IMPROVEMENTS IN THE MANUFACTURE OF CHLORINE
Year: 1881

page_text: LETTERS PATENT to Walter Weldon, of Rede Hall, Burstow, in the County
of Surrey, for an Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
CHLORINE"
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey. " IMPROVE-
MENTS IN THE MANUFACTURE OF CHLORINE."
The method of manufacturing chlorine, which constitutes the present Invention,
consists in the following operations :—
First. A portion of the residual solid product of the third operation, to be
described below, is dissolved in hydrochloric acid. Chlorine is evolved, and there
is at the same time produced a mixed solution of chloride of manganese and
chloride of calcium.
Second. The mixed solution produced in the first operation is evaporated to a
high degree of concentration, and is then mixed with a portion of the solid residual
product of the third operation, and the mixture is formed into cakes, balls,
briquettes, or other small pieces or lumps, such that when charged into a suitable
apparatus air and other gases shall be able to penetrate into and pass through and
among the interstices between them.
Third. The cakes, balls, or briquettes formed in the second operation are heated
in contact with a current of air. Chlorine is thereby driven off from them, and
the solid product which remains consists of a compound of binoxide of manganese
partly with lime and partly with manganese protoxide, or wholly with one or
the other of these, mixed with some undecomposed chloride of calcium. A portion
of this product is then used for a repetition of the first operation, and the other
portion for a repetition of the latter part of the second operation.
The chlorine obtained by the first operation is of course unmixed with other
gases, but that obtained by the third operation is mixed with nitrogen and excess
of air, and may also have associated with it a little vapour of hydrochloric acid.
Any vapour of hydrochloric acid which may thus be contained in the gaseous
current from the third operation must be condensed out therefrom, as will be well

page_text: understood, before the gaseous current is treated for the utilization of its free
chlorine.
It will in some cases be necessary to dry the cakes, balls, or briquettes formed
in the second operation before submitting them to the third operation.
The said third operation may be conducted by applying heat directly to the
exterior of the apparatus in which the operation is performed, and admitting
thereinto either cold or only partially heated air; but I prefer to dispense with
such external heating of the apparatus and to heat the charge simply by treating it
with air previously so highly heated as to be capable of raising the charge to the
temperature at which the required reaction can take place.
but
The third operation may be conducted eitlier intermittently or continuously;
I prefer to conduct it in the continuous manner and by means of the apparatus
forming the subject of another Invention, an application for a Patent for which
will be filed on the same day as these presents.
The mode of proceeding above described may be modified by omitting the latter
part of the second operation, and so performing the third operation upon balls,
cakes, or briquettes of a dried down mixture of chloride of manganese and chloride
of calcium only.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Walter Weldon in the Great Seal Patent Office on the 25th
August 1881.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey. "IMPROVE-
MENTS IN THE MANUFACTURE OF CHLORINE."
This Invention consists in manufacturing chlorine by the following series of
operations :-
First. A portion of the solid residue of the fourth operation, to be described
below, is dissolved in aqueous hydrochloric acid. The said solid residue consists
essentially of peroxide of manganese combined or otherwise associated with lime,
but may also contain some chloride of calcium and some manganese protoxide.
This solid residue of the fourth operation will hereinafter be called manganite of
calcium. The reaction of aqueous hydrochloric acid on this body gives rise to an
evolution of chlorine gas, and there is at the same time produced a residual mixed
solution of chloride of manganese and chloride of calcium.
Second. The aforesaid residual solution is evaporated to a high degree of
concentration.
Third. The residual solution after having been concentrated, as just said, is
mixed with manganite of calcium, and the mixture is formed into cakes, cylinders,
balls, or other small masses, such that when charged into suitable apparatus air
and other gases shall be able to penetrate into and pass through the interstices
between them.
Fourth. The cakes, cylinders, balls, or other small masses which have been
formed as just said are heated in a current of air. A part of the oxygen of the
current of air reacts upon the chlorides in them and transforms these chlorides into
manganite of calcium, at the same time driving off their chlorine, mainly in the
free state, but partly as vapour of hydrochloric acid. The cakes or other small
masses which at the commencement of this operation were a mixture of manganite
of calcium with chloride of manganese and chloride of calcium, at the end of it thus
consist practically wholly of manganite of calcium, a part of which is then used
for a repetition of the first operation and the other part for a repetition of the
fourth, operation.
The first operation above described may be performed in a variety of. ways, and
no particular manner of performing it constitutes any part of the present Invention.
