Acid from Ammonium Chloride.
Year: 1887

page_text: Date of Application, 10th Aug., 1887
Complete Left; 8th May, 1888
Complete Accepted, 22nd June, 1888
Acid from Ammonium Chloride.
I, LUDWIG MOND of Winnington Hall, Northwich, Cheshire, Chemist, do hereby
declare the nature of this invention to be as follows:-
This invention relates to improvements in a process for obtaining ammonia, chlorine
and hydrochloric acid from ammonium chloride, for which I have obtained Letters
Patent numbered and dated respectively Nos. 65 & 66 of the 2nd January 1886,
Nos. 1048 and 1049 of the 23rd January 1886, and No. 3238 of the 8th March 1886.
The main feature of this process consists in bringing the vapour of ammonium
chloride into contact with certain oxides or salts at an elevated temperature whereby
they are converted into chlorides or oxy-chlorides while ammonia and a certain
quantity of steam are set free and in subsequently treating the chlorine compounds
formed by steam or air so as to obtain hydrochloric acid or chlorine. In working out
this process I have found the volatilization of the ammonium chloride a rather tedious
operation. The ammonium chloride when being heated does not melt before
becoming vaporized and consequently the particles of ammonium chloride soon get
surrounded by an atmosphere of vapour which prevents the contact with the hot sides
of the vessel containing it and retards the vaporization. To overcome this difficulty
I propose to introduce ammonium chloride into a vessel to which heat is applied and
which contains a substance which fuses but is not volatile at or near the temperature
required and which is in itself not permanently altered by the ammonium chloride.
I have found zinc chloride a very suitable substance for this purpose but many others
can also be applied.
Another way of expediting the volatilization of the ammonium chloride consists in
carrying on this operation in a partial or complete vacuum or in a current of a gas or
vapour which has no unfavorable chemical action on the ammonium chloride or on
the substances with which the same is to be brought into contact (such as carbonic
acid or steam or the gases escaping from the absorbing apparatus of the ammonia
soda process) whereby the tension of the ammonium chloride is reduced so that its
vaporization takes place at a lower temperature.

page_text: In the next stage of the process I have found that certain of the oxides and salts
named in my specifications more particularly those of magnesia do not allow the
whole of the steam formed by the action of ammonium chloride upon them to escape
with the ammonia but retain a certain proportion of it which on subsequent treatment
with air of the chlorine compounds formed, gives rise to the formation of hydro-
chloric acid which deteriorates the chlorine obtained and has to be separated by
washing or otherwise before the chlorine can be usefully employed. This deterioration
of the chlorine can be considerably decreased by heating the chlorine compounds in
a vacuum before air is admitted when the greater part of the hydrochloric acid which
would otherwise be given off with the chlorine, is obtained in a comparatively pure
state in which it can be easily condensed and obtained as strong marketable hydro-
chloric acid.
In order to obviate more completely the deterioration of the chlorine by hydro-
chloric acid and to obtain chlorine only as the final product of the process I propose
to proceed as follows
I bring the gases resulting from the treatment with air of the chlorine compounds
before mentioned into contact with certain oxides or salts kept at a suitable temperature
say between 100 degrees and 500 degrees C. Any of the oxides or salts mentioned
in my previous specifications as serviceable for obtaining chlorine from ammonium
chloride will also answer for this purpose.
These oxides and salts absorb all the hydrochloric acid from the gases without
acting upon the chlorine and are converted into chlorinated compounds. From these
latter chlorine can be obtained by treating them with air in the same way as if they
had been prepared by the action of the vapour of ammonium chloride upon the
substances named: or the oxides or salts partly converted into chlorinated compounds
by the action of the gases before-mentioned may subsequently be treated with the
vapour of ammonium chloride to complete their conversion into chlorine compounds
before they are submitted to treatment with air for obtaining chlorine.
By this treatment all the hydrochloric acid in these gases is absorbed and subse-
quently obtained in the form of chlorine while the chlorine already present in the gases
subjected to this treatment is obtained free from hydrochloric acid and can immediately
be used in the manufacture of bleaching powder.
When using certain of the oxides or salts mentioned in my specifications such for
instance as silicates and alumino-silicates of calcium which are otherwise well suited
for the purpose I find that the temperature required to obtain chlorine gas in the
last operation of my process is so much higher than the temperature required for the
treatment of the substance with ammonium chloride in the first part of the
that it is inconvenient to carry the operations out in one and the same apparatus as
process,
too much time is required to raise and afterwards again to reduce the temperature.
In these cases I prefer to carry on the operations in two separate apparatus one
superposed over the other; and to treat the substance with ammonium chloride in the
upper apparatus and take it from there to the lower one to be treated with air or
steam. In this way it becomes possible to maintain both parts of the apparatus at
one and the same temperature and to carry on the process as an almost continuous
operation by constantly filling fresh material in small charges into the upper
apparatus; taking out an equivalent quantity from the bottom of this, charging it
into the lower apparatus and again taking out an equivalent quantity from its bottom
or lower end. The operation may be made quite continuous by using mechanical
means for continuously charging and discharging. When it is desired to obtain
chlorine as the final product of the process only I employ three separate apparatus
superposed one above the other. In the upper one the material is treated with the
gases resulting from the treatment with air in the lowest apparatus so as to free
these gases from hydrochloric acid and to make them suitable for immediate use in
the manufacture of bleaching powder. From this upper apparatus the material is
taken to the second one, where it is treated with ammonium chloride; and from there
to the third one where it is subjected to the action of air.
Every apparatus can be used for this purpose which is suitable for the treatment of

