IMPROVEMENTS IN MANUFACTURING VERY PURE AND RICH SUPERPHOSPHATES OF LIME
Year: 1884

page_text: I, EDWARD PACKARD, junior, of The Grove House, Bramford, near Ipswich, in
the County of Suffolk, Chemical Manufacturer do hereby declare the nature of
my invention for "IMPROVEMENTS IN MANUFACTURING VERY PURE AND RICH
SUPERPHOSPHATES OF LIME" to be. as follows:→
This invention relates to the manufacture from native or other phosphate of
lime of very pure and rich superphosphates.
I first obtain a mixed solution containing monocalcic phosphate and free
phosphoric acid by treating a native or other phosphate of lime by either sulphuric.
acid only, or by a mixture of sulphuric acid with phosphoric acid, in presence of a
sufficient quantity of water, the proportion of sulphuric acid used being such that
of the phosphoric acid of the resulting solution which is not combined with iron
or alumina the greater proportion shall be in the state of monocalcic phosphate and
the remainder as free phosphoric acid. I prefer that about seventy per cent. of
such of the phosphoric acid of the said solution as is not combined with iron or
alumina should be in the state of monocalcic phosphate and about thirty per cent of
it in the free state; but these proportions may be varied within wide limits,
according to the proportion of free phosphoric acid which it is desired should be
contained in the final product.
No special method of performing the said treatment of native or other phosphate
of lime by the said proportion of sulphuric acid, mixed or not with phosphoric
acid, forms any part of this invention. Except as regards proportion of sulphuric
acid, the operation may be conducted in all respects in the same way as the known
operation of treating phosphate of lime by either sulphuric acid only or by a
mixture of sulphuric acid with phosphoric acid for obtaining solutions of free
phosphoric acid only.
The said mixed solution of monocalcic phosphate and free phosphoric acid will at
first be mixed with solid sulphate of lime, and may also be mixed with other solid
bodies. Before the said mixed solution can be treated by my present invention,
the said solid sulphate of lime, and other solid bodies, if any, must be separated.
from it; but no particular method of separating it therefrom constitutes any part
of my present invention. A good method of so separating it, however, though I
do not confine myself thereto, is that by means of filter-presses which is described
J

page_text: for the separation of solution of phosphoric acid from the same solid bodies in the
specification of the patent numbered 2182 of the year 1878. A good method of
washing the said solid bodies, and utilizing their wash-waters, is that described
in the specification of a previous invention of mine an application for a patent for
which was deposited at the Patent Office on the 9th of the current month and is
numbered 6176.
The mixed solution obtained as aforesaid always contains in solution sulphate of
lime, and, if it have been prepared by treatment of a native phosphate of lime, it
will usually contain in solution also phosphate of iron and phosphate of alumina,
while it may also, in certain cases, be contaminated with arsenic. The present
invention consists in so treating the said mixed solution, by a method which has
not been hitherto known, but which I have discovered, as to separate from it
either practically the whole or at least a large part of the sulphate of lime which
it always holds in solution and of the phosphate of iron and phosphate of alumina
which it usually holds in solution also, and in applying to the said mixed solution,
when that solution contains arsenic, and it is desired to obtain a product free from
arsenic, a method of separating arsenic which has not hitherto been applied to such
solutions, though one form of it has been applied to other solutions, and the
possibility of the application of that form of which to the solutions which I propose
to treat thereby has not hitherto been known, but has been discovered as one of the
results of my experiments on the subject, while the other form of it is new, and
in then treating the mixed solution from which there has so been separated either
sulphate of lime only, or sulphate of lime, phosphate of iron, and phosphate of
alumina, or any two of these bodies, or any of these bodies and arsenic also, in
such wise as to obtain a commercial product richer in phosphoric acid and freer
from impurities than any which has hitherto been known in commerce.
