Year: 1888

page_text: [Communicated from. abroad by OLIVIER LePrévost-BourGEREL and EDOUARD
PIERRON, of 15, rue Richelieu, in the City of Paris, France, Gentlemen.]
I LORENTZ ALBERT GROTH of No. 3 Tokenhouse Buildings in the city of London,
Civil Engineer, 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 :-
•
This invention relates to an improved method for extracting tin from the scraps
which contain it.
Hydrochloric acid whether dissolved in water, or in a gaseous or humid state has
been tried. for a long time in the extraction of the tin which covers tinned iron.
The results obtained have not been satisfactory on account of the facility with which
the iron dissolved" whether heated or cold.
We employ Hydrochloric Acid gaseous and dry which we produce by one of the
following methods.
1. We heat to 160° Centigrades, Hydrochloric acid of commerce mixed with its
double volume of Sulphuric Acid at 60° Baumé. We operate in an apparatus
perfectly closed to prevent the access of air; and the whole of the Chlorhydric
Acid is set free in a dry state leaving the sulphuric acid diluted to about 50° Baumé.
To restore to this sulphuric acid its concentration to 60° it is sufficient to heat it by
the known methods and it can tlien be used indefinitely.
2. We can also obtain from sulphuric acid at 60° Baumé gaseous and humid
Hydrochloric acid by the action of sulphuric acid more or less concentrated, on a
chloride.

page_text: We employ to obtain dry Hydrochloric acid one or the other of these processes
according to the facility with which we can buy Hydrochloric acid, chlorides, or
sulphuric acid.
With gaseous and dry Hydrochloric acid we obtain the complete attack of the tin,
and the iron remains untouched on account of the disengagement of the hydrogen
which accompanies it.
We dispose our scraps containing tin in a series of chambers communicating
with each other. In order to cause this circulation of gas in the chambers con-
taining scraps to be better understood, we have represented in the drawing herewith
a diagram of an apparatus containing only four chambers communicating with each
other and with the chimney of the works. It is understood that we can in practice
increase or diminish the number of these chambers.
The acid gas penetrates these chambers No. 1, 2, 3, 4 at the bottom by means of
hydraulic sluice valves, or by stoneware taps a, a, as, a. The top of each chamber
communicates with the bottom of the next by communicating valves or taps b₁, b₂, ba, b,
and the gases, exhausted of acid, escape from each chamber into the chimney A of the
works by escape valves C1, C2, C3, C4, of which the pipes lead from the tops of the
chambers, these are furnished at their summit with a hydraulic neck d.
At the commencement of the operation the chambers 1, 2, 3, 4, are supposed to be
filled with scraps containing tin; we then cause the hydrochloric acid to enter
chamber No. 1. for that purpose taps a, a, a, being closed we open tap a₁, wo also
open the connecting valves b₁, ba, b3, and we close return valve b₁; then the escape
valves C₁, Ca, ca are closed whilst that c is open to conduct the exhausted gases to
chimney a.,
When the gas entering at the bottom of chamber No. 1 and driving the air before
it (being heavier than air) has filled that chamber it proceeds by the pipe b₁ passes
through the valve or tap 1, descends the vertical column e to the bottom of
chamber No. 2.
The movement of the gas is made progressively from chamber No. 1 to No: 2 then
No. 3 and No. 4 and the gases escape finally by the valve c. completely exhausted
of acid.
When scraps contained in chamber No. 1 are completely scaled we open valve ag
then we close valves a and b, the chamber No. 1 is thus completely isolated and wo
can water the materials it contains to detach the protochloride of tin which remains in
a state of deposit on the scraps.
The chamber can then be emptied and refilled with fresh scraps.
During the emptying and refilling the circulation is continued in three chambers
the gas entering at No. 2 and leaving at No. 4. When chamber No. 1 is refilled
we open the taps b and c and we close c. Chamber No. 1, becomes thus the last
and the circulation is made in the order No. 2, 3, 4, and 1. So on in circular
permutation. This circulation in which the most concentrated acid acts upon the
scraps the most nearly scaled, reduces the consumption of acid to a minimum and
allows all the tin to be obtained without acting much on the iron.
The liquors we obtain by the watering and washing are collected in tanks.
These liquors contain proto chloride of tin, salts of iron, and salts of lead these
latter being obtained from the dull tinned iron which we meet with.
To obtain the tin in a state of purity almost perfect we precipitate it with zinc,
taking care to cover the ingots of zinc with a wrapper of calico or other appropriate
tissue on which the tin is precipitated on the outside in metallic needles without
being blemished by zinc or other impurities. These needles are collected pro-
portionally as the exhaustion of the liquors of proto chloride, then rapidly pressed
to carry off the greater part of the liquid acid which covered the crystals.
To melt this metallic tin without oxydation we form a bath of chloride of zinc in
which we place these crystalline needles and heat in the open air.
The tin melts and falls to the bottom of the pan whilst the chloride of zinc can serve
a long time until being little by little charged with chloride of tin it is mixed with the
scouring water. The tin thus obtained can have a fineness as high as 99%.

page_text: Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed we declare that what we
claim is :
1st.) The extraction of tin from the scraps which contain it by the action of dry
Hydrochloric acid gas; this gas being obtained either by the action of sulphuric
acid on the Hydrochloric acid of commerce, heated in a closed vessel, or by causing
to give up, the Hydrochloric acid disengaged by the reaction. of sulphuric acid on
a chloride. The dry Hydrochloric acid gas entering slowly a series of chambers
quite closed, in such a way that the purest acid acts upon the most nearly scaled
scraps principally as described and represented.
2nd.) In the production in a state of purity of the tin contained in the liquors of
proto chloride of tin resulting from the washing of the chlorided scraps, by the
precipitation of the tin on the outside of an appropriate tissue enveloping ingots
of zinc.
3rd.) The fusion of the tin precipitated in a bath of chloride of zinc to prevent
oxydation as described and with the object specified.
4th.) An apparatus for methodical and continuous cholidization of the scraps
containing tin, consisting of a series of chambers hermetically closed each com-
municating with the next in circular permutation, and each furnished with an
entrance valve or tap for the acid and with an escape valve or tap for the escape
of the exhausted gas, as described and represented.
Dated this 17th day of September 1888.