IMPROVEMENTS IN THE MANUFACTURE OF CHLORINE
Year: 1867

page_text: LETTERS PATENT to Carl Friedrich Claus, of Middlesbrough-on-Tees, in
the County of York,. Chemist, for the Invention of "IMPROVEMENTS IN
THE MANUFACTURE OF CHLORINE."
Sealed the 1st October 1867, and dated the 8th April 1867.
PROVISIONAL SPECIFICATION left by the said Carl Friedrich Claus
at the Office of the Commissioners of Patents, with his Petition, on the
8th April 1867.
I, CARL FRIEDRICH CLAUS, of Middlesbrough-on-Tees, in the County of
York, Chemist, do hereby declare the nature of the said Invention for "Iм-
PROVEMENTS IN THE MANUFACTURE OF CHLORINE," to be as follows:-
Firstly, I use chromate of lime, such as is produced or reproduced in the
manner described below, together with hydrochloride acid for the manufacture
of chlorine; I also use the chromates of magnesia, baryta, or strontia (instead
of the chromate of lime), together with hydrochloric acid, for the manufacture
of chlorine, but I prefer the chromate of lime; or I use mixtures of any of
these chromates together with hydrochloride acid for the said purpose.
Secondly, I reproduce the chromate of lime (or the chromates of magnesia,
baryta, and strontia), from the liquid resulting from the decomposition of the
chromate of lime (or the chromates of magnesia, baryta, and strontia, or
mixtures of these) with bydrochloric acid, and which consists of chloride of

page_text: chromium or chloride of calcium, (or of chloride of chromium and chloride or
magnesium, barium, or strontium, or of mixtures of these,) by evaporating
the liquid and calcining the residue with admission of air at a temperature
somewhat below the fusing point of chloride of calcium when the chromate of
lime or other chromates are reproduced whilst chlorine is evolved. The
chromate of lime or other chromates thus produced I use again (as in Part I. of
my process) together with hydrochloric acid for the production of chlorine.
During the evaporation and during a part of the calcination hydrochloric acid
is evaporated and evolved, which I again condense into liquid hydrochloric acid;
the chlorine, however (freed by condensation from hydrochloric acid), which is
evolved during the calcination, and the quantity of which is considerable,.
amounting to nearly as much as that obtained in the first part of my process,
I utilise as follows, vizt.-
Thirdly, the chlorine obtained by the calcination of the residuary. chlorides
with admission of air, which being considerably diluted with atmospheric air
cannot be admitted into the bleaching powder chambers,. I cause to be.
absorbed by hydrate of lime or by hydrate of magnesia in an apparatus distinct
from the chambers, and which allows the passage of the air with which the
chlorine is mixed through and out of the same after the chlorine which
accompanied it has been left behind absorbed and combined with the lime-
or magnesia. The hypochlorite of lime or magnesia formed in the above
process I either decompose with hydrochloric acid in the chlorine stills, and
convey the now pure and undiluted. chlorine into the bleaching powder
chambers, or I use the same for any ordinary purpose. I prefer to use the
hydrate of magnesia instead of the bydrate of lime in this. operation, as. I am
enabled by boiling down and calcining the chloride of magnesium formed, to
recover the hydrochloric acid as well as the magnesia of the chloride of
magnesium. The hydrochloric acid evolved during the calcination I condense
in the ordinary way; the magnesia left as residue I use again for the absorbtion
of fresh quantities of chlorine in the manner described above. The chloride
of magnesium obtained in any of the following processes I treat in the same
I also assist at option the evolution of hydrochloric acid from the
chloride of magnesium by a gentle current of steam during the calcination..
Fourthly, I also recover or reproduce the the chromates of lime, magnesia,
baryta, strontia (singly or in mixture), from the solution of chloride of
chromium, and chlorides of calcium, magnesium barium strontium, by
adding hypochlorite of magnesia to the said solution of chlorides (after having
deprived them of any excess of acid) until the colour of the liquid has changed
from green to a perfect chrome yellow. The reproduced, chromates I con-
manner.

