Improvements in the Production of White Lead or Basic Carbonate of Lead from Galena or Sulphide of Lead Ore, or from suitable Residual Products or Substances containing Sulphide of Lead.
Year: 1891

page_text: Date of Application, 28th Mar., 1891
Complete Specification Left, 24th Dec., 1891-Accepted, 6th Feb., 1892
PROVISIONAL SPECIFICATION.
Improvements in the Production of White Lead or Basic Carbonate
of Lead from Galena or Sulphide of Lead Ore, or from suitable
Residual Products or Substances containing Sulphide of Lead.
We, WATSON SMITH, Lecturer in Chemical Technology, University College,
London, and WILLIAM ELMORE, Electro-metallurgist, of 51 Handforth Road,
Clapham Road, London, do hereby declare the nature of this invention to be as
follows:-
In this our present invention we propose to combine together in one entire
process or whole, though with sundry additional details and improvements, already'
known methods, modified and adapted for our present purposes for the production of
oxide of lead, (litharge or massicot) from galena, sulphide of lead ore, or from
other products or substances containing sulphide of lead, and in a suitable condition
of purity, with the methods for the production of white lead or basic carbonate of
lead by the action of acetate of ammonia, cold as in the process of Mac Ivor and
others No. 10,426, 1888 (amended March 11th 1889) in which acetate of ammonia
is caused to act upon oxide of lead in vessels described in that Specification or in
similar vessels, and preferably in the cold, and by introducing carbonic acid gas
into the vessels containing the foregoing substances along with the substances
resulting from their reaction upon each other, also in the cold, thereby producing
white lead; or, as in another process in which the oxide of lead (litharge or
massicot) in fine powder, is treated with a heated solution of acetate of ammonia in
a closed vessel under a certain degree of pressure and with agitation, so as first to
form and then to bring into an ammoniacal solution the tribasic acetate of lead,
leaving behind red lead and insoluble impurities originally contained in the litharge
or oxide of lead used, settling, filtering off the clear liquor, cooling in another
vessel called the carbonator, and when cold (or at the ordinary temperature of the
air) passing carbonic acid gas through the liquid, thereby producing white lead or
basic carbonate of lead of improved quality, the excess gas with any inert gases
before final escape into the air, passing through a catch box or other absorbing
apparatus, to prevent loss of ammonia, cold water, dilute acetic acid or other
absorbing medium being used.
The carbonic acid gas used may be pure, or diluted with inert gases, and obtained
from lime kiln gases, furnace gases or other products of combustion after suitable
treatment to remove deleterious constituents.
Moreover in the case of galenas or other sulphides of lead containing copper and
furnishing litharge also contaminated with copper, the improved method for
separating any copper carried into or accumulated in solution by the treatment
with acetate of ammonia according to either of the processes previously referred to,
may be adopted as will be now described -All lead having been removed from
the solution, the latter is made slightly acid by means of acetic acid and either
treated with zinc or subjected to the action of an electric current from a primary
battery, dynamo or suitable source of electricity, electrodes of carbon being employed
in the cupreous solution. Thus, the copper is deposited from the solution upon the
carbon cathode. The additional detail must be given that if zinc be employed for
the precipitation of the copper it is to be preferably employed in the form of what
is known as "gossamer zinc (fine zinc turnings) such as is used for the precipitation
of gold in the cyanide process for the extraction of gold from ores, known as that
of the Mac Arthur-Forrest process, or some similar finely divided form of zinc may
be used and the solution may be cold or warm, thus a minimum of zinc is required

page_text: for precipitation of the small quantities of copper contained in these acetate
solutions.
Or, for the purpose of removing the copper from the contaminated (cupreous)
acetate of ammonium solutions a digestion with a sufficient quantity of finely divided
or precipitated metallic lead may be adopted, the solution being cold or preferably
warm.
