IMPROVEMENTS IN THE MANUFACTURE OF PRECIPITATED PHOSPHATE OF ALUMINA AND THE MIXED PRECIPITATES OF PHOSPHATE OF ALUMINA AND SULPHATE OF LIME
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
I WILLIAM ARTHUR HILLS of the Chester Chemical Works Saltney in the
County of Flint Manufacturing Chemist do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF PRECIPITATED
PHOSPHATE OF ALUMINA AND THE MIXED PRECIPITATES OF PHOSPHATE OF
ALUMINA AND SULPHATE OF LIME "to be as follows:-
.
I take. the natural or crude phosphate of alumina (such as that found in the
Island of Redonda or Alta Vela) either in the raw state or after calcination and
mix it with a suitable acid (preferably sulphuric acid) and thus separate the
phosphate of alumina from the greater part of the iron and the silica contained in
the said natural or crude phosphate of alumina the phosphate of alumina being
dissolved by the acid and the greater part of the iron and silica remaining as an
insoluble residue which residue I separate from the solution of phosphate of
alumina by filtration or decantation or otherwise. I then reduce the gravity of
the solution by diluting it with water either hot or cold until precipitation of the
phosphate of alumina. is produced which precipitate I remove by filtration or;
decantation or otherwise. After removing the precipitate from the dilute acid the
latter may be brought to the required strength for use in dissolving further.
quantities of the crude phosphate of alumina by boiling the said dilute acid.
To produce precipitation of the phosphate of alumina it is necessary to dilute
the solution to a greater extent if it be treated in a cold state or if cold water be
used to dilute it than if it be treated in a hot state or if hot water be used to dilute
it therefore I prefer to dilute the said solution with hot water or by forcing steam
into it or to heat the said solution after diluting it. by forcing into it either steam
or hot air or a mixture of hot air and steam or by other convenient means.
solution may with advantage be heated nearly or quite to the boiling point.
The
In some cases I force air or carbonic acid into the hot or cold solution in order
to facilitate the precipitation of the phosphate of alumina.
I am aware that phosphate of alumina has been precipitated from an acid
solution thereof by neutralizing the acid by the addition thereto of its chemical
equivalent of an alkali sufficient alkali being added to neutralize the whole of the
Die 1

page_text: acid holding the phosphate of alumina in solution and I wish it to be understood
that the use of alkalies is unnecessary in carrying out my process as hereinbefore
described the essential feature of which consists in producing the precipitation of
phosphate of alumina from an acid solution thereof by reducing the gravity of the
said solution which remains acid after the whole or greater part of the phosphate
of alumina has been precipitated therefrom I do not however confine myself to
the use of absolutely pure water for diluting the acid solution of phosphate of
alumina as water slightly or naturally impregnated with alkalies may be used in
cases where such water may be more conveniently obtained than water not so
contaminated or where from other reasons it may be desirable to use water so
contaminated the only effect of the presence of an alkali being to neutralize its
chemical equivalent of acid which in such cases is small. Beyond this action of the
alkali present the whole effect of the addition of the contaminated water to the acid
solution is to produce precipitation of the phosphate of alumina by the reduction
of the gravity of the acid solution.
When I use sulphuric acid for dissolving the phosphate of alumina I in some
cases add chloride of sodium or chloride of potash or chloride of lime to the
solution of phosphate of alumina which solution I dilute as herein before described.
The addition of the said chlorides to the acid solution causes the phosphate of
alumina to be precipitated more readily than when the said chlorides are not used.
When chloride of sodium or chloride of potash is added to the solution phosphate
of alumina alone is precipitated sulphate of soda or sulphate of potash remaining
in the solution which sulphate of soda or sulphate of potash I crystallize out by
boiling down the solution after removing the precipitated phosphate of alumina.
