provements in the Preparation of Chloride of Lead for Use in Electrical Storage Batteries and for other purposes
Year: 1895

page_text: Date of Application, 4th May, 1895
Complete Specification Left, 4th Feb, 1896-Accepted, 7th Mar, 1896
PROVISIONAL SPECIFICATION
Improvements in the Preparation of Chloride of Lead for Use in
Electrical Storage Batteries and for other purposes
I ALFRED ROLAND DAVIS of 32 Blackfriars Street Manchester Chemical
Engineer do hereby declare the nature of this invention to be as follows
Attempts that have been made hitherto to prepare chloude of lead by bringing
hydrochloric acid into direct contact with oxide of lead have been eith
unsuccessful or only partially successful as commercial processes on account of the
fact that though a certain portion of the oxide of lead is readily converted into
chloride this latter salt is so feebly soluble in water or hydrochloric acid that it
forms a coating upon the unattached portion of the lead oxide which tends to
prevent the further action of the hydrochloric acid It is true that the difficulty
might to a certam extent be overcome by the use of a sufficient quantity of the
solvent but this would amount to such an unwieldy volume per ton of lend
chloride that such a method of overcoming the difficulty is practically out of the
question
My improvements are based upon the readiness with which uydrochloric acid
will attack a certain small proportion of oxide of lead as above described and
further upon the fact that the chloride of lend so formed is very much more
soluble in hot than in cold dilute hydrochloric acid
In carrying out my process I treat oxide of lead with dilute bydrochloric acid
in a suitable dissolving vessel well agitating the mixture and keeping the
temperature as near the boiling point as possible When the solution contains as
much chloride of lead as is possible at that temperature I stop the agitation,
allow the turbid solution to settle for about a minute and run it off into a cooling
vessel o series of cooling vessels On cooling the liquid deposits about three
fourths of the chloride of lead which it held in solution and it is then taken back
to the dissolving vessel and used to dissolve a further quantity of oxide of lead
This latter is also deposited as chloride in the cooling vessels as in the case already
descubed and it will be readily seen that the operation can be carried on continuously
provided that fresh oxide of lead be from time to time charged into the dissolving
vessel and that fresh bydrochloric acid be added to the solution to replace that
which is removed in combination with the lead The chlode of lead which
deposits in the cooling vessels can be collected and removed is desued
necessary it can be washed, allowed to drain and died in any convenient manner
In order to facilitate continuity of working 1 take care to have such a volume
of the solvent liquid in cnculition that while portion of it is being agitated with
the oxide of lead another portion is cooling and depositing lead chloride while yet
another portion is being ehe ited for use again in the dissolving ves el and I prefer
to s proportion my means of cooling whether atmospheric o irtificial that a
supply of the liquor which has been cooled and caused to deposit as much chloride
of lead as was practically possible is always heated cady to replace the liquor
that is in the dissolver
If
All the above operations may be conducted in vessels of wood stone or
earthenware but I prefer to use vessels of enamelled on partly on account of
their greater cleanliness and partly on account of their greater convenience
Moreover if vessels of this material be employed for heatin and dissolving they

page_text: can be steam jacketed and thus the steam used for heating the liquids may if desired
be prevented from diluting them
If the process be carried on as described above such a uniformity of temperature
can be maintained in all the vessels employed that the risk of the enamel cracking
off from the iron through altcinate expansion and contraction is reduced to a
minimum
It will be evident that the volume of the liquid in circulation will always tend
to increase on account of the water present along with the hydrochloric acid that
has to be added to replace what is used I overcome this difhculty by periodically
or continuously withdrawing from circulation a quantity of the cooled solvent and
precipitating the lend which it still cont uns by means of lime or carbonate of soda
The precipitate may be used in tend of an equivalent amount of fresh oxide of
lead in the dissolving vessel, and the liquor after subsidence or filtration may be
run away
In order to expedite the dissolving of the lead oxide I may use instead of dilute
hydrochloic acid a mixture of dilute hydrochloric acid with acetic acid or nitric
acid or with both of them or I may digest the oxide of lead in strong hydrochloric
acid previously to introducing it into the dissolving vessel
Dated this Third day of Mar 1895
ALFRED ROLAND DAVIS
GF Redfern & Co,
4, South Street, Iinsbury, London, Agents for the Applicant
Improvements in the Preparation of Chloride of Lead for Use in
Electrical Storage Batteries, and for other purposes
I, ALFRED ROLAND DAVIS, of 32, Blackfriars Street, Manchester, in the
County of Lancaster, Chemical Engineer, 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
Attempts that have been made hitherto to prepare chloride of lead by bringing
hydrochloric acid into direct contact with oxide of lead have been either
unsuccessful or only partially successful as commercial processes on account of the
fact that though a certain portion of the oxide of lead is readily converted into
chlonde this latter salt is so feebly soluble in water or hydrochloric acid that t
forms a coating upon the unattacked portion of the lead oxide which tends to
prevent the further action of the hydrochloric acid It is true that the difficulty
might to a certain extent be overcome by the use of a sufficient quantity of the
solvent, but this would amount to such an unwieldy volume per ton of lead
chloride that such a method of overcoming the difficulty is practically out of the
question
My improvements are based upon the readiness with which hydrochloric acid
will attack a certain small proportion of oxide of lead as above described, ind
further upon the fact that the chloride of lead so formed is very much more
soluble in hot than in cold dilute hydrochloric acid
In carrying out my process I treat oxide of lead with dilute hydrochloric acid
in a suitable di solving vessel well agitating the mixture and keeping the
temperature as near the boiling point as possible When the solution contains as
much chloride of lead as is possible at that temperature I stop the agitation, allow
the turbid solution to settle for about a minute and run it off into a cooling vessel
or series of cooling vessels On cooling, the liquid deposits about three fourths
of the chloride of lead which it held in solution, and it is then taken back to the
dissolving vessel and used to dissolve a further quantity of oxide of lead
This