It must be so performed, however, that the acid shall be completely neutralized by
the manganite of calcium. To this end towards the latter part of the operation an
excess of manganite of calcium must be employed. Those last portions of the acid,
which would not dissolve peroxide of manganese, will then be neutralized by the
protoxide or protoxides contained in the excess of manganite, but the resulting
neutral solution will have suspended in it undissolved peroxide of manganese and
probably unattacked manganite also. These must be allowed to settle out before
the solution is evaporated, and what has so settled out, after the clear solution has
been decanted or otherwise separated from it should preferably be dissolved in the
next charge of hydrochloric acid before fresh manganite of calcium is added thereto.
The earlier part of this first operation must necessarily take place in chlorine stills,
as will be well understood, but when the free acid remaining has become so dilute
as to be incapable of dissolving more peroxide of manganese, and so incapable of
yielding more chlorine on more manganite of calcium being added to it, the
neutralization of this last part of the acid by means of the protoxide or protoxides
contained in an excess of manganite may be performed either in the chlorine stills
themselves or in separate vessels. In the latter case the apparatus used for the
neutralization by excess of manganite of calcium may be the same as that which

page_text: is employed for the neutralization by carbonate of lime of the acid still-liquors of
the present Weldon process; and the mode of proceeding will be just the same as
that followed in the operation just referred to, except that manganite of calcium
will be used as the neutralizing agent instead of carbonate of lime.
The second operation above described may equally be performed in many ways,
and in its case also no particular manner of performing it constitutes any part of
the present Invention. It may be performed in iron vessels, which the solution
to be evaporated will not materially attack if care have been previously taken that
it be perfectly neutral.
As regards the third and fourth operations which are described above, I do not
confine myself to any particular method of performing them, since they also may
be performed in various ways, and no particular manner of performing them
constitutes any part of the present Invention. I will proceed, however, to set forth
those methods of performing them which I believe to be the best.
The aforesaid third operation may be carried out as follows:-A shallow cast-
iron vessel with a flat bottom is placed near the pan or other vessel in which the
solution of chloride of manganese and chloride of calcium is evaporated. The
dispositions are such that concentrated solution from the evaporating vessel may
be run into the flat-bottomed mixing vessel at will. Solid manganite of calcium
is placed in the mixing-vessel, preferably in the state of powder; and concentrated
solution from the evaporating vessel is then run into the mixing vessel, a workman
meanwhile stirring the contents of that vessel with a suitable rake. The solid'
matter will drink up the concentrated solution the more readily if heat be applied
under the mixing vessel, so as to keep its contents at or above the temperature of
the boiling solution. The proportion of manganite of calcium may be either such
as to give a magma which shall be more or less fluid at and above the temperature
of the concentrated boiling solution, or such that the mixture shall be while hot
a moist but barely moist powder, just capable of being agglomerated by pressure.
In the latter case it may be formed into small cakes, or cylinders, or balls, or other
masses of any desired shape, by such mechanical means as are used for moulding
mixtures of coal dust with a cementing medium, or for moulding other plastic
material, and the resulting cakes, cylinders, balls, or other small masses so formed
will not necessarily require to be desiccated by a special operation before being
treated for the decomposition by heat and air of the chloride of manganese and
chloride of calcium in them; but their desiccation and the decomposition by heat
and air of the chloride of manganese and chloride of calcium in them may in some
cases be part of one and the same operation as that by which the said chlorides
are to be decomposed. The desiccation of this magma can be performed in brick
furnaces, or on brick drying floors heated from below, or otherwise, as will be most
convenient; or if drying floors be used they may be constructed of thick cast-iron
plates if precautions be taken against risk of these plates becoming too highly
heated. The magma should be spread as a thin layer on the beds of these furnaces
or on the drying-floors, as the case may be, a thin layer of powder of manganite of
calcium having preferably first been spread upon these beds or floors. When the
desiccation has proceeded far enough what was magma will now be a thin solid
cake capable, by reason of the intervening layer of manganite, of being easily
detached from the bed or floor and withdrawn in fragments. These should then be
broken if necessary, as will usually be the case, into smaller fragments, suitable to
be charged into the apparatus in which the next or fourth operation is to be
performed.
