THE PREPARATION OF MAGNESIA WITH A VIEW TO ITS USE. IN THE SEPARATION OF AMMONIA FROM EXCREMENTITIOUS MATTER, AND FOR OTHER USES
Year: 1881

page_text: ETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for an
Invention of "THE PREPARATION OF MAGNESIA WITH A VIEW TO ITS USE.
IN THE SEPARATION OF AMMONIA FROM EXCREMENTITIOUS MATTER, AND
FOR OTHER USES." A communication from abroad by Theophile Schloesing,
of 67, Quai d'Orsay, in the City of Paris, France.
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office of
the Commissioners of Patents on the 27th April 1881.
SYDNEY PITT, of Sutton, in the County of Surrey. "THE PREPARATION OF
MAGNESIA WITH A VIEW TO ITS USE IN THE SEPARATION OF AMMONIA FROM
EXCREMENTITIOUS MATTER, AND FOR OTHER USES." [A communication from
abroad by Theophile Schloesing, of 67, Quai d'Orsay, in the City of Paris, France.]
This Invention has for its object the preparation of magnesia with a view to its
use in the separation of ammonia from excrementitious matter, and for other uses.
The constantly increasing use of water in water closets produces a corresponding
dilution of the excrementitious matters, and the time will arrive when the extraction
of ammonia from these liquids by distillation by heat will no longer be a paying
operation. The treatment should be changed by having recourse to the production
of an insoluble combination of ammonia without the aid of heat. It has long been
proposed to precipitate this alkali by the combined operation of a soluble phosphate
and a salt of magnesia, so as to determine the formation of insoluble ammonio-
magnesian phosphate, but the high price of the soluble phosphates has not permitted
the use of processes of this nature.
Now the employment of soluble phosphates is not at all necessary, it may be
replaced by free phosphoric acid on condition that magnesia be simultaneously
presented, and not a salt of magnesia; calculated proportions of acid and of base
Price Ad71

page_text: allow of the ammonio magnesian phosphate being obtained, ammonia being also
liberated by an excess of magnesia.
+
The process of extracting the phosphoric acid from the calcarious phoshates by
displacing it by a suitable dose of sulphuric acid is well known. It remains then
to prepare magnesia in large quantity and at a low price. Magnesian salts abound;
sea water; the mother liquors of salt makers are inexhaustible sources; the question
then is to extract the ammonia by simple and economical means. This is the
principal object of the present Invention.
It is well known that lime precipitates magnesia from its saline solutions; the
precipitate of magnesia is in general light voluminous and almost gelatinous, and
no means are known by which such a precipitate can be produced, filtored, and
washed on a commercial scale. It is also known that light precipitates produced in
weak liquors occupy more space than when they are produced in more concentrated
solutions, and magnesia does not escape from this rule; it is obtained reasonably
compact, when a paste of lime is made to react on a concentrated magnesian salt,
but in this state it opposes too much resistance to filtration and washing.
I have devised very simple means for avoiding these difficulties, consisting in
employing lime previously slacked in the form of small fragments accumulated in a
vat, but having between them interstices in which the magnesian solution is caused
slowly to circulate; each fragment then becomes the seat of a double diffusion, that
of the magnesian salt going from the liquid to the interior of the fragment, and that
of the calcarious salt produced by the precipitation of the maguesia going from the
interior of the fragment to the exterior liquid, so that on the termination of the
operation, the mass of lime is replaced by a similar mass of magnesia, which besides
can be perfectly washed by replacing the magnesian solution by water.