page_text: centrate by evaporation and use them again as in the first part of the
process.
Fifthly, I also reproduce the chromates from the solution of chlorides, and L
also utilise the chlorine obtained in Part II. of my process by causing the
chlorine to pass through the solution of the chloride of. chromium and chloride
of calcium (magnesium, barium, strontium), to which an equivalent quantity
of magnesia has been added previously instead of passing the chlorine into the
hydrate of magnesia separately, and mixing the hypochlorite of magnesia
formed with the chloride of chromium afterwards.
Sixthly, when peroxide or sesquioxide of manganese has been used for the
generation of chlorine I adopt an analogous process for the treatment of the
resulting solution of protochloride of manganese as that described in Parts
III., IV., and V. of my process.
When protochloride of manganese, as has
been suggested by others before me, is dessicated and calcined with. admission.
of air, chlorine is liberated, which chlorine has thus far not been made
practically available owing to its being diluted with air. To utilise the same
is the object of this the sixth part of my Invention, and I purpose to do
so in a similar manner to that adopted in reference to the chromate process,
namely:
A. In a similar apparatus to that described above I cause the chlorine
liberated by the calcining of the protochloride of manganese to be absorbed.
by hydrate of magnesia, that is, magnesia in the form it is obtained in a
subsequent operation by calcination of chloride of magnesia moistened with.
water.
B. When bypochlorite of magnesia is formed the bypochlorite is treated
the same as in the chrome process; or I expose to the action of the said
chlorine a neutral mixture of protochloride of manganese and of chloride of
magnesium, and which is kept neutral by the continued addition of magnesia,
when peroxide of manganese is formed, which I again employ for the manu-
facture of chlorine and the chloride of magnesium, which I separate by
filtration from the peroxide of manganese.. I treat as has been stated
previously in other cases.
C. I add to neutralised protochloride of manganese the hypochlorite of
magnesia obtained as above, until all the manganese therein has been con-
verted into peroxide of manganese. The chloride of manganese is separated.
from the peroxide of manganese, and boiled down and calcined as above.
in the chrome process. The peroxide is to be used for the manufacture of
chlorine. The sesquioxide of manganese left as a residue of the calcination.
of the protochloride of manganese can be used again, as suggested by others,:

page_text: for the production of chlorine instead of the native peroxide. The above
being a continuous process it should be started with a pure per or sesqui oxide
of manganese.
Seventhly, the seventh part of my Invention consists in the application of
superheated steam as a heating agent for the contents of the chlorine stills
instead of the steam of ordinary temperature now used. The superheated steam
may be applied either externally or internally of the stills. When superheated
steam is used inside the stills the acid of the charge does not become so much
diluted as when steam of ordinary temperature is used; the latter is, as is well
known, of great disadvantage to the good working of the charge.
In the above description I have used the term bypochlorite of magnesia for
the compound obtained by acting upon bydrate of magnesia with chlorine gas
(which is even hot and mixed with air), though the said compound contains
also variable quantities of chlorate of magnesia and chloride of magnesium,
but that term best expresses the real chemical value of the compound.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Carl Friedrich Claus in the Great Seal Patent Office on
the 7th October 1867.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CARL
FRIEDRICH CLAUS, of Middlesbrough-on-Tees, in the County of York,
Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eighth day of April, in the year of our Lord One
thousand eight hundred and sixty-seven, in the thirtieth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Carl Friedrich Claus, Her special licence that I, the said Carl
Friedrich Claus, my executors, administrators, and assigns, or such others as
I, the said Carl Friedrich Claus, my executors, administrators, and assigns,
should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for "IMPROVE-
THE MANUFACTURE OF CHLORINE," upon the condition (amongst
others) that I, the said Carl Friedrich Claus, my executors or adminis-
trators, by an instrument in writing under my, or their, or one of their bands
and seals, should particularly describe and ascertain the nature of the said

