in its working, inasmuch as the lyes obtained by it are ready for immediate
evaporation and the oxide of iron recovered may be used for the next process. For
the success of the process it is necessary to have pure oxide of iron. It must not
contain either alumina or silica, a very small percentage of chalk or magnesia,
however, is not injurious. Dense red iron-stone and specular-iron or iron-glance
are very suitable materials. Also the roasted iron pyrites, containing copper,
may, after the extraction of th copper, be used advantageously, however a loss of
soda of 6 to 7 parts on 100 parts of oxide will take place, if pyrites are used; but
this loss will only take place if these pyrites are once used; in subsequent using
the loss will not recur.
It is desirable not to employ the oxide of iron in too fine a state but rather as a
finely granulated powder (such as sand). Thereby a "ferrid" in a granular stato
is obtained, which in consequence of its porous condition will allow of easy and
perfect lixiviation..
The "ferrid" obtained by heating the oxide of iron with soda will always
contain a very small quantity of protoxide, or rather of a combination of protoxide
and oxide, the quantity of which will however not be increased in repeated use
and therefore the oxide of iron may always be re-used for producing caustic soda.
The formation of the protoxide may however be prevented by a very small addition
of saltpetre. As one molecule of oxide of iron in a very fine powdered condition
is able to transform one molecule of soda into caustic soda, it follows, that the smallest
quantity of oxide of iron which can be used is about 150 parts to 100 parts of carbonate
of soda, it is however evident that if such oxide of iron is used in a coarser state, its
quantity must be increased, as it will not then come into such close contact with the
soda. Numerous experiments have proved that a mixture of 13 molecules of oxide of
iron and 1 molecule of carbonate of soda, or in round figures 100 parts of carbonate
of soda, 250 parts of oxide of iron, and 2 parts of saltpetre will, in working on a large

page_text: scale, give the best result. It is, however, to be recommended before commencing
heating the mixture, to ascertain by a trial whether this mixture will give a
"ferrid" free from carbonic acid. If this is not the case after repeatedly strongly
heating the mixture the quantity of the oxide must be increased. This will be
especially the case if the oxide of iron has been repeatedly used, and if it contains
through imperfect lixiviation more or less soda. In using roasted pyrites for the
first time it will partly enter into combination or form a compound which will not act
as a caustifier, and therefor in reusing it the quantity of the oxide must be somewhat
increased. For mixing well known apparatuses may be used; care should be taken
that the mixture is a very thorough one, and that there are no lumps of carbonate of
soda in it. As the carbonate of soda will melt at a temperature at which the formation
of the "ferrid" is still in its first stage, it is absolutely essential to the attainment
of a perfect result that the temperature be elevated above the melting point of the
soda. Experience has shown that carbonate of soda of 100 per cent is far more
difficult to caustify than if it contains 6 to 10% of other salts, as chloride of
sodium (common salt) or sulphate of soda (Glauber salt). Again a large addition
of saltpetre will be a hindrance to the caustifying process.
The heating is advantageously performed in a fire-clay muffle the exit of which
terminates in the chimney, the muffle is entirely filled with the mixture so that it
lies uniformly against the walls. Especial care should be taken that the muffle is
exposed to a uniform red heat throughout its length and remains so during the
entire process. This process is continued until a sample taken out proves to be
free of carbonic acid, which will be the case in two to two and a half hours if the
proper temperature has been attained according to the size of the muffle and the
quantity of the mixture, and, should the above trial fail to be satisfactory, it is of
no use to continue heating, or to increase the temperature up to white heat, as it is
a certain proof that the mixture contains too little oxide. Very good results are
obtained by dividing the heating process into two operations, viz, into the first or
fritting process, and into the second or finishing process.
The first or fritting process. The object of this fritting process is to obtain a
mass, bound together by the melting of the carbonate of soda, and which after
cooling, may be easily powdered and sifted through a coarse sieve; by this process
a perfect mixture of the oxide and soda is obtained. The fritted mass will only
occupy two thirds of the volume or bulk of the original mixture. The temperature
for this process must be raised up to red heat or cherry heat, and must be maintained
for from half an hour to three-quarters of an hour.