G
In order to secure a proper degree of basicity in the white lead produced, and
also, when minute quantities of copper are present, to prevent the formation of a
yellowish tint in the white lead produced, this evil is avoided by only carrying on
the carbonating so as to precipitate a fraction of the whole of the lead present in
solution. The earlier fractions precipitated thus from the ammoniacal solution in
presence of small quantities of copper, are white as well as highly basic, the last
fractions being less basic and of ever increasing yellowishness of tint through copper,
up to the last portion precipitated which is both least basic and most yellowish.
It is thus best to choose a limit of precipitation, determined by a small scale trial
in the laboratory, such that the sufficient purity of colour is obtained, and then to
stop, leaving the rest of the lead in solution to be returned to the process in the
cycle of operations, or if desired to be first rid of the copper by precipitation by
means of zine or by electrolytic deposition, as already referred to.
The galena or other sulphide of lead ore, or residue, or by-product, may be at
once smelted for reduction to metal with collateral elimination of sulphur or
sulphurous acid, which sulphurous acid diluted with air and nitrogen is either passed
into a vitriol chamber system and converted in the usual way into sulphuric acid,
or is absorbed by slaked lime or milk of lime or carbonate of soda solution for the
preparation of sulphites or bisulphites of lime or soda; or other alkalis and alkaline
carths may be similarly used. The rough metallic lead is then collected and melted
again on a bone ash or clay bed, and heated to fusion, whilst a current or blast of
air is allowed to play over it, so as to form oxide of lead or litharge. As the
litharge forms, fuses and flows down from the convex surface of the still molten
metal it accumulates, or, by means of suitable channels and escapes cut in the bed,
overflows into and is collected in a suitable receptacle, or the litharge if not
allowed to fuse may be removed from the surface of the metal by suitable mechanical
means. Any silver that may have been contained in the ore or sulphide of lead
will be left on the bone ash or other bed which has been used for the oxidation of the
lead to litharge, and may be suitably recovered, the lead absorbed by the bed itself
being likewise recovered subsequently, by smelting with a suitable dux.
The litharge properly selected by fractionation, those fractions being chosen
most free from iron, indeed containing not more than mere traces, is allowed to cool
slowly so as to become crystalline, such crystalline litharge being after finely
pulverising, very quickly acted upon by acetate of ammonia.
The presence of more than mere traces of iron in the litharge, causes the formation
inevitably of a white lead with a more or less yellowish tint, but by rejecting the
first portions of litharge formed in the process of oxidising at a high temperature
on a bone ash or other suitable and resisting bed, the metallic lead formed in the
process of reducing galena or other sulphide of lead products, a sufficiently pure
litharge is ultimately obtained as far as regards iron. Litharge containing too
much iron is smelted with a fresh lot of ore or sulphide.
Freedom from iron is generally indicated by the litharge possessing a pure pinkish
or flesh coloured shade, an ochreish shade indicating small quantities of iron.
After finely pulverising and ou testing finding at most only a trace of iron and of
copper the litharge is ready for treatment with acetate of ammonia.
In the process thus sketched out it is obvious that those galenas or other
sulphides of lead which are non-argentiferous and thus command a low price, or
which are rich in zinc and yield a residue after zinc is extracted by any suitable
method, proportionately richer in lead sulphide and also commanding a low-price,
or lead sulphide residues or by-products sufficiently pure for the purpose and also
low priced, will be exceptionally available for making white lead as a final product,

page_text: in the present combined process herein proposed and we have found that such
materials are admirably fitted for the purpose.
Dated 28th March 1891
WATSON SMITH.
WILLIAM ELMORE.
COMPLETE SPECIFICATION.
Improvements in the Production of White Lead or Basic Carbonate
of Lead from Galena or Sulphide of Lead Ore, or from suitable
Residual Products or Substances containing Sulphide of Lead.
