Improvements in Mode of Procedure for Decomposing by Magnesia the Mother-liquor of the Ammonia Soda Process.
Year: 1885

page_text: Improvements in Mode of Procedure for Decomposing by
Magnesia the Mother-liquor of the Ammonia Soda Process.
I, WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey, Fellow
of the Royal Society, do hereby declare the nature of the said Invention for
IMPROVEMENTS IN MODE OF PROCEDURE FOR DECOMPOSING BY MAGNESIA THE
MOTHER-LIQUOR OF THE AMMONIA SODA PROCESS to be as follows:-
:-
"
In the manufacture of soda by the ammonia process, the mother-liquor from
which bicarbonate of soda has been separated is a mixed solution of chloride of
ammonium, chloride of sodium, bicarbonate of soda, and bicarbonate of ammonia.
From this mixed solution, the manufacturer of soda by the ammonia process has to
regenerate his ammonia, for use again.
The first step to this end is simply to heat the said mixed solution. The
bicarbonate of ammonia which the said solution at first contained is thereby driven
off as vapour, and there is also driven off as vapour a further quantity of bicar-
bonate of ammonia, formed by reaction between the bicarbonate of soda which was
contained in the solution before it was heated and some of its ammonium chloride.
The solution which remains when these two quantities of bicarbonate of ammonia
have been driven off contains chloride of ammonium and chloride of sodium only.
The chloride of ammonium of this solution has now to be decomposed, in such
wise that its ammonia shall be yielded in the free state.
Hitherto, the said chloride of ammonium has always been decomposed, and at
present it always is decomposed, by means of lime. The chlorine of the salt
decomposed by the manufacturer of ammonia soda is thus finally obtained as
chloride of calcium, and in that state is thrown away.
As chloride of calcium is a body from which it is not yet possible industrially to
separate its chlorine, either in the free state or as H Cl, while means have recently
been invented by which both chlorine and hydrochloric acid can be readily
manufactured from chloride of magnesium, the correspondents who have communi-
cated to me the present invention have endeavoured to decompose by magnesia,
CD 01

page_text: instead of by lime, the ammonium chloride produced in the ammonia soda process,
and thus to obtain the chlorine of the salt decomposed by that process as
constituent of a compound from which both free chlorine and hydrochloric acid can
afterwards be manufactured economically. They have succeeded in this endeavour,
and the present invention consists in the method of procedure by which they have
found that the decomposition by magnesia of the ammonium chloride produced in
the manufacture of soda by the ammonia process can be executed with advantage.
My correspondents have found that, in order to render industrially practicable
the decomposition by Mg O of the NH, Cl produced in the manufacture of soda by
the ammonia process, the manner of proceeding must be in some respects very
different from the manner of proceeding which is at present followed for the
regeneration of ammonia from that ammonium chloride by means of lime.
When to an aqueous solution of chloride of ammonium one adds an equivalent of
lime, the lime dissolves immediately, and from the resulting mixed solution the
whole of the ammonia corresponding to the ammonium chloride originally present
can be distilled off almost if not quite as readily as from a simple solution containing
water and ammonia only.
For distilling ammonia from the product of the addition of lime to the mother-
liquor of the ammonia soda process, various kinds of apparatus are employed, but
they all consist, essentially, either of a series of distinct vessels, or of one vessel or
column divided into a number of compartments, through which series of vessels or
compartments steam and vapour of ammonia travel in one direction, while liquid
travels through the series of vessels or compartments in the opposite direction.
This liquid is at first the highly ammoniacal product of the addition of lime to the
mother-liquor of the ammonia soda process, but as it passes through the apparatus
it gradually loses its ammonia, and finally becomes simply a mixed solution of
calcium chloride and sodium chloride. The steam employed in this apparatus is
sometimes generated in one of the vessels or compartments of the apparatus itself,
by evaporation therein of the liquid under treatment, after that liquid has had
driven off from it, in other parts of the apparatus, the greater part of the ammonia
which it originally contained; but more usually the steam employed is steam from
a boiler external to the distillation apparatus proper. In both cases equally, from
that vessel or compartment of the apparatus from which the mixed solution of
calcium chloride and sodium chloride, which is the residual product of the operation,
is ultimately discharged, there issues a mixture of steam and vapour of aminonia,
which mixture of steam and vapour of ammonia (or such part of it as does not
become condensed in subsequent vessels or compartments of the apparatus) then
traverses the contents of all the other vessels or compartments composing the
apparatus, and in so doing becomes continually richer and richer in ammonia.
