IMPROVE- MENTS IN SEPARATING TIN AND ZINC FROM IRON AND OTHER IMPURITIES, AND ALSO IN SEPARATING FROM SILVER AND LEAD THE ZINC WHICH HAS BEEN EMPLOYED IN DESILVERIZING THE LEAD
Year: 1874

page_text: LETTERS PATENT to Frederick William Dahne, of Swansea, in the..
County of Glamorgan, Engineer, for the Invention of "IMPROVE-
MENTS IN SEPARATING TIN AND ZINC FROM IRON AND OTHER IMPURITIES, AND
ALSO IN SEPARATING FROM SILVER AND LEAD THE ZINC WHICH HAS BEEN
EMPLOYED IN DESILVERIZING THE LEAD."
-
ealed the 12th February 1875, and dated the 19th November 1874.
PROVISIONAL SPECIFICATION left by the said Frederick William
Dahne at the Office of the Commissioners of Patents, with his
Petition, on the 19th November 1874.
I, FREDERICK WILLIAM DAHNE, of Swansea, in the County of
Glamorgan, Engineer, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN SEPARATING TIN AND ZINC PROM IRON AND OTHER
IMPURITIES, AND ALSO IN SEPARATING FROM SILVER AND LEAD THE ZINC WHICH HAS
BEEN EMPLOYED IN DESILVERIZING THE LEAD," to be as follows:—
•
In separating zinc, tin, and other metals which have beeen used for
galvanizing and such like purposes from iron and other impurities, I take
the muffle as ordinarily used and close a part of the front of same with
3

page_text: the exception of a small opening at the lower part. Into the muffle I
place a bed of coal, coke, charcoal, or other suitable material which I
term a filter, and on this I place the zinc or tin from which the
impurities are to be withdrawn. I close this vessel and affix thereto a
condenser, and I place a certain number of vessels or muffles in the
furnace in an inclined position, then on heat being applied, by reason of
the melting points of zinc or tin being lower than that of iron or other
impurities, the tin or zinc melts and percolates through the filter, and is
tapped [off through the opening provided for that purpose in lower
part of front of muffle, while the iron and other impurities remain in the
spongy matter in the filter which is removed from time to time. Any
zinc vapours arising during this process pass into the condenser and are
condensed into metal.
"
This process may also be effected in what is called a Belgian retort, in
which case I mix the granulated zinc or tin with coal or suitable filter,
charging the retort to about two-thirds of its length, the remaining one-
third being filled up with the filtering material. In this case the action
is similar, tho filter retaining the iron or other impurities in the spongy
matter.
I also separate zinc impregnated with lead and silver which has been
used in desilverizing lead. In this case I also place the above alloy in
similar position into the muffle or retort, and on the vessel or vessels being
closed in the usual manner the melting point of the lead being lower than
zinc the lead percolates through the filter, taking the silver with it, and
is tapped by the opening in the lower part of muffle, after which the
muffle or retort being heated to a sufficient temperature the zinc will
evaporate and be condensed by any suitable arrangement.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Nineteenth day of November, in the
year of our Lord One thousand eight hundred and seventy-four, in `the
thirty-eighth year of Her reign, did, for Herself, Her heirs and suc->
cessors, give and grant unto me, the said Frederick William Dahne, Her
special license that I, the said Frederick William Dahne, my executors,
administrators, and assigns, or such others as I, the said Frederick William
Dahne, my exccutors, 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 Invention for
"IMPROVEMENTS IN SEPARATING TIN AND ZINC FROM IRON AND OTHER IMPURITIES,
AND ALSO IN SEPARATING FROM SILVER AND LEAD THE ZINC WHICH HAS BEEN
EMPLOYED IN DESILVERIZING THE LEAD," upon the condition (amongst
others) that I, the said Frederick William Dahne, my executors or
administrators, by an instrument in writing under my, or their, or
one of their hands and seals, should particularly describe and ascertain
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 I, the said Frederick William Dahne, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement thereof, that is to say:—
J
In separating zinc, tin, and other metals which have been used for
galvanizing and such like purposes from iron and other impurities, I tako
the muffle as ordinarily used and close a part of the front of the same
with the exception of a small opening at the lower part. Into the muffle
I place a bed of coal, coke, charcoal, or other suitable material, which I
term a filter, and on this I place the alloy containing zinc or tin, or zinc
and tin, from which alloy the impurities are to be withdrawn. I close.
this vessel and affix thereto a condenser, and I place a certain number:
of vessels or muffles in the furnace in an inclined position, then on heat:
being applied, by reason of the melting point of zinc or tin being lower.
than that of iron or other impurities, the tin or zinc melts and percolates
through the filter, and is tapped off through the opening provided for.