The said method of treating the said mixed solution for the separation from it of
sulphate of lime, phosphate of iron, and phosphate of alumina, or of one or more
of these bodies, is based on the discovery which I have made that on heating such
a mixed solution a considerable proportion of its sulphate of lime, and also of its
phosphate of iron and phosphate of alumina, if these bodies were at first contained
in it, precipitates and can be separated either by filtration, or by subsidence and
decantation, or by such other means as may be most convenient in each case; and
that on subsequent evaporation the greater portion of the remainder of these bodies
precipitates and may be separated as aforesaid. I have found that the proportion
of the impurities at first contained in the said mixed solution which can be
separated by a single filtration or other corresponding operation depends to a certain
extent upon the degree of density to which the solution has been evaporated before
that filtration or other equivalent operation is performed. I prefer to evaporate
the said mixed solution until it has a specific gravity of from 1·125 to 1.300 before
separating from it, by filtration or otherwise, the impurities which separate out on
heating it; but I do not confine myself to such degree of concentration. I have
found, however, that a single filtration or other equivalent operation will usually
separate practically the whole of the impurities at first dissolved therein when the
liquor is concentrated to a specific gravity of from. 1.125 to 1.300 before that
filtration or other corresponding operation is performed, whereas when the first
filtration or other method of removing the impurities which have separated in the
solid state is performed before the mixed solution has reached that degree of
concentration, a considerable further precipitate will form during its subsequent
further concentration by evaparation, and so two or more successive filtrations
or other equivalent operations be necessary in order to a practically complete
purification.
It is advantageous, though not essential, to perform the separation of the
precipitated impurities, by filtration or otherwise, while the liquor is still hot.
The mixed solution from which impurities have thus been separated may now
be evaporated directly to such degree of dryness as to permit of its. delivery to
commerce, or its evaporation may be interrupted once or oftener for the separation,

page_text: by filtration or otherwise, of any further impurities which may precipitate during
such evaporation.
The evaporation of the said mixed solution may be conveniently performed,
though I do not confine myself to any particular means or method of performing
it, in wood tanks lined with lead and heated by means of steam-coils of lead pipe.
If sulphuric acid centaining arsenic have been used for preparing the said mixed
solution of monocalcic phosphate and free phosphoric acid, the latter will contain
arsenic. In such case, when it is desired to obtain a final product free from arsenic,
I either treat the said mixed solution, at any stage of the operation which may be
most convenient, by a current of sulphuretted hydrogen, or I add thereto a suitable
sulphide, such as sulphide of calcium or sulphide of sodium. The residual product
known as alkali-waste may be used for this purpose. The arsenic is thereby
precipitated, and may be separated by filtration or other equivalent means. By
performing the said treatment by sulphuretted hydrogen or by a suitable metallic
sulphide before the filtration or one of the filtrations or other corresponding
operation or operations for the separation of other impurities above described, the
necessity for a special filtration for the removal of the arsenic will be avoided.
What is new in this invention thus consists in obtaining from native or other
phosphate of lime products richer in phosphoric acid and freer from impurities
than any which have hitherto been manufactured, by treating native or other
phosphate of lime by either sulphuric acid only, or by a mixture of sulphuric
acid with phosphoric acid, in presence of a sufficient quantity of water, as will be
well understood, the proportion of sulphuric acid employed being such that of the
phosphoric acid in the resulting solution which is not in the state of phosphate of
iron or phosphate of alumina a portion shall be in the state of monocalcic phosphate
and the remainder in the state of free phosphoric acid, the latter being in such
proportion to the former as may be preferred in each particular case, then separating
the liquid part of the product from the solid or solids with which it is at first
mixed, heating the liquid part to determine a precipitation of sulphate of lime,
phosphate of iron, and phosphate of alumina, or of one or more of these bodies,
then separating this precipitate by filtration or otherwise, and then evaporating the
purified liquor to a suitable degree of dryness; interrupting this operation, when
need be, to separate any further precipitate which may form during it, these
methods of procedure being combined, when the case requires, with the method of
separating arsenic from the mixed solution of monocalcic phosphate and free
phosphoric acid which consists in either treating that mixed solution by a current
of sulphuretted hydrogen or adding to it either alkali-waste or a specially prepared
sulphide, such as sulphide of calcium or sulphide of sodium.