Г
Now, there are two reasons why, in thus distilling ammonia from the product of
the addition of lime to the mother-liquor of the ammonia soda process, the mixture
of steam and vapour of ammonia which passes off from each successive vessel or
compartment of the distillation apparatus is richer in vapour, of ammonia than the
mixture of steam and vapour of ammonia which entered that vessel or compart-
ment. One of those reasons of course is that in each vessel or compartment which
it successively enters, the said mixture of steam and vapour of ammonia meets a
liquid richer in ammonia than it had met before, and carries off therefrom a larger
quantity of ammonia than it had carried off from any preceding vessel or com-
partment; but another reason is that much of the steam which enters the later
vessels or compartments condenses therein, not passing off therefrom as steam, but
being added to their contents as condensed water. The current of mixture of
steam and vapour of ammonia, as it-travels onwards, thus not only continually
gains more and more vapour of ammonia, but also continually loses steam.
This condensation, in some parts of the apparatus employed, of some of the
steam arriving therein from other parts of it, takes place in every variety of
apparatus which either is employed, or, ever has been employed, for the distillation
of ammonia from the product of the addition of lime to the mother-liquor of the

page_text: ammonia soda process. It is usually due simply to loss of heat by radiation from
the parts of the apparatus in which it takes place; but special appliances (such
as serpentine pipes, through which a refrigerating fluid continually flows) are
sometimes employed ad hoc.
For this condensation, in some parts of the apparatus, of some of the steam
arriving therein from other parts of it, is not accidental. It is absoluely essential
to one of the objects which the manufacturer who regenerates. by lime the ammonia
used in the ammonia soda process always seeks to accomplish!
When a mixture of two vapours, one of which two vapours is more volatile
than the other, is subjected to a limited amount of cooling, the one of the two
vapours which is least volatile condenses in the greatest proportion, and what
remains uncondensed, after the said cooling, is a mixture of the two vapours much
richer in the more volatile of them than was the original mixture of the two,
before it was subjected to the said limited degree of cooling. It is for this
reason that all apparatus for the distillation of ammonia from the product of the
addition of lime to the mother-liquor of the ammonia soda process is always so
constructed and disposed that in certain parts of it steam arriving therein from
other parts of it shall undergo condensation. One of the objects always sought is
that there shall finally issue from the apparatus a mixture of steam and vapour
of ammonia containing a minimum proportion of steam and a maximum proportion
of vapour of ammonia; and to the accomplishment of this object the said
condensation of steam in certain parts of the distillation apparatus is absolutely
essential.
1:
1
While, however, the condensation of steam which takes place in every kind of
apparatus ever used for the distillation of ammonia from the product of the
addition of lime to the mother-liquor of the ammonia soda process thus causes the
mixture of steam and vapour of ammonia which finally issues from the distillation
apparatus to be very much richer in vapour of ammonia than it otherwise would
be, it renders necessary much more evaporation, and consequently a much greater
consumption of fuel, for the distillation of a given quantity of ammonia, than
would suffice therefor if such condensation of steam did not take place. When no
steam is allowed to return as condensed water into the vessel in which that
operation is performed, all the ammonia of the product of the addition of lime to
the mother-liquor of the ammonia soda process may be driven off therefromi by
passing through that product a quantity of steam corresponding to about one-third
of the water contained in that product itself; but at least from three to four times
that quantity of steam is actually employed in regenerating by means of lime the
ammonia of the mother-liquor of the ammonia soda process, when the steam used
is steam from a boiler external to the distillation apparatus proper, as is seen
from the fact that the volume of the residual solution of calcium and sodium
chlorides is always more than twice as great as the volume of the original mother-
liquor this augmentation of volume being of course due to condensation in the
liquid treated of most of the steam sent into it.
:
In generating ammonia from the mother-liquor of the ammonia soda process by
means of lime, the increased amount of evaporation rendered necessary by this
condensation of steam in the liquid treated is compensated by the greater richness
in ammonia of the mixture of steam and vapour of ammonia finally obtained.
