Improved Process for the Precipitation of Tin from Acid Solutions containing same with other Metals.
Year: 1892

page_text: Date of Application, 21st Sept., 1892
Complete Specification Left, 21st June, 1893-Accepted, 22nd July, 1893
PROVISIONAL SPECIFICATION.
Improved Process for the Precipitation of Tin from Acid Solutions
containing same with other Metals.
I, CAMILLE LÉON CHARLES BERTOU, of 11 Rue de St. Petersbourg, Paris,
in the Republic of France, Chemist, do hereby declare the nature of this
invention to be as follows :-
-
In treating scrap and waste tin plate in a bath of which hydrochloric acid is
the base in order to recover the tin therefrom, a certain quantity of other metals
which are associated with the tin in the tin sheets is always dissolved, and the
acid solutions finally obtained always contain beside the tin some iron and lead,
especially iron.
The presence of these other metals has the effect of considerably reducing the
value of the tin recovered from the scrap or waste.
When the tin is precipitated from these solutions by means of carbonate of lime,
as the iron is in the minimum form, (that is in the form of a protosalt or a salt of
protoxide of iron, in fact a ferrous chloride or protochloride of iron) the tin alone
is precipitated in the form of an oxychloride. This process which is theoretically
good in practice presents certain disadvantages, including the great difficulty which
is found in precipitating the froth or foam, and the considerable loss in time which
occurs.
Lime, which does not give rise to any froth or foam, can only be employed with
special precautions for, unlike the carbonate, it precipitates all the metals which
are in solution.
The present invention relates to a process which enables lime to be employed for
precipitating tin alone from this class of solutions. For this purpose I operate as
follows. I first add to the solution a very small quantity of lime; this lime
immediately precipitates not only the tin but at the same time the iron.
But the protoxide of iron itself reacts on the salt of tin and is reconverted into
the protochloride of iron at the same time as it produces an insoluble oxychloride
of tin. I thus continue to add lime little by little, following the operation of
precipitation with care, and withdrawing samples in order to ascertain the moment.
when there remains practically no more tin in the solution, while practically no irou
has been precipitated. The addition of lime is stopped as soon as practically no
more tin remains.
The precipitated oxychloride of tin is then separated by any suitable means from
the chloride of iron remaining in solution, and the product obtained thus contains.
tin only; this precipitate is again suspended in water and milk of lime added until
an alkaline reaction occurs.
After this second treatment with lime the oxychloride of tin is almost entirely.
converted into oxide of tin, from which the tin may be recovered by any of the well
known means.
The precipitation is more especially efficient, both for the first and for the second
treatment with lime, when the solutions have been previously heated to about
60° or 70° centigrade; further, the lime, both for the first and second operations, may
be replaced by an equivalent base, such as baryta, strontia, potash, or soda. It is
even advantageous to conduct the first precipitation entirely with lime and to
subsequently effect the complete dechloridation with soda; by this means the
addition of a slight excess of the reagent will not affect the purity of the precipitated
oxide of tin.
ALLISON BROS.,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improved Process for the Precipitation of Tin from Acid Solutions
containing same with other Metals.
I, CAMILLE LÉON CHARLES BERTOU, of 11 Rue de St. Petersbourg, Paris,
in the Republic of France, Chemist, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :-
In treating scrap and waste tin plate in a bath of which hydrochloric acid is the
base in order to recover the tin therefrom, a certain quantity of other metals which
are associated with the tin in the tin sheets is always dissolved, and the acid
solutions finally obtained always contain beside the tin some iron and lead,
especially iron."
The presence of these other metals has 'the effect of considerably reducing the
value of the tin recovered from the scrap or waste.
When the tin is precipitated from these solutions by means of carbonate of lime,
as the iron is in the minimum form, (that is in the form of a protosalt or a salt of
protoxide of iron, in fact a ferrous chloride or protochloride of iron) the tin alone
is precipitated in the form of an oxychloride. This process which is theoretically
good in practice presents certain disadvantages, including the great difficulty which
is found in precipitating the froth or foam, and the considerable loss in time which
occurs.
Lime, which does not give rise to any froth or foam, can only be employed with
special precautions for, unlike the carbonate, it precipitates all the metals which
are in solution.
The present invention relates to a process which enables lime to be employed for
precipitating tin alone from this class of solutions. For this purpose I operate as
follows. I first add to the solution a very small quantity of lime; this lime
immediately precipitates not only the tin but at the same time the iron.
But the protoxide of iron itself acts on the salt of tin and is reconverted into the
protochloride of iron at the same time as it produces an insoluble oxychloride of
tin. I thus continue to add lime little by little, following the operation of precipi-
tation with care, and withdrawing samples in order to ascertain the moment when
there remains practically no more tin in the solution, while practically no iron has
been precipitated. The addition of lime is stopped as soon as practically no more
tin remains.
The precipitated oxychloride of tin is then separated by any suitable means from
the chloride of iron remaining in solution, and the product obtained thus contains
tin only this precipitate is again suspended in water and milk of lime added until
an alkaline action occurs.
After this second treatment with lime the oxychloride of tin is almost entirely
converted into oxide of tin, from which the tin may be recovered by any of the
well known means.
The precipitation is more especially efficient both for the first and for the second
treatment with lime, when the solutions have been previously heated to about
60° or 70° centigrade; further, the lime, both for the first and second operations,
may be replaced by an equivalent base, such as baryta, strontia, potash, or soda.
It is even advantageous to conduct the first precipitation entirely with lime and to
subsequently effect the complete dechloridation with soda; by this means the
addition of a slight excess of the reagent will not affect the purity of the precipitated
oxide of tin.
Having now particularly described and ascertained the nature of my said inven
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. The process for the anasinis.

page_text: described containing same with other metals, consisting in; (1) the addition of
lime or an equivalent base as described in very small quantities with the object
indicated, and in continuing to add same until there is no appreciable amount of
tin remaining in such solution, but stopping the operation before the iron present
begins to precipitate; (2) in separating from the remaining solution of chloride
of iron the insoluble oxychloride of tin obtained, and (3) in again suspending the
oxychloride of tin in water to which milk of lime or an equivalent base is added
until an alkaline reaction occurs, all substantially as and for the purpose specified.
2. In the process above indicated, the successive employment of an alkaline earth
for precipitating oxychloride of tin and of an alkali for transforming this oxychloride
into oxide substantially as specified.
3. In the process above indicated, the preliminary heating to a temperature of
about 60° or 70° centigrade of the acid solution in which the oxychloride of tin is
precipitated and of the water in which such precipitate is subsequently suspended
to be transformed into oxide.
Dated this 21st do of June 1803
ALLISON BROS.,
Agents for the Applicant.