Purification of Meta-stannic Acid.
Year: 1886

page_text: Date of Application, 23rd Sept., 1886.
Complete Left, 22nd June, 1887.
Complete Accepted, 22nd July, 1887.
Purification of Meta-stannic Acid.
We JOHN JAMES HOOD, Analytical Chemist, of 21 Shepherd's Bush Road in the
County of Middlesex, and ALFRED GORDON SALAMON, Analytical Chemist, of
1 Fenchurch Avenue, in the City of London, do hereby declare the nature of this
invention to be as follows:-
This invention relates firstly to the manufacture of a material which we have
designated meta-stannic acid, because it answers to all the usual tests for meta-stannic
acid, as now known, the object being to prepare the material in a cheap and efficient
manner for use in the purification of sulphate of alumina, according to a patent applied
for by us on the 9th February 1886, and for other purposes; secondly, the invention
relates to the purification of the spent meta-stannic acid, by the removal therefrom of
metallic and organic impurities taken up during its use as a purifier.
According to our invention, we submit metallic tin to the action of sulphuric acid,
and treat the resulting mass, containing more or less stannous salt, with a suitable
oxidising agent. Thus, for example, a convenient quantity of tin is just covered with
oil of vitriol, and heated gently till all action ceases, and a whitish mass is obtained,
more or less pasty in consistency; a small quantity of water is added, heat applied,
and nitrate of soda added, in small quantities at a time, till the stannous salt is com-
pletely oxidised. This stage we consider to be reached when there is no further
evolution of nitrous fumes, when the solution becomes yellowish in colour; a relatively
large bulk of cold water is now added, and the solution boiled for a few minutes to
precipitate the meta-stannic acid, which, after washing from the bulk of free acid, and
subsequent neutralization, is ready for use in the elimination of iron from sulphate of
alumina, or for other purposes for which it may be available. Or the preparation of
meta-stannic acid may be accomplished with sulphuric acid, as above described, but
instead of employing nitrate of soda, ferric sulphate, or other suitable ferric compound,
or a manganic compound may be used. The pasty mass is made into a thin mud with
water, and kept boiling. The ferric sulphate solution, or a dry ferric compound, is
added a little at a time. When the end of the reaction is reached, the ferrous salt is
completely washed out, and some bleaching powder, preferably in solution, is added to

page_text: the meta-stannic mud, to oxidize the last traces of stannous salt. The mud is then
rendered alkaline by means of magnesic carbonate or other suitable agent, and is then
ready for use.
We preferably prepare the ferric sulphate by treating ordinary brown haematite ore
with concentrated oil of vitriol, dissolving the ferric sulphate thus produced in water,
and allowing the silica etc. to settle.
As the meta-stannic acid, when industrially applied to the extraction of iron, in
time becomes so clogged with iron as materially to interfere with the efficacy of its
action, we have found it necessary to devise a method of extracting the iron from the
meta-stannic mud, and to this end we preferably proceed as follows:-The mud is
washed, and allowed to subside to as small a bulk as possible; to this, oil of vitriol is
added, and the mass is then boiled for a few minutes; a suitable proportion of tin,
dissolved in hydro-chloric acid, is now added to the mud, and the whole is then boiled
for about one hour; a little water is occasionally added to prevent the mud becoming
too thick and pasty. The iron impurity being now converted into a ferrous salt, is
washed out, till the washings, when tested, show no trace of iron.-Sufficient "bleach"
is added to oxidize any excess of stannous salt which may have been added to the mud,
and after washing, the mud is rendered alkaline, as before, and is again ready for
use.
.
After several purifications, the tin mud becomes somewhat granular and heavy,
a state in which it seems to be somewhat less active than when in a flocculent
condition; it is also liable to become impregnated with organic matter.
Under these circumstances, we preferably proceed as follows:-The mud is treated
with oil of vitriol and the mass submitted to heat. The heating is continued till acid
fumes begin to come off. The mass will then be found to pass from the pasty state to
one of solution. To the fluid thus obtained, if of a black tarry consistency, a sufficiency
of sodic nitrate, or other suitable oxidizing agent, is added, whilst the mass is still
kept hot, to oxidize the carbonaceous matter. The mass is then allowed to cool, and
cold water is poured over it to decompose it, after which it is allowed to rest till the
solidified mass has become completely disintegrated and white.-It is then boiled for
a few minutes, and a portion of stannous chloride, sufficient to liberate the iron
contained in the mud, is added thereto, after which it is washed, and rendered alkaline
as before, and is again ready for use.
Dated this 23rd day of September 1886.