page_text: '
I, EDWARD PACKARD, junior, of The Grove House, Branford, near Ipswich,
in the County of Suffolk, do hereby declare the nature of my Invention for
"IMPROVEMENTS IN MANUFACTURING VERY PURE AND RICH SUPERPHOSPHATES
OF LIME," 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 from native or other phosphate of lime
of very pure and rich superphosphates.
F
I first obtain a mixed solution containing chiefly monocalcic phosphate and free
phosphoric acid by treating a native or other phosphate of lime by either sulphuric
acid only, or by a mixture of sulphuric acid with phosphoric acid, in presence of a
sufficient quantity of water, the proportion of sulphuric acid used being such that
of the phosphoric acid of the resulting solution which is not combined with iron or
alumina the greater proportion shall be in the state of monocalcic phosphate and
the remainder as free phosphoric acid. I prefer that about seventy per cent. of
such of the phosphoric acid of the said solution as is not combined with iron or
alumina should be in the state of monocalcic phosphate and about thirty per cent.
of it in the free state; but these proportions may be varied within wide limits,
according to the proportion of free phosphoric acid which it is desired should be
contained in the final product.
No special method of performing the said treatment of native or other phosphate
of lime by the said proportion of sulphuric acid, mixed or not with phosphoric acid,
forms any part of this invention. Except as regards proportion of sulphuric acid,
the operation may be conducted in all respects in the same way as the known
operation of treating phosphate of lime by either sulphuric acid only or by a
mixture of sulphuric acid with phosphoric acid for obtaining solutions of free
phosphoric acid only.
The said mixed solution of monocalcic phosphate and free phosphoric acid will at
first be mixed with solid sulphate of lime, and may also be mixed with other solid
bodies.. Before the said mixed solution can be treated by my present invention,
the said solid sulphate of lime, and other solid bodies, if any, must be separated
from it; but no particular method of separating it therefrom constitutes any part
of my present invention. A good method of so separating it, however, though I do
not confine myself thereto, is that by means of filter-presses which is .described for
the separation of solution of phosphoric acid from the same solid bodies in the
specification of the patent numbered 2182 of the year 1878. A good method of
washing the same solid bodies, and utilizing their wash-waters, is that described
in the specification of a previous invention of mine an application for a patent
for which was deposited at the Patent Office on the 9th April, 1884, and numbered
6176.
The mixed solution obtained as aforesaid always contains in solution sulphate of
lime, and, if it have been prepared by treatment of a native phosphate of lime, it
will usually contain in solution also phosphate of iron and phosphate of alumina,
while it may also, in certain cases, be contaminated with arsenic. The present
invention consists partly in so treating the said mixed solution, by a method which
has not been hitherto known, but which I have discovered, as to separate from it
either practically the whole or at least a large part of the sulphate of lime which it
always holds in solution and of the phosphate of iron and phosphate of alumina
which it usually holds in solution also, and in applying to the said mixed solution,
when that solution contains arsenic, and it is desired to obtain a product free from

page_text: arsenic, a method of separating arsenic which has not been applied to such solutions,
though one form of it has been applied to other solutions, and the possibility of the
application of that form of which to the solutions which I propose to treat thereby
has not hitherto been known, but has been discovered as one of the results of my.
experiments on the subject, while the other form of it is new, and in then treating
the mixed solution from which there has so been separated cither sulphate of lime
only, or sulphate of lime, phosphate of iron, and phosphate of alumina, or any two
of these bodies, or any of these bodies and arsenic also, in such wise as to obtain a
commercial product richer in phosphoric acid and freer from impurities than any
which has hitherto been known in commerce.
