AN IMPROVED PROCESS FOR THE PREPARATION OF ACID PHOSPHATE OR SUPERPHOSPHATE OF LIME
Year: 1872

page_text: LETTERS PATENT to Charles Denton Abel, of No. 20, Southampton
Buildings, Chancery Lane, in the County of Middlesex, Patent
Agent, for the Invention of "AN IMPROVED PROCESS FOR THE PREPARATION
OF ACID PHOSPHATE OR SUPERPHOSPHATE OF LIME."-A communication
from abroad by Georges Ville, of No. 23, Boulevard de Strasbourg,
Paris, France, Chemist.
Sealed the 3rd September 1872, and dated the 1st April 1872.
PROVISIONAL SPECIFICATION left by the said Charles Denton Abel
at the Office of the Commissioners of Patents, with his Petition,
on the 1st April 1872.
I, CHARLES DENTON ABEL, of No. 20, Southampton Buildings,
Chancery Lane, in the County of Middlesex, Patent Agent, do hereby
declare the nature of the said Invention for "AN IMPROVED PROCESS FOR
THE PREPARATION OF ACID PHOSPHATE OR SUPERPHOSPHATE OF LIME," to be as
follows:-
In preparing the acid phosphate of lime the usual process is to subject
to the action of sulphuric acid any of the tri-basic phosphates which are
insoluble in water. This mode of operating is attended with two great

page_text: disadvantages; it leaves an insoluble part of the phosphate not acted on,
and the acid phosphate adulterated with sixty to eighty per cent. of
useless matter. The object of the present Invention is to avoid these
evils by converting almost the whole of the insoluble phosphate into.
soluble phosphate without increase of weight. For this purpose the
mineral or other phosphates are first reduced to powder, and are then
thoroughly pugged with hydrochloric acid in a pugging or kneading
machine of any known construction. The proportion of acid is about
60 parts to 100 parts of phosphate, but this proportion may vary accord-
ing to the richness of the phosphate. After half an hour the pasty mass
is subjected to the action of any known squeezing machine suitable for
straining from it the liquid, which is of syrupy consistency, containing
principally chloride of calcium. The strained paste forms a species of
mineral cake, in which almost the whole of the original phosphate of
lime is formed in a soluble condition; and this cake is nearly equal in
weight to the original phosphate.
For more completely effecting this result the hydrochloric acid should
be a little in excess, and when this is the case a small quantity of soluble
phosphate is strained off with the liquid. In order to extract it the
liquid is diluted by adding an equal bulk of water and is then heated to
ebullition by blowing steam into it, when a little milk of lime is added.
'All the soluble phosphate is thus changed into the condition of basic
phosphate, which is easily assimilated and is of nearly the value of the
soluble phosphate.
The cake described above when removed from the straining press is
reduced to an unctious powder, presenting the same appearance as the
original phosphate, although it differs from it essentially in being
perfectly soluble.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
DENTON ABEL, of No. 20, Southampton Buildings, Chancery Lane, in
the County of Middlesex, Patent Agent, send greeting:

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the First day of April, in the year.
of our Lord One thousand eight hundred and seventy-two, in the thirty-.
fifth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Charles Denton Abel, Her special
licence that I, the said Charles Denton Abel, my executors, adminis-
trators, and assigns, or such others as I, the said Charles Denton
Abel, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times there-
after during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention:
for "AN IMPROVED PROCESS FOR THE PREPARATION OF ACID PHOSPHATE OR SUPER-
PHOSPHATE OF LIME," a communication to me from abroad by Georges
Ville, of No. 23, Boulevard de Strasbourg, Paris, France, Chemist, upon
the condition (amongst others) that I, the said Charles Denton Abel,
my executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe
and ascertain the nature of the said Invention, and in what manner the
same was to be performed, and cause the same to be filed in the Great
Seal Patent Office within six calendar months next and immediately
after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Charles Denton Abel, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and by
the following statement thereof, that is to say:-
In preparing the acid phosphate of lime the usual process is to subject
to the action of sulphuric acid of 50 to 56 degrees strength any of the
tri-basic phosphates which are insoluble in water. This mode of operating
is attended with two great disadvantages; it leaves an insoluble part
of the phosphate not acted on, and the acid phosphate adulterated with..
sixty to eighty per cent. of useless matter. The object of the present
Invention is to avoid these evils by converting almost the whole of the
insoluble phosphate into soluble phosphate without increase in weight..
For this purpose natural mineral or other phosphates are first reduced.
to powder, and are then thoroughly pugged with hydrochloric acid in a
pugging or kneading machine of any known construction. The pro-
portion of acid is about 60 parts to 100 parts of phosphate, but this