When the magnesian solution contains a sulphate it is convenient to treat it in
the first place with a soluble calcarious salt, so as to eliminate the sulphuric acid
in the form of insoluble sulphate of lime, otherwise this salt would form and remain
in the midst of the mass of magnesia. There are various ways of giving to the
hydrate of lime the requisite form; a firm paste of lime may be rubbed through a
sieve set over a vat containing a magnesian solution, the paste then takes a worm
like form and falling into the solution becomes incrusted with magnesia, which
imparts to it a consistence such that it may be accumulated to a thickness of many
inches. Or slacked lime in a powdered state may be spread out on a floor and
watered with a magnesian solution made to fall upon it in fine drops; the water
and the magnesia compact the particles of lime so firmly that they may be laid
together in a vat without preventing the circulation of the liquids. It may be
stated in a general manner that the object to be aimed at is to impart to the
fragments of lime as much porosity and as small dimensions as is compatible with
sufficient consistence and free circulation of the liquids. The double carbonate of
lime and magnesia or dolomite lends itself to this agglomeration in small fragments
of the hydrate of lime when having been calcined in a furnace and quenched with
water it is reduced to the form of a paste or powder.
The mass of magnesia when taken out of the vat is dried in the open air or in
any other convenient way.
In order to utilize the solution of magnesia as fully as possible it should be
exhausted by causing it to descend through several lime vats, each of these vats
may be isolated for the purposes of charging and discharging. A methodical
system should be adopted for this purpose such as is employed in numerous
manufactures.
In respect to the precipitation of ammonia by the employment of phosphoric
acid and magnesia it is only necessary to observe that its precipitation from
excrementitious matters may be effected either after or without the previous
elimination of solid matters.
In the first case an almost pure ammonio magnesian phosphate is obtained; in
the second it is mixed with the solid matters which become, when separated by a

page_text: filter press or other apparatus a very rich manure. In either case the magnesia
and the acid should be added alternately in small quantities commencing with the
magnesia, so that the liquid may always remain alkaline.
It is unnecessary to say that this process for the production of magnesia will be
useful not only in relation to the treatment of excrementitious matter, but also as
opening up other uses rendered possible by the large reduction in price which it
brings about.
Another method is as follows:-
The weak magnesian solution, sea water, for example, is mixed with milk of
lime or of dolomite decarbonated by heat, and employed in such proportions as to
precipitate the magnesia almost by itself. After remaining at rest in any suitable
receptacle, vat, tank, or basin, a deposit of hydrate of magnesia is formed distributed
through a large quantity of liquid. However, by decanting off the supernatant
liquor, the greater part of the original liquor may be removed, thus the magnesia
from a cubic metre of sea water may be concentrated into a deposit of 30 to
50 litres.
I have already said that it is scarcely possible to remove the water which
accompanies the magnesia in the deposit by means of filtering apparatus, but it is
possible to convert the precipitate, which is too gelatinous to be readily filtered
into a chemical combination which presents itself in the form of a crystalline
powder, which consequently can be filtered out, and which besides is directly
applicable to excrementitious matter to precipitate the ammonia. This combination
is the basic phosphate of magnesia.
It is obtained immediately by mixing the deposit with a calculated volume of a
solution of phosphoric acid, so that one equivalent of acid encounters at least three
equivalents of magnesia.
On repose the liquid separates in great part and may be removed by filtration;
the remainder containing the whole of the phosphate is filtered in any convenient
manner by a filter press for example.
The magnesian phosphate thus obtained is poured, after having been inixed with
water, into the ammonical liquor from which the ammonia is to be extracted.
Immediately an exchange takes place between the phosphate and the ammonical
salts, the first yields magnesia to the acids combined with the ammonia, and this
passes to the phosphate to form the ammonio-inagnesian phosphate.
It is evident that magnesian solutions are adapted to this method of preparation
of basic phosphate, quite independently of their degree of concentration, for they
can always be diluted; it is also evident that in place of preparing magnesia to
employ it concurrently with phosphoric acid for the separation of ammonia, it may
be more convenient to prepare the basic phosphate of magnesia for the saine
purpose.
The solution of phosphoric acid is obtained, as I have already said, by treating
bones or mineral phosphates with sulphuric acid; this preparation may be
conveniently carried out on the following principles :-
When a bone or mineral phosphate reduced to very small fragments is placed in
a vat in which sulphuric acid diluted with water is made to circulate, diffusion
phenomena result analogous to those which I have described in speaking of the
preparation of magnesia. The sulphuric acid fixes itself upon the lime of the
phosphate, the phosphoric acid passes into solution, and during the process
the interstices necessary to the circulation of the liquid are not obstructed; but
it is as well, with a view to the free circulation of the liquid, to decompose the
carbonates previously by digestion with weak sulphuric acid, otherwise the
carbonic acid liberated in the midst of the mass of fragments of phosphates cause
stoppages or movements of the matters which result in obstructions.
