IMPROVEMENTS IN REFINING LEAD
Year: 1867

page_text: LETTERS PATENT to Oscar Wassermann, Engineer, and Johann Heinrich
Herbst, Proprietor, of Call, in the Kingdom of Prussia, for the Invention
of "IMPROVEMENTS IN REFINING LEAD."
PROVISIONAL SPECIFICATION left by the said Oscar Wassermann and
Johann Heinrich Herbst at the Office of the Commissioners of Patents,
with their Petition, on the 21st May 1867.
We, OSCAR WASSERMANN, Engineer, and JOHANN HEINRICH HERBST, Pro-
prietor, of Call, in the Kingdom of Prussia, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN REFINING LEAD," to be as follows:-
This Invention relates to certain improvements in the means of refining
lead which has been desilvered by means of zinc in order to extract the zine
and also the iron, antimony, or other metal which is contained in the lead.
The process consists in submitting the red hot desilvered lead containing zinc,
iron, and antimony to the action and effects of chloride of lead combines with
the zinc and iron, whilst the lead of the chloride of lead is combined with the
lead to be refined. The desilvered lead is smelted in crucibles of cast or
wrought iron, and the surface of the lead is covered with chloride of lead,
and the temperature is increased till chloride of zinc is produced, which is
indicated by the presence of dross. The chloride of lead is decomposed, and
the crucible is covered with a layer of chloride of zinc. The dross is to be
removed, and a further supply of chloride of lead is to be added, whereby the
purification or refining of the lead will be accomplished. To further ensure
the extraction of any remnant of antimony in the lead caustic soda or potash

page_text: SPECIFICATION filed in pursuance of the conditions of the Letters Patent,
and of an Order of the Lord Chancellor, by the said Oscar Wassermann
and Johann Heinrich Herbst in the Great Seal Patent Office on the
6th December 1867.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, OSCAR
WASSERMANN, Engineer, and JOHANN HEINRICH HERBST, Proprietor, of Call,
in the Kingdom of Prussia, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-first day of May, in the year of our Lord
One thousand eight bundred and sixty-seven, in the thirtieth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto us,
the said Oscar Wassermann and Johann Heinrich Herbst, Her special licence
that we, the said Oscar Wassermann and Johann Heinrich Herbst, our
executors, administrators, and assigns, or such others as we, the said Oscar
Wassermann and Johann Heinrich Herbst, our executors, administrators, and
assigns, should at any time agree with, and no others, from time to time
and at all times thereafter during the term therein expressed, should and
lawfully might make, use, exercise, and vend, within the United Kingdom of
Great Britain and Ireland, the Channel Islands, and Isle of Man, an In-
vention for,"IMPROVEMENTS IN REFINING LEAD," upon the condition (amongst
others.) that we, the said Oscar Wassermann and Johann Heinrich Herbst,
our executors or administrators, by an instrument in writing under our, or
their, or one of their hands and seals, should particularly describe and ascer
tain the nature of the said Invention, and in what manner the same was
to be performed, and cause the same to be filed in the Great. Seal Patent
Office within six calendar months next and immediately after the date of
the said Letters Patent.
NOW KNOW YE, that we, the said Oscar Wassermann and Johann
Heinrich Herbst, do hereby declare the nature of our said Invention, and
in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:-
Our Invention relates to certain improvements in the means of refining
lead which has been desilvered by means of zinc in order to extract the zine
and also the iron, antiniony, or other metal which is contained in the lead.