The second or finishing process. The muffle is entirely filled with the previously
fritted mass which has been sifted, and then closed. The mass is then exposed
without stirring to the necessary red heat, until a sample proves to be free of
carbonic acid; this will require nearly the same time as the foregoing fritting
process. There is no fear of the mass becoming soft or melting even at a very
highly elevated temperature. According to experience, the formation of the
"ferrid" will by this double process be more quickly accomplished than by the
single process and it is with greater certainty-provided the required temperature
has been attained-the "ferrid" will be nearly free from carbonic acid.
The expense of fuel is not materially increased by the double heating. Instead
of a muffle a heating or reverberatory furnace may be employed such as are used
for instance in producing alumina from bauxite. This furnace is for this purpose
preferably divided by a low bridge, so that the one part may be used for fritting,
and the other for finishing, and so that when the finished "ferrid" is withdrawn,
the mixture in the adjacent compartment in its first state is removed to the
finishing compartment and the first compartment is immediately charged with a
fresh mixture.
35
The ferrid if properly produced, has a dark greenish colour and is heavy,
hard and of sandy granulation; it must be able to absorb water without developing
heat and must not lose its granular quality or condition.
If the "ferrid" has these qualities the lixiviation does not offer any difficulty.

page_text: For this purpose a large iron cylinder may be used, into which a second iron
cylinder of smaller diameter is inserted, the latter being provided with a funnel
shape exit pipe provided with a cock or valve. The space between these two
cylinders is filled with water, which may be heated by steam or in any other
manner up to 70 to 80 degrees Celsius. The bottom of the inner cylinder is
covered with an iron sieve and upon this a layer of oxide of iron coarsely powdered
is spread, upon this a second layer of oxide of iron finely powdered is spread so as
to cover uniformly the entire bottom. These layers perform the duty of filter beds.
The "ferrid "to be lixiviated is sifted through a coarse sieve, in order to obtain an
uniform mass, which is essential, if the lixiviation be carried on quickly and
uniformly this latter would not be the case if there were large lumps present.
The inner iron cylinder is filled up to 3% of its bulk with the "ferrid" and cold
water is added simultaneously, so as to uniformly moisten the entire mass. The
"ferrid," properly prepared, will always contain up to 10 to 12% of not
decomposed carbonate of soda, and as cold water has no effect on the "ferrid," the
carbonate of soda, common salt, Glauber salt, or other salt present may be lixiviated
and removed by the cold water. For this purpose cold water is caused to run
through the "ferrid" until all other salts are perfectly lixiviated. Then the water
in the outer cylinder is raised up to 70° to 80° C. and after half an hour's time the
"ferrid" has been decomposed, the lixiviation is performed with hot water. The
concentrated lye first drawn off will be perfectly clear like water. It will, however,
soon become turbid from the separation of a few flakes of oxide of iron. The lye
may immediately be evaporated, if it is intended to produce solid hydrate of soda,
the traces of oxide will, during the concentration, separate perfectly, and may be
easily removed. This removal may, however, also be effectuated by the addition
of a small quantity of a diluted solution of sulphide of sodium, by which the iron
is immediately precipitated; it may be found advantageous to add a small quantity
of slacked lime, for the separation of small quantities of alumina, if the oxide of
iron and more especially if pyrites are used for the first time for the production of
the "ferrid." The oxide of iron remaining after the lixiviation of the "ferrid"
has a red color, and contains, as already stated, a small quantity of protoxide,
which can easily be ascertained by employing a magnet; again the remaining
oxide of iron contains more or less caustic soda, according as the lixiviation has
been more or less perfect. For this reason the oxide must be kept in a dry room.
It is evident that according to the process described theoretically speaking, no
loss of soda can take place (with the exception of that loss which will take place if
pyrites are used for the first time) because the small quantity remaining after the
lixiviation will come into use in the following heating process. However a loss of
several per cent cannot be avoided.
