IMPROVEMENTS IN THE TREATMENT OF CERTAIN MINERAL PHOSPHATES TO OBTAIN USEFUL PRODUCTS THEREFROM
Year: 1882

page_text: LETTERS PATENT to David Perry, of the City of Glasgow, in the County of
Lanark, North Britain, Chemist, for an Invention of "IMPROVEMENTS IN
THE TREATMENT OF CERTAIN MINERAL PHOSPHATES TO OBTAIN USEFUL
PRODUCTS THEREFROM."
PROVISIONAL SPECIFICATION left by the said David Perry at the Office
of the Commissioners of Patents on the 11th January 1882.
DAVID PERRY of the City of Glasgow in the County of Lanark, North Britain,
Chemist, " IMPROVEMENTS IN THE TREATMENT OF CERTAIN MINERAL PHOSPHATES
TO OBTAIN USEFUL PRODUCTS THEREFROM."
My Invention relates to the treatment of mineral phosphates containing either
iron or alumina, or both, in order to obtain the phosphoric acid and the alumina
therein contained as compounds of commercial value; viz an alkaline or earthy
phosphate and alumina hydrate, or any of its compounds.
The alkaline phosphate produced may be either a phosphate of soda or potash
according to the alkali used in the following reaction; but in describing this
Invention it will be convenient to refer only to the compounds produced when
soda salts are used; but all that relates to these compounds applies also to the
compounds produced by using potassium salts, which are equally applicable.
My improved process is as follows:-
The mineral phosphates are by preference (although not necessarily) first calcined,
and then thoroughly ground.
The ground and calcined material is then treated by boiling in a suitable vessel
with caustic soda, the quantity varying according to its strength, made by
preference from that quality of soda ash known as high strength "ammonia ash,"
until practically all the phosphoric acid and the alumina are extracted from the
mineral. The insoluble matter is separated by filtration and washed, the washings
being mixed with the solution.

page_text: First The solution of caustic soda containing the phosphoric acid and the
alumina, is treated by boiling under pressure, in a convenient vessel with a
suitable quantity of silica (preferably calcined flint in excess).
The precipitate is separated and washed free from phosphoric acid. The solution
is evaporated to a convenient strength and crystallized. The crystals are ordinary
rhombic phosphate of soda in an almost chemically pure state, and may be utilized
for any of the known uses of that salt.
The insoluble compound of alumina that remained as precipitate may be utilised
by treating it by boiling, in a suitable vessel, with water and a quantity of burnt
or slaked lime, until it is decomposed. The solution will then contain the soda
(which was in the compound) as hydrate, and can be used in the dissolving of the
calcined and ground mineral of another batch of ore. The precipitate after
separation and washing is then decomposed in any convenient manner with
sulphuric acid (by preference free from iron) so as to produce the sulphates of lime
and alumina. The sulphate of alumina in solution may be separated by filtration
or other means from the silica and sulphate of lime. The solution is then
evaporated to the required state, for giving solid sulphate of alumina, which may
be utilized for any of its known uses.
Secondly I may alternatively treat the caustic soda solution containing the
phosphoric acid and the alumina as previously described, by boiling with a quantity
of solution of silicate of soda according to its strength such silicate to contain as
high a proportion of silica to soda, as can be conveniently obtained, such as 3
equivalents of silica to one equivalent of soda.
The insoluble compound of alumina is treated as before described. The solution
is separated by filtration from the insoluble compounds of alumina, and is then
treated by boiling in a suitable vessel under pressure with silica, (by preference
calcined flints in excess) for a time sufficient to obtain a solution of di-basic
phosphate of soda, which is separated by earlier crystallisation from the silica in
solution. The mother liquor from this may be conveniently used, instead of the
silicate of soda, used in the earlier part of this process.
Thirdly I may alternatively treat the caustic soda solution of phosphoric acid
and alumina in a suitable vessel with such a quantity of burnt or slaked lime as will
form tribasic phosphates of lime with the phosphoric acid in solution. It is then
boiled until the re-action is finished, and the precipitate is separated in a convenient
inanner by filtration. The solution contains the alumina, which may be separated
from the soda by the addition of carbonic or any other suitable acid, and afterwards
can be converted into any desired compound of alumina.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said David Perry in the Great Seal Patent Office on the 11th July
1882.
DAVID PERRY, of the City of Glasgow, in the County of Lanark, North Britain,
Chemist. "IMPROVEMENTS IN THE TREATMENT OF CERTAIN MINERAL PHOSPHATES
TO OBTAIN USEFUL PRODUCTS THEREFROM,"
My Invention relates to the treatment of mineral phosphates containing either
iron or alumina, or both, in order to obtain the phosphoric acid and the alumina
therein contained, as compounds of commercial value; viz an alkaline or earthy
phosphate and alumina hydrate, or any of its compounds.
The alkaline phosphate produced may be either a phosphate of soda or potash,
according to the alkali used in the following reaction, but in describing this
Invention it will be convenient to refer only to the compounds produced when
soda salts are used; but all that relates to these compounds, applies also to the
compounds produced by using potassium salts, which are equally applicable.
My improved process is as follows:-
The mineral phosphates are by preference (although not necessarily) first
calcined, and then thoroughly ground.
The ground and calcined material is then treated by boiling in a suitable vessel
with caustic soda, (made by preference from that quality of soda ash known as
high strength "ammonia ash") the quantity varying according to its strength in
about such proportions, that there will be at least three equivalents of soda to one
equivalent of phosphoric acid, until practically all the phosphoric acid and the
alumina are extracted from the mineral. The insoluble matter is separated by
filtration and washed, the washings being mixed with the solution hereinafter
specified.
First-The solution of caustic soda containing the phosphoric acid and the
alumina, is treated by boiling under a pressure of about sixty pounds above
atmosphere in a convenient vessel, with a suitable quantity of silica (preferably
calcined flint in excess), sufficient to extract one equivalent of the soda used.
The precipitate of silico-aluminate of soda is separated and washed free from the
solution of phosphate of soda. The solution is evaporated to a convenient strength
and crystallized. The crystals are ordinary rhombic phosphate of soda, in an
almost chemically pure state, and may be utilized for any of the known uses of
that salt.
The insoluble compound of silico-aluminate of soda that remained as precipitate,
may be utilized by treating it by digesting in a suitable vessel, with water and a
quantity of burnt or slaked lime, sufficient to liberate the soda from the compound,
until it is decomposed. The solution will then contain the soda (which was in the
compound) as bydrate, and can be used in the dissolving of the calcined and
ground mineral of another batch of ore. The precipitate, silico-aluminate of lime,
after separation and washing, is then decomposed in any convenient manner with
sulphuric acid (by preference free from iron); so as to produce the sulphate of lime
and alumina. The sulphate of alumina in solution may be separated, by filtration
or other means, from the silica and sulphate of lime. The solution is then
evaporated to the required state for giving solid sulphate of alumina, which may
be utilized for any of its known uses.
Secondly; I may alternatively treat the caustic soda solution, containing the
phosphoric acid and the alumina, as previously described, by boiling with a
quantity of solution of silicate of soda, sufficient according to its strength, to
precipitate all the alumina, such silicate to contain as high a proportion of silica

