Improvements in Treating Lead for Purifying it and for Obtaining Litharge, or for Separating the Lead from the Precious Metals contained in it.
Year: 1891

page_text: Date of Application, 1st Aug., 1891
Complete Specification Left, 30th Apr., 1892-Accepted, 18th June, 1892
PROVISIONAL SPECIFICATION.
Improvements in Treating Lead for Purifying it and for Obtaining
Litharge, or for Separating the Lead from the Precious Metals
contained in it. .
I, Dr. BERNHARD RÖSING of Friedrichshütte in the Governmental Department of
Oppeln, Upper Silesia, Prussia, Royal Inspector of Iron Works do hereby declare
the nature of this invention to be as follows:-
:-
It has been hitherto customary to treat raw lead, by heating the same and
simultaneously passing air or wind over it, in order, firstly, to remove by oxidation
the impurities such as arsenic, antimony, zinc, iron, sulphur, and then, in cases
where it may be desirable to oxidise (drive off) the lead itself, so that, in case the
crude lead contain silver, a lead rich in silver, or silver containing lead, may be
obtained, in addition to the litharge.
This process requires a great expenditure of fuel and time, considerable skill, and
great care or attention on the part of the workman in order to obtain a litharge
which is free from silver and metallic lead.
These inconveniences are, to a not inconsiderable extent, owing to the fact
that the layer of oxide instantaneously formed by the contact of the air on the
surface of the lead, even where it is so thin as not to be easily removable therefrom,
hinders more and more the further oxidation.
Further, the serious evil becomes also apparent, especially during the removal of
the zinc from lead desilvered by means of zinc, that, as the oxidation can only take
place on the surface, this is comparatively quickly purified, and then already
the oxidation of the lead takes place on a proportionately larger scale, although the
lead, especially in the deepest lying parts of the same, is still, to a considerable
extent, quite unpurified.
Thus, in the purification of zinky poor lead, it may be observed that the oxidised
impurities driven off are mixed with many times their weight of lead oxide. Such
a product must be again refined on pure lead if it is not to be sold at an extremely
low price.
To remove these drawbacks is the object of this invention, which has been made
as a result of the above observations and considerations after thorough experiments
founded thereon, and the invention is hereinafter described.
According to this invention, in order to avoid the admittedly insufficient and
irrational surface oxidation of the raw lead, the former is replaced by an oxidation
penetrating, if possible, through the whole of the lead.
Numerous experiments have, in fact, shown that, if air be blown into heated,
molten, raw lead, the oxidation of the same and also that of the more easily
oxidised impurities, yields as much heat as is necessary to oxidise the lead without
other addition of heat by means of further blowing, so that, in this case, the further
heat necessary for the evaporation of the lead is supplied merely by the oxidation
heat developed thereby, and the employment of heating material is not further
necessary. Further, I have also ascertained that both the oxidation and, there-
with, the removal of the impurities in the lead, such as arsenic, antimony, zinc,.
sulphur, iron, proceed in a similar manner, and in reality precede the oxidation of
the lead.
By observing these established facts, it is possible, according to the above
invention by blowing air into heated molten lead, not only to remove the impurities
from the lead, but also to cause the lead itself to be driven off. By so blowing in
air, it results that the air acts with an oxidising effect on the whole mass of lead
simultaneously and in all parts (therefore, not merely on the surface), so that, as

