Improvements in the Manufacture of Carbonate of Soda and of Carbonate of Potash, and in the Treatment of Residual Products Obtained in such Manufacture.
Year: 1886

page_text: Date of Application, 8th Apr., 1886.
Complete Left, 8th Feb., 1887.
Complete Accepted, 25th Mar., 1887.
Improvements in the Manufacture of Carbonate of Soda and of
Carbonate of Potash, and in the Treatment of Residual Products
Obtained in such Manufacture.
I CARL FRIEDRICH CLAUS of Merton Road South Wimbledon in the County of
Surrey Chemist do hereby declare the nature of my said invention to be as follows:-
1- decompose alkali waste either moistened with or suspended in water in the
manner known to Chemists by means of impure carbonic acid gas such as fuel gases
or the effluent gases from lime kilns or from similar sources. The sulphide of
hydrogen evolved in this process, together with the gases accompanying it, I mix with
a sufficient quantity of air to form sulphurous acid with the sulphide of hydrogen,
when these two are exposed to a temperature favourable for that reaction to
take place.
The mixture of sulphide of hydrogen and air I pass through masses of heated solid
materials such as oxide of iron, oxide of manganese broken bricks or such like materials
contained in suitable apparatus. The necessary heat in this mass of material is
maintained by the combustion of the sulphide of hydrogen. Sulphurous acid and
water are formed in the operation. The process is also one well known to Chemists.
. The mixture of sulphurous acid, vapour of water and the accompanying gases I now
pass into apparatus or receptacles filled with chloride of sodium in the manner carried
out and practised in the process now known as Hargreaves process for manufacturing
sulphate of soda and hydrochloric acid. However, before I pass the said mixture of
gases into the Hargreaves apparatus I conduct the same through a heating apparatus
which is constructed and worked similarly to a Siemens Regenerator or a Siemens,
Cowper or Whitwell blast heating stove, in order to impart to it that temperature
which is known to be required for the good working of the Hargreaves process.
Steam may be admitted into the mixture of gases in addition to that already existing
in it, if thought desirable.
The result of this process is the production of sulphate of soda and hydrochloric
acid. The latter is condensed in the usual manner whilst the former is employed as
raw material in the Le Blanc's soda process and this process again yields the alkali
waste which formed the starting point of the process described.

page_text: According to a second part of my invention I modify the Hargreaves process in so
far that instead of charging the decomposing apparatus with chloride of sodium alone
I charge the same with a mixture of small coke and chlorides or with small coke
coated with a layer of chloride of sodium. The process may then be carried out in the
usual manner that is to say sulphurous acid obtained in the manner to be described
below (together with the proper quantity of steam) or sulphurous acid from any other
source may be admitted into the apparatus until the chloride of sodium has become
converted into sulphate of soda and the liberated hydrochloric acid has been expelled.
When this has been accomplished I remove the mixture of coke and sulphate of soda
into another apparatus for further treatment, or I treat it in the same apparatus in the
following manner.
I heat the mixture of coko and sulphate of soda, for instance, by passing heated
gases through the same to a temperature at which the sulphate of soda is capable of
being reduced to sulphide of sodium. When this temperature is reached I pass
carbonic oxide or what is better, so called water gas, i.c., a mixture of carbonic oxide
and hydrogen gas into and through the mass until the sulphate of soda has become
reduced to sulphide of sodium. To maintain the temperature required for this
operation the carbonic oxide or the water gas is passed through a Siemens or Whitwell
blast heating stove before it enters the mixture of coke and sulphate of soda and is
heated therein to the temperature at which it is capable of reducing the sulphate of
soda to sulphide of sodium.
When the sulphate of soda has been converted into sulphide of sodium as far as it is
practically possible, I subject the sulphide of sodium in the same vessel to the
combined action of carbonic acid and water or steam, whereby it is converted into
carbonate of soda whilst sulphide of hydrogen is liberated. The carbonate of soda is
lixiviated from this mass and the residual coke may be used again for mixing with
fresh chloride of sodium. The sulphide of hydrogen I convert into sulphurous acid
by the process described above and the sulphurous acid produced I convey into further
quantities of chloride of sodium, whereby again further quantities of sulphate of soda
and hydrochloric acid are obtained, with which the round of operations may be
continued.
When heated carbonic oxide or heated water gas are passed through the mass of
heated sulphate of soda and coke, the carbonic oxide becomes converted into carbonic
acid. This carbonic acid I use, so far as it may suffice, for the decomposition of
sulphide of sodium. Any deficiency I supplement by fuel gases or limekiln gases.
The sulphurous acid used in the cycle of operations forming this process might if
thought desirable be derived from the roasting of pyrites and the sulphide of hydrogen
obtained by the decomposition of sulphide of sodium by means of carbonic acid and
water might then be converted into solid sulphur by the processes described in several
specifications of patents granted to me formerly, such processes being now well known
to Chemists.
What has been described above in reference to chloride of sodium, sulphate of soda,
sulphate of sodium and carbonate of soda, applies equally to the corresponding
compounds of potassium.
Although all the individual operations or chemical reactions named in the above
specification are old and well known to most chemists, the peculiar combination of
them into one process as proposed by me in this specification would yield very valuable
practical advantages.

