Year: 1894

page_text: Date of Application, 22nd Oct., 1894
Complete Specification Loft 22nd July 1805 Accented
24th Ava 1806
Date of Application, 22nd Oct., 1894
Complete Specification Left, 22nd July 1905 A
Accepted 24th Aug
701
1006
A communication from THE DEUTSCHE SOLVAY-WERKE ACTIEN-GESELLSCHAFT,
of Bernburg, in the Duchy of Anhalt, Germany,
I, WILLIAM LLOYD WISE of No. 46 Lincoln's Inn Fields, in the County, of
London, Consulting Engineer and Chartered Patent Agent, do hereby declare the
nature of this invention to be as follows:
Heretofore the manufacture, of, the chromates of the alkalies has usually been
effected by roasting a naturally occurring oxygen, compound, of chromium such as
chrome-iron-ore with lime and carbonate of soda or potash, the resulting mass
being lixiviated with water and treated with potassium or sodium sulphate for the
extraction of the soluble chromates and the partial conversion of the calcium
chromate present into an alkaline chromate and calcium sulphate.
The use of lime in the above process is rendered necessary, in order to limit the
otherwise unavoidable loss of alkali due to the high temperature required and to
prevent fusion of the mass, as in that case the chrome iron ore would sink to the
bottom on account of its high specific gravity and be very slowly acted upon by
the alkali. The use of lime is however attended by several disadvantages, one
being that in consequence of the heated mass being of a pasty consistence, a portion
of the chromium compound present, is not decomposed, and by being thrown away
with the residues is lost. A further cause of loss is the impracticability of perfectly.
exhausting the residual mass by lixiviation. The process is also open to the
objection that the bye-products obtained cannot be used in subsequent operations
and are rendered troublesome by their accumulation.
Now the object of this invention is to obviate the disadvantages above referred
to by substituting for the lime a substance which will assist by chemical action, the
formation of the desired product, and at the same time reduce to a minimum the
valueless bre-products, and thereby the loss attendant on manufacture.
For this purpose the sodium and potassium salts of chromic acid are produced
according to this invention from the naturally occurring minerals, containing
oxygen compounds of chromium such as chrome iron ore, by roasting the pulverized
mineral with carbonate of soda or potash and peroxide of iron whereby a ferrite of
the alkali is formed which under the simultaneous action of the air and chrome iron
ore (or other oxide, of chromium) is converted into a chromate of the alkali and
peroxide of iron. The extraction of the chromate is effected by lixiviation of the
roasted material, the residual product consisting mainly of peroxide of irou which
can be utilised for a subsequent roasting operation.
It will be obvious therefore that by this invention the accumulation of useless
residues is avoided, and also the loss of undecomposed mineral and of the chromates
retained in the residue through imperfect lixiviation and imperfect decomposition
of the calcium chromate. A further advantage is obtained in that the ferrous
oxide already existent in the ore, when chrome iron ore is used, is utilized in the
process.

