IMPROVEMENTS IN PREPARING OXIDE OF IRON FOR PURIFYING GAS AND IN TREATING THE OXIDE OF IRON RESIDUES TO OBTAIN PRODUCTS THEREFROM
Year: 1868

page_text: LETTERS PATENT to Thomas Lesslie Gregson Bell, of Plaistow, in
the County of Essex, for the Invention of "IMPROVEMENTS IN
PREPARING OXIDE OF IRON FOR PURIFYING GAS AND IN TREATING THE
OXIDE OF IRON RESIDUES TO OBTAIN PRODUCTS THEREFROM."
Sealed the 23rd June 1868, and dated the 24th January 1868.
PROVISIONAL SPECIFICATION left by the said Thomas Lesslie
Gregson Bell at the Office of the Commissioners of Patents, with
his Petition, on the 24th January 1868.
I, THOMAS LESSLIE GREGSON BELL, of Plaistow, in the County
5 of Essex, do hereby declare the nature of the said "IMPROVEMENTS IN
PREPARING OXIDE OF IRON FOR PURIFYING GAS AND IN TREATING THE OXIDE
OF IRON RESIDUES TO OBTAIN PRODUCTS THEREFROM," to be as follows:-
This Invention has for its object improvements in preparing oxide
of iron for purifying gas and in treating the oxide of iron residues to
obtain products therefrom.
Heretofore for purifying gas peroxide of iron, either precipitated or
natural, has principally been employed. Precipitated oxide of iron

page_text: purifies gas very readily and perfectly, but is very costly to prepare, and
by any of the ordinary modes of manufacture (such as precipitating a salt
of iron) cannot be made to contain a high per-centage of the iron, owing
to the presence of the precipitant (usually lime) and the necessity for
adding some porous material to enable the gas to permeate it freely,
so that it very soon becomes so charged with sulphur as to be useless.
Natural oxides of iron and burnt pyrites contain a much higher
per-centage of peroxide, and therefore last very much longer before.
becoming exhausted, but they act very slowly and with difficulty until
they have been in use some time. I obviate these difficulties by freshly
precipitating a certain quantity of oxide of iron throughout the substance
of a native peroxide of iron, and so get ready and perfect action at
first combined with lasting qualities and lowered cost of production.
I prefer to take a certain quantity of a natural oxide, to which I add
a solution of salt of iron; or the salt of iron may be added in powder
and afterwards wetted. I then precipitate this salt of iron by the
addition of lime, either dry or in partial solution, or mixed with a
small quantity of sawdust or porous material, or I subject the mixture
to the action of ammonia, and wash out the resulting ammonia salt,
leaving the iron precipitated throughout the natural oxide; this may
require drying, and is then ready for use.
For producing precipitated oxide of iron for gas purification, I also,
according to my Invention, employ the above process of combining
ammonia, either liquid or gaseous, with a salt of iron by itself or mixed
with other materials, and afterwards washing out the ammonia salt.
In order to extract cyanogen compounds and ammonia from oxide
of iron material that has been used for purifying gas, I first separate the
sulphur from the oxide of iron material by bisulphide of carbon or
other solvent of sulphur, and afterwards digest the material with water
which dissolves out the ammoniacal salts, which are principally sulpho
cyanide of ammonium; these I distil over (with the addition of lime) o
convert into merchantable salts of ammonia by any of the ordinary
modes in use. The resulting lime solution contains sulphocyanide o
calcium, to this I add carbonate of potash or soda, which precipitates
the lime, leaving sulphocyanide of potash or soda in solution, which
then crystallize. I then digest the residue (after treatment with wate
as above) with potash, soda, or lime, which dissolves out the cyanid
or ferrocyanide of iron. To this I add an acid (sulphuric or hydro

