Improvements in the Manufacture of Caustic Soda or Caustic Potash, from Carbonate of Soda or Carbonate of Potash.
Year: 1897

page_text: Date of Application, 16th Feb., 1897
Complete Specification Left, 13th Oct., 1897-Accepted, 20th Nov., 1897
Improvements in the Manufacture of Caustic Soda or Caustic Potash,
from Carbonate of Soda or Carbonate of Potash.
We, THOMAS RYAN, Junior, Chemical Engineer; ALFRED DYSON, Manager;
and THE UNITED ALKALI COMPANY LIMITED; all of G11 Exchange Buildings,
Liverpool, in the, County of Lancaster, do hereby declare the nature of this In-
vention to be as follows:-
Hitherto when caustic alkalies have been produced by heating a carbonate of
an alkali with oxide of iron as described in the Specification of Loewig's Patent
No. 43648 the success of the operation has depended upon a most intimate
mixture of the oxide of iron with the alkaline carbonate. With certain special
forms of carbonate of soda, such as low grade Leblanc Ash it has been found
difficult to carry out the process it being necessary to use very finely divided car-
bonate of soda such as is obtained in the ammonia soda process by heating the
crude bicarbonate to temperatures not exceeding 300° Centigrade.
"
A much more intimate mixture of oxide of iron with carbonate of soda or
carbonate of potash is obtained by using solutions of these carbonates and any
ordinary Leblanc soda, such as soda ash,"
black salts," or even the crude solu-
tion obtained by the lixiviation of black ash" known in the trade as vat
liquor" may be advantageously converted into caustic soda.
"
According to this invention a charge of oxide of iron, preferably in a finely
divided condition is placed in a Mactear or other suitable furnace and this charge
is heated to a sufficient temperature and then there is gradually added, whilst
constantly stirring, a suitable amount of concentrated solution of carbonate of
soda or of potash. While the solution is thus gradually added heat is freely
applied, and the heating is afterwards continued until the temperature is reached
at which the oxide of iron decomposes the carbonate and forms what is known as
ferrite of the alkali. When the whole, or nearly the whole, of the carbonic acid
has been driven off, the charge is withdrawn and the caustic soda or caustic
potash (as the case may be) extracted by lixiviation with water.
When ordinary
"
vat liquor" is employed the sulphides contained therein are
decomposed during the formation of the ferrite, so that no special, treatment is
required for their removal.
We prefer to use the oxide of iron obtained from roasted iron pyrites after ex-
traction of the copper and known as purple ore."
66
The process according to this Invention may be carried out in, one stage or in
two or more stages. For instance the mixture of the oxide of iron with the solu-
tion of the alkaline carbonate may be made in one furnace, and the dry mass be
afterwards transferred to another furnace to be therein heated to the necessary
high temperature.
Dated this 16th dow of Fabia 1007
:

page_text: Improvements in the Manufacture of Caustic Soda or Caustic Potash,
from Carbonate of Soda or Carbonate of Potash.
We, THOMAS RYAN, Junior, Chemical Engineer; ALFRED DYSON, Manager;
and THE UNITED ALKALI COMPANY LIMITED; all of G11 Exchange Buildings,
Liverpool, in the County of Lancaster, do hereby declare the nature of this la-
vention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:―
Hitherto when caustic alkalies have been produced by heating a carbonate of
an alkali with oxide of iron as described in the Specification of Loewig's Patent
No. 4364 of 1882 the success of the operation has depended upon a most intimate
'mixture of the oxide of iron with the alkaline carbonate. With certain special
forms of carbonate of soda, such as low grade Leblanc Ash, it has been found
difficult to carry out the process it being necessary to use very finely divided car-
bonate of soda such as is obtained in the ammonia-soda process, by heating the
crude bi-carbonate to temperatures not exceeding 3000 centigrade.
-
A much, more intimate mixture of oxide of iron with carbonate of soda, or
carbonate of potash, is obtained by using solutions of these carbonates and any
ordinary Leblanc soda, such as soda ash," "black salts," or even the crude
solution obtained by the lixiviation of black ash" known in the trade as vat
liquor",may be advantageously converted into caustic soda.
According to this invention a charge of oxide of iron, preferably in a finely
divided condition is placed in a Mactear, or other suitable furnace, and this charge
is heated to a sufficient temperature and then there is gradually added whilst con-
stantly stirring, a suitable amount, of concentrated solution of carbonate of soda,
or of potash. While the solution is thus gradually added heat is freely applied,
and the heating is afterwards continued until the temperature is reached at which
the oxide of iron decomposes the alkaline carbonate and forms what is known as
ferrite of the alkali. When the whole, or nearly the whole of the carbonic acid
has been driven off, the charge is withdrawn and the caustic soda, or caustic
The washed
potash, (as the case may be) extracted by lixiviation with water.
oxide of iron is again mixed with solution of alkaline carbonate and treated as
hereinbefore described.
When ordinary vat liquor" is employed the sulphides contained therein
are decomposed during the formation of the ferrite, so that no special treatment
is required for their removal.
We prefer to use the oxide of iron obtained from roasted iron pyrites after ex-
traction of the copper and known as "purple ore."
The process according to this invention may be carried out in one stage, or in
two, or more stages. For instance the mixture of the oxide of iron with the
solution of the alkaline carbonate may be made in one furnace, and the dry mass
be afterwards transferred to another furnace to be therein heated to the high
temperature necessary to form ferrite of the alkali and to drive off the carbonic
acid.
Having now paricularly described and ascertained the nature of the said in-
vention and in what manner the same is to be performed, we declare that what we
claim is :-
1. In the manufacture of caustic soda, or caustic potash, from carbonate of
soda, or carbonate of potash, mixing, in a Mactear or equivalent furnace, oxide
of iron, in a fine state of division, with a solution of carbonate of soda, or carbonate

page_text: of potash, and heating the mixture until the carbonic acid is driven off sub-
stantially as herein before described.
2. In the manufacture of caustic soda, or caustic potash, from carbonate of
soda, or carbonate of potash, mixing oxide of iron with a solution of carbonate
of soda, or carbonate of potash, in a furnace, and then transferring the dry and
hot mixture to a second furnace wherein it is heated to the necessary high tem-
perature to form ferrite of the alkali and drive off carbonic acid substantially as
hereinbefore described.
Dated this 19th day of Octalion 1007
JOHNSONS & WILLCOX
47 Lincoln's Inn Fields London, W.C., Agents.