IMPROVEMENTS IN THE MANUFACTURE OF CHLORATE OF POTASH, AND IN APPARATUS TO BE EMPLOYED FOR THAT PURPOSE
Year: 1871

page_text: LETTERS PATENT to William Hunt, of Castleford, near Normanton,
in the County of York, Manufacturing Chemist, for the Invention
of "IMPROVEMENTS IN THE MANUFACTURE OF CHLORATE OF POTASH, AND IN
APPARATUS TO BE EMPLOYED FOR THAT PURPOSE."
Scaled the 29th December 1871, and dated the 21st July 1871.
PROVISIONAL SPECIFICATION left by the said William Hunt at the
Office of the Commissioners of Patents, with his Petition, on the
21st July 1871.
I, WILLIAM HUNT, of Castleford, near Normanton, in the County of
York, Manufacturing Chemist, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE MANUFACTURE OF CHLORATE OF POTASH,
AND IN APPARATUS TO BE EMPLOYED FOR THAT PURPOSE," to be as follows:-
In the ordinary method of manufacturing chlorate of potash pure or
nearly pure chlorine obtained by heating a mixture of peroxide of
manganese and muriatic acid is passed into a closed vat containing a
mixture of caustic lime, chloride of potassium, and water. The mixture
is heated and kept in agitation, the chlorine is rapidly absorbed, chlorate

page_text: of potash and chloride of calcium being formed. When the absorption of
chlorine has ceased the charge is run off from the vat, and the chlorate
of potash separated from the chloride of calcium by crystallisation. This
method of manufacture requires the use of pure or nearly pure chlorine.
The object of my Invention is to manufacture chlorate of potash by
the use of chlorine mixed with atmospheric air, or otherwise diluted, and
my said Invention consists of the improvements herein-after described,
whereby dilute chlorine suitable for the manufacture of chlorate of
potash by my method may be obtained, and also in conducting the
process and arranging the apparatus so that chlorate of potash may be
manufactured by the use of dilute chlorine.
The dilute chlorine which I prefer to employ in carrying my Invention
into effect is obtained as follows:-In the manufacture of sulphuric acid
by alkali makers and others iron pyrites containing a small quantity
of copper is burned so as to expel the greater part of the sulphur,
sulphurous acid is obtained thereby, from which sulphuric acid is manu-
factured. The pyrites, called after burning "burnt ore," is afterwards
treated for the purpose of recovering the copper from it. The said burnt
ore is ground fine, mixed with common salt, and roasted at a dull red
heat in a close furnace. During the roasting process chlorides of iron
and copper, muriatic acid, and chlorine pass off. The gases are passed
through a condenser containing water, whereby all or nearly all the
gaseous matter is condensed excepting the chlorine and atmospheric air.
In order to use the dilute chlorine for the manufacture of chlorate of
potash I place between tlie condenser and the stack or chimney by which
the vitiated air and products of combustion are carried away a tower or
column of stone, brick, or other suitable material. This tower is filled
with bricks either whole or broken. Warm milk of lime, either alone or
mixed with chloride of potassium, is made to trickle down the bricks in
the tower, the liquid thus exposing a great surface to the dilute chlorine
which is being slowly drawn through the tower by the draught of the
stack. The milk of lime during its passage through the tower has by
the absorption of the chlorine been mainly converted into chlorate of
lime and chloride of calcium; this is boiled with chloride of potassium,
whereby chlorate of potash and chloride of calcium are formed, and the
chlorate of potash is separated from the chloride of calcium by crystalli-
zation. Where chloride of potassium has been mixed with the milk of

page_text: lime before it was introduced into the tower chlorate of potash is formed
in the tower, and is obtained without any further treatment excepting
boiling and crystallization.
lime before it was introduced into the tower chlorate of potash is formed
in the tower, and is obtained without any further treatment excepting
boiling and crystallization.
Dilute chlorine from any other source may be used for the manufacture
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Hunt in the Great Scal Patent Office
on the 16th January 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
HUNT, of Castleford, near Normanton, in the County of York, Manu-
facturing Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-first day of July, in the year of
our Lord One thousand cight hundred and seventy-one, in the thirty-
fifth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said William Hunt, Her special licence that
I, the said William Hunt, my executors, administrators, and assigns,
or such others as I, the said William Hunt, my executors, adminis-
trators, 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 "IMPROVEMENTS IN THE MANU-
FACTURE OF CHLORATE OF POTASH, AND IN APPARATUS TO BE EMPLOYED FOR THAT
PURPOSE," upon the condition (amongst others) that I, the said William
Hunt, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, should particularly
describe and ascertain the nature of the said 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 William Hunt, do hereby declare
the nature of the said Invention, and in what manner the same is to

