IM- PROVEMENTS IN TREATING RED OXIDE' OF IRON FOR THE PURPOSE OF OBTAINING THEREFROM CERTAIN USEFUL PRODUCTS
Year: 1879

page_text: LETTERS PATENT to Alexander Watt, of 20, Christchurch Terrace, Battersea
Park Road, in the County of Surrey, Chemist, for the Invention of "IM-
PROVEMENTS IN TREATING RED OXIDE' OF IRON FOR THE PURPOSE OF
OBTAINING THEREFROM CERTAIN USEFUL PRODUCTS."
Sealed the 2nd May 1879, and dated the 28th January 1879.
PROVISIONAL SPECIFICATION left by the said Alexander Watt at the
Office of the Commissioners of Patents on the 28th January 1879.
ALEXANDER WATT, of 20, Christchurch Terrace, Battersea Park Road, in the
County of Surrey, Chemist. "IMPROVEMENTS IN TREATING RED OXIDE OF IRON
FOR THE PURPOSE OF OBTAINING THEREFROM CERTAIN USEFUL PRODUCTS."
This Invention relates to the treatment of native red oxide of iron by chemical
and mechanical means, whereby is obtained economically certain products which
are useful in the arts, namely, Prussian blue, jewellers' rouge, and a red pigment
suitable (when mixed with oils and such usual ingredients) for coating iron and
other surfaces.
It is well known that Prussian blue is ordinarily manufactured from the proto-
sulphate of iron and ferrocyanide of potassium, by which process a pale blue
precipitate is at first obtained, which acquires the characteristic dark blue tint by
exposure to the air, whereas the persalts of iron when treated with the ferrocyanide
of potassium at once assume the desired dark blue color directly the respective
salts come in contact with each other, and I have taken advantage of this well
known chemical fact in working out my improvements.
For the purpose of this Invention I treat red iron ore (peroxide or sesquioxide
of iron) with strong hydrochloric acid, and with the assistance of moderate heat,
whereby I obtain a very rich solution of perchloride of iron at a very moderate
cost. The solution thus obtained is afterwards diluted with water, and the Prussian
blue precipitated in the ordinary way by ferrocyanide of potassium. The blue
pigment is then washed and treated as usual.
In the first operation I select by preference the soft iron ore known as "redding,"
or in the case of the harder red oxide of iron I reduce it to powder by grinding,
and then pour upon it sufficient water to enable it to become slackened or moistened ;
that is to say, after it has absorbed a sufficient quantity of water it is readily
reduced to a pasty consistence. In this condition I pour upon the ore a quantity

page_text: of strong hydrochloric acid, the quantity of the acid employed in this first operation
being sufficient to strongly attack and dissolve about one third of the ore under
treatment, and apply-a-moderate-heat_for_several hours to the outside of the pan
until the acid-solution assumes a dark brown or orange color. I then allow the
solution to cool and settle, and carefully decant the concentrated solution of per-
chloride or sesquichloride-of-iron, which is then ready for treatment with the
ferrocyanide of potassium. I-next-wash-the-undissolved-mass, repeatedly employing
-the-washing waters to dilute the first obtained concentrated solution.
After testing the last washing water, which should show-no-trace-of-acid salt, I
pour on to the mass a large quantity of water, and then stir briskly. This liquor
is now allowed to rest for a few moments, so as to permit the heavier particles to
subside, and I then pour off the liquor, which is impregnated with the oxide of
iron in a very fine state of division. This finely divided oxide of iron I allow to
settle, and the water is finally poured off, and when the remaining deposit is care-
fully dried it forms a very useful and cheap pigment, for ironwork more especially.
If necessary I return the washing water left after the last operation to the residual
mass from the previous washings and again stir well, and by pouring off the liquor
as before I obtain a further quantity of the pigment. This process of elutriation
can be repeated several times. The resulting mass is again treated with strong
hydrochloric acid until the whole of the sesquioxide or peroxide of iron is dissolved,
when the silicious or earthy matters in the residium may be put aside.
To make jewellers' rouge I evaporate the concentrated solution of perchloride to
dryness, and heat the resulting mass in a crucible until all the acid is driven off, when
I treat the calcined oxide with water, and collect the finest particles by elútriation
in the ordinary way; or I precipitate .the iron from its solution by ammonia or
potash and calcine as usual.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Watt in the Great Seal Patent Office on the 28th July
1879.