But the case is very different in respect of the regeneration of ammonia from the
said mother-liquor by means of magnesia. .
It has been said that when an equivalent of lime is added to aqueous solution
of ammonium chloride, the lime immediately dissolves therein completely. But
when an equivalent of magnesia is added to aqueous solution of ammonium
chloride, the magnesia does not at once dissolve completely. Only a portion of the
magnesia dissolves at first, setting free a corresponding proportion of the ammonia
of the ammonium chloride; and it is only as the ammonia thus at first set free is
driven off that more magnesia dissolves, setting free more ammonia. As more and'
more magnesia dissolves; and more and more ammonia is driven off; the liquid thus

page_text: becoming poorer and poorer in ammonium chloride and richer and richer in mag-
nesium chloride, for the remainder of the magnesia to react upon the remainder of
the ammonium chloride becomes continually more and more difficult; and hence,
to drive off by means of magnesia all the ammonia of solution of ammonium
chloride requires a much more prolonged ebullition than suffices to drive off all the
ammonia of a similar solution by means of lime. If the product of the addition
of lime to the mother-liquor of the ammonia soda process were evaporated in a
vessel heated externally, under conditions under which no steam could return, as
condensed water, into the vessel in which the operation were performed, all the
ammonia of that product would be driven off by the time that about one-third of
its water had been evaporated; but if one evaporated under the same conditions
the product of the addition of magnesia to the said mother-liquor, its ammonia
would be by no means completely driven off when one third of its water had been
evaporated. On the contrary, much ammonium chloride would remain still
undecomposed, even when the evaporation had been continued nearly to dryness.
To decompose the remainder of the ammonium chloride, one must add very
considerably more water, and then evaporate the greater part of that further
quantity of water..
Seeing, then, that even when the product of the addition of magnesia to the
mother-liquor of the ammonia soda process is evaporated under conditions under
which no steam returns, as condensed water, into the vessel in which the operation
is performed, the amount of evaporation required to drive off all its ammonia is
several times greater than the amount of evaporation required, under similar
conditions, to drive off all the ammonia of the product of the addition of lime to
the said mother-liquor, and seeing that the condensation of steam which takes
place during the distillation of ammonia, by all the methods hitherto employed,
from the product of the addition of lime to the said mother-liquor, involves an
amount of evaporation several times greater than would suffice to drive off all its
ammonia if that condensation of steam did not take place, it follows that the
amount of evaporation which would be required for the regeneration by inagnesia
of the ammonia employed in the ammonia soda process, in such apparatus and by
such methods as those hitherto employed for the regeneration of that ammonia by
means of lime, would be so enormous that the regeneration of the said ammonia
by means of magnesia, in such apparatus and by such methods of procedure, is
absolutely impracticable.
The authors of the present invention have found, however, that the ammonium
chloride of the mother-liquor of the ammonia soda process may be decomposed by
magnesia so economically as to render the operation industrially practicable and
advantageous, if the operation be performed under conditions under which the
addition to the liquid under treatment, in any part of the apparatus employed, of
water condensed from steam arriving there from another part of the apparatus,
is for the most part avoided, and under which the liquid under treatment is always
kept, in all parts of the apparatus, in intimate contact with the magnesia which is
to decompose its aminonium chloride; and their present invention consists in
performing the decomposition by magnesin of the ammonium chloride of the
ammonia soda process under the new conditions thus indicated.
The application of the present invention begins when the mother-liquor of the
ammonia soda process has had its bicarbonate of ammonia driven off from it, and
after a sufficient quantity of magnesia has then been added to it, and the resulting
mixture has been raised to its boiling point or nearly so.
The mixture of magnesia with solution of ammonium chloride, or with mixed
solution of ammonium chloride and sodium chloride, is then passed through a series
of vessels, or through a series of compartments of one vessel, as the case may be,
the mixture being so agitated in all parts of the apparatus as to keep its magnesia
in suspension, and steam is caused to pass through the said mixture, the steam
travelling through the series of vessels or compartments in the opposite direction
to that in which the mixture of solution and magnesia travels through that series

page_text: of vessels or compartments, and the contents of the said vessels or compartments
being maintained at such temperature that in none of them can steam arriving
therein from any other of them undergo condensation, or, if at all, to more than an
insignificant extent. In operating in this way, instead of most of the steam
employed becoming condensed in the apparatus employed, as is the case in all
methods hitherto employed for performing the corresponding operation by means
of lime, and so passing off, as condensed water, from that extremity of the
apparatus from which is discharged the solution which is the residual product of
the operation, practically the whole of the steam employed passes off as such from
the opposite extremity of the apparatus, and the mother-liquor, in passing through
the apparatus,, and having its ammonia driven off from it therein, does not increase
in volume, or, if it increases in volume at all, does so only to an extremely slight
extent.
