IMPROVEMENTS IN THE METHOD OF UTILIZING SLAGS OBTAINED IN THE DEPHOSPHORIZATION OF IRON
Year: 1883

page_text: LETTERS PATENT to Carl Pieper, Civil Engineer and Patent Agent, resident
at 109-110 Gneisenaustrasse, Berlin S.W. Prussia for an Invention of
"
"
IMPROVEMENTS IN THE METHOD OF UTILIZING SLAGS OBTAINED IN THE
DEPHOSPHORIZATION OF IRON a communication to him from Carl Scheibler,
professor of chemistry, residing in Berlin, Kingdom of Prussia
PROVISIONAL SPECIFICATION left by the said Carl Pieper at the Office
of the Commissioners of Patents on the 30th March 1883.
CARL PIEPER, Civil-Engineer and Patent-Agent, resident at 109-110 Gneisenau-
strasse, Berlin, S.W., Prussia, "IMPROVEMENTS IN THE METHOD OF UTILIZING SLAGS
OBTAINED IN THE DEPHOSPHORIZATION OF IRON," a communication to me by Carl
Scheibler, professor of chemistry, residing in Berlin, kingdom of Prussia,
This invention relates to the method of utilizing phosphatic slags described in
any patent specification No 5835 of the 7th December 1882, and according to which
phosphates of lime and magnesia are obtained from the slags by a process comprising
a pulverisation and a roasting of the slag, a treatment of the same by a limited
quantity of muriatic acid diluted with at least 9 parts of water to 1 part of
acid of 21° B., and a precipitation of the earth basic phosphates by lime or
magnesia.
According to the improvements forming the subject matter of my present
specification, the inventor dissolves the powdered and roasted slag in muriatic acid
which is less diluted than required in the former method, the dilution being
limited, solely by the condition that the main portion of the silica of the slag be
dissolved together with the phosphates of lime and magnesia, and that the silica
having thus passed into the solution will remain dissolved and not separate out in
gelatinous state. In addition to the greater strength of the acid, a larger quantity
thereof may be used than formerly.
By proceeding in this manner solutions will be obtained which contain more
or less iron and manganese.

page_text: When these solutions are neutralized by adding a sufficient quantity of lime or
magnesia all at once, the precipitates produced will consist of phosphates of lime
and magnesia together with phosphates of iron and magnesia and silica.
By a fractional precipitation, however, the phosphates of iron and manganese,
the earth basic phosphates and the silica may be obtained separately. For this
purpose at first a limited quantity of lime or magnesia is added, whereby the
phosphates of iron and manganese will be precipitated. A further addition of
lime or magnesia to the solution drawn off from the first precipitate will cause
phosphates of lime and magnesia to separate out, whereupon, by completely
neutralizing the remaining solution, the silica alone or together with magnesia will
be thrown to the bottom. If preferred, the earth-basic phosphates may be
precipitated together with the silica by at once neutralizing the liquid separated
from the compounds of iron and manganese.
The phosphates of iron and manganese obtained in the first stage of the process.
of fractional precipitation are mixed with lime or magnesia, or carbonates thereof,
and roasted. The phosphate of lime or magnesia thereby formed are then
extracted in a like manner as the earth-basic phosphates contained in the roasted
slag. The residue consists mainly of oxides of iron and manganese.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Carl Pieper in the Great Seal Patent Office on the 26th September
1883.
t
CARL PIEPER, Civil-Engineer and Patent Agent, resident at 109-110 Gneisenau-
strasse Berlin S.W. Prussia "IMPROVEMENTS IN THE METHOD OF UTILIZING SLAGS
OBTAINED IN THE DEPHOSPHORIZATION OF IRON, a communication to me from Carl
Scheibler, professor of chemistry, residing in Berlin, kingdom of Prussia.
This invention relates to the method of utilizing phosphatic slags described in
the patent specification No 5835 of the 7th December-1882, and according to which
phosphates of lime and magnesia are obtained from the slags by a process
comprising a pulverization and a roasting of the slag, a treatment of the same
by a limited quantity of muriatic acid diluted with at least 9 parts of water to
1 part of acid of 21° B., and a precipitation of the earth-basic phosphates by lime
or magnesia.
The object of the improved method to be described in the following, consists:
firstly, in producing from the slags by means of muriatic acid diluted less than
heretofore, earth phosphates either mixed with phosphates of iron and manganese
and with silica, or nearly free of these substances; secondly, in converting the
phosphates of iron and manganese proceeding from this process, into phosphates of
lime or magnesia, or of both together, and thirdly, in recovering the iron and
manganese of the slags in the state of oxides together with some compounds of
lime and magnesia.
The slags obtained in the dephosphorization of iron by the Thomas Gilchrist
process, or other similar processes, either in the basic lined Bessemer converter, or
in basic lined reverberatory furnaces, are powdered and thereupon roasted in
oxydizing flame in the same manner as has been described in my former
specification, the roasting process having the purpose, on one hand to convert the
protoxides of iron and manganese into sesquioxides, or combinations of sesqui-
oxides and protoxides, and on the other hand, to effectuate that the part of the
phosphoric acid combined in the unroasted slag with iron and manganese be
transferred to the lime and magnesia of the slag so as to form earth phosphates
therewith, and that the silica of the slag be brought into a state in which it will
be least inclined to gelatinize when the slag is treated with diluted acid. The
roasted slag is washed and thereby freed from the caustic line which it contains,
and which may subsequently be utilized in the precipitation of the phosphates
from the acid solutions.
Hereafter the slag is dissolved in muriatic acid which is less diluted than
required in the former method, the dilution being limited solely by the condition
that the main portion of the silica of the slag be dissolved together with the
phosphates of lime and magnesia, and that the silica having thus passed into the
solution, will remain dissolved and not separate out spontaneously in gelatinous
state. By dissolving the greater portion of the silica, the residue consisting mainly
of oxides of iron and manganese and of magnesia and lime will be comparatively
free from silica and therefore the more valuable for its utilization in the manufacture
of iron.
When acids are employed which are less diluted than with 9 parts of water to
1 part of acid, a considerable quantity of the iron and manganese will pass into
the solution together with the silica and the earth phosphates, the said quantity
being greater in proportion as the degree of dilution is less and the quantity
of acid is increased. The reason herefor is to be found in the fact that the acids