In my provisional specification it was proposed to produce caustic baryta and
caustic strontia by treating carbonate of baryta and carbonate of strontia by
exposure to heat with oxide of iron, but, as the results in practice have not so far
been as satisfactory as was then anticipated no claim is now made thereto. But
what is claimed as secured to me under the Letters Patent first hereinabove in part
recited is
The production of caustic soda and caustic potash by heating carbonate of soda
or carbonate of potash (according as caustic soda or caustic potash is required) with
oxide of iron substantially in the proportions and in the manner hereinabove
described.
In Witness whereof I the said William Lloyd Wise have hereunto set my
hand and seal this fourteenth day of March in the year of our Lord.
ADA

page_text: LETTERS PATENT to William Lloyd Wise of 7 Whitehall Place, in the City
of Westminster for an Invention of IMPROVEMENTS IN THE MANUFACTURE
PRODUCTION OF CAUSTIC ALKALIES, CAUSTIC BARYTA AND CAUSTIC
OR
STRONTIA
T
·
D
A communication to him from abroad by Professor Dr. Carl,
T7
PROVISIONAL SPECIFICATION left by the said William Lloyd Wise at the
Office of the Commissioners of Patents on the 14th September 1882.
WILLIAM LLOYD WISE of 7 Whitehall Place in the City of Westminster
"IMPROVEMENTS IN THE MANUFACTURE OR PRODUCTION OF CAUSTIC ALKALIES,
CAUSTIC BARYTA AND CAUSTIC STRONTIA" (a communication to me from abroad
by Professor Dr. Carl Löwig of Breslau Kingdom of Prussia German Empire)
If a mixture of carbonate of soda or carbonate of potash with oxide of iron is
exposed to a very high temperature, a chemical compound or combination is
obtained of oxide of iron with soda or potash and carbonic acid is evolved, this
compound or combination if treated with water is decomposed into caustic soda
or caustic potash (which is dissolved in the water) and into oxide of iron.
The same reaction will take place if carbonate of baryta or carbonate of strontia
and oxide of iron are exposed to heat; a chemical compound or combination of
baryta or strontia with oxide of iron is obtained, and carbonic acid is evolved.
This compound or combination if treated with boiling water is decomposed into
caustic baryta or caustic strontia (which dissolves in the water) and into exide
of iron. On these facts the improved process is based for manufacturing on a large
scale and for industrial purposes caustic alkalies as well as caustic baryta and
caustic strontia.
The process is characterised by the simplicity and facility of its working
inasmuch as the lyes obtained by it, are ready for immediate evaporation without
any intermediate operation and the oxide of iron recovered may be used for the
next process.
For the success of the process it is necessary to have pure oxide of iron either
artificial or natural. The same must not contain either alumina or silica; a sinall
percentage of chalk or magnesia however is not injurious.
Numerous experiments shew that for the manufacture of caustic alkalies according

page_text: to this invention a mixture of one molecule of carbonate of potash or soda with
two molecules of oxide of iron will give the best result.
In manufacturing caustic baryta or caustic strontia it is preferred to employ a
mixture containing an equal number of molecules of each substance. The oxide
of iron may be employed either finely granulated, like sand, or as a finely ground
powder. In either case the mixture must be made as thoroughly as possible.
The process of heating the above mixture is by preference effected in iron
cylinders or retorts, similar to those which are used in gasworks, and the firing is
performed in a similar manner.
The temperature must be raised up to strong cherry heat. In manufacturing
pure caustic alkalies it is advisable to heat the mixture twice and to regrind and
sift it after the first heating. In manufacturing caustic baryta and caustic strontia
one heating will be sufficient. The heating must be continued for about one hour
or until on trial with diluted acid no effervescence is produced. Heating in
cylinders is preferable to heating in an open oven or in a bauxite oven; but care
must be taken that the cylinder is perfectly filled with the mixture and is brought
uniformly in its entire length up to a cherry heat.
If the oxide of iron is pure, the mixture will stand a very high temperature
without becoming soft or agglutinating.