These mineral phosphates which are found in commerce in the state of powder,
should be first aggregated by a treatment with sulphuric acid at a strength of
50 degrees about; the hardened but yet porous mass is then divided into small
fragments, which are in turn treated with weak sulphuric acid.

page_text: It will be understood without going into more detail that the process which I
,have indicated is perfectly adapted to the employment of methodical washing
apparatus, so arranged that the solid matters come out of the apparatus well
washed from phosphoric acid and even from sulphuric acid, whilst concurrently the
phosphoric solution is drawn off. If this solution, which always contains a small
quantity of sulphate of lime, also includes an excess of lime, this should be
precipitated by the addition of a suitable small quantity of sulphuric acid.
The residue from the treatment of bones contains gelatine, from which the
greater quantity of sulphate of lime may be separated by washing upon sieves.
This matter may then be collected and reserved for uses to which it is adapted.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Sydney Pitt in the Great Seal Patent Office on the 27th October
1881.
SYDNEY PITT, of Sutton, in the County of Surrey. "THE PREPARATION OF
MAGNESIA WITH A VIEW TO ITS USE IN THE SEPARATION OF AMMONIA FROM
EXCREMENTITIOUS MATTER, AND FOR OTHER USES." (A communication from
abroad by Theophile Schloesing, of 67, Quai d'Orsay, in the City of Paris, France.)
This Invention has for its object the preparation of magnesia with a view to
its use in the separation of ammonia from excrementitious matter, and for other
uses.
The constantly increasing use of water in water closets produces a corresponding
dilution of the excrementitious matters, and the time will arrive when the
extraction of ammonia from these liquids by distillation by heat will no longer be
a paying operation. The treatment should be changed by having recourse to the
production of an insoluble combination of ammonia without the aid of heat. It
has long been proposed to precipitate this alkali by the combined operation of a
soluble phosphate and a salt of magnesia, so as to determine the formation of
insoluble ammonio-magnesian phosphate, but the high price of the soluble
phosphates has not permitted the use of processes of this nature.
Now the employment of soluble phosphates is not at all necessary; it may be
replaced by free phosphoric acid on condition that magnesia be simultaneously
presented, and not a salt of magnesia; calculated proportions of acid and of base
allow of the ammonio-magnesian phosphate being obtained, ammonia being also
liberated by an excess of magnesia.
The process of extracting the phosphoric acid from the calcarious phosphates by
displacing it by a suitable dose of sulphuric acid is well known. It remains then
to prepare magnesia in large quantity and at a low price. Magnesian salts abound;
sea water; the mother liquors of salt makers are inexhaustable sources; the question
then is to extract the ammonia by simple and economical means. This is the
principle object of the present Invention.
It is well known that lime precipitates magnesia, from its saline solutions; the
precipitate of magnesia is in general light voluminous and almost gelatinous, and
no means are known by which such a precipitate can be produced, filtered, and
washed on a commercial scale. Filter presses and centrifugal apparatus are alike
unsuitable. It is also known that light precipitates produced in weak liquors
occupy more space than when they are produced in more concentrated solutions,
and magnesia does not escape from this rule; it is obtained reasonably compact
when a paste of lime is made to react on a concentrated magnesian salt, but in
this state it opposes too much resistance to filtration and washing.
I shall first consider the case of magnesian solutions which are to a certain
extent concentrated, such as the mother liquors from salt ponds, or those obtained
from Strassfurt salts. I shall examine afterwards the case of weak solutions, such
as sea water.
FIRST CASE.
