IMPROVEMENTS IN-MAKING WHITE AND OTHER LEAD PIGMENTS AND IN APPARATUS THEREFOR
Year: 1884

page_text: We, ANDREW FRENCH, of 29 Washington Terrace, North Shields, in the County
of Northumberland, Metallurgist, and JAMES BALLANTYNE HANNAY, of Cove Castle,
Loch Long, in the County of Dumbarton, North Britain, Chemist, do hereby declare
the nature of our said invention for "IMPROVEMENTS IN-MAKING WHITE AND OTHER
LEAD PIGMENTS AND IN APPARATUS THEREFOR," to be as follows that is to say --
Our said Invention has for its object to improve the manufacture of white and
other compounds of lead to be used as pigments.
In carrying out our Invention we employ leadores, lead fume, or lead slags
containing sulphur; and when these materials do not contain sufficient sulphur to
form a sulphite with all the lead which sublimes in our 'process, we add to them
pyrites or other sulphur yielding substance to make up the 'deficioncy. We heat
the materials mixed with a suitable proportion of coke in an air-blast cupola
furnace which is by preference of an improved and special construction hereinafter
described; and we thereby produce sulphite of lead as a sublimate which is carried
forward with the current of gases through flues to a fume condenser, which is by
preference of the kind known as Wilsons and French's. As the gases and
sublimate pass through the flues hydrochloric acid is mixed with them being by
preference formed in a chamber in connection with the flue by introducing a
solution of chloride of sodium in spray and by providing a sufficient excess. of
sulphurous acid beyond that required for formning the sulphite of lead: Air is also
present, and a well known reaction takes place yielding hydrochloric acid and
sulphate of soda. The hydrochloric acid thus mixed with the gases and sublimate
causes the formation of chloro-sulphite of lead or a combination of lead, sulphur,
oxygen and chlorine, which forms a white pigment of extremely good quality.
The improved cupola furnace which we employ is formed with. a deep hearth
having a siphon outlet for withdrawing molten lead when necessary. At a level a
little above the top of the siphon outlet, an outlet for slag and scoria is provided,
and the main blast tuyeres enter at about the same or a slightly higher level. With
this arrangement a considerable depth of melted lead is constantly maintained and
the choking of materials is thereby avoided at the level of the tuyeres. For a short
distance above the main tuyeres the interior of the furnace is made with a moderate
and gradual upward widening, and is afterwards continued upwards of uniform

page_text: diameter or width. The charging door is between three and four feet above the
main tuyeres; and the space above the charging door is crossed by two or more
arched diaphragms of brickwork having irregular openings in them, there being
doors above each diaphragm for inspection and cleaning. The purpose of these
diaphragms is to cause the air, gases, and sublimate to become thoroughly intermixed,
and to insure the complete combustion of any black smoke and the oxidation of any
sulphide that may be present. An upper series of small tuyeres or jet pipes is
provided for admitting air a little below the lowest diaphragm, these jet pipes
being supplied by a branch pipe from the main air blast pipe, it being found that
the introduction of the air and heat produced can be best regulated by supplying a
portion at the upper part of the furnace in this way in addition to that supplied
through the inain tuyêres; and a tape or valve is fitted on the 'branch pipe for
adjusting the supplementary supply thus admitted. Above the highest perforated
diaphragm the interior of the furnace communicates with a lateral flue through
which the sublimate and gases pass off'; and at a part of this flue sufficiently near
the furnace for the gases to be still hot enough, an enlargement or chamber is
formed into which a solution of chloride of sodium is introduced as a spray from a
number of jet pipes for the purpose hereinbefore explained. This chamber is
provided with a door at its lower part for périodically removing matters that
become deposited in it.
It is of great importance to keep the temperature of the upper part of the furnace
steadily at a red heat and flaming, as the color of the sublimate will be inferior if
the temperature is either too high or too low. To facilitate the proper regulation of
the temperature we employ a pyrometer (which may be similar to the kind used in
iron works), which pyrometer we place in the flue at a distance from the furnace
where it cannot be injured, and by a few trials we ascertain what temperature
should be indicated by the pyrometer when the temperature in the furnace is what
it should be and the point having been ascertained a glance at the pyrometer will
We also
at any time show whether the furnace is working properly or not.
provide for rapidly cooling the upper part of the furnace without interfering with
the lower part, in the event of the heat becoming too great, by arranging a water
pipe with a set of jets round the top of the funrace, so that on turning a tap on the
supply pipe a spray of water may be applied to the outside of the furnace; and as
it is desirable that water applied in this way should not run down to the lower
part of the furnace we build gutter plates into the sides of the furnace just above
the charging door to lead off any surplus water to a drain pipe.
Sufficient hydrochloric acid is formed or introduced as herein before described not
only for forming chloro-sulphite of lead in the condenser, but also for saturating all
the free oxide of lead, and for combining with and rendering soluble any iron, zinc,
antimony, silver, or other metals. The chlorides thus formed become dissolved in
the water of the condenser, and the solution being separated from the insoluble
white pigment may be treated by known processes for recovery of the metals.
.
The white pigment is washed in the ordinary way and when chloride of zinc is
not completely removed by washing a sinall quantity of sulphuric acid may be
mixed with the pigment to convert the chloride of zinc into sulphate which is not
hygroscopic.
The white pigment made as hereinbefore described is a very good and economical
material for manufacturing into chrome yellow, this being done by mixing a
solution of any suitable chromate or bichromate with the wet pigment; whilst the
chrome yellow thus obtained may be converted into chrome orange or red by
treating it in the usual way.
1001
EDMUND HUNT,
Applicants' Agent.

