IMPROVEMENTS IN THE TREATMENT OF MINERAL PHOSPHATES FOR AGRICUL- TURAL AND MANUFACTURING PURPOSES
Year: 1877

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for the Invention of
"IMPROVEMENTS IN THE TREATMENT OF MINERAL PHOSPHATES FOR AGRICUL-
TURAL AND MANUFACTURING PURPOSES." A communication from abroad by
the Th. Pilter Company, of Paris, France.
aléd the 22nd September 1877, and dated the 10th July 1877.
PROVISIONAL SPECIFICATION left by the said William Robert Lake at
the Office of the Commissioners of Patents on the 10th July 1877.
"
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. IMPROVEMENTS IN THE TREATMENT OF MINERAL
PHOSPHATES FOR AGRICULTURAL AND MANUFACTURING PURPOSES." [A communica
tion from abroad by the Th. Pilter Company, of Paris, France.]
The present Invention has for its object a complete process of treating phosphated
minerals, for their utilisation for agricultural and manufacturing purposes. This
process comprises,―
First. The application of sulphurous acid with the object, on the one hand, of
eliminating the carbonate of lime, and, on the other, of extracting the phosphoric
acid under the form of monobasic phosphate of lime in solution.
Second. The treatment of these solutions for the purpose of preparing either bibasic
phosphate of lime called precipitate or superphosphate or phosphorus.
This process is based principally on the mode of action of the sulphurous acid,
according as it is employed in a close vessel under a high pressure or in an open
vessel under atmospheric pressure.
In the first case the sulphurous acid dissolves not only the carbonate of lime, but,
moreover, carries off two equivalents of lime or insoluble tribasic phosphate, and
transforms it into soluble monobasic phosphate. This reaction is expressed by the
following equation..
Ph 0; 3 Ca O+ n (Ca O CO²) + 1 + 2 (SO) + n (HO)
+ 2 (Ca O, SO²) + n (CO2) + 'n - 2 (HO):
[Price 4d.]
-

page_text: In the second case the sulphurous acid carries off only the carbonate of lime,
leaving intact the tribasic phosphate, as indicated by the following formula :-
Ph O5, 3 Ca 0 + n (Ca O, CÔ) + n (SO) : Ph 0 3 Ca 0+ n (Ca O, S O³)
+ n (CO2).
=
In both cases sulphite of lime is obtained as a sub-product, an article already
largely employed in certain manufactures, and susceptible of considerable appli-
cation.
The first mode of treatment has reference to natural phosphates containing less
than 25 per cent. of carbonate of lime, and of which the gangue or veinstone is
almost entirely insoluble in sulphurous acid.
The second mode of treatment is intended for the enrichment of natural
phosphates designated by the name of phosphated chalk, that is to say, poor rocks
containing from 20 to 35 per cent. of phosphate, the remainder being almost
exclusively formed of carbonate of lime. In fact, the carbonate of lime (which
may attain therein the proportion of 70 per cent.) being transformed into soluble
sulphite the tribasic phosphate remains almost pure, or at least at 90 per cent.
It is understood that these phosphates thus enriched may be like all the varieties
of natural phosphates, whether rich or poor, treated with sulphurous acid at high
pressure, to be transformed into monobasić phosphate in solution, which may be
used either in the manufacture of superphosphates or the manufacture of bibasic
phosphate of lime or of phosphorus, as herein-after explained.
Having thus briefly pointed out the object of my Invention I will now proceed
to describe the manner of carrying the same into effect.
In the treatment of the phosphates by sulphurous acid under pressure, phosphated
rocks, whatever may be their nature and their richness in phosphate, are roughly
crushed and introduced into a closed receiver of cast iron, in which they are
attacked by means of a solution saturated with sulphurous acid. A cylinder
plunger, actuated by steam, rises and falls alternately in order to vary constantly
the level of the liquid in the apparatus, and thereby renew the surfaces of contact
to stimulate the action and to detach the insoluble matters (the sand and the slate)
which fall to the bottom of the receiver. This operation is effected advantageously
under pressure in consequence of the disengagement of the carbonic acid, and when
the sulphurous acid with which the water was charged is nearly saturated and
transformed into sulphite of lime the liquid is made to run off, and is carefully
collected; then it is replaced by a new solution of sulphurous acid. The operation
is thus continued by substituting fresh rock for that dissolved and carried off by
the acids.
