IMPROVEMENTS IN TREATING CERTAIN PHOSPHATIC MINERALS OR ORES IN ORDER TO OBTAIN USEFUL PRODUCTS
Year: 1876

page_text: LETTERS PATENT to William Edward Robinson, of the Albert Chemical Works,
Church, near Accrington, in the County of Lancaster, Manufacturing Chemist,
for the Invention of "IMPROVEMENTS IN TREATING CERTAIN PHOSPHATIC
MINERALS OR ORES IN ORDER TO OBTAIN USEFUL PRODUCTS."
Sealed the 14th October 1876, and dated the 16th May 1876.
PROVISIONAL SPECIFICATION left by the said William Edward Robinson
at the Office of the Commissioners of Patents on the 16th May 1876.
WILLIAM EDWARD ROBINSON, of the Albert Chemical Works, Church, near
Accrington, in the County of Lancaster, Manufacturing Chemist. "IMPROVEMENTS
IN TREATING CERTAIN PHOSPHATIC MINERALS OR ORES IN ORDER TO OBTAIN USEFUL
PRODUCTS."
My Invention consists of the improvements, herein-after described, in treating
natural phosphates of alumina and natural phosphates of iron, and natural phos-
phates containing both alumina and iron, in order to manufacture phosphoric acid
and its compounds, alum and other compounds of alumina and iron, and other useful
products, by which improvements such products are obtained in a purer state than by
the ordinary process of manufacture.
According to one of the processes constituting my Invention I grind any natural
phosphate of alumina to powder, and digest it in sulpho-muriatic acid until it is
thoroughly dissolved, and decomposition has taken place. Or instead of using
sulpho-muriatic acid I first dissolve the ore in muriatic acid alone, and then add
sulphuric acid in quantity equivalent to the alumina and oxides of iron known to
be present. To the acid solution obtained in either of these ways I add ammonia or
dininoniacal gas liquor, till the whole of the alumina and oxido of iron are precipi-
tated. The precipitate thus obtained I separate by filtration or decantation, and
the residual liquid containing phosphate sulphate and muriate of ammonia may then
be used in the preparation of manures or for other purposes. The precipitate of
oxide of iron and alumina is then dissolved in sulphuric acid, and sulphate of am-
monia or of potash is added, and a solution of sulphate of iron and alumina is thus
obtained, which solution is then concentrated and allowed to cool, when ammonia,
alum, or potash alum, as the case may be, is deposited in crystals. Or instead of
concentrating and cooling the aforesaid solution of sulphate of alumina and iron, as
herein-before described, I precipitate its sulphate of alumina in the state of meal

page_text: by concentrating the said solution and adding just sufficient sulphate of potash or
sulphate of ammonia to cause precipitation, or (in case the sulphuric acid is in
excess) potash alone or ammonia alone. Or instead of redissolving the mixed pre-
cipitate of oxide of iron and alumina in sulphuric acid, as herein-before described, I
digest it in caustic soda when the alumina is dissolved, while the oxide of iron
remains insoluble, and is separated from the solution by filtration or decantation.
The solution containing aluminate of soda may then be decomposed by the addition
of a suitable acid, preferably sulphuric or carbonic acid, when alumina is deposited
and the soda may be recovered by evaporation or otherwise, as sulphate or carbonate
of soda. The deposit of alumina may then be converted by known methods into
sulphate, nitrate, acetate, or other marketable salt of alumina.
The residues of iron obtained in any of the processes herein-before and herein-
after described, may be used in the preparation of disinfectants, deodorants, mor-
dants, and painters' colors, and for other purposes.
According to another of the processes constituting my Invention I roast any
natural phosphate of alumina and grind it to a fine powder and digest it in a solu-
tion of sulphuret of sodium, when the iron is precipitated as black sulphuret of
iron, and the alumina remains in solution as aluminate of soda, and the phosphoric
acid as phosphate of soda. Or instead of treating the said phosphate with the said
solution of sulphuret of sodium, I take the said phosphate, either raw or burnt, and
heat it to dull redness with dry sulphuret of sodium. I thus obtain a mixture of
phosphate of soda, aluminate of soda, and sulphuret of iron, which I lixiviate, thus
obtaining the phosphate of soda and aluminate of soda, in solution, while the
sulphuret of iron remains undissolved.
The solution obtained in either of these ways is then run off and allowed to crys-
tallize, when crystals of phosphate of soda are obtained. If I wish to obtain free
phosphoric acid from the aforesaid solution of phosphate of soda I add thereto sul-
phuric acid in such quantity as to saturate all the alkali present, and removing by
crystallization the sulphate of soda thus formed I have the free phosphoric acid in
the mother liquor, which may be concentrated or otherwise treated. Or instead of
treating the aforesaid solution of phosphate of soda with sulphuric acid, as aforesaid,
I decompose the said solution by the addition of some suitable salt of lime or mag-
nesia, with or without the addition of ammonia or ammoniacal salts, and thus
obtain phosphates of lime or of magnesia, or the double phosphate of magnesia
and ammonia (as the case may be), which substances are very valuable as manures.
In order to obtain salts of alumina from the sediment of alumina and sulphuret
of iron aforesaid, I treat the said sediment with a small quantity of caustic soda,
when the alumina dissolves, leaving the iron behind From the solution of
aluminate of soda thus formed, alum and other commercial salts of alumina may bo
obtained by known methods.
My Invention consists further in digesting the natural phosphates of alumina
(roasted and ground as aforesaid) in a mixture of sulphuret of sodium and caustic
soda instead of treating such phosphates with sulphuret of sodium alono, as
hercin-before described, or with caustic soda alone, as has heretofore been done.
I find the said mixture as efficacious as and more economical than caustic soda
alone, and the use of the said mixture renders the subsequent treatment of the
resulting precipitate with caustic soda, as herein-before described, unnecessary. By
digesting the said phosphates in the said mixture black sulphuret of iron is precipi-
tated and an alkaline solution of hydrate of alumina and phosphate of soda is
obtained. This solution, or the solution of phosphate of soda, hercin-before
referred to, may be treated with a suitable salt, such as chloride of calcium, so as to
obtain a soluble salt of alumina and an insoluble phosphate of lime or phosphate of
limo and chloride of sodium, as the case may be.
According to another of the processes constituting my Invention I digest tho
roasted and ground natural phosphate of alumina in a soluble silicate, such as the
silicate of soda, either in open vessels or under pressure, and thus obtain phosphate
of soda in solution and silicate of alumina as a deposit, or precipitate. I thou filter