page_text: Invention, and in what manner the same was to be performed, and cause the
same to be filed in the Great Seal Patent Office within six calendar months
next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Carl Friedrich Claus, do hereby
declare the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:-
My Invention is as follows, firstly, I use chromate of lime, such as is pro-
duced or reproduced in the manner described below, together with hydrochloric
acid for the manufacture of chlorine. I also use the chromates of magnesia,
baryta or strontia (instead of the chromates of lime) together with hydrochloric
acid for the manufacture of chlorine, but I prefer the chromate of lime; or I
use mixtures of any of these chromates together with hydrochloric acid for the
said purpose.
Secondly, I reproduce the chromate of lime (or the chromates of magnesia,
baryta, and strontia) from the liquid resulting from the decomposition of the
chromate of lime (or the chromates of magnesia, baryta, and strontia, or
mixtures of these) with hydrochloric acid, and which consists of chloride of
chromium and chloride of calcium (or of chloride of chromium and chloride
of magnesium, barium or strontium, or of mixtures of these) by evaporating
the liquid and calciuing the residue with admission of air at a temperature
somewhat below the fusing point of chloride of calcium, when the chroinate
of lime or other chromates are reproduced, whilst chlorine is evolved. The
chromate of lime or other chromates thus produced I use again (as in Part I.
of my process) together with hydrochloric acid for the production of chlorine.
During the evaporation and during a part of the calcination hydrochloric acid
is evaporated and evolved, which I again condense into liquid hydrochloric
acid; the chlorine, however (freed by condensation from hydrochloric acid),
which is evolved during the calcination, and the quantity of which is con-
siderable, amounting to nearly as much as that obtained in the first part of my
process, I utilize as follows, viz. :
Thirdly, the chlorine obtained by the calcination of the residuary chlorides,
with admission of air, being considerably diluted with atmospheric air cannot
be admitted into the bleaching powder chambers I cause to be absorbed by
hydrate of lime, or by bydrate of magnesia, in an apparatus distinct from the
chambers, and which allows the passage of the air with which the chlorine is
mixed through and out of the same after the chlorine which accompanied it
has been left behind absorbed and combined with the lime or magnesia. The
hypochlorite of lime or magnesia formed in the above process either

page_text: decompose with hydrochloric acid in the chlorine stills, and convey the now
pure and undiluted chlorine into the bleaching powder chambers, or I use the
same for any ordinary purpose. I prefer to use the hydrate of magnesia
instead of the hydrate of lime in this operation as I am enabled by boiling
down and caleining the chloride of magnesium formed to recover the hydro-
chloric acid as well as the magnesia of the chloride of magnesium. The
hydrochloric acid evolved during the calcination I condense in the ordinary
way, the magnesia left as residue I use again for the absorption of fresh
quantities of chlorine in the manner described above. The chloride of
magnesium obtained in any of the following processes I treat in the same
manner. I also assist at option the evolution of hydrochloric acid from the
chloride of magnesium by a gentle current of steam during the calcination.
Fourthly, also recover or reproduce the chromates of lime, magnesia,.&c.
(singly or in mixture), from the solution of chloride of chromium and chlorides
'cium, magnesium barium strontium, by adding hypochlorite of magnesia
to the said solution of chlorides (after having deprived them of any excess of
acid) until the colour of the liquid has changed from green to a perfect chrome
yellow. The reproduced chromates I concentrate by evaporation and use
them again as in the first part of the process.
Fifthly, I also reproduce the chromates from the solution of chlorides, and
I also utilise the chlorine obtained in Part II. of my process by causing the
chlorine to pass through the solution of the chloride of chromium, &c., to
which an equivalent quantity of magnesia has been added previously, instead
of passing the chlorine into the bydrate of magnesia separately, and mixing
the hypochlorite of magnesia formed to the chloride of chromium afterwards.
Sixthly, when peroxide or sesquioxide of manganese has been used for the
generation of chlorine I adopt an analogous process for the treatment of the
resulting solution of protochloride of manganese as that described in Parts III.,
1V., and V. of my process. When protochloride of manganese, as has been
suggested by others before me, is dessicated and calcined with admission of
air, chlorine is liberated, which chlorine has thus far not been made practically
available owing to its being diluted with air. To utilise the same is the
object of this the sixth part of my Invention, and I purpose to do so in
a similar manner to that adopted in reference to the chromate process,
namely:-
a. In a similar apparatus to that described above I cause the chlorine
liberated by the calcining of the protochloride of manganese to be absorbed by
hydrate of magnesia (that is, magnesia in the form it is obtained in a subse-
quent operation by calcination of chloride of magnesia moistened with water);