To carry out this invention, the said series of vessels or compartments must each
be furnished interiorly with a mechanical agitator, and must be provided with
dispositions for preventing the cooling of their contents to the point at which
steam could condense in them. The said dispositions may be of very various
kinds, as will be well understood by practical men, and no particular means for the
purpose constitutes any part of the present invention; but a suitable such means
consists in surrounding the said vessels or compartments by an envelope of
masonry, and causing products of combustion to pass between the interior surface
of this masonry and the exterior surface of the said vessels or compartments.
It will equally be understood that the apparatus employed for the performance
of the present invention may be of very various kinds; but it is believed that the
most suitable apparatus for the purpose is that described in the specification which
was filed with the application for a patent which is numbered 9227 and dated the
first of August of the current year.
What is new in the present invention is the process of decomposing by magnesia,
the ammonium chloride of the ammonia soda process which commences after that
mother-liquor has had bicarbonate of ammonia driven off from it, and magnesia
added to it, and has been raised to or nearly to the boiling point, and which
consists in then passing the resulting mixture of solution and magnesia through a
series of either distinct vessels or of compartments of one vessel, through which
steam also passes, the mixture of solution and magnesia travelling in one direction
and the steam travelling in the opposite direction and passing through the mixture
of solution and magnesia, the mixture of solution and magnesia being agitated so
as to keep its magnesia constantly in suspension, and the vessels or compartments
through which the said mixture passes being maintained at such temperature that.
none or scarcely any of the steam entering those vessels or compartments can
condense in them.

page_text: Improvements in Mode of Procedure for Decomposing by
Magnesia the Mother-liquor of the Ammonia Soda .Process.
I, WALTER FRANK RAPHAEL WELDON, of 19 Great George Street, Westminster,
in the County of Middlesex, Administrator of the late Walter Weldon, the
Applicant, do hereby declare the nature of the said invention for "IMPROVEMENTS
IN MODE OF PROCEDURE FOR DECOMPOSING BY MAGNESIA THE MOTHER-LIQUOR
OF THE AMMONIA SODA PROCESS," and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:
In the manufacture of soda by the ammonia process, the mother-liquor from
which bicarbonate of soda has been separated is a mixed solution of chloride of
ammonium, chloride of sodium, bicarbonate of soda, and bicarbonate of ammonia.
From this mixed solution, the manufacturer of soda by the ammonia process has to
regenerate his ammonia, for use again.
The first step to this end is simply to heat the said mixed solution. The bi-
carbonate of ammonia which the said solution at first contained is thereby driven
off as vapour, and there is also driven off as vapour a further quantity of bicarbonate
of ammonia, formed by reaction between the bicarbonate of soda which was con-
tained in the solution before. it was heated and some of its ammonium chloride.
The solution which remains when these two quantities of bicarbonate of ammonia
have been driven off contains chloride of ammonium and chloride of sodium only.
The chloride of ammonium of this solution has now to be decomposed, in such
wise that its ammonia shall be yielded in the free state.
Hitherto, the said chloride of ammonium has always been decor
present it always is decomposed, by means of lime. The chi
decomposed by the manufacturer of ammonia soda is thus
chloride of calcium, and in that state is thrown away.
As chloride of calcium is a body from which it is not y
separate its chlorine, either in the free state or as hydroc.
have recently been invented by which both chlorine and h
s
ed, and at
of the salt
obtained as
dustrially to
u, while means
chloric acid can be
readily manufactured from chloride of magnesium, the correspondents who have
communicated to me the present invention have endeavoured to decompose by
magnesia, instead of by lime, the ammonium chloride produced in the ammonia
soda process, and thus to obtain the chlorine of the salt decomposed by that process
as a constituent of a compound from which both free chlorine and hydrochloric
acid can afterwards be manufactured economically. They have succeeded in this
endeavour, and the present invention consists in the method of procedure by which
they have found that the decomposition by. magnesia of the ammonium chloride
produced in the manufacture of soda by the ammonia process can be executed with
advantage.