page_text: chloric) and a salt of iron, which precipitates the ferrocyanide of
iron (Prussian blue). This, if necessary, may be redissolved and
purified or converted into ferrocyanide of potassium (prussiate of
potash); or if I have used lime to dissolve out the cyanides I add
carbonate of potash to the solution, which precipitates the lime,
leaving prussiate of potash in solution, which I crystallize out in
the ordinary way.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas Lesslie Gregson Bell in the Great Seal
Patent Office on the 24th July 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
LESSLIE GREGSON BELL, of Plaistow, in the County of Essex, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-fourth day of January, in the
year of our Lord One thousand eight hundred and sixty-eight, in the
thirty-first year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Thomas Lesslie Gregson Bell, Her
special licence that I, the said Thomas Lesslie Gregson Bell, my
executors, administrators, and assigns, or such others as I, the said
Thomas Lesslie Gregson Bell, my executors, administrators, and
assigns, should at any time agree with, and no others, from time
to time and at all times thercafter 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 "IMPROVEMENTS IN PREPARING OXIDE
OF IRON FOR PURIFYING GAS AND IN TREATING THE OXIDE OF IRON RESIDUES
TO OBTAIN PRODUCTS THEREFROM," upon the condition (amongst others)
that I, the said Thomas Lesslie Gregson Bell, 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.

page_text: NOW KNOW YE, that I, the said Thomas Lesslie Gregson Bell,
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 :-
This Invention has for its object improvements in preparing oxide
of iron for purifying gas, and in treating the oxide of iron residues to
obtain products therefrom.
Heretofore for purifying gas peroxide of iron, either precipitated or
natural, has principally been employed. Precipitated oxide of iron
purifies gas very readily and perfectly, but is very costly to prepare in
a state of purity, and cannot be made to contain a high per-centage
of the iron by any of the ordinary modes of manufacture, such as
precipitating iron from copperas by the addition of lime, owing to the
presence of the large quantity of lime required and the necessity for
adding sawdust or other porous material to enable the gas to permeate
it freely. It is consequently found that although it acts very perfectly
at first, it soon becomes so charged with sulphur as to be useless.
Many natural oxides of iron contain a much higher per-centage of
peroxide than those manufactured as before mentioned, and therefore
last very much longer before becoming spent, but they act very slowly
and with difficulty until they have been in use some time. I obviate
these difficulties by freshly precipitating a certain quantity of iron
throughout the substance of a native or natural peroxide, and so get
ready and perfect action at first combined with great lasting quality
and lowered cost of production.
The mode in which I prefer to carry out my Invention is as follows:-
I first grind the natural oxide of iron; the fineness to which it should
be ground depends on the nature of the substance operated upon.
Oxides of a porous nature do not require to be so finely ground as
others. I place a quantity of this ground oxide in a large shallow vessel
or vat, and pour over it a boiling saturated solution of green copperas
or other salt of iron (or the salt of iron may be added in powder, or may
have becu ground with the oxide and afterwards wetted); when this
is thoroughly mixed I add the equivalent proportion of quicklime
(sufficient to precipitate or decompose the salt of iron), cither dry or in
partial solution, or mixed with a small quantity of fine sawdust, or other
porous material.
This mixture, which then forms a pasty mass, is
turned out of the vat and made into a heap, and when sufficiently dry