page_text: be performed, to be particularly described and ascertained in and by the
following statement thereof, that is to say:-
In the ordinary method of manufacturing chlorate of potash pure or
nearly pure chlorine obtained by heating a mixture of peroxide of
manganese and muriatic acid is passed into a closed vat containing a
mixture of caustic lime, chloride of potassium, and water. The mixture
is heated and kept in agitation, the chlorine is rapidly absorbed, chlorate
of potash and chloride of calcium being formed. When the absorption of
chlorine has ceased the charge is run off from the vat, and the chlorate
of potash separated from the chloride of calcium by crystallization. This
method of manufacture requires the use of pure or nearly pure chlorine.
The object of my Invention is to manufacture chlorate of potash by
the use of chlorine mixed with atmospheric air, or otherwise diluted, and
my said Invention consists of the improvements herein-after described,
whereby dilute chlorine suitable for the manufacture of chlorate of
potash by my method may be obtained, and also in conducting the
process and arranging the apparatus so that chlorate of potash may be
manufactured by the use of dilute chlorine.
The dilute chlorine which I prefer to employ in carrying my Invention
into effect is obtained as follows:-In the manufacture of sulphuric acid
by alkali makers and others iron pyrites containing a small quantity
of copper is burned so as to expel the greater part of the sulphur,
sulphurous acid is obtained thereby, from which sulphuric acid is manu-
factured. The pyrites, called after burning “burnt ore," is afterwards
treated for the purpose of recovering the copper from it. The said "burnt
ore" is ground fine, mixed with common salt, and roasted at a dull red
heat in a close furnace. During the roasting process chlorides of iron
and copper, muriatic acid, and chlorine pass off. The gases are passed
through a condenser containing water, whereby all or nearly all the
gaseous matter is condensed excepting the chlorine and atmospheric air.
In order to use the dilute chlorine for the manufacture of chlorate of
potash I place between the condenser and the stack or chimney by which
the vitiated air and products of combustion are carried away a tower (or
towers) of iron, stone, brick, or other suitable material. This tower is
partially filled with bricks, either whole or broken, or pumice stone, but
I prefer to use spheres or balls of glass. Warm milk of lime, either
alone or mixed with chloride of potassium, is made to trickle down the
bricks in the tower, the liquid thus exposing a great surface to the

page_text: dilute chlorine, which is being slowly drawn through the tower by the
draught of the stack. The milk of lime during its passage through the
tower has by the absorption of the chlorine been mainly converted into
chlorate of lime and chloride of calcium. This is boiled with chloride of
potassium, whereby chlorate of potash and chloride of calcium are
formed, and the chlorate of potash is separated from the chloride of
calcium by crystallization. Where chloride of potassium has been mixeḍ
with the milk of lime before it was introduced into the tower chlorate
of potash is formed in the tower, and is obtained without any further
treatment excepting boiling and crystallization.
Dilute chlorine from any other source may be used for the manufacture
of chlorate of potash with like effect in the apparatus described.
Figure 1 of the accompanying Drawing represents partly in elevation
and partly in section an apparatus constructed according to my Invention
for the manufacture of chlorate of potash. The said apparatus consists
of two towers a and b, or more than two towers may be used. I make
the said towers by preference of cylinders of iron jointed as shown at c,
but the said towers may be made of brick or stone or other material.
When iron is used it becomes rapidly coated with lime, and is thereby
protected from the action of the chlorine. The lower part of each tower
is filled with bricks d placed at a distance apart, and so arranged as to
form a reticulated structure through which liquids and gas may pass
readily. The bottom cylinder of cach tower stands in a shallow tray 9, 9².
Upon the brickwork da mass of coke, pebbles, broken bricks, or other
substance e not acted upon by lime or chlorine is supported as seen in
the tower a, the said material nearly filling the tower. I prefer to use
in the towers, in place of brick or coke or pebbles, spheres or balls of
glass as less likely to retain the carbonate of lime formed during the
working of the apparatus. The top f of each tower is perforated with a
number of holes.
Figure 2 represents a plan of the top of one of the towers. Surmounting
each tower is a reservoir / communicating by a series of pipes i passed
through holes in the top f of the tower with the upper part of the said
tower, so that any liquid poured into the reservoir h passes by the pipes i
into the tower and trickles down the mass of coke or other material e
in the tower. The towers a and b are connected together by a channel k
made of a series of pipes joined as represented. The upper part of the
tower a is put into communication with the lower part of the tower b,

