Phosphate Called Precipitated Phosphate.
Year: 1888

page_text: Date of Application, 8th Dec., 1888
Specification Accepted, 29th Jan., 1889
Phosphate Called Precipitated Phosphate.
A communication from abroad by CAMILLE EMILE DÉSIRÉ WINSSINGER, of Brussels,
in the Kingdom of Belgium, Engineer.
I, GEORGE CECIL DYMOND, M. Inst. M.E., of the Agency for Foreign Patent
Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street, Manchester, both in the
County of Lancaster, and 323, High Holborn in the County of Middlesex, Patent
Agent, do hereby declare the nature of this invention and in what manner the same
is to be performed, to be particularly described and ascertained in and by the following
statement -
The object of this invention is :-
1. The commercial production of précipitated bicalcareous phosphate of a standard
capable of attaining about 40 per cent. of phosphoric anhydride, soluble in ammoniacal.
citrate of ammonia, and containing neither oxide of iron nor alumina.
2. The obtaining of this result by the treatment of any phosphate of lime, natural
or artificial, raw or enriched or other, such as bone ashes, phosphorites, phosphates
from the Mons basin, the mineral known in Belgium as craie grise, phosphates from
the Somme, from Canada, etcetera, in a word any substance containing. as elements
lime and phosphoric anhydride, mixed with accessory bodies such as calcareous
carbonate, silica, clay, oxides of.iron and of aluminium, magnesia, etcetera.
3. To obtain the transformation of the substance used into precipitated phosphate,
at the same time forming residues or subproducts of some value, namely, caustic soda
and gypsum.,:
DESCRIPTION.
A. The phosphate is attacked by the ordinary means, with an excess of sulphuric
acid at 50 to 53 degrees Beaumé, so as to obtain an impure solution of phosphoric
acid, which is separated by filtration from the residuum, consisting of impure gypsum,
known by the name of phosphated gypsum.

page_text: '
B. To the liquid obtained in (A), after cooling, is added milk of lime, sufficient for
the complete precipitation of the iron; or else first carbonate of lime in powder till
the commencement of precipitation of the iron, then lime in powder or inilk till the
complete precipitation of the iron. This operation is carried out in any appropriate
mechanical mixing apparatus. A mixture is thus obtained which, when submitted to
a filtration under pressure, gives a liquid usually yellow which is designated j, and a
mud or cake which is designated a.
The yellow liquid ; essentially consists in an aqueous solution of monocalcic
phosphate.
C. On another sufficient quantity of phosphoric liquid obtained by the means
indicated in (A), is operated as follows:-
To this liquid when cold is added the mud a obtained in the operation (B). The
mixture is shaken in any appropriate mechanical, apparatus, and then submitted to
filtration under pressure.
The solid residuum of the filtration is gypsum formed by means of an excess of
sulphuric acid contained by the phosphoric acid liquor (A). To the filtered substance
milk of lime is then added till the moment that precipitation appears.
D. To this last mixture is then added sulphate of soda, in powder or in solution,
in sufficient quantity to precipitate all the lime which exists in solution, and the whole
is submitted to a short ebullition. Then filter, the solid residuum is gypsum, the
filtered liquor is a solution of impure monosodic phosphate.
E. To this liquor carbonate of soda is added, either in powder or dissolved in water,
until complete precipitation of the iron is effected, then filtered. The filtered liquor is
a solution of neutral phosphate of soda almost chemically pure ; it may contain a
slight excess of carbonate of soda.
F. To this solution milk of lime is added in sufficient quantity, and the mixture is
shaken mechanically, till the complete precipitation of the phosphoric acid contained
is effected. Then filter; the solid residuum of the filtration is phosphate of lime, and
the filtered liquor is a solution of caustic soda.
G. The phosphate of lime obtained in (F) is placed in contact in any appropriate
mechanical mixer, with the liquor (J) obtained in the operation (B). After this
treatment, the whole is filtered or turbinated. The solid part is dried in kilns, at the
lowest possible temperature. It constitutes the precipitated phosphate soluble in
ammoniacal citrate of ammonia, almost without residuum.
H. Instead of making use of the mud a as mentioned in paragraph C, it may be
left out of the operation and may be thrown away or sold as manure.
In this case
the yellow liquid is treated directly with sulphate of soda according to paragraph D,
and the treatment is continued as explained in the following paragraphs E, F, G, K.
Instead of introducing the sulphate and carbonate of soda, only one portion of the
process may be applied and the manufacture of caustic soda abandoned. In this case
it is sufficient to treat the yellow liquid with lime powder or milk, or with
precipitated tricalcic phosphate, or by a mixture of both substances. Even in this
manner bicalcareous phosphate is obtained sufficiently pure for sale.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is :-
In a process, the object of which is to produce precipitated bicalcic phosphate almost
entirely soluble in ammoniacal citrate of ammonia, and to produce as a residuum
caustic soda and phosphated gypsum:
was
1st. The preparation (Sections A and B) and utilization, for the object mentioned
in paragraphs G, H, K, of a liquor J free from iron, obtained by adding lime or
carbonate of lime, then lime to an impure solution of phosphoric acid, as
mentioned in B. This liquor J possesses the property of rendering soluble in
ammoniacal citrate of ammonia the precipitated tricalcic phosphate, or the lime, or a
mixture of the two bodies. This liquid is essentially an aqueous solution of
monocalcium phosphate.

page_text: 2nd. In combination with the liquor J the purification by means of carbonate of
soda which permits of obtaining sodium phosphate free from iron and alumina, in such
manner that when this sodium phosphate is afterwards treated with lime, a very pure
phosphate of lime is obtained.
3rd. In combination with the liquor J and the purification with carbonate of soda,
the utilization of the mud a separated from the liquor J (paragraph B); this mud a
being partly re-dissolved by the phosphoric acid liquor (produced as has been
mentioned in paragraph A) and leaving a residuum of gypsum.
4th. In general the series of operations which are effected, or the course which is
pursued in order to transform any impure phosphate of lime into precipitated bicalcic
phosphate free from iron and almost entirely soluble in ammoniacal citrate of ammonia,
namely, the manufacture of a certain phosphate of lime, for the one part, and the
manufacture of a yellow liquor J for the other part, and finally, the treatment of this
phosphate by this liquor to attain the definite precipitated phosphate; at the same
time obtaining gypsum in quantity corresponding to the sulphuric acid employed
either in a free state or in the shape of sulphate of sodium, and collecting in the
caustic state all the soda used, both in the shape of sulphate and in that of carbonate;
the whole being effected as is stated and detailed and with the object indicated in the
preceding text.