page_text: latter is also deposited a chloride in the cooling vessels as in the case already
described, and it will be readily seen that the operation can be carried on
continuously provided that fresh oxide of lead be from time to time charged into
the dissolving vessel and that fresh hydrochloric acid be added to the solution to
replace that which has entered into combination with the lead The chloride of
lead which deposits in the cooling vessel may be collected and removed as desired
If necessary it can be washed, allowed to drain, and died in any convenient
manner
In order to facilitate continuity of working I take care to have such a volume
of the solvent liquid in circulation that, while a portion of it is being agitated with
the oxide of lead, another portion is cooling and depositing lead chloride, while
yet another portion is being reheated for use again in the dissolving vessel and
I prefer to so proportion my means of cooling, whether atmospheric or artificial,
that supply of the liquor which has been cooled and caused to deposit as much
chloride of lead as was practically possible is always heated ready to replace the
liquor that is in the dissolver
All the above operations may be conducted in vessels of wood, stone or
earthenware but I prefer to use vessels of enamelled iron partly on account of
their greater cleanliness and partly on account of their greater convenience
Moreover, if vessels of this material be employed for heating and dissolving they
can be steam-jachetted and thus the steam used for heating the liquids may, if
desired, be prevented from diluting them
If the process be carried on as described above, such a uniformity of temperature
can be maintained in all the vessels employed that the risk of the enamel cracking
from the iron through alternate expansion and contraction is reduced to a
minimum
It will be evident that the volume of the liquid in circulation will always tend
to increase on account of the water along with the hydrochloric acid that has to be
added to replace that which is used I overcome this difficulty by periodically
or continuously withdrawing from circulation a quantity of the cooled solvent and
precipitating the lead which it still contains by means of lime or carbonate of soda
The precipitate may be used instead of an equivalent amount of fresh oxide of
lead in the dissolving vessel, and the liquor, after subsidence and filtration, may
be run away
In order to expedite the dissolving of the lead oxide I may use, instead of dilute
hydrochloric acid, a mixture of dilute hydrochloric acid with acetic acid or nitric
acid, or with both of them, or I may digest the oxide of lead in strong hydrochloric
acid, pieviously to introducing it into the dissolving vessel
In the accompanying sheet of drawings Figure 1 is an elevation and Figure 2
a plan of the plant which I employ in carrying out my improved process
B represents a steam-Jacketted vessel provided with an agitator in which oxide
of lead is subjected to the solvent action of hot dilute hydrochloric acid When
the hydrochloric acid has dissolved as much oxide of lead as it is capable of doing,
it is allowed to run into a series of cooltis C, C, where the bulk of the chloride of
lead separates out, and from which the liquor overflows into a well E From E
the now cool liquid is raised by an injector D or other suitable means to the
heating vessel A, where it is strengthened if necessary by the addition of strong
hydrochloric acid The heating vessel A is steam Jicketted, or it may be provided
with a steam heating coil so that the liquid contents can be raised to a boiling
temperature As soon as the hydrochloric acid is discharged from the vessel B
into the coolers C, C it receives a fresh charge of liquoi from A, and so the
operation goes on without interruption
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
-
The method of preparing chloride of lead by dissolving oxide of lead in hot

page_text: dilute hydrochloric acid, allowing the solution to cool to cause the bulk of the
chloride of lead to separate out, adding more strong hydrochloric acid when
necessary to the cooled liquor and, after rebeating his, using it to dissolve more
oxide of lead, and so on repeatedly, substantially as hereinbefore set forth
Dated the 4th day of February 1896
G F REDFERN & Co,
4, South Street, Finsbury, London, Agents for the Applicant.