page_text: solid substances by gases at elevated temperatures, such as inclined or vertical retorts
one superposed over the other, with proper arrangements for charging and discharging
and heating the saine, in which the substance will descend by gravity; or retorts or
cylinders may be used set horizontally or at a slight angle through which the material
is transported by revolving the cylinder or by providing it with worms or stirrers
revolving inside. In using the latter kind of apparatus it becomes unnecessary to
prepare the oxides or salts in lumps or balls, but they can be employed in the form of
powder. In working the process in the particular way last described it may become
advantageous to mix the solid ammonium chloride with the oxides or salts before-hand
and to introduce them together into the apparatus withdrawing the ammonia and
steam from or near the end of the apparatus where the mixture is introduced or from
the opposite end as may be found desirable.

page_text: COMPLETE SPECIFICATION.
Improvements in Obtaining Ammonia, Chlorine, and Hydrochloric
Acid from Ammonium Chloride.
I LUDWIG MOND, of Winnington Hall, Northwich, in the County of Chester,
Chemist, do hereby declare the nature of this invention and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement :-
This invention relates to improvements in a process for obtaining ammonia, chlorine,
and hydrochloric acid from ammonium chloride, for which I have obtained Letters
patent numbered and dated respectively Nos. 65 and 66 of the 2nd January, 1886,
and Nos. 1048 and 1049 of the 23rd January, 1886, and No. 3238 of the 8th March,
1886. The main feature of this process consists in bringing the vapour of ammonium
chloride into contact with certain oxides or salts at an elevated temperature, whereby
they are converted into chlorides or oxy-chlorides, while ammonia and a certain
quantity of steam are set free, and in subsequently treating the chlorine compounds
formed by steam or air, so as to obtain hydrochloric acid or chlorine. In working out
this process I have found the volatilization of the ammonium chloride a rather tedious
operation. The ammonium chloride when being heated, does not melt before becoming
vaporized, and consequently the particles of ammonium chloride soon get surrounded
by an atmosphere of vapour, which prevents the contact with the hot sides of the
vessel containing it and retards the evaporization. To overcome this difficulty, I
propose to introduce ammonium chloride into a vessel to which heat is applied, and
which contains a substance which fuses, but is not volatile at or near the temperature
required, and which is in itself not permanently altered by the ammonium chloride.
I have found zinc chloride a very suitable substance for this purpose, but many others
can also be applied.
The zinc chloride becomes liquid on beating being applied to the vessel, and being
thus in intimate contact with the sides of the vessel, takes up heat readily and gives it
up to the ammonium chloride, which I prefer to drop into the molten chloride of zinc
in small quantities from time to time, or by a continuous feeder.
Another way of expediting the volatilization of the ammonium chloride consists in
carrying on this operation in a partial or complete vacuum, or in a current of a gas or
vapour which has no unfavourable chemical action on the ammonium chloride or on
the substances with which the same is to be brought into contact (such as carbonic
acid or steam or the gases escaping from the absorbing apparatus of the ammonia soda
process), whereby the tension of the ammonium chloride is reduced so that its
vaporization takes place at a lower temperature.
In the next stage of the process, I have found that certain of the oxides and salts
named in my specifications, more particularly those of magnesia, do not allow the
whole of the steam formed by the action of ammonium chloride upon them to escape
with the ammonia, but retain a certain proportion of it, which on subsequent treatment