page_text: of higher titre act on the slag-powder under development of heat rising with
their degree of concentration, in consequence whereof the reactions take place in
too violent a manner.
As regards the silica, I have to observe that its tendency to gelatinize in the
solution diminishes in the measure as the slag is roasted at a higher temperature.
It is therefore advisable to heat the slag in the roasting process to a bright
red heat.
In addition to the greater strength of the acid, a somewhat larger quantity
thereof may be used than formerly, i.e. more than is required according to the
analysis of the slag for extracting therefrom the earth phosphates and 'the silica
only. It is consequently not required to operate in this respect, as carefully as is
necessary according to my first method. By the excess of acid an amount of iron
and manganese is dissolved which does not separate out again during the dissolving
process.
The solution is separated from the residue in any suitable manner. The residue
being very heavy, this operation offers no difficulty.
The next step consists in precipitating the phosphates and the silica. This
precipitation is preferably carried out by milk of lime; but instead, of lime,
magnesia or a mixture of lime and magnesia, such as burnt dolomite, or the
carbonates thereof may be employed. When the solutions are completely
neutralized at once by adding a sufficient quantity of the said substances, the
precipitates produced will consist of phosphates of lime, or of phosphates, of lime
and magnesia, together with phosphates of iron and manganese, and silica. These
precipitates are, however, of inferior value, as their percentage of phosphoric acid
is comparatively low on account of the silica which they contain, and as the
phosphates of iron and manganese represent impurities which may be considered
prejudicial' to their application.
I therefore prefer to separate from each other, by means of a fractional precipi-
tation, the substances which have passed into the solution. For this purpose weak
milk of lime or magnesia is added to the acid solution at first in a quantity which
is sufficient for precipitating the phosphates of iron and manganese together with
a small portion of the earth phosphates only. Hereupon a further quantity of
milk of lime or magnesia is added to the solution drawn off from the first
precipitate; but the addition thereof is discontinued before the solution shows
an alcalic reaction; that is, the solution is allowed to remain slightly acid. This
will cause the main portion of the earth phosphates to separate out, while the
greater part of the silica yet remains in solution. By thereupon completely
neutralizing the remaining solution the silica is thrown to the bottom either alone
or together with an amount of magnesia, manganese and lime, or of any of these
substances.
If preferred, the earth-basic phosphates may be precipitated together with the
silica by at once neutralizing the liquid separated from the compounds of iron and
manganese.
The precipitates are separated from the liquid by allowing them to settle, and
decanting the latter, or by filtration on' filter-presses. They are thereupon washed
and eventually dried.
The phosphoric acid contained in the phosphates of iron and manganese obtained
in the first stage of the process of fractional precipitation, may be rendered
profitable in the following manner. The phosphates of iron and manganese are
mixed with lime, or magnesia, or the carbonates thereof, and roasted at a red heat.
This causes a transition of the phosphoric acid from the iron and manganese to
the lime and magnesia to take place, whereby phosphates of lime and magnesia
are formed. These are subsequently extracted in a like manner as the earth; basic
phosphates contained in the roasted slag. The residue which consists mainly of
oxides of iron and manganese, may be utilized for the production of colours, or
it is employed together with the like primary residue in the manufacture of iron.
Having thus described the nature and object of this invention and the manner

page_text: in which it is to be carried out in practice, I hereby claim as new and essential
features of the same :
1., The production of impure earth phosphates from slag obtained in the lime-
basic process of dephosphorization of iron, especially in the process of Thomas, by
treating the powdered and roasted slag with muriatic acid which is diluted but
so little that, in addition to the main portion of the silica and of the earth
phosphates, a part of the oxides of iron and manganese will be dissolved, and
by thereafter precipitating the earth phosphates together with the silica and the
said oxides by means of lime, or magnesia, or the carbonates thereof, substantially
as hereinbefore described.
2., The treatment of the solution obtained from the slag according to claim 1,
and which contains the silica, the earth phosphates and a part of the iron and
manganese, by a fractional precipitation by means of lime or magnesia carried out
in such a manner that at first the phosphates of iron and manganese are precipitated
alone and thereafter the earth phosphates together with the silica, substantially as
specified.
3., In the fractional precipitating process by means of lime or magnesia applied
to the solution obtained from the slag and containing silica, earth phosphates and
phosphates of iron and manganese, and in which process the phosphates of iron
and manganese are first precipitated alone: the fractional treatment of the
remaining solution so that earth phosphates are obtained separate from the silica,
substantially as hereinbefore set forth.
4., The treatment of the phosphates of iron and manganese obtained by the
fractional precipitating process as described, by mixing the said phosphates with
lime or magnesia and roasting the mixture at a red heat, for the purpose of
producing earth phosphates, substantially as specified.
In Witness whereof I, the said Carl Pieper, have hereunto set my hand and
seal this twenty first day of September in the year of our Lord One thousand,.,
eight hundred and eighty three.
-J
CADT
רדרדמזת.
רגזמחזס
CARL PIEPER