Improvements in the Production of Chlorine.
Year: 1891

page_text: Date of Application, 6th Mar., 1891
Complete Specification Left, 20th Nov., 1891—Accepted, 24th Dec., 1891
PROVISIONAL SPECIFICATION.
Improvements in the Production of Chlorine.
I, FARNHAM MAXWELL LYTE of 60, Finboro' Road, S. W., Analytical, Chemist,
do hereby declare the nature of this invention to be as follows:-
The object of this invention is the recovery of chlorine from those chlorides
which are capable of being decomposed by plumbic or other oxides or basic salts
such as basic chloride of lead with formation of a chloride, and it is particularly
applicable to the recovery of the chlorine contained in the ammoniacal liquor from
the ammonia-soda process. This liquor, for instance, may be distilled with the
addition of plumbic oxide in place of the lime generally employed in order to expel
the ammonia which may of course be used over again as usual, plumbic chloride
being thus produced. Plumbic chloride (which may, however, be otherwise
produced) is to be preferred on account of its sparing solubility in the saline
liquor.
The plumbic chloride having been collected, washed if thought desirable, and
dried, may be fused in a crucible or other suitable vessel (made of, say, iron
enamelled or lined if necessary with carbon graphite earthenware or composed
entirely of one of the two latter materials) and submitted to electrolysis in that
condition.
There are a variety of other ways of producing plumbic chloride, such as, for
instance, acting on plumbic oxide with hydrochloric acid, and there are other
chlorides which may be used if the evaporation necessitated and the other dis-
advantages be not considered drawbacks.
Both electrodes, or, in any case, the anode, may be composed of graphite or some
material unattackable by chlorine. The anode may be placed in a bell or inverted
funnel, from electrical contact with which it may be properly insulated at the point
where it traverses the said bell. This bell may also be of iron or other suitable
material enamelled or lined if requisite with graphite or earthenware or it may be com-
posed entirely of either of the two latter. The lower edge of the bell should plunge
just below the surface of the fused chloride so as to prevent any escape of chlorine,
and the anode may be so adjusted that its lower end may then dip to the required
extent into the fused plumbic salt beneath the bell. The other end of the anode
which passes outside the bell may if desired be electrically coated with copper so as
to ensure good electrical contact with the conductor through the clip and the bell
can have an exit pipe in its upper part for the chlorine to pass out. The cathode
may pass in at the lower part of the vessel, and, the temperature of melting lead
chloride (which is superior to that of melting lead) being maintained, the metallic
lead will collect at the bottom in a fused state. The melted lead then being drawn
off from below, while more chloride is added above, the process will be rendered
continuous.
By subsequent fusion in a suitable furnace, the metallic lead may be re-oxidized
into massicot (plumbic oxide) with which the operation may be re-commenced on a
fresh batch of liquor.
The plumbic or other chloride may also be fused cast into pigs and electrolysed
in the solid state but not perhaps so advantageously.
Dated this 6th day of March 1801