page_text: "
that purpose in the lower part of the muffle, while the iron and other
impurities remain in the spongy matter in the filter which is removed
from time to time. Any zinc vapours arising during this process pass
out into the condenser and are condensed into metal.
This process may also be effected in what is called a Belgian retort, in
which case I mix the granulated zinc or tin with coal or other car-
bonaceous matter, charging the retort to about two-thirds of its length,
the remaining one-third being filled up with the filtering material. In
this case the action is similar, the filter retaining the iron or other
impurities in the
spongy matter.
I also separate zinc impregnated with lead and silver which has been
used in desilverizing lead. In this case I also place the above alloy in
a similar position in the muffle or retort, and on the vessel or vessels
being closed in the usual manner, the melting point of the lead being
lower than that of zinc, the lead percolates through the filter, taking the
silver with it, and is tapped at the opening in the lower part of the
muffle, after which the muffle or retort being heated to a sufficient
temperature the zinc will evaporate and be condensed by any suitable
arrangement.
Having explained the nature of my Invention I will proceed to
describe with reference to the accompanying Drawings the manner in
which the same may be performed.
As my Invention is especially applicable to the recovery or separation
of zinc from the alloy of zinc and iron formed in conducting the well
known galvanizing process, and commonly called hard spelter, I will
describe my Invention as applied to the treatment of the said hard
spelter, and the recovery of zinc therefrom.
Figure 1 represents in plan, Figure 2 in side elevation, and Figure 3
in cross vertical section the furnace which I prefer to employ in carrying
my Invention into effect; Figures 4, 5, and 6 represent another kind of
furnace, which may also be employed in carrying my Invention into
effect, Figure 4 being a longitudinal vertical section, Figure 5 a hori-
zontal section, and Figure 6 a side elevation of the latter furnace, the
said furnace, Figures 4, 5, and 6, differing only from the furnace,
Figures 1, 2, and 3, in having calcining chambers a, b, to which
chambers the waste heat from the furnace is conducted and economized
by being made to calcine or roast the ore placed in the said chambers

page_text: a, b. The said furnaces resemble in all essential respects furnaces
commonly employed in the reduction of zinc from its ores, and known
as Silesian furnaces. I therefore do not consider it necessary to describe
in detail the construction of the said furnaces.
The retorts, mufflers, or distillatory vessels c, in which the hard spelter
to be operated upon is put, resemble the ordinary retorts employed in
the reduction of zinc from its ores, the lower part of the front of the
retort being closed, as usual, the said closed part being marked c². In
the closed part c³, and at the lowest point of the interior of the retort, is
a tap hole c³. The retorts c, charged in the manner hercin-after
described, are situated in the furnace in an inclined position (see the
cross section, Figure 3), so that any molten zinc melted out of the hard
spelter may be withdrawn at the tap hole c³.
The manner in which the retorts c are charged is illustrated in
Figures 7, 8, and 9, Figure 7 representing a longitudinal section of one
of the retorts herein-before described. On the floor of the retort, and
marked d, is a layer of coal dust or coke dust, or other carbonaceous
matter, the said layer d having by preference a depth nearly equal to
the height of the closed part c² of the retort c. This layer of carboná-
ceous matter I call a filter. Upon the said carbonaceous layer or filter d
the lumps or pieces of hard spelter are placed; these are represented at c.
After the retort has been charged, as represented in Figure 7, a con-
denser, represented in Figure 8, and marked f, is luted or otherwise
connected thereto. The said Figure 8 represents in perspective the
retort c, the closed part and tap hole being marked c³ and c³ respectively.
Before the commencement of the distillatory or separating process the
tap hole c³ is closed with a plug of clay or other suitable material. By
the application of heat to the retort a large portion of the zinc is melted
out of the hard spelter e, and running through the carbonaceous filter d
collects in the lower part of the retort. By removal of the plug of clay
from the tap hole c³ the melted zinc may be drawn off, that part of the
zine which is volatilized being received in the condenser f, and is con-
densed therein in the usual manner. The filter & of carbonaceous matter
effectually prevents the oxidation of the zinc, any oxygen contained in
the retort being taken up by the heated carbon, and an atmosphere of
carbonic oxide thereby formed, the reducing or deoxidizing property of
which prevents the formation of oxide of zinc. The iron or other infusible

