IMPROVEMENTS IN OBTAINING WHITE COMPOUNDS OF LEAD AND ZINC SUITABLE FOR MAKING PIGMENTS, AND FOR OTHER PURPOSES, FROM LEAD AND ZINC ORES, OR FROM THEIR PRODUCTS OR RESIDUES, AND IN APPARATUS THEREFOR."
Year: 1881

page_text: LETTERS PATENT to Andrew French, of Morriston, in the County of
Glamorgan, Metallurgist, for an Invention of "IMPROVEMENTS IN OBTAINING
WHITE COMPOUNDS OF LEAD AND ZINC SUITABLE FOR MAKING PIGMENTS,
AND FOR OTHER PURPOSES, FROM LEAD AND ZINC ORES, OR FROM THEIR
PRODUCTS OR RESIDUES, AND IN APPARATUS THEREFOR."
PROVISIONAL SPECIFICATION left by the said Andrew French at the
Office of the Commissioners of Patents on the 8th June 1881.
ANDREW FRENCH, of Morriston, in the County of Glamorgan, Metallurgist.
"IMPROVEMENTS IN OBTAINING WHITE COMPOUNDS OF LEAD AND ZINC SUITABLE.
FOR MAKING PIGMENTS, AND FOR OTHER PURPOSES, FROM LEAD AND ZINC ORES,
OR FROM THEIR PRODUCTS OR RESIDUES, AND IN APPARATUS THEREFOR."
This Invention has for its object the treatment of lead and zinc ores or their
products or residues in an improved manner, and so as to obtain white compounds,
which can be advantageously applied in making pigments, and for any purposes for
which ordinary white lead is used.
In carrying out the Invention a low cupola smelting furnace is employed, so as
to produce a white sublimate of carbonate and oxide of lead, or of lead and zinc,
from oxidised ores or materials containing lead or lead and zine; and also so as to.
produce a similar white sublimate of sulphite of zinc and sulphite of lead from-
sulphuretted ores, or from products or residues of such ores, the said ores or
materials having been previously changed into oxides and sulphates by calcination.
The Invention is also applicable to products or residues containing lead or lead and
zinc, and remaining after the treatment of complex ores by wet processes.
The white sublimate last mentioned, although it contains much lead, and
possesses all the good properties of ordinary white lead is not nearly so much or so
easily affected as the latter by sulphuretted hydrogen, and is better suited for the
purposes of the painter. It is also much less noxious to health than ordinary white
lead, and it has combined in it the good qualities of white lead and of zinc white,

page_text: whilst their defects are absent, or much diminished. Its opacity and body equal
those of the best white lead, while its covering power, weight for weight, is 35 per
cent. greater.
A cold blast may be used in the cupola, but a hot blast is preferred, as with it a
more abundant and whiter sublimate is obtained. The cupola should be low
enough to permit of flame being always present at the top of the charge, but high
enough for maintaining a sufficient column of incandescent materials to prevent
the cooling down of the upper part of the furnace when fresh materials aro
charged. A height of from 15 to 30 inches from the tuyere to the charging door
answers well.
In addition to the air supplied at the tuyeres some air is also introduced in
one or more currents at the upper part of the furnace in order to insure the
complete combustion not only of all particles of fuel and volatile carbonaceous
matters, but also of the reguline vapors of lead and zinc, which are always more or
less given off. These matters if allowed to pass off unburned would com-
municate grey color to the sublimate, but this result is prevented by maintaining
sufficient heat at the upper part of the furnace and by introducing air as
described.
The fuel employed in the furnace should be of a kind giving off the least possible
black smoke. Gas coke is suitable, but common coke or charcoal or other sinokeless
fuel may be used.
It is not intended to convert the whole of the lead contained in the materials
into a sublimate, but to reduce at least as much of it as will suffice to absorb the
greater part of the silver and gold present in the materials. The reduced metal is
tapped or run off into moulds in the usual way.