page_text: The desilverizing of pig lead enriched
the Pattinson process by means of
metallic zinc has been carried out on a large scale, but has not been generally
introduced on account of the considerable loss of metal in the process following
the desilverizing, which has for its object the separation from the lead of that
portion of the zinc which after the desilverizing remained in combination with
the lead. This process consisted either in an oxydising, smelting in a rever-
beratory furnace, or in a simple running down with iron puddling slags in a
blast furnace. In the first of these cases a product of oxydation was the
result, which in addition to oxide of lead contained the greater part of the
foreign admixtures; as this product of oxidation had again to be reduced to
metallic lead the process occasioned a loss of lead of from 1 to 12 per cent. In
the other case the zinc contained in the lead is carried into the slag in the form
of oxide; but other metals, and especially iron and antimony, are not removed,
and it becomes necessary that the lead should undergo another oxydising
process in a reverberatory furnace in order to carry off these foreign matters;
such an operation again gives rise to quite as high a loss of lead as that in
the first instance.
The following new method obviates all these losses hitherto experienced
when the pig lead was desilverized by means of metallic zinc, and it also does
away with the extra process just described. This method consists in the
introduction of a lead salt into the fluid bath of metallic lead after its desilveri-
zation by means of metallic zinc, and whilst still containing the zinc, iron,
and antimony. Although various combinations commonly known by chemists
as lead salts will answer this purpose we prefer using the chloride of lead,
and will describe the process for the application of this salt; the chemical
action being that the chlorine which had been introduced in the form of
chloride of lead combines with the zinc and iron, whilst the lead of the chloride
of lead passes into the metallic state and mixes as such with the lead which
has to be freed from the zinc. Before describing the mode of carrying out
this process we will shortly state the particulars of the desilverizing process by
means of zinc as it is practised at present. The lead requires for its complete
desilverization the following quantities of zinc-If containing 8 oz. silver to.
the ton, 1 per cent. of zine; 13 oz. silver, 1 per cent. zinc; 33 oz. silver,
1 per cent. zine; 49 oz. silver; 1 per cent. zinc; 98 oz. silver, 1 per.
cent. zinc; 130 oz. silver, 2 per cent. zinc. The lead is melted down in
cast or wrought iron crucibles or pots of any shape or size, but the greater
the diameter as compared with the depth of the vessels the more advan-.
tageous are they for the desilverization. According to the cubic contents.
of the vessel, and therefore the weight of molteu lead contained therein

page_text: the quantity of zine required for the desilverizing of the lead has to be
calculated from the ascertained silver produce of the lead by the rule laid
down in the above table. In the first instance rds of this quantity of zine
are now added, and as soon as the zine is melted the whole is thoroughly
mixed for about 20 minutes with the skimming ladles; after this the
vessel is allowed to cool slowly, and after an interval of about 2 hours
duration the skimming off of the alloy of zinc, silver, lead, and copper, which
meanwhile has risen to the surface of the metal bath, can commence. As soon
as the well-known crystals of lead, as seen in the Pattinson process, begin to
shew, the skimming must be discontinued; the fire under the vessel is freshened
up; a second portion of zinc equal to one-quarter of the whole quantity is
again added to the lead, and the same operations of stirring, cooling, and
skimming as have just been described are repeated; finally, after this
second portion of the alloy of silver, zinc, and lead has been skimmed off as
before the still remaining th part of the zinc is added, and after this
3rd operation is complete the lead will be found to have been desilverized
down to about 0-16 or 0.19 oz. silver per ton. The desilverizing process requires
from 18 to 24 hours time for its completion. The desilverized lead contains
however from 0.6 to 0.75 of zinc, which destroys its softness, and to
remove this zinc about 3 per cent. of chloride of lead of the whole quantity
of desilverized lead is required. As soon as the third portion of the zinc
silver alloy has been skimmed off, and the fire under the vessel increased, the
chloride of lead is at once added to the metallic lead in the vessel, the latter
having been heated somewhat higher than its melting point. The chloride of
lead is mixed into the melting mass from time to time, and after another 24
hours interval the whole of the chloride of lead will be found to have been
decomposed. A fluid slag composed of chloride of zinc swims on the surface
of the melted charge, and the desilverized lead is free from zinc and iron. If
the chloride of zinc cannot be applied advantageously as such a little slaked
lime is thrown over it, and it is then skimmed off, as it contains more or less
lead prills, it is added to the ore smelting process. The alloy composed of
zinc, silver, copper, and lead is still further enriched by heating it in a pan,
when the greater portion of the lead will sweat out, and at last a substance
very friable and almost powdery containing the silver is left behind. The lead
which has been run out contains a little silver, and is returned to the next
desilverizing charge at the time when the last th portion of zinc is added.
If the pig lead contained antimony it must be removed either by the well-
known process of refining, or it can be done by keeping the iron vessel con-
taining the lead after it has been desilverized and freed from zinc a longer