page_text: is finely sifted and is then ready for use. For some reasons it will in
many cases be found more convenient to first add the quicklime to the
oxide; it may either be added in powder or by grinding it with the oxide,
and afterwards to add the salt of iron in solution, as before mentioned,
the resulting compound in either case being the same.
The salt of iron I prefer to use is the photosulphate of iron called
green copperas, but the protochloride or perchloride of iron may be used
with equal advantage.
The natural oxide I prefer to operate upon is that known as bog ochre,
but there are others, such as kidney ironstone, which may be used;
I find those answer best in which the iron exists as hydrated peroxide of
iron. I find excellent results from using two parts of natural oxide
with one part of copperas and the equivalent proportion of quicklime,
but I vary the proportions according to the nature of the oxide operated
upon. By using a natural oxide containing a high per-centage of
pure peroxide of iron as a basis on which to precipitate the solution
of iron I can produce a inaterial for purifying gas which combines
the advantages of the natural oxide with those of pure precipitated
oxide, and without the disadvantages of either.
The next part of my Invention, which relates to the extraction of
cyanogen compounds and ammonia from oxide of iron material that has
been used for purifying gas (commonly called spent oxide), consists in
first separating the sulphur from the oxide of iron material by means of
bisulphide of carbon or other solvent of sulphur, and then subsequently
treating the oxide of iron material to obtain therefrom the cyanogen
compounds and ammonia, as herein described. For this purpose after
that sulphur has been dissolved from oxide of iron material by bisulphide
of carbon or other solvent, and after that the material has been freed
from the bisulphide or solvent by distillation, as is now well understood,
I put a quantity of the material into a large vat. The description of vat
I prefer is one having a false bottom, through which liquor may filter
and be drawn off, and also a series of taps or plugs in one side, so that
as the contents settle the supernatant liquor may be drawn off at
different heights. Upon the material in this vat I run boiling water
and thoroughly stir it; I find advantage in blowing steam into it or
applying heat in any other way; and if the material operated upon is
not already slightly acid I add a small quantity of sulphuric acid, which

page_text: facilitates the solution of the ammonia salts, principally sulphocyanide,
and the sulphocyanide of iron should there be any present; this is then
allowed to settle, and the clear solution drawn off as closely as possible
by the different taps, the remainder of the solution draining through the
bottom. This operation may be repeated if necessary, or a series of
these vats may be connected in a manner well known to manufacturing
chemists, so as to thoroughly wash out the soluble salts. This clear
solution I run into a boiler or close vessel, in which it may be treated,
and to it I add quicklime in excess, so that on the application of heat the
ammonia distils over, and is condensed in an acid, or converted into a
merchantable salt of ammonia by any of the ordinary modes in use well
known to manufacturing chemists. When the ammonia is all driven off
I run the remaining liquid into another vat or settler, and draw off the
clear solution, which contains principally sulphocyanide of calcium; to
this I add carbonate of potash or soda, which precipitates the calcium as
carbonate of lime, leaving sulphocyanide of potash or soda in solution;
this I filter and then crystallize out. To the solid matter remaining in
the vat (after treatment with hot water as above) I add an alkali, either
potash, soda, or lime, in sufficient quantity to dissolve out the cyanide
or ferrocyanide of iron; this alkaline solution I then draw off, and wash
the solid residue several times with water so as to extract the whole of
the soluble matter. I run these washings over several vats in succession
so as to get them as fully charged as possible. These liquors are allowed
to settle perfectly, and then I add enough acid (sulphuric or hydro-
chloric) to show an acid reaction, and if necessary they are again
allowed to settle, and to the clear solution I add solutions of proto-
sulphate and perchloride of iron sufficient to precipitate the whole of the
alkaline ferrocyanide as ferrocyanide of iron or Prussian blue; this is
thoroughly washed with water and then drained and dried upon a filter;
this if necessary for greater purity may be redissolved as before, and
again precipitated and so purified, or it may be converted into ferro-
cyanide of potassium by dissolving in potash, filtering, and then
crystallizing out the ferrocyanide of potassium (prussiate of potash).
If I use lime to dissolve out the cyanides or ferrocyanides in the first
instance I prefer to add carbonate of potash to the solution; this pre-
cipitates the lime as carbonate, and after filtering and allowing the
solution to settle in a series of settlers or vats I run it into a pan,
where by the application of heat I concentrate it to such a strength

page_text: that when run into a series of vessels which I call crystallizers the
prussiate of potash crystallizes out.
In witness whereof, I, the said Thomas Lesslie Gregson Bell, have
hereunto set my hand and seal, this Twenty-second day of July,
in the year of our Lord One thousand eight hundred and sixty-
eight.