The manner of performing the fourth operation being that of heating in a
current of air the cakes, cylinders, balls, or other small masses or fragments of a
mixture of manganite of calcium with chloride of manganese and chloride of
calcium, may be that of placing the said small masses or fragments in apparatus to
which beat is applied externally, and to which is admitted either cold air or air
which, although it has been heated, has not been heated so highly that it can
supply to the contents of the apparatus all the heat necessary to the accomplish-

page_text: ment of the desired reaction. I prefer however to perform this fourth operation
in apparatus to which heat need not necessarily be applied externally by forcing
into and through the apparatus charged with the small masses of the said mixture
air which has been previously so highly heated, by means of a Cowper-Siemens
stove or otherwise, that it can of itself raise the temperature of the contents of the
apparatus to the point at which its oxygen can react upon the chloride of manganese
and chloride of calcium in them. This fourth operation may be either intermittent
or continuous, and I prefer to perform it in an apparatus consisting of a series of
distinct compartments so arranged and disposed that one or more of the said
compartments shall be capable of being isolated at will to permit of their being
discharged and re-charged while the other compartments are at work, and so that
the gases or mixture of gases and vapours passing from one part of the apparatus
at a high temperature shall be caused to give up much of their heat to those
portions of the charge contained in other portions of the apparatus which have not
yet attained that temperature.
One form of apparatus by which this method of proceeding may be carried into
effect consists of a series of vertical iron cylinders lined internally with brick.
The number of such cylinders which it may be best to employ will vary with
circumstances, but for the purpose of the present dnscription I will suppose it to
be eight, and I will indicate the eight cylinders by the letters A, B, C, D, E, F, G,
and H. I will suppose the eight cylinders to be arranged in two rows of four
each, A, B, C, and D in one row, and E, F, G, and H in another row, the two rows
of four cylinders each being so placed that A and H, B and G, C and F, and
D and E are respectively opposite to each other. Between the two rows of
cylinders is a conduit for conveying to them highly heated air. Each cylinder is
divided vertically into two compartments by a diaphragm or partition of brick-
work, which either does not descend quite to the bottom of the cylinder or, if it
does descend otherwise to the bottom of the cylinder, has in it at the bottom either
an aperture or several apertures for the passage of the gaseous current.
In the top
of each cylinder are two apertures, one over each of the two compartments into
which the cylinder is divided by the vertical partition in it. Through these
apertures the cylinders are charged with the small masses of mixture of manganite
of calcium and chloride of manganese and chloride of calcium from which chlorine
is to be evolved, and by means of elbow-pipes, the extremities of which can make
gas-tight joints with flanges or other convenient appliances surrounding those
apertures, communication can be established at will between each cylinder and the
conduit before mentioned, between each cylinder and the cylinder next in the
series, and between each cylinder and a second conduit. It will be convenient to
speak hereinafter of the first mentioned conduit as "the air-main," and of the other
conduit as the "chlorine-main." In each of the two conduits are apertures by
means of which and elbow pipes either cylinder can be connected at will with or
disconnected at will from either conduit.
I will now suppose that the seven cylinders A to G inclusive are all charged with
small lumps of the mixture of manganite of calcium with chloride of manganese
and chloride of calcium, and that an elbow-pipe connects the air-main with the left
of the two apertures in the top of the cylinder A, and that elbow-pipes similarly
connect the other aperture in the top of A with the left aperture in the top of B,
the right aperture in the top of B with the left aperture in the top of C, the right
aperture in the top of C with the left aperture in the top of D. D similarly with E,
E similarly with F, F similarly with G, and the further aperture in the top of G
with the chlorine-main. All the apertures in the air-main, except that in com-
munication with A, and all the apertures in the chlorine-main except that
communicating with G being closed, and highly heated air from a hot-blast stove
being forced into the air-main, highly heated air will enter A by one of the
apertures at the top of that cylinder will pass down > side of the partition
dividing that cylinder, and will then pass under that partition, and then up on
the other side of it. A mixture of nitrogen, air, free chlorine, and vapour of

page_text: hydrochloric acid will now pass from the top of A by the other aperture in the top
of that cylinder into the elbow-pipe by which A communicates with B, the gaseous
current then successively traversing B, C, D, E, F, and G, just as it had traversed A,
and finally passing from G into the chlorine-main which it will reach at a
comparatively low temperature. While the current is thus passing into A, thence
into and through B, C, D, E, F, and G successively, and from G into the chlorine-
main, workmen will have been charging the cylinder H.
When the charge
contained in the cylinder A has been sufficiently treated the entrance of hot air
into the air-main will be stopped for a moment, A will be disconnected from the
air-main and from B, the air-main will be connected with B instead of with A,
G will be disconnected from the chlorine-main and connected with H, H being now
connected with the chlorine-main, and then air from the hot-blast stove will be
readmitted into the air-main. The gaseous current will now enter B, will traverse
successively B, C, D, E, F, G, and H, and will pass from H into the chlorine-main.
