An Improved Method of Recovering Tin from Tin Plates, Tin Boxes, and other Tin Waste.
Year: 1893

page_text: Date of Application, 9th May, 1893
Complete Specification Left, 9th Mar., 1894-Accepted, 5th May, 1894
PROVISIONAL SPECIFICATION.
An Improved Method of Recovering Tin from Tin Plates, Tin
Boxes, and other Tin Waste.
We CHARLES WILLIAM KRIENS, of 87 Hawksley Road, Analytical Chemist,
and JOHN ROBERT HARPER, of 33 Groombridge Road, South Hackney, Engineer,
both in the County of Middlesex, do hereby declare the nature of this invention
to be as follows:-
The object of our invention is to provide a cheap and effective method of
recovering tin from tin plates, tin boxes, and tin waste, without in the least
affecting the sheet iron, recovering at the same time the chemicals employed in the
process.
In carrying out our invention we employ tanks made of iron, which we fill
with a solution of caustic alkali, into which we throw the tin plates, boxes, or tin
waste.
In a cold state this solution- will dissolve the tin in about 48 hours, if heated
the solution will do the same work within 4 to 6 hours, according to the thickness
of the tin.
The sheet iron is not affected in any way by the solution.
After the material has been sufficiently saturated it is evaporated to such a
degree that the tin is held partly as a soluble salt with the alkali and partly as
oxide.
The dry material is then calcined for the purpose of converting the soluble salt
into insoluble oxide of tin, the said material is then ground and the alkali is washed
out, leaving the insoluble oxide of tin as residue.
The effect of the calcining and the action of the atmosphere carbonizes the
alkali, this carbonized alkali is causticized by the addition of lime through a well
known process, and is ready for future use.
Should the solution during the process of dissolving the tin, become charged with
carbonic acid through contact with the atmosphere milk of lime is added for the
purpose of causticizing it.
It will be seen that by this process, not alone is the tin recovered and the sheet
iron intact, but the chemicals used in the process are also recovered.
Dated this 9th day of May 1893.
CHARLES WILLIAM JULIUS NOLTE,
Agent for the Applicants.
COMPLETE SPECIFICATION.
An Improved Method of Recovering Tin from Tin Plates, Tin
Boxes, and other Tin Waste.
We CHARLES WILLIAM KRIENS of 11 North Wold Road, Stoke Newington,
Analytical Chemist, and JOHN ROBERT HARPER of 33 Groombridge Road,
South Hackney, Engineer, both in the County of Middlesex, 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 :-
The object of our invention is to provide a cheap & effective method of
recovering tin from tin plates, tin boxes, & tin waste, without in the least.

page_text: affecting the sheet iron, recovering at the same time the chemicals employed in the
process.
In carrying out our invention we employ suitable iron tanks, which we fill
with a solution of caustic alkali (the solution to be of a specific gravity of
about 1200).
In this solution we immerse the material to be treated, such as tin plates, tin
boxes or tin waste of any description.
When the solution is used in a cold state, it will dissolve the tin in about 48 hours,
if heated, it will accomplish the same work within 4 to 6 hours, according to the
thickness of the tin.
The sheet iron is not affected in any way by the solution & can be utilized
again.
Where boiling is employed to quicken the work, we preferably heat the tank or
tanks by means of a jet of superheated steam, whereby air is introduced into the
tank at the same time.
After the solution has been saturated sufficiently it is evaporated to dryness.
This dry material is then roasted or calcined and during that process ground
charcoal is introduced in sufficient quantities to produce the carbonic acid required
to carbonize the whole mass.
By this treatment the salts of tin are transformed into an insoluble carbonate
and the carbonized alkali salts easily soluble, are washed out.
The fluid obtained is caustizised with milk of lime and then evaporated to the
required specific gravity of about 1200, when it is fit to used again.
The solution employed is ready to be evaporated when the soda contained in it
is saturated with tin.
62 lbs. of absolute oxide of natron are equivalent to 118 lbs. of tin & same
proportions are used in the solution.
The amount of carbon added is in proportion to the amount of natron and tin
contained in solution.
The solution in which the waste is boiled, contains in the beginning, about
15% of natron.
It will be seen that by this process, not alone is the tin recovered, & the sheet
iron preserved intact, but the alkalis used in the process are also recovered.
Having now particularly described & ascertained the nature of our said inven-
tion & in what manner the same is to be performed, we declare that what we
claim is :-
1. An Improved Method of Recovering Tin from Tin Plates, Tin Boxes, &
other Tin Waste, by means of immersing them in suitable tanks containing a solution
of alkali either in a cold or heated state, substantially as hereinbefore described.
2. The method of recovering the alkalis used for treating the tin boxes, tin
plates, & other tin waste, substantially as hereinbefore described.
Dated this 9th day of March 1894.
CHARLES WILLIAM JULIUS NOLTE,
Agent for the Applicants.
CHARLES WILLIAM JULIUS NOLTE,
Agent for the Applicants.