page_text: when hypochlorite of magnesia is formed the hypochlorite of magnesia formed
is treated the same as in the chrome process.
Or, b, I expose to the action of the said chlorine a neutral mixture of
protochloride of manganese and of chloride of magnesium, and which is kept
neutral by the continued addition of magnesia, when peroxide of manganese
is formed, which 1 again employ for the manufacture of chlorine, and the
chloride of magnesium, which I separate by filtration from the peroxide of
manganese. I treat as has been stated previously in other cases.
Or, c, I add to the neutralized protochloride of manganese the hypochlorite
of magnesia obtained as above until all the manganese therein has been con-
verted into peroxide of manganese. The chloride of magnesium is separated
from the peroxide of manganese and boiled down and calcined as above in
the chrome process. The peroxide is to be used for the manufacture of chlorine.
The sesquioxide of manganese left as a residue of the calcination of the proto-
chloride of manganese can be used again, as suggested by others, for the
production of chlorine instead of the native peroxide. The above being a con-
tinuous process it should be started with a pure per or sesqui oxide of manganese.
In the above description I have used the term bypochlorite of magnesia for
the compound obtained by acting upon hydrate of magnesia with chlorine gas
(which is even hot and mixed with air), though the said compound contains
also variable quantities of chlorate of magnesia and chloride of magnesium,
but that term best expresses the real chemical value of the compound.
The first part of the Invention scarcely needs any further detail to explain
its application in practice, except that I use the chromates named before in
exactly the same manner as is now done with manganese, instead of which I
apply the same together with rather more than its equivalent of hydrochloric
acid, which is well understood by every chemist.
The second part of my Invention, namely, the evaporation and calcination
of the residuary chlorides from the first operation, I carry out in the following
manner: The evaporation I conduct in a brick furnace or a shallow brick
pan (so to speak), arched over similarly to a covered evaporating pan for
sulphuric acid, only I use a brick tank instead of a lead pan. The beat is
applied to the surface of the liquid, and is derived from coke or other smokeless
fuel. Very little, about an inch deep, of the liquid is run into this beiling-
down furnace at once, and when this is dry another small quantity is run in
until the pan is nearly full of dry chloride, which is then broken up and raked
out and is ready to be calcined. The vapours of hydrochloric acid arising
during this concentration I convey into an ordinary muriatic acid condenser
to be there condensed. The dry chlorides of chromium and calcium or mag-

page_text: nesium, &c., are now broken small and placed into a blind furnace, similar to
a blind salt cake roaster, which, however, is constructed and heated in such a
manner that a uniform temperature of any desired degree can be maintained
throughout the whole length of the same, which is effected by heating the
furnace by means of hot gases, such as the waste gases of other furnaces, the
admission of which is regulated by means of dampers. The heat to be applied
to the charge, which is spread thinly over the bed of the furnace, should not
reach the fusing point of the chloride of calcium contained in the chlorides, as
otherwise it would form dense lumps of the charge and prevent the good
working of the process; this, however, is easily seen and prevented by the
workman, and the right temperature can easily be maintained, as the remark-
able changes in the appearance of the charge form the best indications for the
right working. When the right temperature (which lies somewhere between
the fusing point of lead and zinc) has been maintained for a few hours the
charge assumes gradually from a dark colour that of a beautiful chrome yellow
colour. As soon as the whole mass has assumed this colour throughout the
operation is complete and the above-mentioned chlorides have become con-
verted into chromates. This calcining furnace is furnished like a salt cake
roaster with a gas draught or flue, and has also several working doors; through
the latter the charge is occasionally turned over, and through which also a
current of air must be maintained over the surface of the charge. An occa-
sional absorption of moisture by the charge caused by any convenient method
greatly bastens the conversion into chromates.
Part 3 of my Invention. At the same rate, in the same degree as the con-
version of the charge into chromates proceeds or progresses, the elimination of
chlorine takes place; the chlorine escapes along with the air and some
muriatic acid gas with which it is mixed through the gas flue, and is drawn
by means of the chimney draught, with which the gas flue is connected, through
a system of towers similar to muriatic acid condensing towers; the first of these
towers is filled with coke, and in it the muriatic acid accompanying the
chlorine is condensed in the usual way. Freed from the muriatic acid the
chlorine passes next into two or three more towers and is met in its ascent
from the bottom upwards by a shower of fluid hydrate of magnesia (obtained
as described before); the latter two or three towers, instead of being filled
with coke like the first, are fitted with stone shelves having a very slight
inclination alternately from one side of the tower to the other; the shelves are
as many in number as can be got into the tower, down these the magnesia
and water slowly run, and cause the same magnesia to descend from one to the
other, and to expose as much surface to the chlorine in its ascent as possible;