The fumes ordinarily obtained in smelting lend and zinc ores or materials may
be satisfactorily treated according to the present Invention after they have been
agglomerated by calcination. One of the advantages of thus treating lead fumme is
that the small quantity of silver which it invariably contains becomes concentrated
in the reduced lead, and is thereby rendered worth separating, whilst on the other
hand the pigment produced is the better for the absence of the silver.
Litharge containing silver may be treated in a similar way, so as to yield lead
in which the silver is comparatively concentrated, and also a very pure white
sublimato, consisting chiefly of carbonate and oxide of lead.
The sublimate is caught or collected by means of a fume condenser containing
water, or water having in it any suitable acid or alkali or chemical reagent.
There should be a sufficient length of passage between the furnace and the con-
denser to allow gritty particles carried over by the current to subside; and the
portion of the fume lodging in the passage may be resmelted to obtain a good
sublimate and metallic lead, but before smelting it it should be agglomerated by
calcination. The fume condenser believed to be best suited for the purposes of the
present Invention is of the kind described in the Specification of Letters Patent,
No. 5239, of 1878, obtained by Henry Joseph Wilson, John Wycliffe Wilson, and
the present applicant; but other kinds of wet fume condensers inay also be used.
The water of the condenser, aided if necessary by chemical agents, will separate
from the sublimate certain substances which might injure its quality as a
pigment

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Andrew French in the Great Seal Patent Office on the 6th December
1881.
ANDREW FRENCH, of Morriston, in the County of Glamorgan, Metallurgist.
"IMPROVEMENTS IN OBTAINING WHITE COMPOUNDS OF LEAD AND ZINC SUITABLE
FOR MAKING PIGMENTS, AND FOR OTHER PURPOSES, FROM LEAD AND ZINC ORES,
OR FROM THEIR PRODUCTS OR RESIDUES, AND IN APPARATUS THEREFOR."
My said Invention has for its object the treatment of lead and zinc ores, or
materials obtained as products or residues, and consisting of or containing load and
zinc, in an improved manner, and so as to economically obtain white compounds
which can be advantageously applied in making pigments, and for any other
purposes for which ordinary white lead is used.
The
In carrying out my Invention a special furnace is employed in a manner to
produce a white sublimate consisting principally of sulphite of lead and sulphite of
zinc from sulphureted ores, or from products or residues of such ores, the materials
having been previously changed into oxides and sulphates by calcination.
purpose of the calcination is to facilitate the subsequent formation of sulphites and
to assist in the elimination of arsenic, selenium, antimony, and such like volatile
substances, the presence of which would injure the product sought to be obtained.
My Invention is also applicable for treating products or residues remaining after
the treatment of complex ores by what are known as wet processes when such
products or residues contain lead or lead and zinc.
The white sublimate consisting of sulphites of lead and zinc although it contains
much lead and possesses all the good properties of ordinary white lead is not nearly
so much or so easily affected as the latter by sulphureted hydrogen, and is better
suited for the purposes of the painter. It is also much less noxious to health than
ordinary white lead, and it has combined in it the good qualities of white lead and
of zinc white whilst their defects are absent or much diminished.
Two Sheets of explanatory Drawings are hereunto appended, Figure 1 being a
vertical section of the furnace employed, and Figures 2 and 3 elevations of the
apparatus used in connection with the furnace, but which is placed at a greater
distance therefrom than as shown. Figure 4 is a horizontal section of the furnace
as taken at the upper part. In these Drawings the same reference numerals are
used to mark the same or like parts wherever they are repeated.