The process for the extraction of magnesia consists in employing lime previously
slaked in the form of small fragments accumulated in a vat, but having between
them interstices in which the magnesian solution is caused slowly to circulate;
each fragment then becomes the seat of a double diffusion, that of the magnesian
salt going from the liquid to the interior of the fragment, and that of the
calcarious salt produced by the precipitation of the magnesia going from the

page_text: interior of the fragment to the exterior liquid, so that on the termination of the
operation the mass of lime is replaced by a similar mass of magnesia, which
besides can be perfectly washed by replacing the magnesian solution by water.
When the magnesian solution contains a sulphate it is convenient to treat it in the
first place with a soluble calcarious salt, so as to eliminate the sulphuric acid in the
form of insoluble sulphate of lime, otherwise this salt would form and remain in the
midst of the mass of magnesia. There are various ways of giving to the hydrate of lime
the requisite form; a firm paste of lime may be rubbed through a sieve set over a
vat containing a magnesian solution; the paste then takes. a worm like form, and
falling into the solution becomes. incrusted with magnesia, which imparts to it a
consistance such that it may be accumulated to a thickness of many inches. Or
slaked lime in a powdered state may be spread out on a floor and watered with a
magnesian solution made to fall upon it in fine drops; the water and the magnesia
compact the particles of lime so firmly that they may be laid together in a vat
without preventing the circulation of the liquids. It may be stated in a general
manner that the object to be aimed at is to impart to the fragments of lime as
much porosity and as small dimensions as is compatible with sufficient consistance
and free circulation of the liquids. The double carbonate of lime and magnesia or
dolomite lends itself to this agglomoration in small fragments of the hydrate of
lime when having been calcined in a furnace and quenched with water it is
reduced to the form of a paste or powder.
The mass of magnesia when taken out of the vat is dried in the open air or in
any other convenient.way.
In order to utilize the solution of magnesia as fully as possible it should be
exhausted by causing it to descend through several lime vats; each of these vats
may be isolated for the purposes of charging and discharging. A methodical
system should be adopted for this purpose, such as is employed in numerous
manufactures.
I have stated that the cohesion of the hydrate of magnesia, obtained as above
described, is in direct relation with the degree of concentration of the magnesian
solution. If this contains more than 40 grammes of magnesia to the litre, the
cohesion of the magnesian precipitate is so great as to much retard and even to
stop the phenomena of diffusion. If on the contrary the solution contains less
than 20 grammes of magnesia to the litre, the cohesion of the precipitated
magnesia is too slight, the fragments disagregate, they give way and form a pastey
matter through which the solution can no longer circulate; the phenomena of
diffusion then no longer occur. When a magnesian solution is too concentrated it
can always be diluted with water to the point desired, but when it is too weak it
may be too expensive to concentrate it by evaporation, either spontaneously or by
artificial heat. For this reason the means alluded to above, and which refer to the
'second case, namely, that the very dilute solutions have been worked out.
SECOND CASE.
The weak magnesian solution, sea water, for example, is mixed with milk of
lime or of dolomite decarbonated by heat, and employed in such proportions as to
precipitate the magnesia alinost by itself. After remaining at rest in any suitable
receptacle, vat, tank, or basin, a deposit of hydrate of magnesia.is formed distributed
through a large quantity of liquid. However by decanting off the. supernatent
liquor the greater part of the original liquor may be removed; thus the magnesia.
from a cubic metre of sea water may be concentrated into a deposit of 50 to
80 litres.
It is possible to convert the precipitate which is too gelatinous to be readily
filtered into a chemical combination which presents itself in the form of a crystalline
powder which consequently can be filtered out, and which besides is directly
applicable to excrementitious matter to precipitate the ammonia. This combination
is the tribasic phosphate of magnesia. It is obtained immediately by mixing the

page_text: deposit with a calculated volume of a solution of phosphoric acid, so that one
equivalent of acid encounters at least three equivalents of magnesia. On repose
the liquid separates in great part and may be removed by filtration, the remainder
containing the whole of the phosphate is filtered in any convenient manner by a
filter press, for example.
The magnesian phosphate thus obtained is poured, after having been mixed with
water, into the ammoniacal liquor from which the ammonia is to be extracted.