0
°
This will not be the case if the oxide of iron contains 10% to 12% of silica.
The lixiviation of the heated mass is preferably effected in a vessel provided with
a stirring or agitating apparatus with iron blades and with pipes for the admission
of steam. In manufacturing on a large scale it is preferable to employ two such
vessels for alternate use. The vessel is first of all two thirds or three quarters filled
with hot water or diluted lye and the above named mixture after it has undergone
the heating process, is introduced into it. During the addition of the mass to the
water or lye the agitator or stirring apparatus must be continuously and rapidly
worked and steam must be admitted. The addition of the compound is stopped
when the lye has arrived at the desired strength shown by a hydrometer. Stirring
must be continued for say half or three quarters of an hour and the temperature
must be kept up to
The agitator is then stopped and after a
quarter or half an hour the clear lye is drawn off into an iron vessel remaining
there until the lye has become quite clear. It is advisable to determine before
evaporation of the lye, whether any iron is contained in it, this is ascertained by
adding to a small quantity of it a few drops of a solution of sulphide of ammonium;
the presence of iron will be shown by a dark color and in this case the lye must
remain warm for some time longer. In manufacturing caustic baryta and caustic
strontia clear solutions or lyes are obtained at once.
90° Celsius
194° Fahrenheit
If the solutions of caustic alkalies still contain small quantities of carbonic acid,
it may be removed by carefully adding caustic baryta.
The oxide of iron remaining and recovered after the lixiviation is more or less
of a dark colour and will always contain a small portion of protoxide and several
per cent of soda, because the lixiviation must not be carried on for too long a
period or the lyes will be too much diluted. Therefore in reusing the oxide of iron
its quantity must be increased or added to in proportion.
As a rule it is desirable to have the oxide of iron in excess as too much will do
no harm and is not lost. It is therefore advisable to ascertain by a sample trial
whether a product free from carbonic acid can be obtained. If this is not the case
after repeatedly strongly heating the mixture the quantity of oxide of iron must
be increased.
It is obvious that in the production of caustic alkalies a loss of alkali (strictly
speaking) cannot take place as the small quantity of soda remaining with the
oxide of iron after lixiviation will be recovered when re-employing the latter, but
still as a matter of practice it is found that a loss of say 4 to 6° can hardly be
avoided.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Lloyd Wise in the Great Seal Patent Office on the
14th March 1883.
WILLIAM LLOYD WISE late of 7 Whitehall Place in the City of Westminster,
now of 46 Lincoln's Inn Fields in the County of Middlesex, "IMPROVEMENTS IN
THE MANUFACTURE OR PRODUCTION OF CAUSTIC ALKALIES, CAUSTIC BARYTA AND
CAUSTIC STRONTIA" (a communication to me from abroad by Professor Dr. Carl
Löwig, of Breslau, Kingdom of Prussia, German Empire.)
If a perfect mixture of carbonate of soda with oxide of iron is exposed to a
very high temperature (high red heat) "ferrid" (ferrate) of soda is formed, being
a chemical compound or combination of soda with oxide of iron, which, if treated
with hot water will be rapidly decomposed into caustic soda and oxide of iron. If
instead of carbonate of soda, carbonate of potash is used, "ferrid" of potash is
produced in the same manner and which if treated with hot water will decompose
into caustic potash and oxide of iron; the "ferrids" are however decomposed only
slowly in cold water.
Upon these facts the following method is based for producing caustic alkalies on
a large scale and for industrial and commercial purposes; it is remarkable for its
simplicity in its working, inasmuch as the lyes obtained by it are ready for immediate
evaporation and the oxide of iron recovered may be used for the next process. For
the success of the process it is necessary to have pure oxide of iron. It must not
contain either alumina or silica, a very small percentage of chalk or magnesia,
however, is not injurious. Dense red iron-stone and specular-iron or iron-glance
are very suitable materials. Also the roasted iron pyrites, containing copper,
may, after the extraction of the copper, be used advantageously, however a loss of
soda of 6 to 7 parts on 100 parts of oxide will take place, if pyrites are used; but
this loss will only take place if these pyrites are once used; in subsequent using
the loss will not recur.