page_text: and when a third tower is used, the upper part of the tower b is put
into communication with the lower part of the said third tower, and so
on. 1, m, are vats containing milk of lime; ², m², are the pistons of
small force pumps, by the working of which the milk of lime from the
vats l, m, is pumped up through the pipes q, r, into the reservoirs h of
the towers a and 6 respectively. The milk of lime in the vats l, m, is
kept hot by a jet of steam passed into the said vats o, p; and o, p, repre-
sent man-holes situated near the bottom of each tower for gaining access
to the interior of the tower.
The apparatus is worked in the following manner :-The dilute chlorine
to be absorbed enters the bottom of the tower a at 8, rising through the
mass of coke, brick, or other material e, and passing out at the top of
the tower a through the pipe k enters the lower part of the tower b, in
which it ascends through the mass of coke or material therein, and out
by the pipe b at the top of the tower beither to a chimney stack or to
the bottom of a third tower. During the passage of the dilute chlorine
through the towers the working of the force pumps 12, m², causes the
delivery of a stream of milk of lime to the top of the said towers, which
trickling down the materials e meets the ascending current of dilute
chlorine, which chlorine is more or less absorbed by the hot milk of
lime. The milk of lime collects in the trays 9, 92, and passes by the
spouts 93, 94, into the vats and m respectively. After the milk of lime
has been passed two or three times through the tower bit is conveyed
by a pipe connected with the spout 9' into the vat 1, from which it is
passed two or three times through the tower a, and is finally by means
of a pipe conveyed from the spout g³ away from the apparatus. Fresh
milk of lime is supplied to the vat m and tower 6, while only that milk
of lime which has been passed through the tower 6 is supplied to the
vat and tower a. As the chlorine is more dilute in the tower b than
in the tower a the fresh milk of lime supplied to the tower 6 more
effectually absorbs the chlorine passing through the tower b, while the
partially saturated milk of lime passing through the tower a readily
absorbs a large portion of the less dilute chlorine passing through the
said tower a. By the absorption of chlorine the milk of lime is converted
wholly or mainly into chlorate of lime and chloride of calcium. The
mixture is transferred from the spout g³ into a boiler, where chloride of
potassium is added thereto; but as this stage of the manufacture is
conducted in the ordinary way I do not think it necessary further to

page_text: +
describe the same. Chloride of potassium may be added to the milk
of lime before the latter is passed through the towers a and b. Instead
of filling the towers with a mass of material e, as represented, each tower
may be filled with perforated trays carrying the material e.
The apparatus, Figures 1 and 2, may be employed for manufacturing
chlorate of potash when the dilute chlorine is absorbed by other absorbent
than milk of lime.
Having now described the nature of my Invention, and the manner in
which the same is to be performed, I wish it to be understood that I do
not limit myself to the precise details herein described and illustrated,
as the same may be varied without departing from the nature of my
Invention; but I claim as my Invention,-
Firstly. The improvements in the manufacture of chlorate of potash
herein-before described and illustrated in the accompanying Drawing,
that is to say, manufacturing chlorate of potash by the use of dilute
chlorine obtained during the roasting of burnt. iron pyrites or "burnt
ore" in the process resorted to for the recovery of copper from the said
"burnt ore," or from dilute chlorine otherwise obtained, the said dilute
chlorine being absorbed by milk of lime, substantially in the manner
described and illustrated.
Secondly. The arrangement or combination of the parts of apparatus
herein-before described and illustrated in the accompanying Drawing to
be used in the manufacture of chlorate of potash, whether the said
apparatus be employed for the manufacture of chlorate of potash by the
process or processes herein described, or by other processes in which
dilute chlorine is employed.
In witness whereof, I, the said William Hunt, have hereunto set
my hand and seal, this Thirteenth day of January, in the year of
our Lord One thousand eight hundred and seventy-two.
Witness,
GEORGE SHAW.
WILLIAM HUNT. (L.S.)