page_text: COMPLETE SPECIFICATION.
We, ANDREW FRENCH, of 29 Washington Terrace, North Shields in the County
of Northumberland, Metallurgist, and JAMES BALLANTYNE HANNAY, of Cove Castle,
Loch Long, in the County of Dumbarton, North Britain, Chemist do hereby
declare the nature of our said invention for "IMPROVEMENTS IN MAKING WHITE
AND OTHER LEAD PIGMENTS AND IN APPARATUS THEREFOR," and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement that is to say -
Our said Invention has for its object to improve the manufacture of white and
other compounds of lead to be used as pigments.
.
In carrying out our Invention we employ lead ores, lead fume, or lead slags
containing sulphur; and when these materials do not contain sufficient sulphur to
forin a sulphate with all the lead which sublimes in our process, we add to them
pyrites or other sulphur yielding substance to make up the deficiency. We heat
the materials mixed with a suitable proportion of coke in an air-blast cupola
furnace, which is by preference of an improved and special construction shown on
an accompanying sheet of explanatory drawings and hereinafter described; and
we thereby produce sulphite of lead as a sublimate, provided that there are no.
chlorides such as common salt present in the charge, in which case sulphate and
chloride of lead will be formed. The sublimate is carried forward with the current
of gases through flues to a fume condenser, which is by preference of the kind
known as Wilsons and French's. As the gases and sublimate pass through the
flues hydrochloric acid is mixed with thein, being by preference formed in a
chamber in connection with the flue by introducing a solution of chloride of sodium
in spray and by providing a sufficient excess of sulphurous acid beyond that
required for forming the sulphite of load. Air is also presen; and a well known
reaction takes place yielding hydrochloric acid and sulphate of soda, the operation
taking place at a part of the flue near enough to the furnace to be always at a red
heat. The hydrochloric acid thus mixed with the gases and sublimate causes the
formation of chloro-sulphite of lead or other combinations of lead, sulphur, oxygen,
and chlorine of variable constitution depending on the proportions of the several
constituents, but in most cases the product is a body which forms a white pigment
of extremely good quality.
Figure, 1, on the accompanying sheet of drawings is an elevation of our improved
cupola furnace, figure, 2, is a corresponding vertical section and figure, 3, is a
horizontal section as at the level of the principal tuyeres.
This cupola furnace is formed with a deep hearth, 4, (like the American lead
smelting cupola) having a siphon outlet, 5, for withdrawing molten lead when
necessary. At a level a little above the siphon outlet; 5, an outlet, 6, for slag and
scoria is provided, and the main blast tuyeres, 7, enter at about the same or a
slightly higher level. With this arrangement a considerable depth of melted lead
is "constantly maintained and the choking of materials is thereby avoided at the
level of the tuyères. For a short distance above the main buyeres, 7, the interior