page_text: with air of the chlorine compounds formed, gives rise to the formation of hydrochloric
acid, which deteriorates the chlorine obtained, and has to be separated by washing or
otherwise, before the chlorine can be usefully employed.
This deterioration of the chlorine can be considerably decreased by heating the
chlorine compounds before they are submitted to the action of air in a current of an
inert gas (such as carbonic acid or the gases escaping from the absorbing apparatus of
the animonia soda process) or in a vacuum, until no more hydrochloric acid is given
off. In my former patents I have described the use of these gases or a vacuum for
sweeping out of the apparatus, the ammonia, which remains in it after the treatment
of the oxides or salts by chloride of ammonium, and I now propose to continue this
treatment after the aminonia is driven out until no more hydrochloric acid is given
off. As long as any aminonia is contained in these gases they are led to the
ammonia condenser, and when the hydrochloric acid appears they are led to another
condenser in which the latter is absorbed and can be obtained as strong, marketable
acid.
In order to obviate more completely the deterioration of the chlorine by hydrochloric
acid and to obtain chlorine only as the final product of the process, I propose to
proceed as follows:-
I bring the gases resulting from the treatment with air of the chlorine compounds
before mentioned, into contact with certain oxides or salts kept at a suitable temperature,
say between 100 degrees and 500 degrees Centigrade. Any of the oxides or salts
mentioned in my previous specifications as serviceable for obtaining chlorine from
ammonium chloride will also answer for this purpose.
These oxides or salts absorb all the hydrochloric acid from the gases without acting
upon the chlorine, and are converted into chlorinated compounds. From these latter,
chlorine can be obtained by treating them with air in the same way as if they had
been prepared by the action of the vapour of ammonium chloride upon the substances
named; or the oxides or salts partly converted into chlorinated compounds, by the
action of the gases before mentioned, may subsequently be treated with the vapour of
ammonium chloride to complete their conversion into chlorine compounds before they
are submitted to treatment with air for obtaining chlorine.
By this treatment all the hydrochloric acid in these gases is absorbed, and subse-
quently obtained in the form of chlorine, while the chlorine already present in the
gases subjected to this treatment is obtained free from hydrochloric acid, and can
immediately be used in the manufacture of bleaching powder.
When using certain of the oxides or salts mentioned in my specifications, such for
instance as silicates and alumino-silicates of calcium, which are otherwise well suited
for the purpose, I find that the temperature required to obtain chlorine gas in the last
operation of my process is so much higher than the temperature required for the
treatment of the substance with ammonium chloride in the first part of this process,
that it is inconvenient to carry the operation out in one and the same apparatus, as too
much time is required to raise and afterwards again to reduce the temperature..
In these cases I prefer to carry on the operations in two separate apparatus, one
superposed over the other, or so arranged that the solid material operated upon can be
readily transferred from one to the other, and to treat the substance with ammonium
chloride in the upper or first apparatus, and take it from there to the lower or second
one to be treated with air or steam. In this way it becomes possible to maintain
both parts of the apparatus at one and the same temperature, and to carry on the
process as an almost continuous operation, by constantly filling fresh material in small
charges into the upper or first apparatus, taking out an equivalent quantity from the
bottom of this, charging it into the lower or second apparatus, and again taking out
an equivalent quantity from its bottom or lower end. The operation may be made
quite continuous by using mechanical means for continuously charging and dis-
charging.
When it is desired to obtain chlorine as the final product of the process only, I
employ three separate apparatus superposed one above the other, or so arranged that
the solid material operated upon can be transferred from one to the other. In the