page_text: Improvements in the Manufacture of Carbonate of Soda and of
Carbonate of Potash, and in the Treatment of Residual Products
Obtained in such Manufacture.
I, CARL FRIEDRICH CLAUS, of Merton Road, South Wimbledon, in the County of
Surrey, Chemist, do hereby declare the nature of my said invention and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement:—
1st. I decompose alkali waste either moistened with or suspended in water in the
manner known to chemists by means of carbonic acid gas derived from any available
source, such as lime kiln gases or other sources, the particular method by which the
carbonic acid is obtained not forming any part of my present invention.
Sulphide of hydrogen is evolved by this process more or less mixed with other
gases. I mix with the sulphide of hydrogen a sufficient quantity of air so as to form
Sulphurous acid with the same, when the mixture of gases is exposed to a temperature
favorable for the reaction to take place. The mixture of sulphide of hydrogen and
air I pass through masses of solid materials such as oxide of iron, oxide of manganese,
whole or broken bricks contained in suitable apparatus. The heat necessary for the
combustion of the sulphide of hydrogen is in this mass of material maintained by the
combustion of the sulphide of hydrogen itself. Sulphurous acid and water are formed
in this operation. The mixture of sulphurous acid, vapour of water, the required
excess of air and the accompanying gases, I now pass into apparatus or receptacles
filled with chloride of sodium or with chloride of potassium in the manner carried out
and practised in the process known as Hargreaves process for manufacturing sulphate
of soda and hydrochloric acid. The sulphate of soda or of potash produced by the
operation just now described is employed as raw material in the Leblanc's alkali
process. That process again yields the alkali waste, which formed the starting point
of the process that constitutes the subject of the present invention. The hydrochloric
acid produced simultaneously with the sulphates is condensed in the usual manner.
The second part of my invention consists in a process forming a cycle of operations
of which the Hargreaves process also forms a part and in another part of which
sulphide of hydrogen is evolved. The sulphurous acid used for the Hargreaves
process might therefore also be produced by the combustion of sulphide of hydrogen.
But if it be thought desirable, the sulphurous acid could be produced by the roasting
of pyrites and the sulphide of hydrogen could be converted into solid sulphur or partly
into sulphur and partly into sulphurous acid by the processes described in several
specifications of patents granted to me formerly, such processes being now well known.
In the ordinary mode of carrying out the Hargreaves process the sulphurous acid is
passed into the decomposing apparatus at the temperature at which it leaves the pyrites
burners. For the purpose however of my present invention I pass the mixture of
sulphurous acid, steam, excess of air and other gases which accompany the same first
through a heating apparatus which may be constructed and worked similarly to a
Siemens regenerator or a Siemens, Cowper or Whitwell blast heating stove, in order to
impart to it that temperature, which is known to be required for the good working of

page_text: the Hargreaves process. By this improvement the necessity of using cast iron vessels
for the decomposition of the chlorides is dispensed with and the use of cheaper
structures such as brick chambers is rendered practicable for the process.
The said improvement may therefore also be applied with advantage to the
Hargreaves process as now otherwise practised.
Now in order to carry out the second part of my invention which consists in a
process formed by a complete cycle of operations, I employ a series of apparatus,
which are worked in rotation. For the sake of illustration I will assume, that five
apparatus are used for each individual operation. The apparatus may be called
chambers. They are worked in a continuous manner. Five of the chambers are then
used for the decomposition of the chlorides by sulphurous acid, five are used for the
reduction (by means of reducing gases to be mentioned hereafter) of the sulphates
which were produced in the previous operations, whilst five others are used for the
treatment by means of carbonic acid of the sulphides, produced in the operation
preceding this. Each individual set of five apparatus may be worked in rotation
amongst such five. The product of the five chambers used as Hargreaves plant, that
is to say, the finished sulphate, is transferred into the next set of chambers. These
may be worked in sets of five each, or all the ten chambers may be worked together so
as to permit one continuous circuit through the same.
The first five chambers are charged with chlorides of sodium (or of potassium) in
the manner practised in the Hargreaves process, but in view of the operations to
follow, I may if found desirable mix the chlorides in any convenient manner with
small coke or the like material, in order that it may aid in the subsequent operation
and to insure a more complete permeability or penetrability (of the mass) to the gases
to be passed through it during these subsequent operations. Sulphurous acid and
steam produced by the combustion of hydrogen (obtained in one of the subsequent
operations to be described below) after having passed through the heating stove, are
conveyed into one of the chambers charged with the chlorides. After the gas leaves
this chamber, it enters the next and passes through it and then the following one and
so forth, until it is completely absorbed.
Sulphate of soda (or of potash) is produced in this operation and hydrochloric acid
is liberated. The latter is conducted away and condensed.
After the decomposition of the charge in the first chamber is completed it is
removed from the chamber and transferred to one of the chambers in the next set of
chambers. Instead of mixing small coke with the chloride before it enters the
Hargreaves apparatus, the latter may be charged with chloride only and the coke may
be mixed with the sulphate before it is charged into the set of chambers in which it is
acted upon by the reducing gases.
The emptied chamber is then recharged with fresh chloride, whilst the sulphurous
acid gas is conducted into the chamber next to the one just emptied and so on in
rotation in the well known manner.
I then heat the mixture of coke and sulphate in the chamber of the second set by
passing heated gases through it until the charge in it has assumed a temperature
somewhat lower than that at which the sulphate is capable of being reduced to
sulphide by the following treatment. When this temperature is reached I pass
carbonic oxide or what is better so called water gas that is a mixture of carbonic oxide
and hydrogen gas, into and through the mass until the sulphate of soda (or of potash)
has become reduced to sulphide. To maintain the temperature required for the
continuance or maintainance of this reaction, the carbonic oxide or the water gas is
passed through a Siemens or Whitwell blast heating stove before it enters the mixture
of coke and sulphate and is heated therein to the temperature at which it is capable of
reducing the sulphate of soda (or of potash) to sulphide. When the sulphate has been
converted into sulphide as far as it is practically possible, the gas connection between
the next chamber, (which is also charged with the mixture of coke and sulphate) of the
same set of chambers is then cut off by means of dampers or valves and the heated
reducing gases are now conveyed into this next one. After the charge in it has in its
turn become converted into sulphide the gases are turned into the chamber next to it