While this is going on A will be discharged and re-charged. When the charge in B
has been sufficiently treated, and A has been discharged and re-charged, B will be
isolated for discharging and re-charging, C now becoming the cylinder which the
hot air enters, and A the cylinder from which the gaseous current passes into the
chlorine-main after having traversed successively C, D, E, F, G, H, and A. From
these examples the other successive changes in the course of the gaseous current
will be understood.
.
For the purpose of discharging the cylinders they are provided with doors in
their lower part.
Instead of the series of cylinders being arranged in two straight rows, as above
described, they may be arranged in a circle or otherwise, as may be more convenient
in each case.
Instead of their being charged by the apertures by which the
gaseous current enters and leaves them they may be charged by special apertures,
and the apertures by which the gaseous current enters and leaves them may be in
the upper part of their sides instead of in the positions above indicated. Instead
of the connections of cylinder with cylinder, and of the cylinders with the air-main
and the chlorine-main being made by means of movable elbow-pipes as above
described, they may be made by means of fixed pipes having valves or dampers in
them. The cylinders may moreover be without internal partitions, the gaseous
current in such case passing either down one cylinder and up the next, or passing
from the bottom of one cylinder to the upper part of the next by a pipe or conduit
placed externally to the cylinders themselves.
Another form of apparatus on the same principle consists of a series of horizontal
furnaces arranged and disposed and connected together by movable or fixed
passages for the gaseous current in the same manner as I have described for a
series of vertical cylinders. Such horizontal furnaces however can best be charged
through the doors by which they are discharged. In each such furnace I prefer that
there should be several vertical partitions, so disposed as to cause the gaseous
current to pass over one partition, then under the next partition, and so on
alternately. Such horizontal furnaces may be so disposed as to admit of the
charges treated in them being heated otherwise than simply by means of heat
previously communicated to the air by which the charges are treated, that is to
say, they may be furnaces in the ordinary sense having fire-places or combustion
chambers, in which fuel can be burnt for the direct heating of their charges.. When
they are such I prefer that they should be adapted for the burning of producer-gas,
and that the dispositions should be such that any one or more of the series of
furnaces may be being heated externally while the other members of the series are
not being so heated, and moreover such that the fuel gases may be turned off from
any one member of the series and on to the next at will.
The horizontal furnaces last described will be best suited to the treatment of the
mixture of manganite of calcium with chloride of manganese and chloride of
calcium when a large proportion of manganite is employed in making such mixture,
and it is aggregated by pressure and moulded into small masses of such shape as

page_text: may be desired by mechanical means. Such masses may be charged into that one
of the series of horizontal furnaces which for the time being is coolest without
being previously subjected to desiccation, and their desiccation be effected by the
hot mixture of chlorine and other gases which will subsequently pass into that
furnace from the furnaces, which during the operation then in progress will be
earlier members of the series, the desiccation of the small masses of mixture and
the subsequent decomposition of the chlorides in them being thus parts of one and
the same operation. The vertical cylinders above described will be better adapted
for the treatment of mixtures containing smaller proportions of manganite of
calcium, and which have been desiccated previously to their treatment for the
decomposition of the chlorides contained in them. When the charge is treated by
bot air, without heat being applied to it otherwise, the temperature to which the
air has been previously raised should preferably be such that the heated air shall
be capable of raising to or nearly to dull redness the portions of the charge with
which it first comes into contact.
The gaseous current passing off from the apparatus in which the mixture of
manganite of calcium with chloride of manganese and chloride of calcium is treated
by air will contain not only free chlorine but also inert gases, vapour of hydro-
chloric acid, and vapour of water. It must first be passed into apparatus in which
these vapours will be condensed out from it, as will be well understood, and then
into apparatus in which its chlorine shall be absorbed.
The method and apparatus for the treatment by heat and air of mixtures of
manganite of calcium with chloride of manganese and chloride of calcium which I
have just described constitute no part of the present Invention, but are part of the
subject-matter of another Invention for which the Letters Patent, numbered 968 of
the current year, have been granted to me. What I regard as constituting the
present Invention is the process for manufacturing chlorine, which is above set
forth, and especially those parts of it which are above described as its third and
fourth operations.
In witness whereof, I, the said Walter Weldon, have hereunto set my hand
and seal, this Twentieth day of August, in the year of our Lord One
thousand eight hundred and eighty one.
WALTER WELDON. (L.S.)