page_text: of the furnace is made with the sides, S, moderately and gradually widening
upwards and is afterwards continued upwards of uniform diameter or width. The
charging door, 9, is between three and four feet above the main tuyeres, 7, and
the space above the charging door is crossed by two or more arched diaphragms, 10,
11, of brickwork having irregular openings in them, there being doors, 12, 13, in
the side of the furnace above each diaphragm for inspection and cleaning. The
purpose of these diaphrgms is to cause the air, gases, and sublimate to become
thoroughly intermixed, and to insure the complete combustion of any black smoke
and the oxidation of any sulphide of lead that may be present.
An upper series of small tuyeres or jet pipes, 14, is provided for admitting air a
little below the lowest diaphragm, 10, these jet pipes, 14, being supplied by a
branch pipe, 15, from the inain air blast pipe, 16, it being found that the intro-
duction of the air and the production of heat can be best regulated by supplying
a portion at the upper part of the furnace in this way in addition to that supplied
by the main tuyeres, 7, and a tap or valve, 17, is fitted on the branch pipe, 15, for
adjusting the supplementary supply thus admitted. Above the highest perforated
diaphragm, 11, the interior of the furnace communicates with a lateral flue, 18,
through which the gases and sublimato pass; and at a part of this flue, 18,
sufficiently near the surface for the gases to be still hot enough, an enlargement or
chamber, 19, forming a descending part of the flue is constructed. Into this
chamber, 19, a solution of chloride of sodium is introduced as a spray from a
number of jet pipes, 20, for the purpose hereinbefore explained. This chamber, 19,
is provided with a door, 21, at its lower part for periodically removing matters
that become deposited in it. The continuation, 22, of the flue communicates with
the lower part of the chamber, 19. We prefer to have the spray of chloride of
sodium fine enough to allow of all or nearly all of the water being instantly
evaporated so as to leave the salt in fine particles and in a favorable condition for
being acted upon by the sulphurous acid, steam, and oxygen present in the gaseous
currents. The temperature of the chamber, 19, should not be allowed to fall
below red heat. The proportion of chloride of sodium used will depend on the
amount of chlorination of the lead that may be desired in addition to what is
necessary for converting the zinc and other metals into chlorides. In practice a
proportion of salt 2 to 5 per cent. of the weight of the sublimate formed answers
the purpose and yields a good product, but a larger proportion may be used without
injury.
It is of great importance to keep the temperature of the upper part of the
furnace steadily at a red heat and flaming, as the color of the sublimate will be
inferior if the temperature is either too high or too low. To facilitate the proper
regulation of the temperature we employ a pyrometer (which may be similar to
the kind used in iron works) which pyrometer we place in the fiue at a distance
from the furnace where it cannot be injured, and by a few trails we ascertain what
temperature should be indicated by the pyrometer when the temperature in the
furnace is what it should be; and the point having been ascertained, a glance at
the pyrometer will at any time show whether the furnace is working properly or
not. We also provide for rapidly cooling the upper part of the furnace without
interfering with the lower part, in the event of the heat becoming too great, by
arranging a water pipo, 23, with a set of jets round the top of the furnace, so that
on turning a tap on the supply pipe a spray of water may be applied to the outside
of the furnace and as it is desirable that water applied in this way should not
run down to the lower part of the furnace we build gutter plates, 24, into the sides
of the furnace just above the charging door, 9, to lead off any surplus water to a
drain pipe.
Sufficient hydrochloric acid may be formed or introduced as hereinbefore
described not only for forming chloro-sulphite of lead in the condenser, but also
for saturating all the free oxide of lead, and for combining with and rendering
soluble any iron, zinc, antimony silver, or other metals. The chlorides thus formed
become dissolved in the water of the condenser and the solution separated from the

page_text: insoluble white pigment may be treated by known processer for recovery of the
inetals. When the lead ores or other lead yielding materials contain silver to a
greater extent than 5 ounces per ton, a notable quantity of the silver is volatilised,
and if it is left in the white pigment it renders the latter sensitive to sunlight;
whereas if rendered soluble in the manner hereinbefore described and separated by
any of the known processes it becomes a source of profit.
The white pigment is washed in the ordinary way and when chloride of zinc is
not completely removed by washing, a small quantity of sulphuric acid may be
mixed with the pigment, by adding the same to the last washing water, to convert
the chloride of zinc into sulphate which is not hygroscopic.
The white pigment made as hereinbefore described is a very good and econo-
mical material for manufacturing into chrome yellow, this being done by mixing
a solution of any suitable chromate or bichromate with the wet pigment; whilst
the chrome yellow thus obtained may be converted into chrome orange or red by
treating it in the usual way.
Having now particularly described and ascertained the nature of our said
Invention and in what manner the same is to be performed we declare that
what we claim is
1-The making of white lead pigments consisting of compounds of lead,
sulphur, oxygen and chlorine by the improved process substantially as hereinbefore
described.
2 The improved combination of parts forming the complete furnace the parts
being arranged substantially as and for the purposes hereinbefore described.
3 The application of the improved white lead compound for making chrome
yellow substantially as hereinbefore described.
Dated thin fourth day of July 1985
EDMUND HUNT,
Per pro. David Ferguson,
Applicants' Agent.