At their exit from the dissolving apparatus the liquids are collected in a series of
wooden tubs where they deposit the sand and the slate carried off in suspension.
These tubs are arranged in steps, and in such manner as to permit a rapid and easy
decantation of the clear liquids. These clear liquids, containing now only dissolved
sulphite and monobasic phosphate of lime, are poured into vessels of a special
construction, and raised to boiling point either by means of the lost heat from the
furnaces, or by a circulation of steam in metal worms. This operation has for its
object the elimination of the sulphite of lime, which is precipitated in the form of
small white crystals in proportion as the excess of sulphurous acid, by means of
which it was dissolved, is disengaged from the liquids under the action of heat.
The excess of sulphurous acid being completely driven off the liquid is allowed to
cool;
then the sulphite of lime is separated by decantation, then by turbinage, and
finally a solution is obtained containing only monobasic phosphate of lime. It is
this solution which is used either for the preparation of superphosphates, or for the
preparation of bibasic phosphate of lime, or for the preparation of phosphorus.
In the production of the superphosphates of lime of different descriptions by
means of a solution, suitably concentrated, of monobasic phosphate of lime, and of
burnt and ground gypsum or plaster of Paris, I proceed as follows:-
Having obtained solutions more or less diluted of monobasic phosphate of lime
free from the sulphite of lime, as above explained, I concentrate them to varying

page_text: degrees, according to the desired strength of the superphosphates. For this purpose
I employ either apparatus called treble-acting for evaporation in vacuo, or, by
preference, furnaces of the well-known "Porrion" class, by means of which 12 and
13 kilogrammes of water are evaporated for one kilogramme of coal burned.
In order to prepare rich superphosphates containing 20 to 22 per cent. of phos-
phoric acid really soluble in water I concentrate the solution to a syrupy consistence,
that is to say, between 45 and 50° Beaumé.
Whatever may be the degree of concentration of the solutions I incorporate
therewith plaster of Paris, or gypsum burnt and ground, in quantity sufficient to
absorb the water in excess and to solidify the mass. After about 24 hours this
mass will be dry and very friable, and can be very easily divided.
For the purpose of avoiding the formation of bibasic phosphate of lime insoluble
in water it is indispensable to employ gypsum free from carbonate of lime.
In case
this condition cannot be complied with it will be necessary to add to the solution of
monobasic phosphate a small quantity of sulphuric acid proportioned to the quantity
of carbonate of lime contained in the gypsuin, and which will have to be converted
into sulphate of lime in order to avoid all retrogradation of the soluble phosphoric
acid.
This improved manufacture of the superphosphates presents the following incon-
testable advantages, namely
--
First. The utilisation of poor phosphated rocks, however small their strength, in
phosphoric acid, the composition of the products obtained being independent of the
nature and richness of the rocks treated.
Second. The establishment of the work of production upon the very places of
extraction of the phosphates, and avoiding the necessity of transport of the raw
material.
Third. The complete avoidance of the employment of sulphuric acid, the use of
which is inconvenient, dangerous, and very expensive.
Fourth. The avoidance of the pulverisation and sifting of the phosphated rocks
to be transformed into superphosphates.
Fifth. The incorporation of the natural sulphite of lime, that is to say, in the
state of gypsum, and which has a value much less than that produced by means of
sulphuric acid by the processes at present in use for the manufacture of super-
phosphates.
Sixth. The obtainment of a sub-product, that is to say, sulphite of lime, suscep-
tible of the most numerous and varied applications.
Seventh. Finally, the production of superphosphates in which the whole of the
phosphoric acid is really soluble in water, and not susceptible of retrogradation,
even after the lapse of years.