Immediately an exchange takes place between the phosphate and the ammoniacal
salts, the first yields magnesia to the acids combined with the ammonia, and this
passes to the phosphate to form the ammonio-magnesian phosphate.
It is evident that magnesian solutions are adapted to this method of preparation
of basic phosphate, quite independently of their degree of concentration, for they can
always be diluted; it is also evident that in place of preparing magnesia to employ
it concurrently with phosphoric acid for the separation of ammonia, it may be
more convenient to prepare the basic phosphate of magnesia for the same purpose..
As to the solution of phosphoric acid it may be obtained in the following
way-The animal or mineral phosphate of lime is reduced to a fine powder and
treated with the quantity of sulphuric acid suitable to convert it into solid
superphosphate; this is then reduced to fragments and digested in weak sulphuric
acid employed in such quantity that the superphosphate of lime is decomposed
into phosphoric acid and sulphate of lime. The solution of phosphoric acid is
separated from the mass of fraginents by displacement and washing with water.
The manufacture of tribasic phosphate of magnesia is only for the special use of
the magnesia, the precipitation of ammonia; it is desirable also to be able to
extract the magnesia from sea water and other very weak solutions for other uses
requiring free magnesia, such as the manufacture of bricks for metallurgical
purposes. Not being able to separate, by means of filtering apparatus, the
magnesia contained in the magnesian deposit extracted from sea water, recourse
is had to a natural filter of unlimited surface, the land, so as to compensate for
the slowness of filtration by the extent of the filtering surface. A certain tract
of land is arranged in flats surrounded by low banks of earth; the magnesian
deposit is run on to these flats, covering them at first to a depth of 20, 30, 40,
centimetres. The earth sucks up the liquid slowly and the magnesia remains
upon the surface. After some days the flats are covered with a magnesian pasto
containing 1 part of magnesia to 3 or 4 of water.
In hot countries, under the action of the sun's rays, this paste dries and shells
off in a multitude of small crusts which are easily removed for the operation to be
recommenced. In less favoured countries it is necessary to collect the magnesia
in a pasty state and to dry it in suitable apparatus by artificial heat.
The dry or the pasty magnesia collected from the flats is soiled on the under
surface by adherent earth material, this inconvenience may be avoided in various
ways, either by spreading upon the flats a thin layer of dry and powdered magnesia
which will be in part carried away with the crop, taking the place of earthly
matters, or more simply, by spreading upon the flats a layer of fine siliceous sand.
When the magnesia, soiled by this sand has been dried, it is only necessary to rub
up and to agitate it with water in a tank, and the sand will be deposited to the
bottom of the tank, and the pure magnesian mud may be run off.
it
Magnesia extracted from sea water and dried in the air or artificially contains
chloride of sodium, a small quantity of chloride of calcum, and carbonate of lime.
It is separated from these impurities by washing it, when in the state of powder,
first in cold water and then by giving it a short boil in a weak solution of chloride
of magnesium; by double decomposition the carbonate of lime is transformed into
carbonate of magnesia and chloride of calcium which is eliminated by washing.
Having thus described the nature of the said Invention, and the manner of
performing the same, I would have it understood that I claim,―
First. The manufacture of magnesia by submitting fragments or pellets of limo
to the action of a magnesian solution as herein described, so that by diffusion the

page_text: lime is replaced by magnesia throughout the fragment or pellet whilst the fragment
or pellet retains its form permitting the free access of the magnesian solution.
Second. The separation of magnesia from sea water or other weak solution in
the form of tribasic phosphate by precipitating a magnesian mud with lime, and
then converting it into the tribasic phosphate by a suitable addition of phosphoric
acid as herein described.
Third. The manufacture of magnesia. by precipitating sea water with an
equivalent proportion of lime, then concentrating the precipitate by deposition in
tanks into a small quantity of water, and finally obtaining the magnesia in a dry
or pasty state by draining away the remaining water, substantially as herein
described.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand
and seal, this Twenty fourth day of September, in the year of our Lord
One thousand eight hundred and eighty one.