page_text: hai an hour the pasty mass is subjected to
squeezing machine suitable for straining from it the liquid, which is of
syrupy consistency, containing principally chloride of calcium. The
strained paste forms a species of mineral cake, in which almost the
whole of the original phosphate of lime is found in a soluble condition,
and it is remarkable that this cake is nearly equal in weight to the
original phosphate.
The new and distinctive feature of this process is the expulsion by
pressure of the liquid containing in solution the matters useless as
manure, and the concentration on the other hand of the superphosphate
resulting from the action of the hydrochloric acid on the natural phos-
phates, that is to say, of the useful product in the form of a mineral
cake, which can be easily pulverized. By this expulsion superphosphates
of an exceptionally high character are obtained, but several practical
difficulties attend the application of the pressure for effecting it. After
several different methods had been tried it has been found that the mode
of operating usually employed in oil works is practically available. The
paste produced by the action of the hydrochloric acid on the natural
phosphate is enclosed in a felt bag or wrapper which has been in the first
place lined with a sheet of unsized paper, which acts as a filter and
prevents the pores of the fabric from being obstructed and the cake from
adhering. The bag or wrapper with its edges folded back is then enclosed
in a second wrapper of hair cloth of great strength, and the material is
then subjected to a slowly increasing pressure, which may be raised to a
ton per square inch. This is preferably effected by means of hydraulic
presses, such as are usually employed in oil works.
In pressing out oils the edges of the cake are generally found to be
less compressed than the middle. The same result attended the pressing
of the phosphate until means were devised for obviating it in the follow-
ing manner :-The bag or wrapper containing the paste is surrounded by
a collar of hair or wool stuff, which forms a kind of barrier round the
bag. The pressure fixes this collar, which thus serves as an insur-
mountable obstacle to the extension laterally of the cake, while it
permits the liquid to be strained through it, and at the same time protects
the fabric of the bag or wrapper from the lateral straining which is the
principal element of destruction.

page_text: For applying the pressure fifteen or twenty bags are piled side by side
in the press, and to facilitate the flow of the liquid, which is viscous,
between each pair of bags is laid a sheet of iron ¾ inch or ½ inch thick,
with grooves or furrows about 1/8 inch deep, and to prevent these furrows
from being obstructed the plate is covered with very fine wire gauze.
With these arrangements the process can be carried on with the greatest
ease and rapidity, which contributes materially to its industrial value.
16
Instead of employing the hydraulic press a centrifugal strainer may be
used. In some cases, particularly in treating bones or poor phosphates, this
method presents considerable advantages; it is carried out as follows:―
The bones or phosphates are acted on as described above, and after about
2 hours the product is placed in the centrifugal strainer, which should
be of large diameter and driven at high speed. Before charging the!
drum it is lined internally with flannel or thin felt, with unsized paper
inside. For every fresh charge the paper is removed and the lining;
moistened with a brush, whereon the paper being applied it adheres after
the first few turns. The fluid paste is run into the drum until it forms a
layer of about 1 inch thick against the side of the drum, when the flow
is stopped and the drum is rotated for about ten minutes, which com-
pletes the operation. The unsized paper prevents the cake from adhering
to the lining, and allows it to be detached with the greatest ease, while
at the same time the pores of the lining are kept free from obstruction.
The sheets of cake removed from the drum are then treated in either of
the two following ways:-
1. They may be subjected to the action of the hydraulic press in the
manner described above in order to complete their straining, but the
pressing is rendered much more rapid and economical by the previous
action of the centrifugal strainer.
Or, 2. They may be dried in a stove, which owing to the thinness of
the cakes is effected very rapidly, and then reduced to powder.
In the above description of the new process for manufacturing super-
phosphate of lime it has been stated that a quantity of hydrochloric acid
is employed sufficient to act on the whole of the tribasic phosphate
contained in the materials operated on.
In some cases it may be advantageous to modify the progress of the
acid action. The charge of acid may be regulated so as to leave in the
cake four to five per cent. of the tribasic phosphate not acted on. This

page_text: cake being pulverized as above described has poured over it 15 to 20 per
cent. of sulphuric acid of the strength of 50 degrees, which is intimately
mingled with it. This addition produces two effects; it completes the
conversion into superphosphate of the tribasic phosphate remaining in
the cake, and it destroys the greater part of the chloride of calcium
which remained mixed with the superphosphate, which in certain cases
is of great advantage. And farther, by thus moderating the initial
charge of hydrochloric acid the proportion of superphosphate strained out
with the liquid is reduced with great advantage.
Having thus described the nature of this Invention, and in what
manner the same is to be performed, as communicated to me by my
foreign correspondent, I claim, the treatment of tribasic phosphates of
lime with hydrochloric acid so as to form a paste, and the subsequent
expulsion by pressure or centrifugal force of the useless matter from the
paste, substantially as herein described.
In witness whereof, I, the said Charles Denton Abel, have here-
unto set my hand and seal, this Twenty-fourth day of September,
in the year of our Lord One thousand eight hundred and seventy-
two.