In the production of the bibasic phosphate of lime called precipitate the solution
of monobasic phosphate of lime may be precipitated cold by means of a lime wash;
but it is preferable to bring it to boiling heat by means of an injection of steam,
then to add to it a sufficient quantity of lime in dust, which precipitates the whole
of the phosphoric acid to the state of bibasic phosphate of lime. The phosphated
chalk, suitably burnt like limestone, can be substituted for the lime in the operation
of precipitation. A mixture is thus obtained of bibasic and tribasic phosphates.
In the application of the processes based upon sulphurous acid to the preparation
of phosphorus I obtain the following advantages, namely:-Simplification of the
labor, economy in the manufacture, and production of the phosphorus by means of
poor phosphated rocks.
During the last two or three years phosphorus has been manufactured from
mineral phosphates, but this manufacture is being abandoned by reason of the
impossibility of procuring rich phosphates of 75 or 80 per cent. at a reasonable cost.
The application of my processes allows me to produce phosphorus with rocks
phosphated with less than 5 per cent. of phosphoric acid. As regards this manu-
facture the application of my processes presents the following advantages:-
First. The faculty of utilising any kind of phosphates.

page_text: :
Second. The avoidance of their treatment by sulphuric acid.
Third. The avoidance of multiple filtrations having for their object the elimination
of the sulphate of lime.
Fourth. The simplification of the labor, the liquors I employ containing neither
sulphur nor sulphuric acid; of which the necessary elimination presents the most
serious difficulties.
I shall now describe the treatment of the phosphates by sulphurous acid at the
norinal pressure of the atmosphere. This mode of treatment, of which the principal
object is to increase the relative proportion of the tribasic phosphate of lime in
consequence of the elimination of the carbonate of lime with which it is associated,
is only applicable to certain varieties of natural phosphates wherein the dominating
matter is the carbonate of lime. These rocks are known by the name of carbonated
phosphated lime, phosphated limestone, and phosphated chalk.
To separate the carbonate of lime and leave intact the tribasic phosphate
conformably to the formula given at the commencement hereof, the following is the
manner of proceeding:-The phosphated rock is mechanically pulverised, and then
passed through a sieve about No. 60 mesh. If the said rock contains enough
carbonate of lime this preliminary operation will be unnecessary; in fact, by
burning it the same manner as limestone a product is obtained crumbling by
contact with water, that is to say, a product possessing the properties of lime itself.
In this case the rock is hydrated after burning to the suitable point for reducing it
to dust; then it is sifted to separate foreign substances, principally flint.
The matter reduced to powder by one or other of the processes above specified is
treated in wooden tubs provided with mechanical agitators by a concentrated
solution of sulphurous acid; or I may employ gaseous sulphurous acid.
The carbonate of lime dissolves by disengaging from the carbonic acid and
passing into the state of soluble sulphite of lime.
As to the tribasic phosphate of lime remaining intact it is deposited at the bottom
of the tubs, where it is collected.
The washing and drying of the tribasic phosphate, as well as the treatment of
the liquors charged with sulphite of lime, are effected as above described.
According to the composition of the rocks operated upon I obtain, as the result
of my process, a product containing from 80 to 95 per cent. of real tribasic
phosphate completely free from carbonate of lime.
With regard to sulphurous acid I have in the above description supposed it to be
employed in the forin of an aqueous solution; but I may employ it either in a
liquid or gascous state, according to the cases and the conditions in which it is to be
operated upon.
I may also adapt the above process, based upon the action of sulphurous acid, in
the treatment of minerals and carbonated or oxidized ores of all kinds :-
First. To isolate and separate the utilisable base of a carbonate or of any mineral
oxide whatever, and to disencumber it from the insoluble gangues in the sulphurous
acid.
And, Secondly. To disengage insoluble substances in sulphurous acid from a
carbonate or any mineral oxide with which they are intimately mixed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Robert Lake in the Great Seal Patent Office on the 9th
January 1878..
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. .." IMPROVEMENTS IN THE TREATMENT OF MINERAL
PHOSPHATES FOR AGRICULTURAL AND MANUFACTURING PURPOSES." A communica-
tion from abroad by the Th. Pilter Company, of Paris, France.