My correspondents have found that, in order to render industrially practicable
the decomposition by MgO of the NH, Cl produced in the manufacture of soda by
the ammonia process, the manner of proceeding must be in some respects very
different from the manner of proceeding which is at present followed for the
regeneration of ammonia-from that ammonium chloride by means of lime,

page_text: When to an aqueous solution of chloride of ammonium one adds an equivalent
of lime, the lime dissolves immediately, and from the resulting mixed solution the
whole of the ammonia corresponding to the ammonium chloride originally present
can be distilled off almost if not quite as readily as from a simple solution
containing water and ammonia only.
For distilling ammonia from the product of the addition of lime to the mother-
liquor of the ammonia soda process, various kinds of apparatus are employed, but
they all consist, essentially, either of a series of distinct vessels, or of one vessel or
column divided into a number of compartments, through which series of vessels or
compartments steam and vapour of ammonia travel in one direction, while liquid
travels through the series of vessels or compartments in the opposite direction.
This liquid is at first the highly ammoniacal product of the addition of lime to the
mother-liquor of the ammonia soda process, but as it passes through the apparatus
it gradually loses its ammonia, and finally becomes simply a mixed solution of
calcium chloride and sodium chloride. The steam employed in this apparatus is
sometimes generated in one of the vessels or compartments of the apparatus itself,
by evaporation therein of the liquid under treatment, after that liquid has had
driven off from it, in other parts of the apparatus, the greater part of the ammonia
which it originally contained; but more usually the steam employed is steam from
a boiler external to the distillation apparatus proper. In both cases equally, from
that vessel or compartment of the apparatus from which the mixed solution of
calcium chloride and sodium chloride, which is the residual product of the
operation, is ultimately discharged, there issues a mixture of steam and vapour of
ammonia, which mixture of steam and vapour of ammonia (or such part of it as
does not become condensed in subsequent vessels or compartments of the apparatus).
then traverses the contents of all the other vessels or compartments composing the
apparatus, and in so doing becomes continually richer and richer in ammonia.
Now, there are two reasons why, in thus distilling ammonia from the product of
the addition of lime to the mother-liquor of the ammonia soda process the mixture
of steam and vapour of ammonia which passes off from each successive vessel or
compartment of the distillation apparatus is richer in vapour of ammonia than the
mixture of steam and vapour of ammonia which entered that vessel or com-
partment. One of those reasons of course is that in each vessel or compartment
which it successively enters, the said mixture of steam and vapour of ammonia
meets a liquid richer in ammonia than it had met before, and carries off therefrom
a larger quantity of ammonia than it had carried off from any preceding vessel or
compartment; but another reason is that much of the steam which enters the later
vessels or compartments condenses therein, not passing off therefrom as steam, but
being added to their contents as condensed water. The current of mixture of
stean and vapour of ammonia, as it travels onwards, thus not only continually
gains more and more vapour of ammonia, but also continually loses steam.
This condensation, in some parts of the apparatus employed, of some of the steam
arriving therein from other parts of it, takes place in every variety of apparatus
which either is employed, or ever has been employed, for the distillation of
ammonia from the product of the addition of lime to the mother-liquor of the
ammonia soda process. It is usually due simply to loss of heat by radiation from
the parts of the apparatus in which it takes place; but special appliances (such as
serpentine pipes, through which a refrigerating fluid constantly flows) are some-.
times employed ad hoc.
For this condensation, in some parts of the apparatus, of some of the steam
arriving therein from other parts of it, is not accidental. It is absolutely essential
to one of the objects which the manufacturer who regenerates by lime the aminonia
used in the ammonia soda process always seeks to accomplish.