page_text: or docant the supernatant liquid from the deposit, which I then decompose with
sulphuric acid, and thus separate the silica from the sulphato of alumina, and I.
propare alum from the said sulphate. The silica may be used to make more silicate
of soda. Or instead of digesting the roasted and ground natural phosphate of
alumina, as described, I fuse the said phosphate with silicate of soda, and lixiviato.
the product and treat the lixivium as herein-before described with reference to the
solution.
According to another of the processes constituting my Invention I mix tho.
roasted and ground natural phosphate of alumina with finely ground silica, and heat
the mixture in cylinders, through which a current of superheated steam is or may.
be passed. I thus obtain free phosphoric acid and a silicate of alumina and iron.
I remove the phosphoric acid by lixiviation with water, and then decompose the
silicate of alumina and iron with muriatic or sulphuric acid, obtaining silica, which
may be used in subsequent operations, and a sulphate or muriate of alumina and
iron, useful for sanitary or tinctorial purposes.
According to another of the processes constituting my Invention I add to tho.
mixture of phosphate of alumina and silica finely ground coke, charcoal, or other
kind of carbon, and heat the mixture, as herein-before described. By thus decom-
posing the phosphoric acid I obtain free phosphorus and the silicate of alumina
and iron aforesaid.
According to another of the processes constituting my Invention I hent in a
suitable vessel the ground natural phosphate of alumina (either raw or roasted), or
ores or minerals containing phosphates of alumina and iron, and pass through it or
them a current of chlorine gas, thus obtaining chlorides of iron and aluminium,
which may be sublimed away, leaving phosphoric acid behind. This process is also
particularly applicable to coprolites, apatites, or phosphorites, which, in common
with phosphates of lime and magnesia, contain phosphates and other salts of
alumina and iron, which much detract from their value for the manufacture of
superphosphate. Such alumina and iron are thus volatilized and removed, a great
improvement being thus effected in the quality of the superphosphate manufactured
from such coprolites or apatites.
According to another of the processes constituting my Invention I dissolve the
roasted and ground natural phosphate of alumina and iron in muriatic acid, and add
common salt, so that the soda it contains may be equivalent to the phosphoric acid
known to be present. I then evaporate the mixture to dryness and heat it gently,
thus obtaining insolulable oxide of iron. On then raising the heat chloride of
aluminium is volatilized, and may be condensed while phosphate of soda remains.
Phosphates of iron, such as vivianite, may bo roasted, ground, and treated either
with a caustic, alkali, or with sulphuret of sodium, or with chlorine, or with silica,
or with silica and carbon, as herein-before described with referenc to natural
phosphates of alumina.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Edward Robinson in the Great Seal Patent Office on the 16th
November 1870.
WILLIAM EDWARD ROBINSON, of the Albert Chemical Works, Church, near
" IMPROVE
Accrington, in the County of Lancaster, Manufacturing Chemist.
MENTS IN TREATING CERTAIN PHOSPHATIC MINERALS OR ORES IN ORDER TO OBTAIN
USEFUL PRODUCTS."
My Invention consists of the improvements, herein-after described, in treating
natural phosphatic minerals or ores containing alumina or iron, or both, in order to
manufacture therefrom phosphoric acid and some of its compounds, and other use-,
ful products, as bye products.