page_text: long as impurities still exist in the lead, air must also encounter them, whereby the
whole of the impurities are oxidised and the same are separated as poor in lead
oxides as possible. Further, a quicker oxidation is produced so that, apart from
the considerable saving of fuel, the whole process is completed in a considerably
shorter time. Again, in this process, the success of the work does not depend, to
so great an extent as before, on the care of each single workman, as the removal,
in proportion as produced, of the oxidised impurities detached from the surface is
not so absolutely necessary to be done, as they are now no longer in a position to
interfere with the further oxidation taking place within the mass of lead. The
process forming the object of this invention may be performed as follows:-
Air or wind is blown into the lead to be operated on, which is kept in a vessel in a
heated, molten condition, which vessel is preferably provided with a basic lining.
For this purpose, an apparatus similar to the well known Bessemer or Manhès
converter may be preferably employed. However, vessels of any suitable form,
which are provided with a blowing apparatus, may also be employed. Molten lead
also, which has been previously heated in a separate apparatus, or such as may be
obtained in course of the process in an already molten liquid form, may be run into
this receptacle, instead of heating it in the apparatus itself. When the blowing in
of the air is first commenced, it is generally preferable to give the lead a
temperature which about corresponds to the melting point of litharge.
In consequence of the blowing in, an active oxidation takes place together
with a spontaneous heating of the lead mass, so that separate heating is no longer
necessary.
If, now, this lead contain impurities principally such as arsenic, antimony, zinc,
sulphur, iron, these are immediately oxidised, and settle on the surface, and
from there may be preferably removed in any suitable way such as by being poured
off, scraped off or skimmed off, whereby lead practically free from such impurities
is obtained.
If litharge is to be obtained from such lead, or if the lead to be treated be already
free from such impurities, air is blown into the same while in a heated, molten
condition in a similar manner, whereby the oxidation of the lead is caused and
litharge produced. If the lead contain precious metals such as silver or gold,
such metals are obtained with more or less metallic lead in addition to the
litharge.
In the above described process, the air may be replaced by more or less pure
oxygen, without, on the whole, essentially altering anything in the process described.
Dated this 31st day of July 1891.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Treating Lead for Purifying it and for Obtaining
Litharge, or for Separating the Lead from the Precious Metals
contained in it.
I, Dr. BERNHARD RÖSING of Friedrichshütte in the Governmental Department
of Oppeln, Upper Silesia, Prussia, Royal Inspector of Iron Works, 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:-
It has been hitherto customary to treat raw lead, by heating the same and
simultaneously passing air or wind over it, in order, firstly, to remove by oxidation
the impurities such as arsenic, antimony, zinc, iron, sulphur, and then, in cases
where it may be desirable to oxidise (drive off) the lead itself, so that, in case the
crude lead contain silver, a lead rich in silver, or silver containing lead, may be
obtained, in addition to the litharge.

page_text: This process requires a great expenditure of fuel and time, considerable skill, and
great care or attention on the part of the workman in order to obtain a litharge
which is free from silver and metallic lead.
These inconveniences arise, to a not inconsiderable extent, from the fact that the
layer of oxide instantaneously formed by the contact of the air on the surface of
the lead, even where it is so thin as not to be easily removable therefrom hinders
more and more the further oxidation.
Further, the serious evil becomes also apparent, especially during the removal of
the zinc from lead desilvered by means of zinc, that, as the oxidation can only take
place on the surface, this is comparatively quickly purified, and then already the
oxidation of the lead takes place on a proportionately larger scale, although the
lead, especially in the deepest lying parts of the same, is still, to a considerable
extent, quite unpurified.
Thus, in the purification of zinky poor lead, it may be observed that the oxidised
impurities driven off are mixed with many times their weight of lead oxide. Such
a product must be again refined on pure lead if it is not to be sold at an extremely
low price.
To remove these drawbacks is the object of this invention, which has been made
as a result of the above observations and considerations after thorough experiments
founded thereon, and the invention is hereinafter described.
According to this invention, in order to avoid the admittedly insufficient and
irrational surface oxidation of the raw lead, the former is replaced by an oxidation
penetrating, if possible, through the whole of the lead.
Numerous experiments have, in fact, shown that, if air be blown into heated;,
molten, raw lead, the oxidation of the same and also that of the more easily
oxidised impurities, yields as much heat as is necessary to oxidise the lead without
other addition of heat by means of further blowing, so that, in this case, the further
heat necessary for the evaporation of the lead is supplied merely by the oxidation
heat developed thereby, and the employment of heating material is not further
necessary. Further, I have also ascertained that both the oxidation and, there-
with, the removal of the impurities in the lead, such as arsenic, antimony, zinc,
sulphur, iron, proceed in a similar manner, and in reality precede the oxidation of
the lead.
By observing these established facts, it is possible, according to the above inven-
tion by blowing air into heated molten lead, not only to remove the impurities
from the lead, but also to cause the lead itself to be driven off. By so blowing in
air, it results that the air acts with an oxidising effect on the whole mass of lead
simultaneously and in all parts (therefore, not merely on the surface), so that, as
long as impurities still exist in the lead, air must also encounter them, whereby all
the impurities are oxidised and the same are separated as poor in lead oxides as
possible. Further, a quicker oxidation is produced so that, apart from the con-
siderable saving of fuel, the whole process is completed in a considerably shorter
time. Again in this process, the success of the work does not depend, to so great
an extent as before, on the care of each single workman, as the removal, in proportion
as produced, of the oxidised impurities detached from the surface, is not so absolutely
necessary to be done, as they are now no longer in a position to interfere with the
further oxidation taking place within the mass of lead.
The process forming the object of this invention may be performed in such a way
that the oxidation in a vessel protected as much as possible against loss of heat is
performed and accelerated so that not only is the cooling prevented but even a
considerable excess of heat is obtained, which produces a sensible increase in
temperature of the metals and the oxides resulting therefrom.
For this purpose, it is necessary-
a) To introduce the air requisite for oxidising a given quantity of lead in as short
a space of time as possible, further
6) To prevent the oxide produced, which floats on the surface of the metal bath,
from hindering the further action of the air;