page_text: upper or first one, the material is treated with the gases resulting from the treatment
with air in the lowest or last apparatus, so as to free these gases from hydro-chloric
acid and to make them suitable for inmediate use in the manufacture of bleaching
powder. From this upper or first apparatus the material is taken to the second one,
where it is treated with ammonium chloride, and from there to the third one, where it
is subjected to the action of air. In some cases it is desirable to employ a series of
four apparatus, in the first of which the material is treated with the gases obtained
in the last apparatus, in the second one with ammonium chloride, in the third
with a current of an inert gas or a vacuum, and in the last subjected to the action
of air.
The volatilization of the ammonium chloride I prefer to carry out in a separate
apparatus, which is placed as near as can conveniently be done to the second of the series
of apparatus named, and connected with the same by suitable pipes or otherwise. For
this purpose I find a cast iron cylinder with covers at both ends, or a cast iron still,
lined with a material that will withstand the action of the ammonium chloride vapour,
such as fireclay, or a similar vessel made of metallic nickel, the most suitable.
I introduce into these vessels a substance such as zinc chlorido, which is fusible but
not volatile at the desired temperature, and after this has been once liquefied by the
application of heat, I introduco ammonium chloride in small quantities or feed it in
continuously by suitable arrangements such as are frequently used for such purposes,
or, in place of introducing a fusible material such as named, I introduce from the
beginning a large quantity of ammonium chloride so as to nearly fill the apparatus
and have the ammonium chloride in contact with all the heated parts of it, and then
continue to feed in ammonium chloride in small quantities or continuously, so as to
maintain the apparatus filled, and to obtain a constant stream of ammonium chloride
vapour.
For the treatment of the solid material by the various gases as before described,
every apparatus can be used which is suitable for the treatment of solid substances by
gases at elevated temperatures, such as inclined or vertical retorts one superposed
over the other, with proper arrangements for charging and discharging and heating
the same, in which the substance will descend by gravity, or retorts or cylinders may
be used set horizontally or at a slight angle, through which the material is transported
by revolving the cylinder, or by providing it with worms or stirrers revolving inside,
but I prefer to use an apparatus which I have fully described in an application for
Letters Patent No. 10957, and of even date with this, entitled "Improvements in
apparatus for treating solids by gases, also applicable to other purposes," and I place
three or four of the apparatus there described by preference one on a higher level
than the other, so that the solid material issuing from the upper can be readily taken
to the lower ones.
In using the latter kind of apparatus it becomes unnecessary to prepare the oxides
or salts in lumps or balls, but they can be employed in the form of powder. In
working the process in the particular way last described, it may become advantageous
to mix the solid ammonium chloride with the oxides or salts beforehand, and to
introduce them together into the apparatus, withdrawing the ammonia and steam from
or near the end of the apparatus where the mixture is introduced, or from the opposite
end as may be found desirable.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In the manufacture of ammonia and chlorine or hydrochloric acid from
ammonium chloride, volatilizing the ammonium chloride by heating the same,
(a) with a substance such as chloride of zinc, which is fusible but not volatile at
the temperature required, and which is in itself not permanently acted upon
by the ammonium chloride, or
(6) under exhaustion or a vacuum, or
in a current of a chemically indifferent gas or vapour, such as described.

page_text: 2. Exposing to a partial or nearly perfect vacuum or to a current of an inert gas,
the chlorine compounds formed by the action of aminonium chloride on one or more
of the oxides or salts described, while still in the heated state, and continuing this
treatment after all the ammonia is given off, whereby hydrochloric acid is evolved
and can be condensed, and whereby also the chlorine subsequently obtained by
oxidation of said compounds, is nearly free from said acid.
3. In the manufacture of chlorine from the chlorine compounds formed by chlori-
dising one or more of. certain oxides or salts as described, passing the gases formed
by oxidising said compounds in the manner described through one or more of such
heated salts or oxides, as are useful for forming the aforesaid chlorine compounds,
by the action upon them of ammonium chlorides, whereby the hydrochloric acid is
absorbed, and its chlorine can be separated afterwards by means of air, whereby
nearly the whole of the chlorine of the ammonium chloride is obtained as free
chlorine.
4. The process of obtaining ammonia and chlorine from ammonium chloride, which
consists in successively treating one or more of certain heated oxides or salts as
described with (1) the impure chlorine obtained by the third operation, (2) with the
vapour of ammonium chloride, and (3) a current of air or oxygen, whereby nearly the
whole of the chlorine is obtained, and in a sufficiently pure state for immediate use in
the manufacture of bleaching powder.
5. The herein described improvements, whereby the process for obtaining chlorine
or hydrochloric acid and ammonia by the action of ammonium chloride on certain
salts or oxides as described, is made nearly or quite continuous, the two steps in the
process, (the chloridising of the oxides or salts by ammonium chloride, and the
oxidising of the resulting chlorine compounds, by air or steam) being carried on in
two separate apparatus each kept as near as possible at the special temperature
required, and the solid material to be treated, being taken in small quantities or
continuously from the first to the second apparatus, while fresh material is from time
to time introduced into the first.
6. The mode of carrying on the process hereinbefore described, in which three or
four retorts or equivalent apparatus are kept at their respective requisite temperatures,
placed one above the other, or so arranged that the solid materials operated upon can
be transferred from one to the other, and,
(A) the oxides or salts are placed in the first apparatus, and treated with the gases
from the third, when partially chloridised they are transferred to the second, and
treated with vapour of ammonium chloride, when chloridised, passed to the third,
where they are treated with air or oxygen, or
(B) the oxides or salts are placed in the first apparatus, and treated with the gases
from the fourth, they are then transferred to the second and treated with chloride of
ammonium, they are then passed to the third, and treated with an inert gas or partial
vacuum, whereby hydrochloric acid is separated, and are then passed to the fourth,
where they are treated with air or oxygen.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool,
Patent Agents for the Applicant.