When a mixture of two vapours, one of which two vapours is more volatile than
the other, is subjected to a limited amount of cooling, the one of the two vapours
which is least volatile condenses in the greatest proportion, and what remains
uncondensed, after the said cooling, is a mixture of the two vapours much richer

page_text: in the more volatile of them than was the original mixture of the two, before it
was subjected to the said limited degree of cooling. It is for this reason that all
apparatus for the distillation of ammonia from the product of the addition of, lime
to the mother-liquor of the ammonia soda process is always so constructed and
disposed that in certain parts of it steam arriving therein from other, parts of it
shall undergo condensation. One of the objects always sought is that there shall
finally issue from the apparatus a mixture of steam and vapour of ammonia con-
taining a minimum proportion of steam and a maximum proportion of vapour of
ammonia; and to the accomplishment of this object the said condensation of steam
in certain parts of the distillation apparatus is absolutely essential.
While, however, the condensation of steam which takes place in every kind of
apparatus ever used for the distillation of ammonia from the product of the
addition of lime to the mother-liquor of the ammonia soda process thus causes the
mixture of steam and vapour of ammonia which finally issues from the distillation
apparatus to be very much richer in vapour of ammonia than it otherwise would
.be, it renders necessary much more evaporation, and consequently a much greater
consumption of fuel, for the distillation of a given quantity of ammonia, than
would suffice therefore if such condensation of steam did not take place. When no
steam is allowed to return as condensed water into the vessel in which that
operation is performed, all the ammonia of the product of the addition of lime to
the mother-liquor of the ammonia soda process may be driven off therefrom by
passing through that product a quantity of steam corresponding to about one-third
of the water contained in that product itself; but at least from three to four times
that quantity of steam is actually employed in regenerating by means of lime the
ammonia of the mother liquor of the ammonia soda process, when the steam used
is steam from a boiler external to the distillation apparatus proper, as is seen from
the fact that the volume of the residual solution of calcium and sodium chlorides is
always more than twice as great as the volume of the original mother-liquor: this
augmentation of volume being of course due to condensation in the liquid treated
of most of the steam sent into it.
In generating ammonia from the mother-liquor of the ammonia soda process by
means of lime, the increased amount of evaporation rendered necessary by this
condensation of steam in the liquid treated is compensated by the greater richness
in ammonia of the mixture of steam and vapour of ammonia finally obtained.
But the case is very different in respect of the regeneration of aminonia from the
said mother-liquor by means of magnesia.
It has been said that when an equivalent of lime is added to aqueous solution of
ammonium chloride, the lime immediately dissolves therein completely. But when
an equivalent of magnesia is added to aqueous solution of ammonium chloride, the
magnesia does not at once dissolve completely. Only a portion of the magnesia
dissolves at first, setting free a corresponding proportion of the ammonia of the
ammonium chloride; and it is only as the ammonia thus at first set free is driven
off that more magnesia dissolves, setting free more ammonia. As more and more
magnesia dissolves, and more and more ammonia is driven-off, the liquid thus
becoming poorer and poorer in ammonium chloride and richer and richer in
magnesium chloride, for the remainder of the magnesia to react upon the re-
mainder of the ammonium chloride becomes continually more and more difficult;
and hence, to drive off by means of magnesia all the ammonia of solution of
ammonium chloride requires a much more prolonged ebullition than suffices to
drive off all the ammonia of a similar solution by means of lime. If the product
of the addition of lime to the mother-liquor of the ammonia soda process were
evaporated in a vessel heated externally, under conditions under which no steam
could return, as condensed water, into the vessel in which the operation were
performed, all the ammonia of that product would be driven off by the time that
about one-third of its water had been evaporated; but if one evaporated under the
same conditions the product of the addition of magnesia to the said mother-liquor,
its ammonia would be by no means completely driven off when one-third of its

page_text: water had been evaporated. On the contrary, much aminonium chloride would
remain still undecomposed, even when the evaporation had been continued nearly
to dryness. To decompose the remainder of the ammonium chloride, one must add
very considerably more water, and then evaporate the greater part of that further
quantity of water.