This Invention relates to the treatment of mineral phosphates for agricultural
and manufacturing purposes.
It consists in the employment of sulphurous acid for the extraction of phosphoric
acid in the shape of monobasic phosphate of lime in solution, and the treatment of
such solution for the purpose of preparing either bibasic phosphate of lime or
superphosphate or phosphorus.
The process is mainly based upon the mode of action of sulphurous acid in closed
vessels under high pressure.
The sulphurous acid dissolves the carbonate of lime, and deprives the insoluble
tribasic phosphate of two equivalents of lime, and transforms the same into mono-
basic phosphate of lime in solution. This reaction may be expressed by the following
formula:
PhO, 3 CaO + n (Ca 0, CQ) + n + 2 (SO) + n(EO)
= Ph 05, Ca O, 2 HO
A sub-product of sulphite of lime is tlius obtained, which article is. already
applied in certain manufactures, and is susceptible of more extensive applications.
Having thus summarily indicated the object of the said Invention I shall now
proceed to describe the manner in which the same is or may be carried into effect.
The mineral phosphates, whatever be their nature or richness in phosphate, are
coarsely broken up and put into a receiver or closed vessel of cast iron, in which
vessel they are attacked by means of a saturated solution of sulphurous acid. A
piston of special construction, actuated by steam, alternately rises and falls within
the receiver in order constantly to vary the height of the liquid, and thus to renew
the surfaces of contact and increase the action, and detach the insoluble matters
which fall to the bottom of the receiver. This operation is effected under pressure
in consequence of the disengagement of carbonic acid gas from the carbonate of lime
contained in variable proportions in nearly all classes of phosphates, which carbonic
acid gas is allowed to accumulate in the apparatus and to give the pressure required.
But I may use any other means of obtaining the pressure, and notably by the
injection and compression in the receiver containing the phosphates of sulphurous
acid in a gaseous form. When the sulphurous acid is saturated and transformed
into sulphite of lime the liquid is allowed to run out of the receiver (care being
taken to collect it), and is replaced by a fresh solution of sulphurous acid.
operation may thus be continued indefinitely by replacing from time to time the
phosphated rock which is dissolved and carried off with the acid.
+ n + 2 (CaO, SO) + n(CO) + n 2 (HO).
The
On leaving the receiver the liquids are collected in a series of wooden tubs, where
they are allowed to deposit the sand and clay which are carried along mechanically.
These tubs are arranged in gradients so as to allow of the successive overflow and
consequent easy and rapid clarification of the liquid.. Any other means by which
the same result is obtained may be employed. The clear liquids, containing only
sulphite of lime and monobasic phosphate of lime in solution, are poured into.
suitable receivers, and boiled by means of steam admitted into metal pipes. This
operation has for its object the elimination of the sulphite of lime, which precipitates
in the shape of small white crystals as fast as the excess of sulphurous acid is
expelled from the liquid by the action of heat. I may employ any other means for
eliminating the sulphite of lime, and, notably, by double decomposition, or by the
injection of air in and through the liquids raised to a suitable temperature. The
excess of sulphurous acid being thus driven off, which is easily ascertained by the

page_text: odour, the liquid is allowed to cool.
It is then separated from the sulphite of lime
by decantation, and then by centrifugal machines; and, finally, a solution is
obtained which contains only monobasic phosphate of line. This is the solution
which is used in the preparation of superphosphates of bibasic phosphate of lime
and of phosphorus.
I shall now proceed to examine these three manufactures in the order stated.
FIRST. To prepare superphosphates containing from twenty to twenty-two per
cent. of phosphoric acid soluble in water I concentrate by evaporation in suitable
apparatus the monobasic phosphate of lime, obtained as above, until it acquires a
syrupy consistency, say of 45° to 50° Baumé.
Whatever may be the degree of the solutions (and they may and should vary
according to richness of the superphosphate to be obtained) anhydrous plaster of
paris, obtained by calcination, is incorporated therein in sufficient quantity to absorb
the excess of water and solidify the mass. In about twenty-four hours the mass
becomes dry and friable, and may then be reduced or divided with the utmost
facility.