page_text: impurity contained in the hard spelter remains upon the filter of carbo-
naceous matter d.
As in the several Drawings of the furnaces the retorts c are represented
in an uncharged state, the condensers f, Figure 8, are omitted.
Figure 9 shows another method of carrying my Invention into effect,
the said Figure 9 representing in longitudinal section a retort such as is
commonly used with the ordinary Belgian furnace. Instead of charging
the retort in the usual manner, that is, with a mixture of hard spelter
and coal dust, from which the zinc is extracted by vaporization, I charge
the said retort in the manner represented in the Drawing, that is to say,
the retort is filled to about two-thirds of its, capacity with hard spelter,
by preference granulated, mixed with a little coal dust or other carbona-,
ceous matter, as represented at 9, Figure 9, while in front of the
mixture g is a layer,h of coal or other carbonaceous matter constituting
the carbonaceous filter. A large portion of the melted zinc is tapped
out through the carbonaceous filter h, and through the condenser before
it has time to vaporize, and the remainder, which is vaporized, is collected
in the condenser in the usual way.
In separating zinc from the alloy of silver, lead and zinc obtained in
the process of desilverizing lead, I treat the said alloy in either of the
ways herein-before described with respect to hard spelter. The appli-
cation of heat causes the lead to percolate through the carbonaceous
filter, carrying the silver with it, and the alloy of lead and silver is drawn
off by the tap hole in the lower part of the retort. By subsequently
raising the temperature of the retort the zinc is volatilized, and is con-
densed in the usual way.
When an alloy of zinc, tin, and iron is operated upon according to my
Invention, which alloy is formed in the manufacture of what is called
galvanized iron, the tin will be found in that portion of the zinc which
has been tapped off from the retort in a liquid state, while that part of
the zinc collected in the condenser will be free or nearly free from tin.
By my Invention the recovery of zine and tin from the alloys herein-
before referred to is effected with much greater rapidity and at much
less cost than by the processes ordinarily employed for that purpose, as
by my said Invention the greater part of the zinc is obtained without
volatilization, whereas in the ordinary processes the whole of the zinc is
converted into vapour, which is afterwards condensed.

page_text: Having now described the nature of my Invention, and the manner
in which the same is to be performed, I wish it to be understood that I
do not limit myself to the precise details herein described and illustrated,
as the same may be varied without departing from the nature of my
Invention; but I claim as my Invention of improvements in separating
tin and zinc from iron and other impurities, and also in separating from
silver and lead the zinc which has been employed in desilverizing the
lead,
First. Operating upon hard spelter or other alloys of zinc by means
of the apparatus herein-before described and illustrated in Figures 1 to 8
of the accompanying Drawings, whereby a portion of the zinc is tapped
off from the apparatus in a liquid form without volatilization, and another
portion volatilized and condensed.
Secondly. The use of a carbonaceous filter in a retort, muffle, or dis-
tillatory apparatus, for the purpose of economically obtaining zinc from
hard spelter or other alloys of zinc, the said hard spelter or alloy being
supported upon the said carbonaceous filter, as illustrated in Figure 7 of
the accompanying Drawings.
Thirdly. The modification herein-before described and illustrated in
Figure 9 of the accompanying Drawings, in which the carbonaceous
filter is placed in front of the retort, muffle, or distillatory apparatus.
In witness whereof, I, the said Frederick William Dahne, have
hereunto set my hand and seal, this Twentieth day of April, in
-the year of our Lord One thousand eight hundred and seventy-
five
'
FREDERICK WILLIAM DAHNE. (L.S.)
Witness,
J. HERNAMAN JAMES,
Swansea.