"
ALEXANDER WATT, of 20, Christchurch Terrace, Battersea Park Road, in the
County of Surrey, Chemist. IMPROVEMENTS IN TREATING RED OXIDE' OF IRON
FOR THE PURPOSE OF OBTAINING THEREFROM CERTAIN USEFUL PRODUCTS."
This Invention relates to the treatment of native red oxide of iron by chemical
and mechanical means, whereby are obtained economically certain products which
are useful in the arts, namely, Prussian blue, jewellers' rouge, and a red pigment
suitable when mixed with oils, &c. for coating iron and other surfaces.
It is well known that Prussian blue is ordinarily manufactured from the proto-
sulphate of iron and ferrocyanide of potassium, by which process a pale blue or
whitish precipitate is at first obtained, which acquires the characteristic dark blue
tint by exposure to the air, or by means of certain oxidizing agents, as is well
known, whereas the persalts of iron when treated with the ferrocyanide of potas-
sium at once assume the desired dark blue color directly the respective salts come
in contact, and I have taken advantage of this well known chemical fact in working
out my improvements.
For the purpose of this Invention I treat native red iron ore (peroxide or sesqui-
oxide of iron) with strong hydro chloric acid with the assistance of moderate heat,
whereby I obtain a very rich solution of perchloride of iron at a very moderate
cost. The solution thus obtained is afterwards diluted with water, and the Prussian
blue precipitated in the ordinary way by ferrocyanide of potassium. The blue
pigment is then washed and treated as usual.
In the first operation I select by preference the soft iron ore known as "redding,"
and pour upon it sufficient water to enable it to become slackened or moistened.;
that is to say, after it has absorbed a sufficient quantity of water it is readily
reduced to a pasty consistence. In this condition I pour upon the ore a quantity
of strong hydrochloric acid, the quantity of acid employed in this first operation
being sufficient to strongly attack and dissolve say about one third of the peroxide
of iron contained in the ore under treatment, and apply a moderate heat for several
hours until the acid solution assumes a dark orange color. I then allow the
solution to cool, when I carefully decant the concentrated solution of perchloride or
sesquichloride of iron, which is then ready for use.. I next wash the undissolved
mass repeatedly, employing the washing waters to dilute the first obtained con-
centrated solution. After testing the last washing. water, which should exhibit
little or no trace of acid salt, I pour on to the mass a large quantity of water, and
then stir briskly. This liquor is now allowed to rest for a few seconds, so as to
permit the heavier particles to subside, when I run off the liquor, which is
impregnated with the red oxide of iron in a very fine state of division, and this
finely divided oxide of iron I allow to settle, and the water is finally run off.
When the resulting deposit is carefully dried it forms a very useful and cheap red
pigment, for iron work more especially. If necessary I return the washing water
left after the last operation to the residual mass from the previous washings, and
again stir well, and by running off the liquid as before I obtain a further quantity
of the red pigment. This process of elutriation can be repeated several times.
The residuum may be again treated with strong hydrochloric acid until the.
greater part of the sesquioxide or peroxide of iron is dissolved, when the silicious
or earthy matters in the residuum may be put aside; or the whole, or nearly the
whole, of the red color may be obtained by continuing the above process of washing
by further grinding or pulverising the mass before washing.
To make jewellers' rouge I evaporate the concentrated solution of perchloride to
dryness, and heat the resulting mass in a crucible until all the acid is driven off,

page_text: when I treat the calcined oxide with water, and collect the finest particles by
elutriation in the ordinary way; or I precipitate the iron from the perchloride
solution by ammonia-or-potash,-and.calcine and wash as usual.
To-carry-out-my Invention I take, say, one ton of the soft iron ore known as
"redding," or native red oxide or peroxide of iron, and moisten it with water until
it has become soft. In-this-state-I-reduce it to a pasty consistence by means of an
iron "punner," or by any other suitable contrivance, -the-object being to render the
peroxide more readily attacked by the hydrochloric acid employed for that purpose,.
as hereinafter described; or when the ore is hard; as is sometimes-the-case, I reduce
it to powder by crushing, grinding, or pulverising. I next take any required
quantity of the above paste or powder of red oxide of iron, and place it in a vessel
made of stoneware or other suitable material not acted upon by the acid employed,
and pour on to it sufficient hydrochloric acid to dissolve a portion, say about one
third, of the peroxide of iron contained in the ore. To assist the action of the
hydrochloric acid I prefer applying gentle heat, which may be conveniently done
by employing a steam jacketed dissolving vessel.