To avoid the formation of bibasic phosphate of lime, which is insoluble in water,
it is necessary to use plaster which is free of carbonate of lime; but if such cannot
be obtained a small quantity of sulphuric acid should be added to the solution of
monobasic phosphate, a quantity proportionate to the quantum of carbonate of lime
contained in the plaster, which carbonate is thereby converted into sulphate of lime,
thus obviating retrogradation of the soluble phosphoric acid.
This process of manufacture of superphosphates offers the following advantages:-
First. Utilization of phosphated rocks, however small the quantity of phosphoric
acid contained therein may be, the composition of the product obtained being
wholly independent of the nature or richness of the rocks.
Secondly. Facility of establishing works in the locality where the phosphates
are extracted, thereby saving cost of transportation.
Thirdly. Dispensing, except in the case above referred to, with the use of
sulphuric acid.
Fourthly. Dispensing with the pulverization of the mineral phosphates.
Fifthly. Incorporation of sulphate of lime in the form of plaster of Paris, the
cost of which is much less than that obtained by means of sulphuric acid employed
in processes in use for the manufacture of superphosphates.
Sixthly. The obtaining, as a sub-product, of the sulphite of line which is being
used in various manufactures, and is susceptible of further considerable application.
Seventhly. The production of superphosphates in which all the phosphoric acid is
soluble in water and not susceptible of retrogradation, even after the lapse of
several years.
SECONDLY. As to bibasic phosphate of lime. The solution of monobasic phosphate
of lime may be precipitated by means of lime water. This can be done at the
ordinary temperature; but I deem it preferable to boil the solution by means of
jets of steam admitted to and through the mass, and to add afterwards sufficient
quantity of lime in powder, which will precipitate all the phosphoric acid in the
state of bibasic phosphate of lime or a mixture of bibasic and tribasic phosphate
of lime.
THIRDLY. As to phosphorus. It was recently attempted to manufacture phos-
phorus from mineral phosphates, but the manufacture hail to be abandoned because
of the difficulty or impossibility of obtaining rich phosphates containing seventy-five
to cighty per cent. of tribasic phosphate of lime at a reasonable price.
The use of my process renders this manufacture possible and profitable with
phosphated rocks containing as little as ten per cent. of tribasic phosphate of lime.
The application of my process to this manufacture presents the following
advantages:-
First. Utilization of the poorest class of phosphates.
Secondly. Avoidance of treatment by sulphuric acid.
Thirdly. Avoidance of repeated filtrations having for their object the elimination
of the sulphate of lime.

page_text: Fourthly. Simplification of the operation in so far as the liquids treated upon
contain neither sulphur nor sulphuric acid, the elimination of which always presents
serious difficulties.
I have described the use of sulphurous acid in the shape of an aqueous solution
but by modifications of apparatus, and according to circumstances, sulphurous acid
may be used either in the liquefied or the gaseous form.
I would observe also that the process based upon the action of sulphurous acid is
applicable to the treatment of minerals, which are carbonates or oxides, for isolating
and separating their utilizable base, and freeing it of " gangues insoluble in
Bulphurous acid.
33
Having thus fully described the said Invention as communicated to me by my
foreign correspondents, and the manner of performing the same, I wish it-understood
that I claim,
First. The process herein described of transforming tribasic phosphate of lime
into monobasic phosphate of lime in solution by the treatment of natural phosphates
in closed vessels under high pressure by means of sulphurous acid, substantially as
herein described.
Second. The manufacture of rich superphosphates by treating monobasic phos-
phate of lime in solution obtained by the sulphurous acid process, and concentrated
by evaporation, and by the addition of anhydrous plaster of Paris, substantially as
herein described.
Third. The manufacture of phosphorus by the use and application of monobasic
phosphate of lime in solution obtained by the sulphurous acid treatment, substan-
tially as herein described.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Ninth day of January, in the year of our Lord One
thousand eight hundred and seventy-eight.
W. ROBT, LAKE. (L.S.)