AN IMPROVED MODE OF UTILIZING TIN PLATE SCRAPS OR CLIPPINGS AND WASTE ARTICLES MADE OF TIN PLATE
Year: 1876

page_text: LETTERS PATENT to Edward Andrew Parnell, of Swansea, in the County of
Glamorgan, Chemical Manufacturer, for the Invention of "AN IMPROVED MODE
OF UTILIZING TIN PLATE SCRAPS OR CLIPPINGS AND WASTE ARTICLES MADE
OF TIN PLATE."
Sealed the 28th October 1876, and dated the 11th August 1876.
COMPLETE SPECIFICATION filed by the said Edward Andrew Parnell at the
Office of the Commissioners of Patents on the 11th August 1876.
"
EDWARD ANDREW PARNELL, of Swansea, in the County of Glamorgan, Chemical
Manufacturer. AN IMPROVED MODE OF UTILIZING TIN PLATE SCRAPS OR
CLIPPINGS AND WASTE ARTICLES MADE Of Tin Plate.”
The object in my improved process for utilizing tin plate clippings and waste
articles made of tin plate is to separate the coating of metallic tin from the iron
so as to obtain the latter in the metallic state, and the former as a saleable con-
pound containing that metal. This separation of metallic tin from sheet iron, and
also from lead, which may likewise be present as solder, I effect by means of an
aqueous solution of a fixed alkaline sulphide, that is to say, sulphide of sodium
or sulphide of potassium. The tin dissolves in the solution of the alkaline sulphide,
and may be recovered therefrom by various methods, that which I prefer being
herin-after described; metallic iron remains undissolved by the solution of alkaline
sulphide; and lead, which may be present, is also undissolved, but is converted to
sulphide. I prepare the alkaline sulphide in the usual way, namely, by heating
in a furnace to a 'melting heat a mixture of either sulphate of soda or sulphate of
potash with small coal. By lixiviating the melted mass in water a solution is
obtained of mono-sulphide of sodium or potassium, adapted for my process herein
described. But I prefer making use of an alkaline sulphide containing more sulphur
than the mono-sulphide prepared as above; the bi-sulphide or per-sulphide being
more effective and more rapid in its operation. This bi-sulphide or per-sulphide
I obtain by simply adding sulphur to the solution of the inono-sulphide. With
the aid of heat, the sulphur readily dissolves in this liquid, thus forming the yellow
bi-sulphide or other per-sulphide. One part of common brimstone may be taken
for four parts of sulphate of soda originally used, or one part of brimstone to five
parts of sulphate of potash. A convenient strength for the solution of alkaline
sulphide, both for dissolving sulphur, and also for acting on tin scraps is 40°
[Price 2d.]

page_text: Twaddell. The application of heat is not essential to enable the solution of alkaline
sulphide to dissolve tin; but I prefer applying heat as the dissolving of the tin is
much accelerated thereby. For the purpose of digesting the tin scraps in the
solution of alkaline sulphide I employ a series of four rectangular iron tanks or
vats, heated by means either of small fire-places or " 'dry steam" pipes. Thoso
tanks are so arranged and so connected with each other that the liquid which
enters into the first, which I call No. 1 tank, passes successively through the
other three, finding exit from the fourth, or No. 4 tank. The tin scraps, contained
in an iron cage, are caused to transverse the four tanks in the direction opposite to
the flow of sulphide liquor, being placed first in tank No. 4, afterwards in tank
No. 3, next in tank No. 2, and lastly in tank No. 1, which receives the fresh
alkaline sulphide liquid. From this the iron scraps, are transferred to another
tank and washed with water, after drying they are ready for use. By this
continuous operation the liquor passes out of No. 4 tank fully charged with tin,
while on the other hand the iron scraps being in contact with fresh alkalino
sulphide liquor in No. 1 tank are there deprived of all traces of tin. If lead is also
present this metal passes into the state of sulphide, which is insoluble in the
alkaline sulphide liquor, and may be separated therefrom by filtration. To obtain
the tin from the alkaline sulphide liquor I evaporate this to dryness in an iron
pan, and roast the dry residue in a calcining furnace. By exposure to air at a
moderate heat oxidation takes place, and the result of such roasting is a mixture of
oxide of tin and sulphate of the alkali. I effect the separation of these two
substances from each other by lixiviation in water, the alkaline sulphate dissolves
and leaves the oxide of tin undissolved. The latter after being washed may be
reduced to the metallic stato by smelting in the usual way, or else it may be used
for making stannate of soda. The solution of alkaline sulphate obtained as above
described I concentrate by evaporation, so as to obtain solid sulphate, which I
employ for the reproduction of alkaline sulphide.
Having thus described the nature of my "Improved Mode of Utilizing Tin Plate,
Scraps, or Clippings and Waste Articles made of Tin Plate," and having explained
the manner of carrying the same into effect, I would have it distinctly understood
that I do not confine myself to the details herein described, as they may be some-
what varied without interfering with the nature of my improvement, but I claim-
First. The treatment of tin plate clippings and waste tin plate with an aqueous
solution of sulphide or per-sulphide of sodium, as a solvent for metallic tin.
Second. The use for the same purpose of an aqueous solution of sulphide or per-
sulphide of potassium.
And third. The extraction of tin in the state of oxide from the solutions thus
obtained by the method herein set forth.
In witness whereof, I, the said Edward Andrew Parnell, have hereunto set my
hand and seal, this Seventh day of August, in the year of our Lord One
thousand eight hundred and seventy-six.
EDWARD ANDREW PARNELL. (L.S.)