page_text: In order to obviate the contamination of the peroxide of iron residue with
alumina, silicic acid, or other impurities contained in the gangue, it is preferred to
use a slight excess of alkali.
Dated this 22nd day of October 1894:
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.
A communication from THE DEUTSCHE SOLVAY-WERKE ACTIEN-GESELLSCHAFT,
of Bernburg, in the Duchy of Anhalt, Germany.
I, WILLIAM LLOYD WISE of No. 46 Lincoln's Inn Fields, in the County of
London, Consulting Engineer and Chartered Patent Agent, do hereby declare the
nature of this invention and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement:-
Heretofore the manufacture of the chromates of the alkalies has usually been
effected by roasting a naturally occurring oxygen compound of chromium such as
chrome-iron-ore in a finely powdered condition with lime and carbonate of soda or
potash, in the presence of an oxidising flame, the resulting mass being lixiviated
with water and treated with potassium or sodium sulphate for the extraction of the
soluble chromates and the partial conversion of the calcium chromate present into
an alkaline chromate and calcium sulphate.
The use of lime in the above process is rendered necessary in order to causticize
the carbonate of soda or potash, and to prevent fusion of the mass, as in that case
the chrome-iron-ore would sink to the bottom on account of its high specific
gravity, and be very slowly acted upon by the alkali. The use of lime is however
attended by several disadvantages, one being that in consequence of the heated
mass being of a pasty consistence, a portion of the chromium compound present is
A further
not decomposed, and by being thrown away with the residues is lost.
cause of loss is the impracticability of perfectly exhausting the residual mass by
lixiviation. The process is also open to the objection that the bye-products
obtained cannot be used in subsequent operations and are rendered troublesome by
their accumulation.
Now the object of this invention is to obviate the disadvantages above referred
to by substituting for the lime wholly or partially, a substance which will assist,
by chemical action, the formation of the desired product, and at the same time
reduce to a minimum the valueless bye-products, and thereby the loss attendant on
manufacture.
For this purpose the sodium and potassium salts of chromic acid are produced
according to this invention from the naturally occurring minerals containing
oxygen compounds of chromium, such as chrome-iron-ore, by roasting the
pulverized mineral with carbonate of soda or potash and peroxide of iron (Fe,O,)
whereby carbon dioxide is evolved from the alkaline carbonate and a ferrite of the
alkali formed, which, under the simultaneous action of the air and chrome-iron-ore
(or other oxide of chromium) is converted into a chromate of the alkali and
peroxide of iron. The extraction of the chromate is effected by lixiviation of the
roasted material by water.
In consequence of the lime being absent, or present only in very small amount in
the roasted material, the impurities of the chrome ore, especially the silicic acid, and
alumina, are upon washing such roasted material dissolved out and pass into the
solution of the chromate from which they can be readily separated by neutralizing
the said solution with sulphuric acid or carbon dioxide. As a result the washed

page_text: residue consists practically only of oxide of iron, undecomposed chrome-ore,
chromate that has not been washed out, and a small quantity of calcic hydrate.
To assist in obviating contamination of the peroxide of iron residue with
alumina, silicic acid, or other impurities contained in the chrome-ore used, it is
preferred to use a slight excess of the alkaline carbonate. The wash residue, in
consequence of its purity, can, after being dried, be again used in conjunction with
a fresh charge of chrome-ore.
It will thus be obvious that by this invention the accumulation of useless
residues is avoided, and also the loss of undecomposed mineral, and of the
chromates retained in the residue through imperfect lixiviation and imperfect
decomposition of the calcium chromate present. A further advantage is obtained
in that the ferrous oxide already existent in the ore, when chrome-iron-ore is used,
is utilized in the process.
Suitable proportions of material for the manufacture of chromate of sodium
according to this invention are the following:-
240 kilogs. of chrome-iron-ore containing 50% of oxide of chromium, 170 kilogs.
of carbonate of soda, and 150 kilogs. of oxide of iron to which may be added, if
desired 50 to 80 kilogs. of lime. These substances are intimately mixed together,
and roasted in the usual manner the resulting mass being washed, also in the usual
manner, with water to extract the chromate of sodium. In this way a residue is
left which, when dried, contains from about 3 to 5% of oxide of chromium. This
residue may be used over again in lieu of an addition of fresh peroxide of iron and
lime in the proportion of about 200 kilogs. of residue to 170 kilogs. of carbonate
of soda and 220 to 230 kilogs. of chrome-iron-ore, the proportions being varied
according to the percentage of oxide of chromium in the residue. The addition
of a little lime to the mixture is not essential and may be omitted but better results
will be obtained if it be used.
The oxide of iron used may be that obtained as a bye-product in the process of
roasting pyrites in the manufacture of sulphuric acid.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what 1
claim is :-
The improved manufacture of chromates wherein peroxide of iron is used as
hereinabove described.
Dated this 22nd day of July 1895.
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.