We, WATSON SMITH, Lecturer in Chemical Technology, University College,
London, and WILLIAM ELMORE, Electro-metallurgist, Worcester House,
Walbrook London, 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 :-
In this our present invention we propose to combine together in one entire process
or whole, though with certain additional details and improvements, already known
methods, modified and adapted for our present purposes for the production of oxide
of lead (litharge or massicot) from galena, sulphide of lead ore, or from other
products or substances containing sulphide of lead, and in a suitable condition of
purity, with the methods for the production of white lead or basic carbonate of lead
by the action of acetate of ammonia, cold as in the process of Mac Ivor and others
No. 10,426 of 1888 (amended March 11th 1889) in which acetate of ammonia is caused
to act upon oxide of lead in vessels described in that Specification or in similar vessels,
and preferably in the cold, and by introducing carbonic acid gas into the vessels con-
taining the foregoing substances along with the substances resulting from their reaction
upon each other, also in the cold, thereby producing white lead; or, as in another
process patented by Mac Ivor and Smith No. 16093 of October 10th 1890, with
other improvements and additions, in which the oxide of lead (litharge or massicot)
in fine powder, is treated with a heated solution of acetate of ammonia in a closed
vessel under a certain degree of pressure and with agitation, so as first to form and
then to bring into an ammoniacal solution the tribasic acetate of lead, leaving
behind the small amounts of red lead and insoluble impurities originally contained
in the litharge or oxide of lead used, settling, filtering off the clear liquor, cooling
in another vessel called the carbonator, and when cold (or at the ordinary
temperature of the air, or nearly so) passing carbonic acid gas through the liquid,
BO as thereby to produce white lead or basic carbonate of lead of improved
quality.
The excess gas with any inert gases before final escape into the air, passing
through a catch-box or other absorbing apparatus charged or supplied with either
dilute acetic acid or cold water or other absorbing medium, to prevent loss of
ammonia.
The carbonic acid used may be pure, or diluted with inert gases, and obtained
from lime-kila gases, furnace gases or other products of combustion, after suitable
treatment to remove deleterious constituents.
Moreover in the case of galenas or other sulphides of lead, containing copper
and furnishing litharge or oxide of lead also contaminated with copper, the improved
method of separating any copper carried into or accumulated in solution by the
treatment with acetate of ammonia according to either of the processes previously
referred to, may be adopted as will now be described :-
All lead, or all but minute quantities, having been removed from the solution, the
latter is made slightly acid with acetic acid and either treated with zinc or subjected
to the action of an electric current from a primary battery, dynamo or suitable
source of electricity, electrodes of carbon being employed in the cupreous solution.
Thus, the copper is deposited from the solution upon the carbon cathode. The

page_text: additional detail must be given that if zinc be employed for the precipitation of the
copper it is to be preferably employed in the form of what is known as gossamer
zine (fine zinc turnings) such as is used for the precipitation of gold in the
cyanide process for the extraction of gold from ores, known as that of the
Mac Arthur-Forrest process, or some similar finely divided form of zinc may
be
used and the solution may be cold or warm. Thus, a minimum of zinc is required
for precipitation of the small quantities of copper contained in the acetate
solution.
Or, for the purpose of removing the copper from the contaminated (cupreous).
acctate of ammonium solutions, a digestion with a sufficient quantity, preferably an
excess of finely divided or precipitated metallic lead may be adopted, the solution
being cold, or preferably warn, and distinctly acid with acetic acid.
In order to secure a proper degree of bascity in the basic carbonate of lead or
white lead produced, care is taken not to pass in the carbonic acid gas in the
carbonating process too quickly and to considerably slacken the supply towards the
close of the process, and especially when minute quantities of copper are present,
and under the same conditions also, in order to prevent the formation of a yellowish
tint in the white lead produced, to only carry on the carbonating so as to precipitate
a fraction of the whole of the lead present in solution. The earlier fractions
precipitated thus from the ammoniacal mixture or solution in presence of small
quantities of copper, are white as well as highly basic, the last fractions of the white
lead being less basic (less possessed of the valued body and covering power) and
besides being of ever increasing yellowishness of tint due to co-precipitation of
copper which begins to take place after a certain point in carbonating process and
continues up to the point of complete precipitation.