The said method of treating the said mixed solution for the separation from it of
sulphate of lime, phosphate of iron, and phosphate of alumina, or of one or more of
these bodies, is based on the discovery which I have made that on heating such a
mixed solution a considerable proportion of its sulphate of lime, and also of its
phosphate of iron and phosphate of alumina, if these bodies were at first contained
in it, precipitate and can be separated either by filtration or by subsidence and
decantation, or by such other means as may be most convenient in each case; and
that on subsequent evaporation the greater portion of the remainder of these bodies
precipitates and may be separated as aforesaid. I have found that the proportion.
of the impurities at first contained in the said mixed solution which can be
separated by a single filtration or other corresponding operation depends to a
certain extent upon the degree of density to which the solution has been'
evaporated before that filtration or other equivalent operation is performed.
I prefer to evaporate the said mixed solution until it has a specific gravity of
from 1125 to 1.300 before separating from it by filtration or otherwise the
impurities which separate out on heating it; but I do not confine myself to such
degree of concentration. I have found, however, that a single filtration or other
equivalent operation will usually separate practically the whole of the impurities
at first dissolved therein when the liquor is concentrated to a specific gravity of
from 1.125 to 1.300 before that filtration or other corresponding operation is per-
formed, whereas when the first filtration or other method of removing the impurities
which have separated in the solid state is performed before the mixed solution has
reached that degree of concentration, a considerable further precipitate will form
during its subsequent further concentration by evaporation, and so two or more
successive filtrations or other equivalent operations be necessary in order to a
practically complete purification.
It is advantageous, though not essential, to perform the separation of the
precipitated impurities, by filtration or otherwise, while the liquor is still hot.
The mixed solution from which impurities have thus been separated may now be
evaporated directly to such degree of dryness as to permit of its delivery to com-
merce, or its evaporation may be interrupted once or oftener for the separation, by
filtration or otherwise, of any further impurities which may precipitate during such
evaporation.
The evaporation of the said mixed solution may be conveniently performed,
though I do not confine myself to any particular means or method of performing
it, in wood tanks lined with lead and heated by means of steam coils of lead pipe.
If sulphuric acid containing arsenic have been used for preparing the said mixed
solution of monocalcic phosphate and free phosphoric acid, the latter will contain
arsenic. In such case, when it is desired to obtain a final product free from
arsenic, I either treat the said mixed solution, at any stage of the operation
which may be most convenient, by a current of sulphuretted hydrogen, or I add
thereto a suitable sulphide, such as sulphide of calcium or sulphide of sodium,
The residual product known as alkali-waste may be used for this purpose. The
arsenic is thereby precipitated, and may be separated by filtration or other
equivalent means. By performing the said treatment by sulphuretted bydrogen or
by a suitable metallic sulphide before the filtration or one of the filtrations or other

page_text: corresponding operation or operations for the separation of other impurities above,
described, the necessity for a special filtration for the removal of the arsenic will
be avoided.
"
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 the manufacture from native or other phosphate of lime of products
very rich in phosphoric acid and of a high degree of purity, by treating native or
other phosphate of lime by either sulphuric acid only, or by a mixture of sulphuric
acid with phosphoric acid, in presence of a sufficient quantity of water, as will be
well understood, the proportion of sulphuric acid employed being such that of the
phosphoric acid in the resulting solution which is not in the state of phosphate of
iron or phosphate of alumina a portion shall be in the state of monocalcic phosphate
and the remainder in the state of free phosphoric acid, the latter being in such
proportion to the former as may be preferred in each particular case, but being.
preferably from about one-fourth to about one-third of the total phosphoric acid
present in solution otherwise than as phosphate of iron and phosphate of alumina,
then separating the liquid part of the product from the solid or solids with which
it is at first mixed, then heating the liquid part to determine a precipitation of
sulphate of lime, phosphate of iron, and phosphate of alumina, or of one or more of
these bodies, then separating this precipitate by filtration or otherwise, and then
evaporating the purified liquor to a suitable degree of dryness, interrupting this
operation, when need be, to separate any further precipitate which may form
during it these methods of procedure being combined, when the case requires, with
the method of separating arsenic from the mixed solution of monocalcic phosphate
and free phosphoric acid which consists in either treating that mixed solution by a
current of sulphuretted hydrogen or adding to it either alkali-waste or a specially
prepared sulphide, such as sulphide of calcium or sulphide of sodium.
100
ן.