IMPROVEMENTS IN OBTAINING FROM NATIVE OR OTHER PHOSPHATE OF LIME PRODUCTS RICH IN PHOSPHORIC ACID AND OF A HIGH DEGREE OF PURITY
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
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 OBTAINING FROM NATIVE OR OTHER
PHOSPHATE OF LIME PRODUCTS RICH IN PHOSPHORIC ACID AND OF A HIGH
DEGREE OF PURITY" to be as follows:-
This invention relates to the manufacture from native or other phosphate of
lime of products very rich in phosphoric acid and of a high degree of purity.
I first obtain what will hereinafter be called phosphoric acid liquor, by treating
native or other phosphate of lime either by sulphuric acid only, or by a mixture of
sulphuric acid and phosphoric acid, in presence of a sufficient quantity of water.
The methods of performing this treatment will be well understood, and constitute
no part of my invention, and therefore need not be here described.
I prefer to use such proportion of sulphuric acid that the whole or nearly the
whole, but in any case a large part, of the phosphoric acid in the resulting
phosphoric acid liquor shall be in the free state.
The said phosphoric acid liquor will at first be mixed with solid sulphate of lime,
and may be mixed with other solid bodies also. Before that liquor 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 there-
from constitutes any part of my present invention, and I need therefore only say
with respect to such preparation that I prefer, but do not confine myself to, the
method of effecting it, by means of filter-presses with frames of wood, which is
described in the specification of the patent numbered 2182 of the year 1878. I
also prefer, but do not confine myself to, the method of washing the said solid body
or bodies, and of treating and utilizing their wash-waters, which is the subject of
another 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 crude phosphoric acid liquor 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 in certain cases it may also be contaminated by arsenic. The present
invention consists in so treating the said crude phosphoric acid liquor, by a method
n
71

page_text: which has not been hitherto known, but which I have discovered, as to separate
from it either practically the whole or at least an appreciable 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 such
phosphoric acid liquor, when that liquor contains arsenic and it is required to obtain
a product free from arsenic, a method of separating arsenic which has never been
applied to solutions of phosphoric acid, although one form of it has been applied to
other solutions, and the possibility of the application of that form of which to
solutions of phosphoric acid 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 phosphoric acid liquor from which there has been
so 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 crude phosphoric acid liquor for the
separation from it of sulphate of lime, phosphate of iron, and phosphate of alumina,
or of one or more of these, is based on the discovery which I have made that on
adding to such crude phosphoric acid liquor a certain quantity of lime, either as
phosphate of lime, as carbonate of lime, or as free lime, hydrated or not, and then
applying heat, a considerable proportion of the said sulphate of lime, phosphate of
iron, and phosphate of alumina, or of such one or more of these bodies as the crude
phosphoric acid liquor may have contained, is caused to precipitate, and can then
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 present in the crude
phosphoric acid liquor which can be thus separated by a single heating depends.to a
certain extent upon the degree of density of the phosphoric acid liquor treated.
"The weaker that liquor the smaller the proportion of the impurities present which
will precipitate on a single heating; while if the liquor treated be of a certain
density, practically the whole of its impurities will be precipitated by a single
heating.
The proportion of phosphate of lime, carbonate of lime, or free lime to be added
to the crude phosphoric acid liquor will of course vary according to circumstances;
but I find that a proportion which gives very good results is the proportion after
the addition of which from 28. to 30 per cent. of such of the phosphoric acid present
as is not combined with alumina or iron is still in the free state. I do not confine
myself to this proportion, however, since the desired purification of the crude
phosphoric acid liquor can be effected, more or less completely, by means of other
proportions; but the proportion which I have mentioned I have found to combine
advantageously the two conditions of effecting a practically complete purification
and permitting the obtainment of a final product which while very rich in
phosphoric acid shall be in a suitable state for delivery to commerce.
I prefer that the crude phosphoric acid liquor, before being treated by my
invention, should be concentrated until it has a specific gravity of from 1·125 to
1.300. I do not confine myself to such degree of concentration; but I have found
that a crude phosphoric acid liquor of a specific gravity between 1.125. and 1.300,
after the addition to it of phosphate of lime, carbonate of lime, or free lime, as
aforesaid, will usually precipitate practically the whole of its impurities on a single
heating, whereas a weaker liquor precipitates a smaller proportion of its impurities
on a single heating, and can be purified practically completely only by separating
the further precipitate which forms during its subsequent evaporation.
In carrying out this method of treating a crude phosphoric acid liquor, I treat'
the said liquor in vessels which may conveniently be wood tanks lined. with lead,
furnished with steam coils of lead pipe by which to heat their contents.