The last portion precipitated is both least basic and most yellowish. It is thus
best to choose a limit of precipitation which will depend upon a). The degree of
basicity required in the product, and b) The amount of copper present in the oxide
of lead (litharge or massicot) employed. This is best determined by a small scale
laboratory trial, such as to indicate when a sufficient purity of colour will be
obtained, then stopping and leaving the rest of the lead in solution to be returned
to the process in the cycle of operations, for the treatment of a fresh quantity of
oxide of lead (litharge or massicot), unless the experiment demonstrate the necessity
of a too early cessation of the carbouating process, and it is desirable to remove
the copper before proceeding further. This is then, in such case, done by precipita-
tion by means of zinc, finely divided lead or by electrolytic deposition as already
referred to and described.
The galena or other sulphide of lead ore or residue or by-product, may be at once
smelted for reduction to metal with collateral elimination of sulphur as sulphurous
acid, which sulphurous acid diluted with air and nitrogen is either passed into a
vitriol chamber system and converted in the usual way into sulphuric acid, or is
absorbed by slaked lime or milk of lime, or carbonate of soda solution for the
preparation of sulphites or bisulphites of lime or soda; or other alkalies and
alkaline carths may be similarly used.
The rough metallic lead is then collected and melted again on a bone ash or clay
bed, and heated to fushion, whilst a current or blast of air is allowed to play over
it, so as to form oxide of lead or litharge.
As the litharge forms, fuses and flows down from the convex surface of the still
molten metal, it accumulates, or, by means of suitable channels and escapes cut in
the bed, overflows into and is collected in a suitable receptacle, or, the litharge if
not allowed to fuse, may be removed from the surface of the metal by suitable
mechanical means.
Any silver that may have been contained in the ore or sulphide of lead, will be
left on the bone ash or other bed, which has been used for the oxidation of the lead
to litharge, and may be suitably recovered, the lead absorbed by the bed itself being
likewise recovered subsequently by smelting with a suitable flux.
The litharge properly selected by fractionation, those fractions being chosen

page_text: most free from iron, indeed containing not more than mere traces, is allowed to cool
slowly so as to become crystalline, such crystalline litharge after finely pulverising,
being very quickly acted upon by acetate of ammonium solution.
The presence of more than mere traces of iron in the litharge causes the
formation inevitably of a white lead with a more or less yellowish tint, but by
rejecting the first portions of litharge formed in the process of oxidising at a high
temperature on a bone-ash or other suitable and resisting bed, the metallic lead
formed in the process of reducing galena or other sulphide of lead product, a
sufficiently pure litharge is ultimately obtained as far as regards iron. Litharge
containing too much iron is smelted with a fresh lot of ore or sulphide.
Freedom from iron is generally indicated by the litharge possessing a pure
pinkish or flesh coloured shade, an ochre-ish shade indicating the presence of small
quantities of iron. After finely pulverising, and on testing, finding only a trace of
copper and at most only a minute trace of iron, the litharge is ready for treatment
with acetate of ammonia.
In the process thus sketched out it is obvious that these galenas or other
sulphides of lead which are uon-argentiferous and thus command a low price, or
which are rich in zinc and yield a residue after zinc is extracted by any
suitable method, proportionately richer in lead sulphide and also commanding a
low price, or lead sulphide residues or by-products sufficiently pure for the
purpose and also low priced, will be exceptionally available for making white
lead as a final product in the present combined process herein proposed, and we
have found that such materials are admirably fitted for the purpose.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
Firstly. The combined process as a whole, in which white lead or basic
carbonate of lead is prepared and manufactured from galena or sulphide of lead
ores, or, from suitable residual products or substances containing sulphide of
lead, as described.
Secondly. In the combined process as a whole and as described, that part of
it more particularly in which an excess of finely divided or precipitated metallic
lead is used to precipitate the copper from the cold or heated acetate of
ammonium solutions made acid with acetic acid, as described and for the
purpose described.
Thirdly. In the combined process as a whole that part of it more particularly,
in which besides galenas or sulphides of lead on the market as argentiferous
products, also the cheaper non-argentiferous galenas or sulphides of lead, besides
suitable lead sulphides as by-products as are obtained from zinciferous galenas or
sulphides of lead, after the zinc has been extracted by any suitable methods,
are used as specified and for the purpose described.
Dated 24th December 1891
WATSON SMITH.
WILLIAM ELMORE.