page_text: the chlorine passing through this tower becomes absorbed, and what remains
unabsorbed passes into a second or a third, so that from the last (whatever
number they may be) nothing but air free of chlorine escapes. When the
magnesia has become sufficiently saturated with the chlorine it is collected in
tanks on the bottom of the towers, that which is not saturated is pumped up.
again for a second or third descent until it also is saturated. The chlorine
gas escaping from the calcining furnace is rather hot, and forms if not cooled
a greater or less quantity of chlorate of magnesia. If such is not thought
desirable it should first be cooled before entering the towers.
The arrangement and construction of apparatus in this and the following
processes forming no part of my Invention may be varied by the mauufac-
turers without therefore altering the nature of my Invention.
The hypochlorite or chlorate of magnesia or whatever chlorine compound
of magnesia may have been formed in the towers I run into the chlorine stills,.
add its equivalent of muriatic acid, apply steam, and the chlorine gas evolved
I convey into the bleaching powder chambers.
The chloride of magnesium resulting from the action of the hydrochloric
acid upon the bypochlorite of magnesia, as well as that resulting in any of the
following processes after being neutralized with magnesia, I boil down to
dryness in any convenient evaporating vessel and calcine the same, either with
or without the aid of steam, in an ordinary blind salt cake roaster; the hydro-
chloric acid gas evolved during the calcining operation I convey into an ordinary
muriatic acid condenser, and condense the same in the usual way. The
magnesia remaining behind, and which may contain still a little chloride of
magnesium undecomposed, I use mixed with water for the purpose of again
absorbing fresh quantities of chlorine in the way described above.
I may here mention that it is not absolutely necessary to absorb the chlorine
by means of a fluid mixture of hydrate of magnesia and water, but that I
could also do so in a kind of chamber upon hurdles, by means of the dry or
partially dry hydrate of magnesia or in any other similar way.
Part Four of my Invention is not an absolutely necessary operation in this
process, and not of as much practical utility as the former ones, as if it were
carried out the quantity of chloride of magnesium accompanying the chromate
would very soon inconveniently accumulate, and would therefore enforce a
process of separation before the chromates could be used again; however, the
practical execution of the same requires no further explanation beyond those
given in the outlines of the process.
Part Five of my Invention is carried out in the manner described in Part 3
with reference to bydrated magnesia and water alone, except that more water

page_text: is required to make the mixture fluid enough to flow down the shelves. The
hotter the chlorine is admitted into the towers the better will the reaction
take place.
The operations and apparatus used for Part Six of my Invention are identical
with those described in reference to Parts 2 and 3 of the Invention, except
that the heat applied to the charge in the roaster may be somewhat stronger
(without doing injury), and that the changes of colour not being the same, the
cessation of escape of gas being the culminating point in caleining the charge.
Further, division b in Part VI. is carried on in the towers in exactly the
same manner as described in reference to the chrome compounds. Division c
in Part VI. requires also very little practical explanation; the process is carried
out in a tank provided with an agitator and covered gas-tight, so that should
chlorine escape during the operation it can be conveyed into the absorbing
towers described by means of pipes, the hypochlorite of magnesia is cautiously
added to the protochloride of manganese liquor until the precipitation of
peroxide is complete.
In witness whereof, I, the said Carl Friedrich Claus, have hereunto set
my hand and seal, this 4th day of October, in the year of our Lord
One thousand eight hundred and sixty-seven..