Or instead of boiling down the solution only to crystallizing strength after removing
the precipitated phosphate of alumina, I drive off the muriatic acid by further
heating the remaining solution in a suitable furnace and condense the muriatic acid
so driven off the sulphate of soda or sulphate of potash remaining in a solid state,
When muriate of lime is used the resulting sulphate of lime is either held in solution
or wholly or partially precipitated with the phosphate of alumina according to the
degree to which the acid solution of phosphate of alumina has been diluted. When
the solution is diluted only to a sufficient degree to cause the phosphate of alumina
to be precipitated I remove the sulphate of lime from the remaining solution by
concentrating the latter.
"
"
Or I add salts of lime soluble in water such as are produced by the lixiviation of
"Alkali waste or "vat waste to a solution of phosphate of alumina when
sulphuric acid or muriatic acid or other mineral acid has been used for dissolving
the phosphate of alumina. This addition in the case of a very dilute solution of
the crude phosphate in sulphuric acid causes phosphate of alumina to be precipitated
all or nearly all the lime remaining in solution in the form of sulphate of lime. In
the case of a strong solution of the crude phosphate in sulphuric acid the said
addition causes a precipitate of mixed phosphate of alumina and sulphate of lime.
In the case of a solution of the crude phosphate in muriatic acid the said addition
causes phosphate of alumina to be precipitated whether the said solution be strong
or weak the muriate of lime remaining in solution.
T
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1004

page_text: Improvements in the Manufacture of Precipitated Phosphate
of Alumina and the Mixed Precipitates of Phosphate of
I WILLIAM ARTHUR HILLS of the Chester Chemical Works Saltney in the
County of Flint Manufacturing Chemist do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE MANUFACTURE OF PRECIPITATED PHOSPHATE
OF ALUMINA AND THE MIXED PRECIPITATES OF PHOSPHATE OF ALUMINA AND
SULPHATE OF LIME" and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement:-.
I take the natural or crude phosphate of alumina (such as that found in the
Islands of Rodonda and Alta Vela) either in the raw state or after calcination and
mix it with a suitable acid (preferably sulphuric acid) and thus separate the
phosphate of alumina from the greater part of the iron and the silica contained in
the said natural or crude phosphate of alumina the phosphate of alumina being
dissolved by the acid and the greater part of the iron and silica remaining as an
insoluble residue which residue I separate from the solution of phosphate of
alumina by filtration or decantation or otherwise. I then reduce the gravity of the
solution by diluting it with water either hot or cold until precipitation of the
phosphate of alumina is produced and I remove the precipitate by filtration or
decantation or otherwise. After removing the precipitate from the dilute acid
the latter may be brought to the required strength for use in dissolving further
quantities of the crude phosphate of alumina by boiling the said dilute acid.
To produce precipitation of the phosphate of alumina it is necessary to dilute
the solution to a greater extent if it be treated in a cold state or if cold water be
used to dilute it than if it be treated in a hot state or if hot water be used to dilute
it therefore I prefer to dilute the said solution with hot water or by forcing steam
into it or to heat the said solution after diluting it by forcing into it either steam
or hot air or a mixture of hot air and steam or by other convenient means. The
solution may with advantage be heated nearly or quite to the boiling point.
In some cases, I force air or carbonic acid into the hot or cold diluted solution in
order to facilitate the precipitation of the phosphate of alumina.
I am aware that phosphate of alumina has been' precipitated from an acid"
solution thereof by neutralizing the acid by the addition thereto of its chemical
equivalent of an alkali sufficient alkali being added to neutralize the whole of the
acid holding the phosphate of Alumina in solution and I wish it to be, understood
that the use of alkalies is unnecessary in carrying out the process herein before
described the essential feature of which consists in producing the precipitation of
phosphate of alumina from an acid solution thereof by reducing the gravity of
said solution which remains acid after the whole or the greater part of the
phosphate of alumina has been precipitated therefrom: I do not however, confine
myself to the use of absolutely pure water for diluting the acid solution of
phosphate of alumina as water slightly or naturally impregnated with alkalies may
be used in cases where such water may be more conveniently obtained than water
fl.)
the
.

page_text: .