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Meta-stannic Acid and in the
Purification of Meta-stannic Acid.
We, JOHN JAMES HOOD of 2.1 Shepherd's Bush Road in the County of Middlesex,
Analytical Chemist and ALFRED GORDON SALAMON of 1. Fenchurch Avenue, in the
City of London, Analytical Chemist, 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 firstly to the manufacture of a material which we have
designated meta-stannic acid, because it answers to all the usual tests for meta-stannie
acid as now known, the object being to prepare the material in a cheap and efficient
manner for use in the purification of sulphate of alumina according to a process
patented by us on the 9th day of February 1886, and for other purposes. Secondly,
the invention relates to the purification of the spent meta-stannic acid by the removal
therefrom of metallic and other impurities taken up during its use as a purifier.
According to our invention, we submit metallic tin to the action of sulphuric acid,
and treat the resulting mass, containing more or less stannous salt, with a suitable
oxydizing agent. Thus, e.g., a convenient quantity of tin is just covered with
sulphuric acid, and heated gently until all chemical action ceases, when a whitish mass
will result, of a more or less pasty consistency; a small quantity of water is then added,
and heat applied.-During the heating, nitrate of soda is added in small quantities at
a time, until the stannous salt is completely oxydized.-This stage we consider to be
reached when there is no further evolution of nitrous fumes, the small quantity of
water dissolving the mass to a yellow solution.-A relatively large bulk of cold water
is next added, and the solution is boiled for a few minutes to precipitate the meta-
stannic acid, which, after being washed from the bulk of free acid, and subsequently
neutralized, or rendered alkaline, by suitable material (when a meta-stannic acid of a
neutral or alkaline character is desired) is ready for use in the elimination of iron
from sulphate of alumina, or for other purposes to which it is applicable.
Or, the preparation of meta-stannic acid with sulphuric acid as above described,
may (instead of employing nitrate of soda) be treated with ferric sulphate or other
suitable ferric compound, or a nianganic compound such as the native di-oxyde, or by
preference that forin of artificial di-oxyde known as Welden mud. If a ferric com-
pound be used as an oxydizing agent, the pasty mass of tin is made into a thin mud
with water, and kept boiling.-At this stage, the ferric sulphate solution, or a dry
ferric compound, is added a little at a time. When the end of the reaction is reached,
the ferrous salt is completely washed out, and bleaching powder, or so-called Chloride
of Lime (Ca.O.Cl₂), preferably in solution, is added to the meta-stannic mud, sufficient
to oxydise the last traces of stannous salt.-The mud is then rendered alkaline, if so
required, by means of magnesic carbonate, or other suitable agent, and is then ready
for use.

page_text: We preferably prepare the ferric sulphate by treating ordinary brown haematite ore
with concentrated sulphuric acid.-The ferric sulphate thus produced we dissolve in
water, and allow the silica &c. to settle out before using the solution.
As the meta-stannic acid, when industrially applied. to the extraction of iron, in
time becomes so clogged with iron as materially to interfere with the efficacy of its
action, we have found it necessary to devise a method of extracting the iron from the
meta-stannic mud, and to this end we preferably proceed as follows.-The mud is
washed, and allowed to subside to as small a bulk as possible; to this sulphuric acid
is added, and the mass is then boiled for a few minutes.-A suitable proportion of
tin, dissolved in hydrochloric acid, is now added to the mud, sufficient in amount to
reduce the ferric oxyde contained in the mud to ferrous oxyde, and the whole is then
boiled for about one hour; a little water is occasionally added to prevent the mud
becoming too thick and pasty:-The iron impurity, being now converted into a
ferrous salt, is washed out, the washing being continued until no trace of iron is
detected. To oxydize any excess of stannous salt which may have been added to
the mud, sufficient "bleach," or so called chloride of Lime (Ca. O. Cl,) is now applied,
and, after washing, the mud is rendered alkaline as before, and is ready for use.
When organic matters have been taken up by the meta stannic acid, we get rid of
them, and purify the tin mud by boiling with sulphuric acid to which an oxydizing
agent is added. By preference we use sodic nitrate or manganese di-oxyde, in the
form of Welden mud.
After several purifications, the tin mud becomes somewhat granular and heavy, a
state in which it seems to be less active than when in a flocculent condition.-Under
these circumstances we preferably proceed as follows-The mud is treated with
sulphuric acid, and the mass submitted to heat.-The heating is continued till acid
fumes begin to come off: the mass will then be found to pass from the pasty state to
one of solution. To the thick fluid thus obtained, if of a black tarry consistency, a
sufficiency of sodic nitrate or other suitable oxydizing agent is added, whilst the mass
is still kept hot to oxydize the carbonaceous matters. The mass is then allowed to cool,
and cold water is poured over it to decompose it, after which it is allowed to rest until
the solidified mass has become completely disintegrated and white.-The material is
then boiled with stannous chloride sufficient in amount to reduce the ferric oxyde
contained in the mud, after which it is washed free from iron as before.
Having now particularly described and ascertained the nature of our said invention
and in what manner the same is to be performed, we declare that what we claim is ;-
1st. The preparation of meta-stannic acid by first acting upon tin with sulphuric
acid, and then oxydizing the resulting mass by means of sodic nitrate or ferric
sulphate, or manganic di-oxyde, as above set forth.
2nd. The purification of meta-stannic acid from iron and from organic matters in the
manner above described.
Dated this 22nd day of June 1887
NEWTON & SON,
Agents for the Applicants.