During the operation of dissolving the peroxide from the ore I cause the mass to
be occasionally stirred, so as to diffuse the acid well through the mass.
After a
few hours, and when the acid solution has acquired a rich golden brown tint, I
allow the undissolved residue to subside, when I draw off (by means of a syphon
.or otherwise) the supernatant liquor and transfer it to another vessel. I then
dilute the solution of perchloride with water, and it is then ready for treatment
with ferrocyanide of potassium to form Prussian blue in the ordinary way. To
make soluble Prussian blue I allow the ferrocyanide of potassium to be in
excess.
After having drawn off the solution of perchloride of iron as aforesaid, I next
nearly fill the dissolving vessel before mentioned with water (hot water by pre-
ference), and again stir well to wash out the remaining perchloride solution. I
again allow the undissolved ore to subside when the clear liquor is to be decanted,
and may be used to dilute the first named concentrated solution. Having thus
obtained a certain quantity of solution of perchloride of iron to convert into
Prussian blue, I next proceed to treat the undissolved mass, so as to obtain a red
pigment suitable as a protective coating for iron or wood work for out door or other
purposes, and which may also be mixed with other pigments for various useful
purposes. To obtain the red pigment-I remove the whole of the remaining undis-
solved mass, and place it in a vessel capable of holding a large quantity of water.
I then nearly fill this vessel with water and stir well, so as to diffuse the finer
particles of the residuum throughout the liquid. After allowing the heavier par-
ticles to subside, which only occupies a few seconds of time, I run off by means of
taps or plugs placed at various distances in the vessel, the water holding in
suspension the finer particles, and the runnings are conveyed by means of a shoot
or otherwise to a receiving vessel. -This-process-of--elutriation, which is well
understood, I repeat several times, adding water, and stirring each time, so as to
collect as much of the fine matter as may be desired. I then allow the washed
color to subside, when the water is poured off, and the color may be dried in the
usual way.
After having obtained a sufficient quantity of the red pigment as above described,
the remainder of the undissolved mass may be replaced in the dissolving vessel and
again treated with hydrochloric acid as before, so as to obtain a further supply of
solution of perchloride of iron either for the production of Prussian blue or
jewellers' rouge, or by crushing or pulverising the residuum and washing, as before,
a further supply of red pigment of a somewhat darker color may be obtained. To
make jewellers' rouge from the perchloride solution the oxide may be precipitated
by ammonia or potash, and after being washed is converted into rouge by drying
and subsequent ignition, after which the finest particles of the peroxide formed are
'obtained by elutriation, as before described.
In carrying out iny Invention as herein described.the order in which the various

page_text: operations are conducted may be varied and applied according to requirement, that
is to say, if the demand for Prussian blue renders it desirable I dissolve the whole,
or nearly the whole, of the peroxide contained in the red ore, and convert the
solution obtained into Prussian blue; or when rouge is in greater demand I make
a larger proportion of this substance, or for the red pigment I convert a larger
proportion of the red mass into the red pigment as aforesaid.
After having washed out the finest particles of peroxide in the manufacture of
rouge, as above described, I treat the residue, consisting of the coarser particles,
with hydrochloric acid to form perchloride of iron for future use, or by trituration
and washing as before described of this residue from the making of rouge there
will be obtained a red pigment of great beauty and excellent body.
:
Having now described the nature of the said Invention, and particularized the
same in such wise that any one acquainted with the art may readily carry the
same into practical effect, I claim,―
The improvements in treating red oxide of iron, as and for the purposes herein
set forth.
In witness whereof, I, the said Alexander Watt, have hereunto set my hand
and seal, this Twenty eighth day of July, in the year of our Lord One
thousand eight hundred and seventy nine.
Witness,
WALTER A. BARLOW,
Patent Agent & Engineer,
6, St. Paul's Churchyard,
London, E.C.
ALEXANDER WATT. (L.S.)