Improved Process for Obtaining Iron Oxides.
Year: 1899

page_text: Date of Application, 24th Oct., 1899-Accepted, 9th Dec., 1899
COMPLETE SPECIFICATION.
Improved Process for Obtaining Iron Oxides.
I, HERBERT JOHN HADDAN, of the Firm of Herbert Haddan & Co., of 18,
Buckingham Street, Strand, W.C.. London, Consulting Engineer, do hereby
declare the nature of this invention a communication to me from abroad by
Alexander Sydney Ramage, of Cleveland, in the County of Cuyahoga, and State
of Ohio, United States of America, Chemist, and in what manner the same is
to be performed to be particularly described and ascertained in and by the
following statement:--
My invention relates to a new and improved process of obtaining ferric oxide
from sulphate or chloride of iron, and it relates more particularly to an improved
process of obtaining ferric oxide of various shades and colors; and sulphate
or chloride of magnesia as a by-product, from a mixture of sulphate or chloride
of iron and magnesite, dolomite, calcined magnesia or other carbonates of
magnesia.
My invention consists in placing a mixture composed of sulphate or chloride
of iron and magnesite, dolomite, calcined magnesia or carbonate of magnesia,
or a mixture of the said salts of iron with magnesia or a suitable carbonate of
any alkaline earth (which will give a soluble sulphate or chloride when heated
with a sulphate or chloride of iron), with or without a small quantity of sodium
chloride being added thereto, in a suitably closed furnace preferably so con-
structed that a partial vacuum can be formed therein, and heating the said
mixture under suitable conditions of pressure and temperature until new sub-
stances are formed by chemical action and certain desired results are obtained.
The object of my invention is to secure a suitable quantity of ferric oxide
of any particular shade or color desired and, in the same operation, to obtain
sulphate or chloride of magnesia as a by-product whereby I obtain iron oxide
possessing finer and more brilliant shades of color at a greatly reduced cost.
I secure results in a few hours which otherwise, by the methods heretofore used,
would require several days, and I also accomplish other objects as hereinafter
set forth and claimed.
In the accompanying drawings, Fig. I is a plan view, partly in section, of an
apparatus capable of carrying out my process, and Fig. II is a vertical section
on the line II-II of Fig. I.
The manner in which I prefer to carry out my process is as follows:-The
sulphate of iron is first dried by gentle heat until all the water of crystalization
is, as far as possible, dispelled. It is then mixed with a suitable quantity, prefer-
ably about twenty per cent. of magnesia or calcined magnesia and placed in a
furnace A, preferably a plus pressure muffle furnace, such as the type employed
in the well known Leblanc soda process having its fire-box located about twelve
feet below the bed of the furnace, so constructed as to permit a partial vacuum
being formed therein. The furnace is heated to a dull red heat, or to approxi-
mately that temperature, and a partial vacuum is produced within the same
by means of exhaust mechanism provided for this purpose, comprising a vacuum

page_text: pump B, a lead lined box C and an asbestos filled cylinder D are interposed
between the furnace A and pump B, these parts of the apparatus being connected
together and to the furnace and pump by suitable pipes E, F and G. A pipe or
cylinder H is arranged within the box C communicating with the pipes F and G.
The box C is supplied with water which surrounds the cylinder H to cool the
gases, and the asbestos filled cylinder D serves to further cool them. Double
decomposition of the substances composing the said mixture takes place and the
chemical elements recombine to form ferrous oxide and sulphate of magnesia.
The ferrous oxide is oxidized to ferric oxide by the oxygen contained in the
air which remains in the furnace.
The length of time the mixture remains in the furnace varies from two to
twelve hours according to the shade or color required.
In order to produce the deeper shade of red, such as the Indian, Tuscan and
purple reds, a small quantity of sodium chloride, preferably from two to ten
per cent. according to the shade required, is added to the above mixture of iron
sulphate and magnesite or calcined magnesia before it is placed in the furnace.
The sodium chloride is decomposed by the heat of the furnace and the chlorine
which is evolved forms ferric chloride which is instantly converted to ferric
oxide of a deep shade.
Instead of magnesite or calcined magnesia, ground or calcined dolomite can
be used, which gives less sulphate of magnesia and an impure oxide of iron.
This impure oxide, technically known as Venetian red, can be utilized in the
art and is valuable for various commercial purposes.
It will be observed that chloride of iron can be treated in a similar manner
according to the above described process, the resulting products being ferric
oxide and chloride of magnesia instead of sulphate of magnesia.
After the mixture has remained in the furnace a sufficient length of time
to develop the particular shade or color of ferric oxide desired, it is withdrawn
from the furnace and thoroughly ground with water, and is then run into a tank
and allowed to settle. The ferric oxide settles to the bottom and the water con-
taining the sulphate or chloride of magnesia in solution can be run off and
the sulphate or chloride of magnesia crystalized out and used for commercial
purposes. The iron oxide which remains in the bottom of the tank is filtered,
washed, dried and ground and is then ready for the market.
It will be understood that I lay great stress in the use of a partial vacuum
in practicing my process, as by the use of said partial vacuum the chemical
reactions take place in the furnace at a much lower temperature than would be
possible if said changes occurred under ordinary atmospheric pressure. It will
be understood however, that by using a partial vacuum and owing to the porosity
of the brick walls of the furnace, there is always sufficient oxygen present to
change any ferrous salts to the ferric state.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. The herein described process of obtaining ferric oxide and sulphate of
magnesia, which consists in heating a mixture of sulphate of iron and calcined
magnesia, in a partial vacuum until the desired shade is obtained, substantially
as and for the purpose set forth.
2. The herein described process of obtaining ferric oxide, which consists in
heating a mixture of sulphate or chloride of iron, magnesite or calcined magnesia,
and sodium chloride in a partial vacuum, substantially as and for the purpose
set forth.
3. The herein described process of obtaining certain shades of ferric oxide
and sulphate of magnesia, from a mixture of sulphate of iron, magnesia and
sodium chloride, which consists in heating said mixture to approximately a

page_text: dull red heat in a partial vacuum until the desired shade is obtained, substantially
as described.
4. The herein described process of obtaining ferric oxide, which consists in
forming a mixture composed of sulphate or chloride of iron and approximately
twenty per cent. of magnesia heating said mixture in a suitable furnace to
approximately a dull red heat in a partial vacuum produced in said furnace
by suitable means provided for this purpose until the desired color is obtained,
substantially as and for the purpose set forth.
5. The herein described process of obtaining certain shades of ferric oxide
and sulphate of magnesia as a by-product, which consists in forming a mixture
composed of sulphate of iron and approximately twenty per cent. of magnesia
adding thereto from two to ten per cent. of sodium chloride, and heating said
mixture in a suitable furnace under reduced atmospheric pressure to approxi-
mately a dull red heat, substantially as and for the purpose set forth.
6. The herein described process of obtaining ferric oxide and sulphate of
magnesia as a by-product, which consists in providing a mixture composed of
sulphate of iron with magnesia or any suitable alkaline carth (which on being
heated with sulphate of iron would be changed to a soluble sulphate), then
adding thereto approximately two to ten per cent. of sodium chloride, and heating
said mixture in a suitable furnace under a partial vacuum to a dull red heat,
substantially as and for the purpose set forth.
Datal 41.
5.111
atalan 1900