page_text: COMPLETE SPECIFICATION.
Improvements in the Production of Chlorine.
I, FARNHAM MAXWELL LYTE, of 60, Finborough Road, London, England,
Analytical 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 :-
The object of this invention is the recovery of chlorine from native chlorides or
from chlorides which are the waste or bye-products of commercial manufactures
(such as the calcic chloride of the ammonia soda process for example) or from
commercial hydrochloric acid (produced by the Leblanc process or any process by
which commercial hydrochloric acid is obtained from a native or from a waste
chloride) by the decomposition of such chloride or acid with formation of plumbic
chloride, followed by the fusion of the plumbic chloride so formed and by its
decomposition whilst in the fused state, into metallic lead and chlorine by electro-
lysis. I have found that plumbic chloride is eminently adapted to such electrolytic
decomposition by reason of its easy fusibility, the low electrical resistance of the
fused salt and the fusibility and remarkable purity of the lead produced.
Assume the source of the chlorine to be the ammoniacal liquor of the ammonia
soda process. This liquor may be distilled with the addition of plumbic monoxide,
such as massicot or with a basic salt of lead such as basic lead chloride in place of
the lime generally used in order to expel the ammonia which of course may be used
over again, plumbic chloride being thus produced.
Assuming native chloride to be used, chloride of sodium for instance, this may be
treated by the ordinary Leblanc process; or assuming waste chloride such as the
calcic chloride of the ammonia soda process to be used, this may be treated by the
Lyte and Steinhart process described in the Specification of Letters Patent dated
December 30th, 1890 No. 21225 for the production of commercial hydrochloric
acid with which plumbic chloride is produced in one of the ways hereafter described;
or if the Stassfurt salt, (magnesic chloride) be the native chloride, this also may be
treated by the Lyte and Steinhart process aforesaid (omitting the preliminary
conversion of calcic chloride into chloride of magnesium) for the production of
hydrochloric acid and therefrom of plumbic chloride, but the hydrochloric acid may
also be produced if desired from magnesic chloride alone with the assistance or not
of steam.
The commercial hydrochloric acid produced in any of those ways is converted
into plumbic chloride in one of the following ways.
(a) By boiling the hydrochloric acid with plumbic monoxide, decanting, and
cooling the liquor to crystallize out the plumbic chloride, the mother liquor
being evaporated down and used over again with fresh acid for treating a
fresh batch of plumbic oxide.
A
(b) By adding the hydrochloric acid to a solution of a lead salt such as the
nitrate or acetate of lead, wherefrom the plumbic chloride is precipitated,
the mother liquor being decanted off and used (after evaporation down to
the required strength) for the further production of the soluble lead salt.
convenient way to make the lead nitrate or acetate is by wetting granulated
lead, which is at the same time exposed to the air, with the dilute nitric or
acetic acid when the lead oxidises and the oxide is dissolved by the acid whilst
any silver present remaining undissolved may here be recovered. Or the
plumbic acetate or nitrate may be made by dissolving lead oxide in nitric or
acetic acid.
Where plumbic acetate is employed for the production of plumbic chloride a
mode of working to be recommended, but which I do not wish to limit myself to,
is as follows:
Suppose one commences with a 25% solution of plumbic acetate. Granulated or

page_text: other finely divided lead is to be alternately wetted with this, and exposed to the
air so long as the solution continues to increase in density. It is then allowed to
settle and the clear liquor drawn off. This liquor is to be divided into two equal
portions. One may be completely or nearly completely precipitated as plumbic
chloride by an addition of hydrochloric acid, the solution separated from the
precipitate, neutralised or rendered slightly basic by the addition of the second
portion of the liquor, and finally concentrated if requisite. The operation may be
recommenced by passing the solution over the metallic lead as before so that it may
take up more base, and so on &c. As the plumbic chloride may even by this
method still be slightly basic, it may be treated with a little dilute hydrochloric
acid, after which it may be finally washed and dried.
(c) By alternately adding hot dilute hydrochloric acid to granulated lead
and exposing the latter to the air repeatedly, the lead chloride formed in the
liquor separating out on cooling.
The plumbic chloride obtained in any of the above ways having been collected
(washed if necessary) and dried is to be fused in a crucible or other suitable vessel
and submitted to electrolysis whilst in the fused condition in the manner hereafter
described.
The electrolytic decomposition cell may be a trough, preferably of earthenware
or of enamelled iron, and it may be heated in a sand or air bath or directly by gas
or other means, whereby it may be maintained at a constant temperature. In this
vessel or cell are to be placed a number of plates, say of carbon graphite or other
suitable material unattackable by chlorine and unaffected by the fused plumbic
chloride in which they are immersed, said plates being alternately anodes and
cathodes, or the cell may be otherwise arranged. Two or more such cells may be
used grouped by preference in series, the anode of the one cell being coupled to the
cathode of the other cell whereby a more economical production of chlorine may be
obtained than by the employment of a single cell. This trough is closed by
convenient cover sealed (say by means of a liquid joint) to avoid loss of chlorine,
a pipe being connected thereto to convey away the chlorine. The electrodes are
so supported in the trough, that they do not touch one another or the metallic lead
which collects on the bottom of the trough, sufficient space being left for the said
metallic lead (resulting from the electrolytic decomposition of the fused chloride)
to flow beneath them without touching and so short circuiting them, the bottom
of the trough sloping down to one end where the molten metallic lead will collect
and whence it may be caused to run off spontaneously by means of a syphon or
other means.
a
Such a trough is represented, by way of illustration only, in longitudinal vertical
section in Figure 1 of the accompanying drawings forming part of this Specifi-
cation "a" being the anode and "c" the cathode plates.
In this example the trough "t" is shewn as heated in a sand bath but this,
although often advantageous to equalize the heat, is not necessary as the trough
may be directly heated by gas jets beneath it. The plates "a" and "c" are shewn
as passing through slots in the cover of the trough with which they make gas-tight
joints. They do not extend the full width of the trough, in order to allow the
chlorine generated to flow past them to the outlet pipe, and they are provided with
external binding clips by which they are coupled respectively to the anode and
cathode conductors. Instead of the plates passing through the cover, they may be
attached to the underside thereof by any suitable means, their terminals only
passing through for connection with the main conductors. Or the plates might be
supported in grooves in the sides of the trough and connected inside the trough,
the anode and cathode plates respectively with one anode and one cathode terminal
passing through the cover, the electrical connections being suitably protected
against the action of the chlorine. Instead of arranging the anodes and cathodes
alternately all the plates in one half of the trough may be anodes and all in the
other half cathodes,

