IMPROVEMENTS IN THE MANUFACTURE OF PHOSPHATES
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
I PHILIP MIDDLETON JUSTICE of 55 and 56 Chancery Lane in the County of
Middlesex Fellow of the Institute of Patent Agents do hereby declare the nature
of said invention for "IMPROVEMENTS IN THE MANUFACTURE OF PHOSPHATES"
a communication to me from abroad by Sidney Gilchrist Thomas of 61-Avenue
Marceau, Paris, France Metallurgist to be as follows:-
This invention relates to the manufacture of phosphates free from iron from
phosphoric slags and minerals containing iron. In carrying out my invention
I dissolve the material in acid and thus nearly neutralize the solution, and then
pass the current from a dynamo electric machine into the solution until the iron is
precipitated.
The deposited iron may with advantage be removed continuously from the pole
on which it is deposited.
I sometimes first precipitate the whole or part of the phosphoric acid from the
first solution as phosphate of iron by chalk, lime, or magnesia, and redissolve the
separated precipitated phosphate and then separate the nearly neutral solution by
the action of a dynamo current thus separating free phosphoric acid in solution,
which can be used for preparing high class phosphates or otherwise.

page_text: COMPLETE SPECIFICATION.
I PHILIP MIDDLETON JUSTICE of 55 and 56 Chancery Lane in the County of
Middlesex Fellow of the Institute of Patent Agents do hereby declare the nature
of the said invention for IMPROVEMENTS IN THE MANUFACTURE OF PHOSPHATES
a communication to me from abroad by Sidney Gilchrist Thomas of 61 Avenue
Marceau Paris France Metallurgist 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 the manufacture of phosphates free from iron, from
phosphoric slags and minerals containing iron.
In carrying out this invention the slag or mineral to be treated is ground or
broken up sufficiently fine to allow of its being dissolved by acida. In treating
phosphoric slags which contain much lime, hydrochloric acid should always be
used for effecting the solution. Acid containing from 10 to 15 per cent of real
hydrochloric acid is most convenient but stronger acid may be used.
The insoluble silicious matter is allowed to settle and the clear solution run off
or filtered. Should there be much iron in the solution in the ferric state it should
be reduced to the ferrous, this may be effected by any of the ordinary reducing
agents known to chemists.
It is preferable however to reduce the ferric salts by digesting the solution on
pieces of scrap iron by which means not only is the ferric salt reduced but more
iron is taken up into solution.
Should the iron chiefly exist in solution in the ferrous state this preliminary
reduction may be dispensed with. The solution should always be made as neutral
as possible before introducing the current for the purpose of depositing the iron.
It is well to have an excess of the powdered slag present as by this means the
acid set free during the re-action is neutralized by dissolving more of the mineral.
The iron is deposited on a suitable electrode by means of a constant current from a
dynamo-electric machine, the strength of current most suitable for the purpose
varies with the amount of iron salt there is in the solution. When the whole of
the iron is deposited, the solution should be run off and the phosphoric acid
precipitated by means of lime, magnesia, or chalk.
Sometimes, when the amount of iron in the material is not large it is preferable,
instead of treating the solution of the dissolved 'slag directly with the current to
first precipitate the iron together with the whole or part of the phosphoric acid as
phosphate of iron by means of chalk or lime or magnesia, the iron is best
precipitated as ferric phosphate but should be reduced by iron to ferrous before
treating with the current. The phosphate of iron thus precipitated is then
dissolved in acid, for this purpose either sulphuric or hydrochloric may be used,
but phosphoric acid produced from a former operation is preferable. The iron is
then deposited on a suitably placed negative electrode as before to neutralize the
phosphoric acid left free in the solution, blocks of compressed phosphate of iron
may be placed on and around the positive electrode, these blocks are dissolved by
the free acid produced and the solution is thus kept supplied with dissolved iron
salt. The free phosphoric acid produced by these means may be utilized for
preparing high class phosphates or otherwise.

page_text: Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed as communicated to
me by my foreign correspondent I declare that what I claim is
The production of iron free solutions of phosphoric acid or phosphate of lime
from minerals and slags containing iron and phosphoric acid, by first dissolving the
mineral in a suitable acid, and subsequently depositing the dissolved iron as
metallic iron by means of a dynamo-electric current all substantially as and for
the purposes described.
A