page_text: liberated.
and so forth in rotation throughout the five or ten chambers the same course being
repeated again and again. The sulphide contained in these five chambers I subject
now without removal from the same to the combined action of carbonic acid and
steam. It is thereby converted into carbonate whilst sulphide of hydrogen is
The carbonate is lixiviated from the mass and the residual small coke may be used
again for mixing with fresh chloride or sulphate. The sulphide of hydrogen I either
convert into free sulphur or convert it into sulphurous acid by the process described
above. The sulphurous acid I convey into further quantities of chloride. Further
quantities of sulphate are obtained with which the round of operations is continued.
The heated mixture of carbonic oxide and hydrogen gas, passing through the mass of
heated sulphate of soda (or of potash) and coke, becomes converted into a mixture of
steam and carbonic acid. The carbonic acid and steam so produced I use, so far as it
may suffice, for the decomposition of the sulphide, any deficiency I supplement by
carbonic acid from other sources and by additional steam. The carbonic acid and
steam may be heated before entering the sulphide chambers. Their admission to the
charge in the sulphide chambers is carried on in such a way, that they are made to
enter the one, which has been the longest time subjected to their action, passing
through all of them in the direction of the one the contents of which have last been
subjected to the action of the heated reducing gases and which has last been converted
into sulphide. From this the gases issue into the sulphide of hydrogen combustion
chamber, the carbonic acid in the original gas being now replaced by sulphide of
hydrogen.
The gas from the water gas producer is made to issue from it under a convenient
amount of pressure with which pressure it travels through closed pipes and flues
through the heating stove and thence through the chambers of the reduction and
carbonating plant and after passing these, through the sulphide of hydrogen
combustion chamber and thence into the Hargreaves plant which it leaves mixed with
hydrochloric acid gas.
Having now particularly described and ascertained the nature of my said Invention,
and in what manner the same is to be performed, I declare that what I claim is :-
1. Converting sulphide of hydrogen obtained by decomposing alkali waste by means
of carbonic acid, into sulphurous acid and employing such sulphurous acid in the
manufacture of sulphates of soda (and of Potash) by the Hargreaves process.
2. In the Hargreaves process of manufacturing sulphates of soda and of potash
heating sulphurous acid, steam, atmospheric air and other gases accompanying the
same, in regenerative blast heating stoves, previous to their entering into the
decomposing vessels instead of heating such apparatus from the outside.
3. Converting sulphate of soda (or of potash) into the respective sulphides, by
passing carbonic oxide or so called water gas, heated in regenerative blast heating
stoves to the temperature necessary for this reduction, into mixtures of the sulphate
with carbonaceous matter.
4. Decomposing, by means of carbonic acid the sulphides of sodium (or of potassium)
which were produced as above described, whereby carbonate of soda (or of potash) is
produced and sulphide of hydrogen liberated.
5. The production of free sulphur, by known processes from the sulphide of
hydrogen obtained as described and also the conversion of the sulphide of hydrogen
into sulphurous acid for the purpose of employing the same in the Hargreaves process.
6. The cycle of operations whereby the carbonates of the alkalies are obtained from
their chlorides in the manner described.
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