page_text: According to one of the processes constituting my Invention I take natural phos-
phatic minerals or ores containing alumina or iron, or both, and roast them in any
suitable way, and then grind them to a fine powder in a suitable mill. I then
digest this powder in a suitable pan or vessel (having by preference a flat bottom)
with a mixture of a solution of caustic soda and a solution of sulphuret of sodiuin,
at a temperature which should not be lower than, say, 200° Fahrenheit, and I con-
tinue and by preference increase this temperature until the mass becomes pasty and
almost dry. It is desirable that the mass should be kept well stirred during the whole
process in order that the materials may be properly intermixed and the necessary
reactions be facilitated. I vary the proportions of the solutions of caustic soda
and sulphuret of sodium according to the per centages of phosphoric acid, alumina,
and iron in the mineral or ore which I am treating, using sufficient sulphuret of
sodium to render all the iron present insoluble, and using sufficient caustic soda to
dissolve nearly all the phosphoric acid and alumina present. I then remove the
pasty and almost dry mass to a suitable and deeper vessel, in which I add water,
and boil the said mass and water by means of steam or otherwise, stirring it at the
same time until all lumps are broken up. I then allow the mixture to stand some time
in order that the undissolved portions of mineral or ore and the sulphide and oxide of
iron may subside. I then draw off the hot clarified liquid into a suitable crystallizing
vessel, where, if the proper amount of water has been used to boil the aforesaid
pasty mass, the phosphoric acid will crystallize out in combination with the soda,
as tribasic phosphate of soda (trisodic phosphate), leaving aluminate of soda, phos-
phate of alumina, and some phosphate of soda in solution as mother liquor. I draw
off this mother liquor as completely as possible and slightly wash the crystals, in
order to free them as much as possible from alumina or adhering mother liquor, and
I mix the washings with the mother liquor. The washed crystals are the crude
phosphate of soda which I obtain by this process from the mineral or ore. If it be
desired to purify the said crystals further, so as to convert them into the ordinary or
rhombic phosphate of soda of commerce they may be dissolved in water and treated
with a current of carbonic acid gas, which serves the double purpose of precipitating
a small portion of alumina as phosphate of alumina, and converting the solution of
tribasic phosphate of soda (trisodic phosphate) into a solution of a mixture of
ordinary or rhombic phosphate of soda and carbonate of soda, which solution may
after filtration be concentrated so as to crystallize out the ordinary phosphate of
soda (rhombic), and leave a mother liquor containing carbonate of soda in solution.
This inother liquor may be causticized and used again.
The mother liquor and washings from the aforesaid crystals of tribasic phosphate
of soda may be decomposed by the addition of any suitable salt of lime, such as
chloride of calcium, so as to precipitate the phosphoric acid present in the form of
phosphate of lime (tricalcic phosphate), which is a useful commercial product. It
is preferable to wash this precipitate in order to free it from adhering alumina..
The supernatant liquid or filtrate from the phosphate of lime aforesaid will con-
tain aluminate of soda and chloride of sodium. The aluminate of soda may be
decomposed by known means, so as to convert it into an alum or other compound of
alumina.
According to the other process constituting my Invention I take the minerals or
ores, herein-before specified, and after roasting and grinding them as herein-
before described with reference to my first process, I treat them as follows:-
1 digest the powder thus produced in a suitable pan or vessel (having by
preference a flat bottom) with a solution of highly basic silicate of soda, in the
same manner and under the same conditions as that and those described with refer-
ence to my first process.
I vary the proportion of silicate of soda according to the per centage of alumina
contained in the mineral or ore which I am treating, using a sufficient proportion to
extract the phosphoric acid as phosphate of soda, but leaving the alumina and other
constituents of the mineral or ore in an insoluble condition. I then boil the pasty
or nearly dry mass with water, in the manner described in my first process, and-

page_text: allow it to stand, in order that the undissolved and the insoluble residue may subside.
I then draw off the hot clarified liquid and treat it with a suitable acid, such as
sulphuric acid or carbonic acid, which will precipitato the silica which is present as
silicate of soda, and convert the soda in combination with the silica into sulphato
or carbonate of soda. The liquid after filtration will be a solution of ordinary
(rhombic) phosphate of soda and sulphate or carbonate of soda, according as sul-
phuric or carbonic acid has been used. This solution on being concentrated will
yield crystals of the ordinary (rhombic) phosphate of soda. The mother liquor will
contain the sulphate or carbonate of soda, as the case may be, and may be utilized
by well known means.
"
Having now described the nature of my said Invention, and the manner in which
the same is to be performed, I claim as my said Invention,―
Firstly. The treatment of phosphatic minerals or ores containing alumina or iron,
or both, with sulphuret of sodium and caustic soda in solution, essentially as
herein-before described, for the purpose of extracting from such minerals or ores their
phosphoric acid in the form of a phosphate of soda.
Secondly. The treatment of the said minerals or ores with a solution of basic
silicate of soda, essentially as hercin-before described, for the purpose of extracting
from such minerals or ores their phosphoric acid in the form of pliosphate of soda.
In witness whereof, I, the said William Edward Robinson, have hereunto set
my hand and scal, this Fifteenth day of November, in the year of our
Lord One thousand eight hundred and seventy-six.
Witness,
. H. H. MURDOCII,
Staple Inn,
London.
W. E. ROBINSON.
(L.B.)