Year: 1886

page_text: Date of Application, 9th Feb., 1886.
Complete Left, 8th Apr., 1886.
Complete Accepted, 14th Jan., 1887.
We, JOHN JAMES Hoon, Analytical Chemist, of 21 Shepherds 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 to the elimination of Iron compounds from aluminic Sulphate,
or other salts of alumina, with a view to render the latter available for those purposes
for which aluminic Sulphate containing Iron compounds is unfitted.
For this purpose we use suitable tin compounds; but, preferably, insoluble stannic
compounds.
We employ a solution of the aluminic salt, and to this solution we add the tin
compound. The tin compound we prefer to use is that prepared by the action of
nitric acid upon tin, the resulting product being subsequently washed from impurities
before it is introduced into the aluminic solution.
When the tin compound is introduced into the aluminic solution, we agitate the
solution with air, or by other mechanical means, until the iron is altogether removed,
or sufficiently removed for practical and commercial purposes.-We preferably conduct
the action in the cold.
We prefer that the iron should be present in the aluminic solution in the Ferric
condition, and, if necessary, we bring it into this condition (previous to adding the
tin compound) by the addition thereto of small quantities of a solution of bleaching
powder or other available oxidizing agent.
When the agitation of the solution is concluded, the tin compound is allowed to
subside, and the aluminic solution is removed by the usual methods. The tin com-
pound now contains the iron previously embodied in the aluminic compound.-It is
purged from this by suitable treatment with acids, and after efficient washing, is again
available for the further purification of aluminic compounds, as above indicated.
NEWTON & SON,
Agents for the Applicants.

page_text: Improvements in the Preparation of Sulphate of Alumina.
Wo JOHN JAMES HOOD, Analytical Chemist, of 21 Shepherds 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 and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention refers to the purification of sulphate of alumina, with a view to
render the same available in the preparation of the better classes of paper; in those
processes of mordaunting in which the presence of iron in the salt constitutes an
objectionable feature; and in all technical processes in which a pure sulphate of
alumina is required. The price which sulphate of alumina will command, for the
purposes above mentioned, may be said to be regulated almost entirely by the
comparative freedom of the salt from contamination with iron compounds.
In order to extract the iron from the sulphate of alumina, we employ the compound
of tin known as meta-stannic acid.
In our provisional specification filed at the time of applying for a patent for our
invention, we stated that we make use of the compounds of tin, but subsequent
experiment has revealed to us the fact that all compounds of tin cannot be used with
advantage for the purpose, and we now desire to confine our invention to the use of
meta-stamic acid or its salts, for the purposes above set forth.
In order to prepare the meta-stannic acid, we preferably proceed as follows:-
Metallic tin is treated with concentrated nitric acid until it is fully converted into
the white hydrated oxide of the metal. This is washed several times by decantation
in the vessel in which the nitric acid was added to the tin, and is then transferred to a
filter, or other suitable contrivance, which will allow of its being washed free from
acid, a sufficiency of washing being indicated by the filtrate, or washings, being
non-acid to blue litmus paper.
The meta-stannic acid is now ready for immediate addition to the solution of the
sulphate of alumina.-The meta-stannic acid should be kept in a moist condition, and
should not be allowed to become dry, otherwise the efficiency of its action will become
impaired.
The sulphate of alumina, from which it is desired to remove the iron, should be
brought into a state of solution previous to the addition to it of the meta-stannic acid.-
The solution should, preferably, he concentrated, and if necessary, heat may be
employed to effect the due dissolving of the compound.
Before the addition of the meta-stannic acid, we bring the iron in the sulphate of
alumina into the ferric condition.
In order to effect this object, we add the necessary quantity of bleaching powder,
or other suitable oxidizing agent, the quantity depending upon the amount of ferrous
iron in the solution. We further prefer that the sulphate of alumina should be some-
what basic, and to this end, in neutralizing the free acid in the sulphate of alumina,
we add a slight excess of carbonate of lime or other suitable compound.
The above mentioned precautions having been observed, we introduce the solution of
sulphate of alumina into a vessel provided with a suitable contrivance for permitting

page_text: of mechanical agitation or aëration. We then add the meta-stannic acid, and allow
the agitation to proceed until the usual qualitative, or if necessary quantitative tests,
show that the solution of sulphate of alumina has been efficiently or sufficiently purged
of the iron which it contained previous to agitation with the meta-stannic acid.
The exact quantity of meta-stannic acid which it is desirable, or necessary, to add,
will obviously depend upon the amount of iron which the solution of alumina com-
pound originally contained, but with a view of expediting the operation, we prefer to
add a large excess of meta-stannic acid over that chemically necessary to effect a
combination with the iron. In any case, however, it will constitute but a small per
centage upon the total quantity of sulphate of alumina present. If desired, the
meta-stannic acid may be added in instalments.
The termination of the purification having been reached, which is ascertained by
chemical test, the agitation of the liquid compound is stopped, and the meta-stannic
acid, which has combined with the iron, is allowed to subside in virtue of its greater
specific gravity. The solution of sulphate of alumina is next run off, and treated as
may be desired; or the mixture of meta-stamic acid and iron and the solution of
sulphate of alumina may be conveyed together into a suitable filtering apparatus, and
the solution separated from the residue by this means. Any trace of tin present in
the solution may be removed by the addition of sulphuretted hydrogen, water, and
subsequent filtering.
The meta-siannic acid may be used again and again until it has taken up so much
iron that its efficiency has become impaired, and its further action on the sulphate of
alumina is sluggish.
It then requires revivifying, which is preferably effected in the manner presently to
be described, or the original meta-stannic acid, which has been used for purification,
may be refreshed by the addition of a small quantity of meta-stannic acid free from
iron.
The meta-stannic acid so charged with iron as to render the removal of the latter
desirable, we treat, not in very great bulk, with sulphuric acid, preferably concentrated,
and allow it to stand for some hours.-The iron sulphate thus formed is then washed
out with water, and if necessary more acid is added, until it is ascertained, by suitable
tests, that, for practical purposes, the whole of the iron is removed from the meta-
stannic acid, and in this condition it is again available for use. If necessary, however,
it may be refreshed by the further addition of nitric acid, and subsequent washing, as
above described.
It will be understood that within the limits of manufacturing loss, the tin originally
converted into meta-stannic acid is not used up, inasmuch as none, or only a trace,
remains suspended in the solution, and the tin, therefore, employed constitutes merely
a portion of the requisite plant; thus, the high price of the material does not militate
against its use in the purification of sulphate of alumina.
We may here remark that we are aware that it has been proposed to treat metallic
salts for the removal of iron and other impurities therefrom, by the use of stannic acid,
but so far as our experiments have gone, we are satisfied that no practically useful
treatment of sulphate of alumina for the removal of iron therefrom, would result from
the use of stannic acid.
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:-
1. Treating sulphate of alumina in solution with meta-stannic acid in the manner
and for the purpose above set forth.
2. Re-vivifying the saturated meta-stannic acid in the manner and for the purpose
above set forth.