page_text: The overflow siphon "s
د,
is made of earthenware or enamelled iron and the over-
flow of the molten lead is caused by the internal pressure in the tank and brought
about by an alteration in the specific gravity of the liquids, the bend of the
overflow pipe being at such a height that the level of the molten lead will remain
constant, provided the fused chloride is kept at the same level. Suitable provision
should therefore be made for supplying the chloride to the tank without removing
This may be done by fusing the chloride in a separate crucible (not
shewn) connected with the trough by a pipe and running it in in such a way as to
keep the level of the chloride constant as will be readily understood.
the cover.
The arrangement of the cell may also be further varied, for instance by omitting
the plates "c" and making the molten lead the cathode, in which case sufficient
lead for the purpose would be put into the trough at the outset, enough always
being retained to form a cathode of extended area, the conductor connected with
the negative terminal of the source being in that case made of some suitable
material, preferably of iron tinned to ensure good electrical contact with the molten
lead into which it is led.
Instead of a trough a number of separate crucible like cells may be used, similar
to the one represented in Fig. 2, in which a is the anode composed of graphite or
other material unattackable by chlorine, "" a bell dipping into the fused chloride
contained in a vessel "d" (which is kept heated in any suitable manner) into which
the anode " a is also immersed. "is the cathode which passes in at the bottom
of the vessel "d" and which may be made of iron tinned to ensure good electrical
contact.
"
The form of apparatus employed for the electrolytical decomposition of the
plumbic chloride may be still further varied, (those illustrated being given merely
by way of examples,) but whatever form is adopted care should be taken that the
areas of the exposed surfaces of the anode and cathode should respectively
correspond.
Owing to the exceptionally low resistance of fused lead chloride a large current
of low voltage, say 5 volts or less, may be employed, the conductors and dynamo
being similar to those used in electroplating.
The metallic lead resulting from the electrolytical decomposition of the plumbic
chloride may be granulated and converted into a salt of lead as above described, or
may be oxidized into massicot for conversion into fresh plumbic chloride.
It may here be observed that this metallic lead if made from a chloride which
has been precipitated from a soluble salt of lead such as nitrate or acetate, will be
chemically pure metallic lead, any silver and other impurities it contained
originally having been left in the vat when the soluble salt of lead was formed.
Therefore it would be more advantageous to use fresh impure lead, for the manu-
facture of chloride at each operation and produce pure lead for sale.
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. The herein described process of producing chlorine on a commercial scale
from the ammoniacal liquors of the ammonia soda process by distilling the said
liquors with plumbic monoxide (say massicot) or a basic salt of lead, (say basic lead
chloride) to form plumbic chloride and then fusing the plumbic chloride by heat
and decomposing it by electrolysis, substantially in the manner described.
2. The herein described process of producing chlorine on a commercial scale
from commercial hydrochloric acid obtained in any of the ways described either
from native chlorides or from the waste chloride liquors of commercial manu-
factures, which process consists in first forming plumbic chloride with such acid
and then fusing the plumbic chloride and decomposing it by electrolysis, substan-
tially in the manner described.
3. The herein described process of producing chlorine on a commercial scale by

page_text: the electrolytic decomposition, substantially in the manner described, of fused
plumbic chloride produced by any known commercial process.
Dated November 19th 1891.
F. MAXWELL LYTE.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.