IMPROVEMENTS IN OBTAINING CERTAIN SOLUTIONS CONTAINING FREE PHOS- PHORIC ACID
Year: 1884

page_text: I, EDWARD PACKARD, junior, of The Grove House, Bramford, near Ipswich, in
the County of Suffolk, do hereby declare the nature of my said invention for
"IMPROVEMENTS IN OBTAINING CERTAIN SOLUTIONS CONTAINING FREE PHOS-
PHORIC ACID," to be as follows:-
This invention relates to the preparation of solutions containing free phosphoric
acid by decomposing native or other phosphate of lime by sulphuric acid in the
presence of a suitable quantity of water.
When a pure phosphate of lime is treated, in presence of a sufficient quantity of
water, as will be well understood, by more sulphuric acid than the quantity
necessary to convert such of the said phosphate of lime as it reacts upon into
monocalcic phosphate, the product, according to the proportion of sulphuric acid
which has been employed, is a solution of either free phosphoric acid and sulphate
of lime, or of free phosphoric acid, sulphate of lime, and more or less phosphate of
lime, and the said solution holds in suspension either solid sulphate of lime only, or
solid sulphate of lime and a portion of the phosphate of lime treated which has not
been attacked by sulphuric acid. When the phosphate of lime used is an impure
native phosphate, the said solution may also contain phosphate of alumina and
phosphate of iron, and may hold in suspension various solid bodies in addition to
those above mentioned. In what follows, the said solution will be spoken of as
"the phosphoric acid liquor," and the body or bodies which it holds in suspension
will be spoken of as "the solid residue." By "the phosphoric acid liquor" is to be
understood the liquid part of the product of the decomposition of native or other
phosphate of lime by sulphuric acid, employed in such proportion as is above
indicated and in presence of a sufficient quantity of water, the said sulphuric acid
being associated or not with phosphoric acid, and by "the solid residue" is to be
understood the sulphate of lime or mixture of sulphate of lime and other bodies
which the said phosphoric acid liquor at first holds in suspension, according to
circumstances, as above explained.
Before phosphoric acid liquor obtained by decomposing a native or other
phosphate of lime by sulphuric acid as aforesaid can be utilized, it has to be
separated from the said solid residue, and after separation therefrom it has to be
concentrated by evaporation. The solid residue has moreover to be well washed,
and the wash-waters have then to be concentrated by evaporation.

page_text: The object of the present invention is to diminish the present excessive cost for
the evaporation of the said liquor and wash-waters.
I accomplish this object as follows.
Having treated native or other phosphate of lime by the desired proportion of
sulphuric acid, in presence of a sufficient quantity of water, the said sulphuric acid
being associated or not with phosphoric acid, I separate the resulting phosphoric
acid liquor from the solid residue which it holds in suspension by means of wooden
filter-presses. I then subject the said solid residue, while it is still contained in the
said filter-presses, to several but at least two successive washings, using for the
first washing, or for one of the earlier washings when I wash the said residue more
than twice, the dilute phosphoric acid liquor constituted by the wash-waters from a
preceding operation, and then completing the washing with fresh water, the final
wash-waters being then used for the first washing, or for one of the earlier
washings, when more than two washings are performed, of a subsequent quantity
of the said solid residue. The wash-waters from the first washing of each charge
of the said solid residue are thus wash-waters which have passed through the
filter-press at least twice, and which have been used first for the final washing of
one charge of solid residue and afterwards for the first washing of another charge
of the said solid residue. To the wash-waters which have thus been used at least
two successive times, I then add strong sulphuric acid, and I then treat native or
other phosphate of lime by the resulting mixed solution of sulphuric acid,
phosphoric acid, and other body or bodies, as the case may be. I thus obtain a
much stronger phosphoric acid liquor, much less costly for subsequent concentration
by evaporation than is obtained by the method of working in use hitherto. Having
separated this liquor from the solid residue at first suspended in it, by means of
wooden filter-presses as aforesaid, I then repeat the operations already described.
What is new in the present invention thus consists, firstly, in subjecting the
aforesaid solid residue to several but at least two successive washings in wooden
filter-presses, using for the first of the said washings wash-waters from a preceding
operation, and afterwards completing the washing with fresh water, the wash-
waters from the final washing being used for the first or one of the earlier washings
of a subsequent quantity of the said solid residue, and, secondly, in treating native
or other phosphate of lime by the solution obtained by adding strong sulphuric acid
to the liquor yielded by the first washing in wooden filter-presses, as aforesaid, of
the said solid residue, there being used for such first washing wash-waters which
have been employed for one or more of the washings of a previous quantity of
such solid residue.
D