.

page_text: Having run into such a vessel the crude phosphoric acid liquor to be treated,
I add to it either native or other phosphate of lime, or carbonate of lime, or free
lime, hydrated or not, as aforesaid, in such proportion as I have above indicated, or
in such other proportion as may be preferred, and I then apply heat in order to
determine the required precipitation. When the desired precipitate has formed,
I discontinue the heating, and separate the precipitate either by subsidence and
decantation, or by means of filter-presses, or by any more convenient means as
aforesaid. It is advantageous, but not essential, to perform this operation while
the liquor is still hot.
The liquor which has been separated from the said precipitate has now to be
submitted to evaporation. The means of evaporating such liquors will be well
understood, and constitute no part of the present invention, and therefore need not
be here described. Its evaporation may either be at once continued to such degree
of dryness that the product can be delivered to commerce, or it may be interrupted
once or oftener for the separation of any further precipitate which may have
formed during it.
I find that by these means I can obtain products containing more than 54 per
cent. of soluble phosphoric acid.
If sulphuric acid containing arsenic have been used for preparing the crude
phosphoric acid liquor, the latter will contain arsenic. In such case, when it is
desired to obtain a final product free from arsenic, I either treat the phosphoric
acid liquor, at any stage of the process 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
necessary for the separation of other impurities as above described, the necessity
for a special filtration for the removal of the arsenic is 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 adding to crude phosphoric acid
liquor obtained by treating such native or other phosphate of lime by sulphuric
acid, or by a mixture of sulphuric acid and phosphoric acid, either native or other
phosphate of lime, or carbonate of lime, or free lime, hydrated or not, in such
proportion as to leave a part of the phosphoric acid of the crude phosphoric acid
liquor in the free state after phosphate of lime, carbonate of lime, or free lime has
so been added to it, then applying heat to determine a precipitation of sulphate of
lime, phosphate of iron, and phosphate of alumina, or of one or more of these
bodies, such precipitate being accompanied or not as the case may be by more or
less phosphate of lime and other body or bodies, in then separating this precipitate
by filtration or otherwise, and in then evaporating the purified liquor to a suitable
degree of dryness, interrupting this operation, when need be, once or oftener, 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 phosphoric acid liquor which consists in either treating the phosphoric
acid liquor by a current of sulphuretted hydrogen or adding to the phosphoric acid
liquor 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, Bramford, near Ipswich;
in the County of Suffolk, do hereby declare the nature of my Invention for
"IMPROVEMENTS IN OBTAINING FROM NATIVE OR OTHER PHOSPHATE OF LIME
PRODUCTS RICH IN PHOSPHORIC ACID AND OF A HIGH DEGREE OF PURITY," 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 products very rich in phosphoric acid and of a high degree of purity. .
I first obtain what will hereinafter be called phosphoric acid liquor by treating
native or other phosphate of lime either by sulphuric acid only, or by a mixture of
sulphuric acid. and phosphoric acid, in presence of a sufficient quantity of water.
The methods of performing this treatment will be well understood, and constitute
no part of my invention, and therefore need not be here described.
I prefer to use such proportion of sulphuric acid that the whole or nearly the
whole, but in any case a large part, of the phosphoric acid in the resulting
phosphoric acid liquor shall be in the free state.
The said phosphoric acid liquor will at first be mixed with solid sulphate of lime,
and may be mixed with other solid bodies also. Before that liquor 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 there-
from constitutes any part of my present invention, and I need therefore only say
with respect to such separation that I prefer, but do not confine myself to, the
method of effecting it, by means of filter-presses with frames of wood, which is
described in the specification of the patent numbered.2182 of the year 1878. I
also prefer, but do not confine myself to, the method of washing the said solid body
or bodies, and of treating and utilizing their wash-waters, which is the subject of
another invention of mine, an application for a patent for which was deposited at
the Patent Office on the 9th. April, 1884, and is numbered 6176.
The crude phosphoric acid liquor 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 in certain cases it may also be contaminated by
arsenic. The present invention mainly consists in so treating the said crude
phosphoric acid liquor, 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 an
appreciable 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 such phosphoric acid liquor, when that liquor contains
arsenic and it is required to obtain a product free from arsenic, a method of
separating arsenic which has never been applied to solutions of phosphoric acid,
although one form of it has been applied to other solutions, and the possibility of
the application of that form of which to solutions of phosphoric acid 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 phosphoric acid. liquor from which there has been so 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.