Seeing, then, that even when the product of the addition of magnesia to the
mother-liquor of the ammonia soda, process is evaporated under conditions under
which no steam returns, as condensed water, into the vessel in which the operation
is performed, the amount of evaporation required to drive off all its ammonia is
several times greater than the amount of evaporation required, under similar con-
ditions, to drive off all the ammonia of the product of the addition of lime to the said
mother-liquor, and seeing that the condensation of steam which takes place during
the distillation of ammonia, by all the methods hitherto employed, from the product
of the addition of lime to the said mother-liquor, involves an amount of evaporation
several times greater than would suffice to drive off all its ammonia if that con-
densation of steam did not take place, it follows that the amount of evaporation
which would be required for the regeneration by magnesia of the ammonia employed
in the ammonia soda process, in such apparatus and by such methods as those
hitherto employed for the regeneration of that ammonia by means of lime, would
be so enormous that the regeneration of the said ammonia by means of magnesia,
in such apparatus and by such methods of procedure, is absolutely impracticable.
The authors of the present. invention have found, however, that the ammonium
chloride of the mother-liquor of the ammonia soda process may be decomposed by
magnesia so economically as to render the operation industrially practicable and
advantageous, if the operation be performed under conditions under which the
addition to the liquid under treatment, in any part of the apparatus employed, of
water condensed from steam arriving there from another part of the apparatus, is
for the most part avoided, and under which the liquid under treatment is always
kept, in all parts of the apparatus, in intimate contact with the magnesia which is
to.decompose its ammonium chloride; and their present invention consists in per-
formning the decomposition by magnesia of the ammonium chloride of the ammonia
soda process under the new conditions thus indicated.
The application of the present invention begins when the mother-liquor of the
ammonia soda process has had its bicarbonate of ammonia driven off from it, and
after a sufficient quantity of magnesia has then been added to it, and the resulting
mixture has been raised to its boiling point or nearly so.
The mixture of magnesia with solution of ammonium chloride, or with mixed
solution of ammonium chloride and sodium chloride, is then passed through a
series of vessels, or through a series of compartments of one vessel, as the case may
be, the mixture being so agitated in all parts of the apparatus as to keep its
magnesia in suspension, and steam is caused to pass through the said mixture, the
steam travelling through the series of vessels or compartments in the opposite
direction to that in which the mixture of solution and magnesia travels through
that series of vessels or compartments, and the contents of the said vessels or com-
partments being maintained at such temperature that in none of them can steam
arriving therein from any other of them undergo condensation, or, if at all, to more
than an insignificant extent. In operating in this way, instead of most of the
steam employed becoming condensed in the apparatus employed, as is the case in
all methods hitberto employed for performing the corresponding operation by means
of lime, and so passing off, as condensed water, from that extremity of the apparatus
from which is discharged the solution which is the residual product of the operation,
practically the whole of the steam employed passes off as such from the opposite
extremity of the apparatus, and the mother-liquor, in passing through the apparatus,
and having its ammonia driven off from it therein, does not increase in volume, or,
if it increases in volume at all, does so only to an extremely slight extent.
To carry out this invention, the said series of vessels or compartments must
each be furnished interiorly with a mechanical agitator, and must be provided with

page_text: dispositions for preventing the cooling of their contents to the point at which steam
could condense in them. The said dispositions may be of very various kinds, as
will be well understood by practical men, and no particular means for the purpose
constitutes any part of the present invention; but a suitable such means consists
in surrounding the said vessels or compartments by an envelope of masonry, and
causing products of combustion to pass between the interior surface of this masonry
and the exterior surface of the said vessels or compartments.
It will equally be understood that the apparatus employed for the performance
of the present invention may be of various kinds; but it is believed that the most
suitable apparatus for the purpose is that described in the specification filed with
the application for a patent which is numbered 9227 of the 1st. August 1885.
Having now particularly described and ascertained the nature of the said
Invention, and in what manner the same is to be performed, I declare that what
I claim is:
The process of decomposing by magnesia the ammonium chloride of the ammonia
soda process which commences after that mother-liquor has had bicarbonate of
ammonia driven off from it, and magnesia added to it, and has been raised to or
nearly to the boiling point, and. which consists in then passing the resulting
mixture of solution and magnesia through a series of either distinct vessels or of
compartments of one vessel through which steam also passes, the mixture of solution
and magnesia travelling in one direction and the steam travelling in the opposite
direction and passing through the mixture of solution and magnesia, the mixture
of solution and magnesia being agitated so as to keep its magnesia constantly in
suspension, and the vessels or compartments through which the said mixture passes
being maintained at such temperature that none or scarcely any of the steam
entering those vessels or compartments can condense in them.