The furnace, which may be described as a kind of low cupola smelting furnace, is
of a square form in plan, the lower part 5 being smaller than the upper part 6,
and the walls of the upper part being supported on a plate 7 resting partly on the
lower walls and partly on pillars 8. An arched top 9 with flat end walls closes in
the upper part of the furnace, an outlet 10 for the gases and volatile matters being
formed in one of the end walls at the top and communicating with a horizontal
flue 11. The door 12 for charging in the materials is just above the lower smaller
part of the furnace. The lower part of the furnace is provided with what is
known as a brasque bottom 13, usually made up of equal parts of fireclay and
coke dust; and at what may be termed the front there are the usual tymp 14, and
fore hearth plate 15. A cold blast may be used in the cupola, but a hot blast is
preferred, as with it a more abundant and whiter sublimate is obtained. The
Tower part 5 of the cupola should be low enough to permit of flame being always
present at the top of the charge, but high enough for maintaining such a column
of incandescent materials as will prevent too great a cooling of the upper part in
the furnace when fresh materials are charged. A height of from 15 to 30 inches
from the tuyere 16 to the charging door 12 answers well.

page_text: In addition to the air supplied at the tnyere 10 some air is also introduced in one
or more jets or currents at the upper part of the furnace in order to insure the
complete combustion not only of all particles of fuel and volatile carbonaceous
matters but also of the reguline vapors of lead and zine which are always given off
to a greater or less extent. These matters, if allowed to pass unburned, would
communicate a grey color to the sublimate, but this result is effectually prevented
by maintaining sufficient heat at the upper part of the furnace and by introducing
air as described. The air for supplying the tuyere 16 is led through piping 17,
18, 19, constructed and arranged so as to serve at the same time for henting the
air and for introducing the jets above the charge. The air supply pipe 17 commu-
nicates with a number of horizontal pipes 18 placed across the upper part of the
furnace and connected at alternate ends so that the air has to pass through thom
successively, finding its way from the last of them by a pipe 19 to the tuyere 16.
The pipes 18 which cross the furnace have a number of holes formed in their
upper parts, from which holes jets of air issue for the purpose already explained.
A special and important object which is attained by my Invention and the means
described for carrying it out is to produce sulphites of lead and zinc with as little
sulphates of those metals as possible, as such sulphates are injurious to the pigment.
Sulphate of lead, unlike the sulphite, does not mix or combine well with oil, and
its covering quality is very poor. The sublimate obtained is not a definite
compound of the two sulphites in a chemical sense. The sulphite of lead in it may
vary between 40 and 95 per cent., the remainder being sulphite of zinc; the moro
general proportions are however 80 per cent. of sulphite of lead and 20 per cent. of
sulphite of zinc.
The fuel or carbonaceous matter employed in the furnace should be of a kind
giving off the least possible black smoke. Gas coke is suitable, but common coke
or charcoal or other comparatively smokeless fuel may be used.
The furnacing operations are not conducted so as to convert the whole of the
lead contained in the materials into a sublimate, but to reduce at least as much of
it as will suffice to absorb or hold the greater part of the silver and gold present in
the materials. The reduced metal is tapped and run off in the usual way at a tap
holo 20 and received in moulds.
Fumes obtained in the ordinary processes in use for smelting lead and zinc ores
or similar materials may be satisfactorily treated, according to this Invention, after
they have been agglomerated by calcination, and in this case one of the advantages
of the treatment is that the small quantity of silver which such fumes invariably
contain becomes concentrated in the reduced lead, and is thereby rendered worth
separating, whilst on the other hand the pigment produced is the better for the
absence of the silver.
Litharge containing silver, instead of being entirely reduced to metallic lead as
is usually done, may be treated according to this Invention, so as to yield partly
lead in which the silver is comparatively concentrated, and partly a pure white
Bublimate consisting chiefly of carbonate and oxide of lead, and possessing excellent
drying properties when used as a pigment.
An important part of the present Invention consists in collecting the sublimate
by means of water in any suitable modification of the kind of apparatus known as
fume condensers. In the ordinary manufacture of white lead by volatilising
processes, bags are employed for catching or collecting the product. A very large
number of such bags are required together with flues and piping to which they are
connected, and a great extent of buildings is needed to contain them, whilst the
bags become rapidly corroded and have to be frequently renewed. Not only is a
very large proportion of the expense thus indicated saved by the use of wet
condensers, but the water, to which any suitable chemical ngent may be added,
also dissolves out of the sublimate certain substances which injure its quality as
a pigment. For example, when operating with ores containing zinc there is
frequently produced along with the sulphites of lead and zine some sulphate of zinc
which being very soluble is washed out by the water, but which if allowed to

page_text: remain in the pigment would affect its stability where exposed to moisture; also.