page_text: time in the state of red heat. If the contents of antimony in the pig lead
do not amount to more than 16th per cent. zinc will carry this quantity
completely off in the desilverizing process, and it will enter with the other
foreign substances into the silver alloy. A portion of the chloride of zinc
formed by the treatment with chloride of lead escapes during the process in
the form of fumes; and in order to protect the workman from the ill effects,
probably arising from the inhalation of these metallic fumes, the pan is kept
covered with an iron bonnet, and the fumes are carried by means of a pipe
through the roof into the open air. It is advisable from an economical point
of view in case the chloride of lead has to be prepared from lead ores to choose
an ore poor in or free from silver. In the culvert deposits from the lead
smelting furnaces the silver is principally contained as antimoniațe of the
oxide of silver, which is not soluble in muriatic acid; and if therefore the
chloride of lead is prepared from such deposits all the silver contained in them
will afterwards be found in the chloride of zinc slags; but such deposits from
smelting furnaces are only applicable for the preparation of chloride of lead
if the lead in them is in the form of a sulphuret and not oxydised.
Another and perhaps the most advantageous mode of procuring the chloride
of lead is by mixing sulphate of lead, such as, for example, is constantly formed
in chemical works by the action of acid gases on the lead of sulphuric acid
chambers, with rd of its weight of common salt; if this mixture is brought
into contact with lead containing zine at a temperature bordering on red heat
sulphate of soda and chloride of lead are formed. Of the mixture of sulphate
of lead with rd of its weight of common salt we would require about 3 per
cent. instead of 3 per cent. of chloride of lead; in case the pig lead contained
copper the whole of the copper is concentrated in the silver zinc alloy. Up to
the present time such an alloy with copper could only be treated before a blast
under the addition of iron puddling slags and lead regulus, by which operation
a copper regulus and a tolerably soft lead of a high silver per-centage were
produced; this latter bad of course to be cupelated; but better still the silver
could be extracted from the zinc silver alloy containing copper by the wet way.
If the pig lead in the first instance contained no copper the silver zinc alloy can
very easily be refined by the wet process. The material is treated with an equal
weight of muriatic acid first, without the application of heat, and then the
whole is heated in a cast-iron pan, when rich silver lead and a slag compound
of chloride of zinc and containing also a little oxide of lead are formed. The
chloride of zinc slag is mixed with slaked lime and turned over to the ore
smelting process; the rich silver lead is cupelated.
We have already
remarked that other salts of lead besides the chloride of lead answer the

page_text: purpose of extracting the zinc from the desilverized lead, and we mention,
for example, sulphate of lead; but its action of removing the zinc takes place
only at a very high temperature, and even then but partially, because there is
no proper slag formed, and the oxide of lead parts with its oxygen very
unreadily to the zinc.
Having now described the nature of our said Invention, and the manner
in which the same is to be performed, we claim and desire to be secured to us
by the herein in part recited Letters Patent, the method of refining lead which
has been desilverized by zinc by the application of a lead salt, which we prefer
to be the chloride of lead, in order to extract the zinc, iron, antimony, or other
metal contained in the lead, substantially as herein specified.
In witness whereof, we, the said Oscar Wassermann and Jobann
Heinrich Herbst, have hereunto set our hands and seals, this Fifteenth
day of November, in the year of our Lord One thousand eight hundred
and sixty-seven.
Witness,
J. WELTER,
Berlin.
OSCAR WASSERMANN.
(L.S.)
JOHANN HEINRICH HERBST. (L.S.)