It is desirable not to employ the oxide of iron in too fine a state but rather as a
finely granulated powder (such as sand). Thereby a "ferrid" in a granular state
is obtained, which in consequence of its porous condition will allow of easy and
perfect lixiviation.
The "ferrid" obtained by heating the oxide of iron with soda will always
contain a very small quantity of protoxide, or rather of a combination of protoxide
and oxide, the quantity of which will however not be increased in repeated use
and therefore the oxide of iron may always be re-used for producing caustic soda.
The formation of the protoxide may however be prevented by a very small addition
of saltpetre. As one molecule of oxide of iron in a very fine powdered condition
is able to transform one molecule of soda into caustic soda, it is however evident
that if such oxide of iron is used in a coarser state, its quantity must be increased,
as it will not then come into such close contact with the soda. Numerous experi-
ments have proved that a mixture of 1 molecules of oxide of iron and 1 molecule
of carbonate of soda, or in round figures 100 parts of carbonate of soda, 250 parts
of oxide of iron, and 2 parts of saltpetre will, in working on a large scale, give the
best result. It is, however, to be recommended before commencing heating the
mixture, to ascertain by a trial whether this mixture will give a "ferrid" free from
carbonic acid. If this is not the case after repeatedly strongly heating the mixture
the quantity of the oxide must be increased. This will be especially the case if
the oxide of iron has been repeatedly used, and if it contains through imperfect
ixiviation more or less soda. In using roasted pyrites for the first time it will.

page_text: partly enter into combination or form a compound which will not act as a caustifier,
and therefor in reusing it the quantity of the oxide must be somewhat increased.
For mixing well known apparatuses may be used; care should be taken that the
mixture is a very thorough one, and that there are no lumps of carbonate of soda
in it. As the carbonate of soda will melt at a temperature at which the formation
of the "ferrid" is still in its first stage, it is absolutely essential to the attainment
of a perfect result that the temperature be elevated above the melting point of the
soda. Experience has shown that carbonate of soda of 100 per cent is far more
difficult to caustify than if it contains 6 to 10% of other salts, as chloride of
sodium (common salt) or sulphate of soda (Glauber salt). Again a large addition
of saltpetre will be a hindrance to the caustifying process.
The heating is advantageously performed in a fire-clay muffle, the exit of which
terminates in the chimney, the muffle is entirely filled with the mixture so that it
lies uniformly against the walls. Especial care should be taken that the muffle is
exposed to a uniform red heat throughout its length and remains so during the
entire process. This process is continued until a sample taken out proves to be
free of carbonic acid, which will be the case in two to two and a half hours if the
proper temperature has been attained according to the size of the muffle and the
quantity of the mixture, and, should the above trial fail to be satisfactory, it is of
no use to continue heating, or to increase the temperature up to white heat, as it is
a certain proof that the mixture contains too little oxide. Very good results are
obtained by dividing the heating process into two operations, viz, into the first or
fritting process, and into the second or finishing process.
The first or fitting process. The object of this fritting process is to obtain a
mass, bound together by the melting of the carbonate of soda, and which after
cooling, may be easily powdered and sifted through a coarse sieve; by this process
a perfect mixture of the oxide and soda is obtained. The fritted mass will only
occupy two thirds of the volume or bulk of the original mixture. The temperature
for this process must be raised up to red heat or cherry heat, and must be maintained
for from half an hour to three-quarters of an hour.
The second or finishing process. The muffle is entirely filled with the previously
fritted mass which has been sifted, and then closed. The mass is then exposed
without stirring to the necessary red heat, until a sample proves to be free of
carbonic acid; this will require nearly the same time as the foregoing fritting
process. There is no fear of the mass becoming soft or melting even at a very
highly elevated temperature. According to experience, the formation of the
"ferrid" will by this double process be more quickly accomplished than by the
single process and it is with greater certainty-provided the required temperature
has been attained-the "ferrid" will be nearly free from carbonic acid.