when operating with ores containing arsenic, as lead and zinc ores frequently do,
the greater part of the arsenic sublimes as arsenious acid, which is a virulent
poison, but which readily dissolves in the water of the condenser and becomes.
separated; or again if the ores, products, or residues operated on contain iron
together with chlorine, a minute quantity of the iron sublimes, and would impart a
yellowish tint to the pigment did not the water dissolve out the iron salt and
thereby render the pigment of a more pleasing color.
The flue 11 by which the sublimate and accompanying gases leave the furnace
extends for some distance in brick work, and the flue is continued by an iron pipe 21
which communicates with a blower 22 (which may be of any suitable kind). The
blower 22 propels the sublimate and gases into a large sheet iron receiver 23, from
which a pipe 24 leads them up into the condenser 25. The extended course for tho
sublimate and gases from the furnace to the condenser is provided in order that
dust or unconverted particles carried over mechanically by the current may become
deposited in the flue 11, also in order that the sublimate and gases may become
cooled, the metal pipe 21 and receiver 23 favoring this action, whilst the
receiver 23 also serves for equalising the flow of the current into the condenser 25
by moderating inequalities due to varying impulses caused by the blower or
otherwise.
I am aware it is not new to produce a white lead pigment by a subliming
process, but with any such process as hitherto practised it has been necessary to
employ either granulated metallic lead or only the purest galena, whereas with my
process and apparatus the most impure ores or compounds containing lead can bo
treated with perfect success. By previous subliming processes when applied to
sulphureted ores manufacturers have sought to produce sulphate of lead, whereas
the object I have in view and which I attain is to produce sulphite of lead having
sulphite of zinc associated with it, both bodies being excellent white piginents and-
superior to sulphate of lead.
Having thus particularly described my said Invention and the inanner of
performing the same, I have to state that I do not restrict myself to the preciso
details herein described or delineated, but that what I believe to be novel and
original, and claim as the Invention secured to me by and in terms of the herein-
before in part recited Letters Patent is,—
1. The process for producing white compounds or pigments composed of sulphite
of lead and sulphite of zinc, in which process calcined ores or materials containing
lead and zinc are partly reduced and partly sublimed in a cupola smelting furnace,
air being introduced amongst the volatile matters above the charge as well as at
the tuyere, combined with the use of a wet condenser in which the sublimate is
collected and simultaneously purified by means of water, substantially as and for
the purposes set forth.
2. The process for producing a white sublimate composed of sulphite of lead and
sulphite of zinc, in which process calcined ores or materials containing lead and zinc
are partly reduced and partly sublimed in a cupola smelting furnace, air being
introduced amongst the volatile matters above the charge as well as at the tuyere,
substantially as and for the purposes set forth.
3. In a cupola smelting furnace employed for subliming ores or materials
containing lead and zinc, the introduction of air not only at the tuyere but also
amongst the volatile matters above the charge, substantially as and for the purposes
set forth.
4. A cupola smelting furnace for subliming or partly subliming and partly
reducing ores or other materials containing lead and zinc, made of a square form in
plan with the lower part containing the charge smaller than the upper part, and
with pipes across the upper part for the passage and heating of air on its way to
the tuyere, such pipes also having jet holes for the issue of air into the upper part
of the furnace, substantially as hereinbefore described.
5. The combination of a cupola smelting furnace for treating ores or materials

page_text: containing lead and zinc with a brickwork flue (11), iron continuation pipe (21),
blower (22), receiver (23), connecting pipe (24), and wet condenser (25), the parts
being arranged and operating together, substantially as and for the purposes set
forth.
In witness whereof, I, the said Andrew French, have hereunto set my hand
and seal, this Third day of December, in the year of our Lord One thousand
eight hundred and eighty-one.
ANDREW FRENCH. (L.s.)