page_text: to soda, as can be conveniently obtained, such as three equivalents of silica to one
equivalent of soda.
The insoluble compound of alumina is treated as before described. The solution
is separated by filtration from the insoluble compound of alumina, and is then
treated by boiling in a suitable vessel under pressure with silica, (by preference
calcined flints in excess) for a time sufficient to obtain a solution of di-basic
phosphate of soda, which is separated by earlier crystallisation from the silica in
solution. The mother liquor from this may be conveniently used, instead of the
silicate of soda, used in the earlier part of this process.
Thirdly, I may alternatively treat the caustic soda solution of phosphoric acid
and alumina in a suitable vessel, with such a quantity of burnt or slaked lime as
will form tribasic phosphate of lime with the phosphoric acid in solution. It is
then boiled until the re-action is finished, and the precipitate is separated in a
convenient manner by filtration. The solution contains the alumina, which may
be separated from the soda by the addition of carbonic or any other suitable acid,
and afterwards can be converted into any desired compound of alumina.
And having now fully described and ascertained the nature of my Invention and
the manner in which the same is to be performed, be it known that what I claim
as novel and desire to protect by Letters Patent is :-
1st The treatment of the caustic soda solution of phosphate of alumina with
silica under pressure, substantially as and for the purpose described.
2nd The treatment of the silico-aluminate of soda with lime and afterwards
with sulphuric acid substantially as and for the purpose described.
3rd The treatment of the solution of the alkaline phosphate of soda (after
precipitation with silicate of soda) with silica under pressure, substantially as and
for the purpose described.
4th The treatment of the caustic soda solution (after separation of the insoluble
matter of the mineral) with lime, substantially as and for the purpose described.
5th The treatment of the phosphate of alumina generally, for the production
of phosphate of soda, phosphate of lime, and alumina, or sulphate of alumina,
substantially as described.
In witness whereof I, the said David Perry, have hereunto set my hand
and seal this Tenth day of July in the year of our Lord One thousand
eight-hundred and eighty-two.