page_text: The said method of treating the said crude phosphoric acid liquor for the
separation from it of sulphate of lime, phosphate of iron, and phosphate of
alumina, or one or more of these, is based on the discovery which I have made that
on adding to such crude phosphoric acid liquor a certain quantity of lime, either as
phosphate of lime, as carbonate of lime, or as free lime, hydrated or not, and then
applying heat, a considerable proportion of the said sulphate of lime, phosphate of
iron, and phosphate of alumina, or of such one or more of these bodies as the crude
phosphoric acid liquor may have contained, is caused to precipitate, and can then
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 present in the crude phosphoric acid liquor which can thus be separated
by a single heating depends to a certain extent upon the degree of density of the
phosphoric acid liquor treated. The weaker that liquor, the smaller the proportion
of the impurities present which will precipitate on a single heating; while if the
liquor treated be of a certain density, practically the whole of its impurities will be
precipitated by a single heating.
The proportion of phosphate of lime, carbonate of lime, or free lime to be added
to the crude phosphoric acid liquor will of course vary according to circumstances;
but I find that a proportion which gives very good results is the proportion after
the addition of which from 28 to 30 per cent. of such of the phosphoric acid
present as is not combined with alumina or iron is still in the free state. I do not
confine myself to this proportion, however, since the desired purification of the
crude phosphoric acid liquor can be effected, more or less completely, by means of
other proportions; but the proportion which I have mentioned I have found to
combine advantageously the two conditions of effecting a practically complete
purification and permitting the obtainment of a final product which while very
rich in phosphoric acid shall be in a suitable state for delivery to commerce.
I prefer that the crude phosphoric acid liquor, before being treated by my
invention, should be concentrated until it has a specific gravity of from 1125
to 1.300. I do not confine myself to such degree of concentration; but I have
found that a crude phosphoric acid liquor of a specific gravity between 1.125
and 1.300, after the addition to it of phosphate of lime, carbonate of lime, or free
lime, as aforesaid, will usually precipitate practically the whole of its impurities on
a single heating, whereas a weaker liquor precipitates a smaller proportion of its
impurities on a single heating, and can be purified practically completely only by
separating the further precipitate which forms during its subsequent evaporation.
In carrying out this method of treating a crude phosphoric acid liquor, I treat
the said liquor in vessels which may conveniently be wood tanks lined with lead,
furnished with steam-coils of lead pipe by which to heat their contents.
Having run into such a vessel the crude phosphoric acid liquor to be treated,
I add to it either native or other phosphate of lime, or carbonate of lime, or free
lime, hydrated or not, as aforesaid, in such proportion as I have above indicated,
or in such other proportion as may be preferred, and I then apply heat in order to
determine the required precipitation. When the desired precipitate has formed,
I discontinue the heating, and separate the precipitate either by subsidence and
decantation, or by means of filter-presses, or by any more convenient means as
aforesaid. It is advantageous, but not essential, to perform this operation while
the liquor is still hot.
The liquor which has been separated from the said precipitate has now to be
submitted to evaporation. The means of evaporating such liquors will be well
understood, and constitute no part of the present invention, and therefore need not
be here described. Its evaporation may either be at once continued to such
degree of dryness that the product can be delivered to commerce, or it may be
interrupted once or oftener for the separation of any further precipitate which may
have formed during it.

page_text: f.
I find that by these means. I can obtain products containing more than 54 per
cent of soluble phosphoric acid.
If sulphuric acid containing arsenic have been used for preparing the crude
phosphoric acid liquor, the latter will contain arsenic. In such case, when it is
desired to obtain a final product free from arsenic, I either treat the phosphoric
acid liquor, at any stage of the process 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
necessary for the separation of other impurities as above described, the necessity
for a special filtration for the removal of the arsenic is 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
rich in phosphoric acid and of a high degree of purity, by taking crude phosphoric
acid liquor which has been obtained by treating such native or other phosphate of
lime by sulphuric acid, or by a mixture of sulphuric acid and phosphoric acid,
adding thereto either native or other phosphate of lime, or carbonate of lime, or
free lime, hydrated or not, in such proportion that of the phosphoric acid contained
in the liquid part of the product a portion shall be in the free state, then applying
heat to determine a precipitation of sulphate of lime, phosphate of iron, and
phosphate of alumina, or of one or more of these bodies, such precipitate being
accompanied or not as the case may be by more or less phosphate of lime and other
body or 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, once or oftener, 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 phosphoric acid liquor
which consists in either treating the phosphoric acid liquor, at any convenient
stage of the operation, by a current of sulphuretted hydrogen, or in adding to the
phosphoric acid liquor either alkali-waste or a specially prepared sulphide, such as
sulphide of calcium or sulphide of sodium.
Dated this 19th day of December 1884.