page_text: I, EDWARD PACKARD, junior, of The Grove House, Bramford, near Ipswich,
in the County of Suffolk, do hereby declare the nature of my Invention for
"IMPROVEMENTS IN OBTAINING CERTAIN SOLUTIONS CONTAINING FREE PHOSPHORIC
ACID," 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 preparation of solutions containing free phosphoric
acid by decomposing native or other phosphate of lime by sulphuric acid in the
presence of a suitable quantity of water.
When a pure phosphate of lime is treated, in presence of a sufficient quantity of
water, as will be well understood, by more sulphuric acid than the quantity
necessary to convert such of the said phosphate of lime as it reacts upon into
monocalcic phosphate, the product, according to the proportion of sulphuric acid
which has been employed, is a solution of either free phosphoric acid and sulphate
of lime, or of free phosphoric acid, sulphate of lime, and more or less phosphate of
lime, and the said solution holds in suspension either solid sulphate of lime only,
or solid sulphate of lime and a portion of the phosphate of lime treated which has
not been attacked by sulphuric acid. When the phosphate of lime used is an
impure native phosphate, the said solution may also contain phosphate of alumina
and phosphate of iron, and may hold in suspension various solid bodies in addition
to those above mentioned. In what follows, the said solution will be spoken of as
"the phosphoric acid liquor," and the body or bodies which it holds in suspension
will be spoken of as "the solid residue." By "the phosphoric acid liquor" is to
be understood the liquid part of the product of the decomposition of native or
other phosphate of lime by sulphuric acid, employed in such proportion as is above
indicated, and in presence of a sufficient quantity of water, the said sulphuric acid
being associated or not with phosphoric acid, and by "the solid residue" is to be
understood the sulphate of lime or mixture of sulphate of lime and other bodies
which the said phosphoric acid liquor at first holds in suspension, according to
circumstances, as above explained.
Before phosphoric acid liquor obtained by decomposing a native or other
phosphate of lime by sulphuric acid as aforesaid can be utilized, it has to be
separated from the said solid residue, and after separation therefrom it has to
be concentrated by evaporation. The solid residue has moreover to be well
washed, and the wash-waters have then to be concentrated by evaporation.
The object of the present invention is to diminish the present excessive cost for
the evaporation of the said liquor and wash-waters.
I accomplish this object as follows.
Having treated native or other phosphate of lime by the desired proportion of
sulphuric acid, in presence of a sufficient quantity of water, the said sulphuric acid
being associated or not with phosphoric acid, I separate the resulting phosphoric
acid liquor from the solid residue which it holds in suspension by means of wooden
filter-presses. I then subject the said solid residue, while it is still contained in the
said filter-presses, to several but at least two successive washings, using for the first
washing, or for one of the earlier washings when I wash the said residue more
than twice, the dilute phosphoric acid liquor constituted by the wash-waters from
a preceding operation, and then completing the washing with fresh water, the final
wash-waters being then used for the first washing, or for one of the earlier
washings, when more than two washings are performed, of a subsequent quantity

page_text: of the said solid residue. The wash-waters from the first washing of each charge
of the said solid residue are thus wash-waters which have passed through the filter-
press at least twice, and which have been used first for the final washing of one
charge of solid residue and afterwards for the first washing of another charge of
the said solid residue. To the wash-waters which have thus been used at least two
successive times, I then add strong sulphuric acid, and I then treat native or other
phosphate of lime by the resulting mixed solution of sulphuric acid, phosphoric
acid, and other body or bodies, as the case may be. I thus obtain a much stronger
phosphoric acid liquor, much less costly for subsequent concentration by evaporation,
than is obtained by the method of working in use hitherto. Having separated
this liquor from the solid residue at first suspended in it, by means of wooden
filter-presses as aforesaid, I then repeat the operations already described.
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: Firstly, the method of procedure which consists in subjecting to several
but at least two successive washings in wooden filter-presses the residue which
remains after the liquid part of the product of the treatment of a native or other
phosphate of lime by either sulphuric acid only or by a mixture of sulphuric acid
with phosphoric acid has been separated from the solid body or solid bodies which
that product at first holds in suspension, using for the first of the said washings
wash-waters from a preceding operation, and afterwards completing the washing
with fresh water, the wash-waters from the final washing being used for the first
washing or for one of the earlier washings of a subsequent quantity of the said
solid residue; and, Secondly, the treatment of native or other phosphate of lime by
the solution obtained by adding strong sulphuric acid to the liquor yielded by the
first washing in wooden filter-presses of the aforesaid solid residue, there being
used for such first washing wash-waters which have been employed for one or more
of the washings of a previous quantity of such solid residue."
Dated this 19th day of December 1884.
EDWARD PACKARD, JR.