'
not so contaminated or where from other reasons it may be desirable to use water
80 contaminated the only effect of the presence of an alkali being to neutralize its
chemical equivalent of acid which in such cases is small. Beyond this action of
the alkali present the whole effect of the addition of the contaminated water to
the acid solution is to produce precipitation of the phosphate of alumina by the
reduction of the gravity of the acid solution..
2
When I use sulphuric acid for dissolving the phosphate of alumina I in some
cases add chloride of sodium or chloride of potassium or chloride of lime to the
solution of phosphate of alumina which solution I dilute as hereinbefore described
either before or after the addition of the chloride. The addition of the said
chlorides to the acid solution causes the phosphate of alumina to be precipitated
more readily than when the said chlorides are not used.
When chloride of sodium or chloride of potassium is added to the solution
phosphate of alumina alone is precipitated sulphate of soda or sulphate of potash
remaining in the solution which sulphate of soda or sulphate of potash I crystallize
out by boiling down the solution after removing the precipitated phosphate of
alumina. Or instead of boiling down the solution only to crystallizing strength
after removing the precipitated phosphate of alumina I drive off the muriatic acid
by further heating the remaining solution in a suitable furnace and condense the
muriatic acid so driven off the sulphate of soda or sulphate of potash remaining in
a solid state. A furnace of the kind used for finishing "Salt Cake" is suitable for
this purpose. When muriate of lime is used the resulting sulphate of lime is either.
held in solution or wholly or partially precipitated with the phosphate of alumina
according to the degree to which the acid solution of phosphate of Alumina has
been diluted. When the solution is diluted only to a sufficient, degree to cause the-
phosphate of alumina to be precipitated I remove the sulphate of lime from the
remaining solution by concentrating the latter.
"
Or I add salts of lime soluble in water such as are produced by the lixiviation
of "Alkali waste ΟΙ "vat waste" to a solution of phosphate of alumina when
sulphuric acid or muriatic acid or other mineral acid has been used for dissolving
the phosphate of alumina. The said salts of lime may be added to the solution of
phosphate of alumina either in a solid form or in the form of an aqueous solution.
The addition of the said salts of lime to a solution of the crude phosphate in
sulphuric acid produces a mixed precipitate of phosphate of alumina and sulphate
of lime the quantity or proportion of sulphate of lime precipitated being greater or
less according as the solution of phosphate is strong or weak.
In the case of a solution of the crude phosphate in muriatic acid the addition of
the said salts causes phosphate of alumina to be precipitated whether the said
solution be strong or weak the lime remaining in solution in the form of muriate
of lime.
Having now particularly described and ascertained the nature of my said.
invention and in what manner the same is to be performed I declare that what
I claim is
First-Effecting the precipitation of phosphate of alumina from an acid solution
of phosphate of alumina by reducing the gravity of the solution with water either'
hot or cold.
Secondly-Facilitating the precipitation of phosphate of alumina from an acid
solution thereof by heating the said solution after reducing the gravity of the
solution with water.
Thirdly-Facilitating the precipitation of phosphate of alumina from an acid
solution thereof by blowing atmospheric air or carbonic acid gas through or into
the said solution after reducing the gravity thereof with water and while the said
solution is either hot or cold.
$
Fourthly-The precipitation of phosphate of alumina from a solution thereof in
sulphuric acid by adding to the said solution chloride of sodium or chloride of
potassium or chloride of lime, either before or after reducing the gravity of the
solution with water,

page_text: Fifthly Producing a mixed precipitate of phosphate of alumina and sulphate of
lime by adding chloride of lime to a solution of phosphate of alumina in sulphuric
acid and reducing the gravity of the solution by the addition of water thereto.
Sixthly Adding salts of lime soluble in water (such as are obtained by the
lixiviation of "alkali waste" or "vat waste.") to an acid solution of phosphate of
alumina thereby producing either precipitated phosphate of alumina or mixed
precipitates of phosphate of alumina and sulphate of lime according to the strength
of the solution and the description of acid in which the phosphate of alumina has
been dissolved.
3