IMPROVEMENTS IN THE TREATMENT OF CARBONATED MINERAL PHOSPHATES FOR AGRICULTURAL AND MANUFACTURING PURPOSES
Year: 1878

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 CARBONATED MINERAL PHOSPHATES
FOR AGRICULTURAL AND MANUFACTURING PURPOSES." A communication from
abroad by the Th. Pilter Company, of Paris, France.
Sealed the 5th April 1878, and dated the 9th January 1878.
PROVISIONAL SPECIFICATION left by the said William Robert Lake at
the Office of the Commissioners of Patents 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
CARBONATED MINERAL PHOSPHATES FOR AGRICULTURAL AND MANUFACTURING
PURPOSES." [A communication from abroad, by the Th. Pilter Company, of Paris,
France.]
This Invention relates to the treatment of carbonated mineral phosphates for
agricultural and manufacturing purposes.
The process is mainly based upon the mode of action of sulphurous acid employed
in open vessels at the normal atmospheric pressure.
The mode of treatment has for its object the enrichment of natural mineral phos-
phates designated under the name of phosphated chalks or "carbonated phosphated
limes," that is to say, poor phosphates containing from 20 to 25 per cent. of tribasic
phosphate of lime, the balance being formed exclusively of carbonate of lime.
The sulphurous acid removes the carbonate of lime, leaving the tribasic phosphate
intact, as shown by the following formula, that is to say :-
Ph 0, 3 Ca O+ n (Ca O, CO2) + n (SO²) = Ph 0%, 3 Ca 0 + n (Ca O, SO⁹) + n
(CO³).
It will be understood that the carbonate of lime, which sometimes attains the
proportion of 70 per cent., is transformed into a soluble sulphite, and the remainder

page_text: is a tribasic phosphate of lime, which is almost pure, or at least to the proportion of
90 per cent.
The sub-product of sulphite of lime which is obtained is already employed in
certain manufactures, and is susceptible of more extensive applications.
To separate the carbonate of lime and to obtain the tribasic phosphate in
accordance with the formula above given, I proceed as follows:-The phosphated
rock is mechanically pulverized, and put through a fine screen or sieve. If the
mineral contains sufficient carbonate of lime this operation can be dispensed with,
as by roasting or burning (in the same manner as is done with lime) a product is
obtained which, like lime itself, disintegrates in contact with water. In such case
the mineral after roasting is hydrated until it is reduced to powder. It is then
screened through a wire cloth or sieve to separate therefrom foreign bodies mostly
composed of gravel or stones of silex. The matter thus reduced to powder by either
of the processes described is treated in wooden vessels provided with mechanical
stirrers by means of a solution of concentrated sulphurous acid; carbonate of lime
dissolves, setting free carbonic acid gas, and is transformed into soluble sulphite of
lime; the tribasic phosphate of lime falls to the bottom of the vessel. It is then
collected, and washed once or twice; it is afterwards dried as far as possible in
centrifugal machines, and the drying is completed by means of the waste heat from
the furnaces. A product is thus obtained which, according to the composition of
the mineral treated, yields from 80 to 95 per cent. of tribasic phosphate of lime,
which is entirely free from carbonate of lime.
The liquids charged with sulphite of lime are poured into suitable receivers, and
boiled by means of steam admitted into jackets or pipes, or by any other suitable
means. The sulphite of lime 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 have supposed the use of sulphurous acid in the condition of an aqueous solution,
but by modifications of the apparatus I may employ sulphurous acid in a gaseous
form.

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
July 1878.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN THE TREATMENT OF
CARBONATED MINERAL PHOSPHATES FOR AGRICULTURAL AND MANUFACTURING
PURPOSES." A communication from abroad by the Th. Pilter Company, of Paris,
France.
This Invention relates to the treatment of carbonated mineral phosphates for
agricultural and manufacturing purposes.
The process herein described is mainly based upon the mode of action of sulphurous
acid employed in open vessels at the normal atmospheric pressure.
The mode of treatment has for its object the enrichment of natural mineral
phosphates, designated under the name of " phosphated chalks” or “carbonated
phosphated limes," that is to say, poor phosphates containing from 20 to 25 per
cent. of tribasic phosphate of lime, the balance being formed exclusively of carbonate
of lime.
The sulphurous acid removes the carbonate of lime, leaving the tribasic phosphate
intact, as shewn by the following formula, that is to say :-
Ph O*, 3 Ca O + n(CaO, CO, +n(SO)
(CO2).
-
Ph 0,3 Ca O+ n (Ca O. SO2) + n
It will be understood that the carbonate of lime, which sometimes attains the
proportion of 70 per cent., is transformed into a soluble sulphite, and the remainder
is a tribasic phosphate of lime, which is almost pure, or at least to the proportion of
90 per cent.
The sub-product of sulphite of lime which is obtained is already employed in
certain manufactures, and is susceptible of more extensive applications.
To separate the carbonate of lime and to obtain the tribasic phosphate in
accordance with the formula above given, I proceed as follows:-The phosphated
rock is mechanically pulverized, and put through a fine screen or sieve. If the
mineral contains sufficient carbonate of lime this operation can be dispensed with,
as by roasting or burning (in the same manner as is done with lime) a product is
obtained which, like lime itself, disintegrates in contact with water. In such case
the mineral after roasting is hydrated until it is reduced to powder. It is then
screened through a wire cloth or sieve to separate therefrom foreign bodies, mostly
composed of gravel or stones of silex. The matter thus reduced to powder by either
of the processes described is treated in wooden vessels provided with mechanical
stirrers by means of a solution of concentrated sulphurous acid; carbonate of lime
dissolves, setting free carbonic acid gas, and is transformed into soluble sulphite of
lime; the tribasic phosphate of lime falls to the bottom of the vessel. It is then
collected, and washed once or twice; it is aftewards dried as far as possible in
centrifugal machines, and the drying is completed by means of the waste heat from
the furnaces. A product is thus obtained which, according to the composition of
the mineral treated, yields from eighty to ninety-five per cent. of tribasic phosphate
of lime, which is entirely free from carbonate of lime.
The liquids charged with sulphite of lime are poured into suitable receivers, and
boiled by means of steam admitted into jackets or pipes, or by any other suitable
mcans. The sulphite of lime 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
the heat.
I have supposed the use of sulphurous acid in the condition of an aqueous
solution, but by modifications of the apparatus I may employ sulphurous acid in a
gaseous form.
Having thus fully described the said Invention as communicated to me by my
foreign correspondents, and the manner in which the same is or may be carried into

page_text: effect, I wish it understood that I am aware of bone phosphates having been treated
for various purposes by means of sulphurous acid, but I am not aware that mineral
phosphates have been treated in the manner or for the purpose herein-before
described, and I claim, the process herein-described for the application of sulphurous
acid for eliminating carbonate of lime from natural mineral phosphates, known as
carbonated "phosphated limes," or "phosphated chalks," and thereby obtaining from
the poorest classes of such phosphates a product with from eighty to ninety-five
per cent. of tribasic phosphate of lime entirely free from carbonate of lime.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Ninth day of July, in the year of our Lord One thousand
eight hundred and seventy-eight.