IMPROVEMENTS IN THE PROCESS OF SEPARATING TIN FROM TINNED PLATE OR OTHER TINNED ARTICLES
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by Adolf Gutensohn at the Office of
the Commissioners of Patents on the 15th May 1877.
ADOLF GUTENSOHN, of Bow, in the County of Middlesex.
"IMPROVEMENTS IN
THE PROCESS OF SEPARATING TIN FROM TINNED PLATE OR OTHER TINNED
ARTICLES."
My Invention relates to improvements in the process of separating tin from
tinned plates, scrap tin, or other tinned articles, or waste pieces of iron coated with
tin.
I place in a suitable vessel, preferably of earthenware, the tinned plate or scraps
which are to be operated on, and I add a sufficient quantity of muriatic acid to cover
them. The strength of the acid may vary, but I prefer to use the ordinary commer-
cial muriatic acid. When the tin has been thus sufficiently dissolved from the
plates or scraps, I draw off the acid and apply it to a fresh supply of tinned plates
or scraps, and I continue to repeat this process until the acid hias dissolved all the
tin of which it is capable. From this solution "tin crystals" (or crystals of muriate
of tin) may be obtained in the usual way by evaporation. I then place in a vessel
a small quantity of copper ore, or salt of copper (such as sulphate), the quantity of
which may be varied, but which I prefer to be from one to two per cent. of the
weight of tin scraps, or plates, of which I add a fresh supply until the vessel is
sufficiently filled, and I then add the acid saturated with tin, as above described,
having first added to it about two per cent. in weight of liquid ammonia.
By treating the saturated acid as above described with copper and ammonia, it
can be again used for the purpose of dissolving fresh quantities of tin, and so on
over and over again for a great number of times, copper ore or salt being added
between each such treatment, and fresh ammonia as often as required, which will be
after about every three or four fresh treatments. By this method I obtain a solution
of muriate of tin. very much stronger than that obtained by the ordinary process of
treatment with muriatic acid without the additions as above described. From this
solution crystals of metallic copper gradually precipitate. These I remove and
expose to the air, which by its gradual action produces marketable (green) copperas.
To the remaining solution of muriate of tin I add liquid ammonia, which precipitates
Dmine 71

page_text: insoluble oxide of tin, but I first preferably neutralize the solution of muriate of tin
by carefully adding ammoniacal liquor (or gas water).
Another part of my Invention consists in obtaining the oxide of tin, precipitated
in the way just described, as free as possible from iron. For this purpose I add to
the solution of muriate of tin (neutralized in the way just described) about one to
three per cent. by weight of a saturated solution of a permanganate (such as per-
manganate of potash or of soda) which on stirring combines with the iron without
affecting the tin, and in this way the oxide of tin retains not more than one per
cent. of iron.
After the oxide of tin has been precipitated as described, the remaining solution
of muriate of ammonia may be sold, or the salt first crystallized out. I dissolve in
diluted sulphuric acid the oxide of tin, precipitated as above described, and from
this solution I precipitate spongy metallic tin by adding metallic zinc in fragments
or cuttings. The remaining strong solution of sulphate of zinc may be sold, or the
salt may be crystallized out. The metallic spongy tin may be melted into ingots
for sale.