The expense of fuel is not materially increased by the double heating. Instead
of a muffle a heating or reverberatory furnace may be employed such as are used
for instance in producing alumina from bauxite. This furnace is for this purpose
preferably divided by a low bridge, so that the one part may be used for fritting,
and the other for finishing, and so that when the finished "ferrid" is withdrawn,
the mixture in the adjacent compartment in its first state is removed to the
finishing compartment and the first compartment is immediately charged with a
fresh mixture.
The "ferrid" if properly produced, has a dark greenish colour and is heavy,
hard and of sandy granulation; it must be able to absorb water without developing
heat and must not lose its granular quality or condition.
If the "ferrid" has these qualities the lixiviation does not offer any difficulty.
For this purpose a large iron cylinder may be used, into which a second iron
cylinder of smaller diameter is inserted, the latter being provided with a funnel
shape exit pipe provided with a cock or valve. The space between these two
cylinders is filled with water, which may be heated by steam or in any other
manner up to 70 to 80 degrees Celsius. The bottom of the inner cylinder is
covered with an iron sieve and upon this a layer of oxide of iron coarsely powdered

page_text: is spread, upon this a second layer of oxide of iron finely powdered is spread so as
to cover uniformly the entire bottom. These layers perform the duty of filter beds.
The "ferrid " to be lixiviated is sifted through a coarse sieve, in order to obtain an
uniform mass, which is essential, if the lixiviation be carried on quickly and
uniformly; this latter would not be the case if there were large lumps present.
The inner iron cylinder is filled up to 3% of its bulk with the "ferrid" and cold
water is added simultaneously, so as to uniformly moisten the entire mass. The
"ferrid," properly prepared, will always contain up to 10 to 12 % of not
decomposed carbonate of soda, and as cold water has no effect on the "ferrid," the
carbonate of soda, common salt, Glauber salt, or other salt present may be lixiviated
and removed by the cold water. For this purpose cold water is caused to run
through the "ferrid" until all other salts are perfectly lixiviated. Then the water
in the outer cylinder is raised up to 70° to 80° C. and after half an hour's time the
"ferrid" has been decomposed, the lixiviation is performed with hot water. The
concentrated lye first drawn off will be perfectly clear like water. It will, however,
soon become turbid from the separation of a few flakes of oxide of iron. The lye
may immediately be evaporated, if it is intended to produce solid hydrate of soda,
the traces of oxide will, during the concentration, separate perfectly, and may be
easily removed. This removal may, however, also be effectuated by the addition
of a small quantity of a diluted solution of sulphide of sodium, by which the iron
is immediately precipitated; it may be found advantageous to add a small quantity
of slacked lime, for the separation of small quantities of alumina, if the oxide of
iron and more especially if pyrites are used for the first time for the production of
the "ferrid." The oxide of iron remaining after the lixiviation of the "ferrid"
has a red color, and contains, as already stated, a small quantity of protoxide,
which can easily be ascertained by employing a magnet; again the remaining
oxide of iron contains more or less caustic soda, according as the lixiviation has
been more or less perfect. For this reason the oxide must be kept in a dry room.
It is evident that according to the process described theoretically speaking, no
loss of soda can take place (with the exception of that loss which will take place if
pyrites are used for the first time) because the small quantity remaining after the
lixiviation will come into use in the following heating process. However a loss of
several per cent cannot be avoided.
In my provisional specification it was proposed to produce caustic baryta and
caustic strontia by treating carbonate of baryta and carbonate of strontia by
exposure to heat with oxide of iron, but, as the results in practice have not so far
been as satisfactory as was then anticipated no claim is now made thereto. But
what is claimed as secured to me under the Letters Patent first hereinabove in part
recited is
The production of caustic soda and caustic potash by heating carbonate of soda
or carbonate of potash (according as caustic soda or caustic potash is required) with
oxide of iron in the manner hereinabove described.
In Witness whereof I the said William Lloyd Wise have hereunto set my
hand and seal this fourteenth day of March in the year of our Lord, one
thousand eight hundred and eighty three