page_text: heat;
d) To employ an apparatus which permits of the above named objects a band c
being attained, and at the same time permits only a small loss of heat, and
e) At the same time this apparatus must be protected against the action of lead,
litharge and any other oxides."
These conditions are fulfilled in none of the processes hitherto employed, but
they can alone lead to the desired result which is indeed attained by none of the
existing processes.
Keeping in view the above named points, the process forming the object of this
invention is performed as follows:-
Air or wind is blown into the lead to be operated on, which is kept in a vessel
in a heated, molten condition, which vessel is preferably provided with a basic
lining. For this purpose, an apparatus similar to the well known Bessemer
or Manhès converter may be preferably employed. However, vessels of any
suitable form, which are provided with a blowing apparatus, may also be employed.
Molten lead, also, which has been previously heated in a separate apparatus, or
such as may be obtained in course of the process in an already molten liquid form,
may be run into this receptacle, instead of heating it in the apparatus itself. When
the blowing in of the air is first commenced, it is generally preferable to give the
lead a temperature which about corresponds to the melting point of litharge, but a
lower temperature, not sensibly exceeding the melting point, is also suitable
especially for large masses of lead.
In consequence of the blowing in, an active oxidation takes place together with
a spontaneous heating of the lead mass, so that separate heating is no longer
necessary.
If now, this lead contain impurities principally such as arsenic, antimony, zinc,
sulphur, iron, these are immediately oxidised, and settle on the surface, and from
there may be preferably removed in any suitable way, such as by being poured off,
scraped off or skimmed off, whereby lead practically free from such impurities is
obtained.
If litharge is to be obtained from such lead, or if the lead to be treated be already
free from such impurities, air is blown into the same while in a heated, molten
condition in a similar manner, whereby the oxidation of the lead is caused and
litharge produced, which remains liquid till the process is finished, and thus allows
any particles of metal forced into the same to again fall down and re-unite with the
main mass of metal.
A litharge is thus obtained free from particles of metal and thoroughly crystalline.
With a suitable size of the blow holes and a suitable air pressure, this oxidation is
so vigorous a one that not only no cooling of the metal and of the oxides resulting
therefrom can take place, but, on the contrary, I have evolved such a heat in the
course of my experiments that the temperature of about 400 degrees Celsius at the
commencement was within 15 minutes raised to about 1200 degrees Celsius. As
soon as the desired purpose is attained, that is to say, either all the impurities have
been removed by oxidation, or all or a given quantity of lead has been oxidised,
the converter is tilted back, the blast shut off and the contents of the converter
poured out into suitable vessels. If the lead contain precious metals, such as silver
or gold, such metals are obtained with more or less metallic lead in addition to the
litharge.
In the above described process, the air may be replaced by more or less pure
oxygen, without, on the whole, essentially altering anything in the process described.
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 :-
1. The improvements in treating lead consisting in heated molten lead being
oxidised in a vessel having a basic lining by means of air or oxygen blown in, and

page_text: thereby heated without any further supplement of heat to such an extent that the
litharge remains liquid to the close of the process.
2. The application of the process described in Claim 1 for obtaining molten
litharge.
3. Freeing lead from impurities, such especially as arsenic, antimony, zinc, iron
and sulphur, by means of the process described in Claim 1, in which air or oxygen
is blown into the heated molten lead until the impurities are mainly oxidised, that
is to say, up to the point at which the formation of litharge merely begins, and by
removing the oxidised impurities which collect on the surface.
4. The separation of lead from the precious metals contained therein, by means
of the process described in Claim 1, by continuing the blowing of air or oxygen
into the heated, molten lead until the main mass of the lead is oxidised so that the
precious metals, perhaps still mixed with more or less lead, remain behind after the
removal of the litharge.
5. The improvements in treating lead for purifying it and for obtaining litharge
or for separating the lead from the precious metals contained in it, which consist
in blowing air or oxygen into the heated molten lead in such way that, first,
any impurities present are oxidised, separating on the surface, and may then be
removed before the subsequent oxidation of the main mass of lead, then the lead is
oxidised in a similar manner, whereby molten litharge, as pure as possible, is
obtained, whilst any precious metals contained remain behind mixed with more or
less lead, all substantially as herein before described.
Dated this 29th day of April 1892.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.