IMPROVEMENTS IN UTILIZING CERTAIN RESIDUES OF THE MANUFACTURE OF SULPHURIC ACID AND ALKALI, PARTLY APPLICABLE ALSO TO THE UTILIZATION OF A RESIDUE OF THE MANUFACTURE OF CHLORINE."
Year: 1881

page_text: LETTERS PATENT to Walter Weldon, of Rede Hall, Burstow, in the County
of Surrey, for an Invention of "IMPROVEMENTS IN UTILIZING CERTAIN
RESIDUES OF THE MANUFACTURE OF SULPHURIC ACID AND ALKALI, PARTLY
APPLICABLE ALSO TO THE UTILIZATION OF A RESIDUE OF THE MANUFACTURE
OF CHLORINE."
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the Office
of the Commissioners of Patents on the 16th August-1881.
" IMPROVE-
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey.
MENTS IN UTILIZING CERTAIN RESIDUES OF THE MANUFACTURE OF SULPHURIC
ACID AND ALKALI, PARTLY APPLICABLE ALSO TO THE UTILIZATION OF A
RESIDUE OF THE MANUFACTURE OF CHLORINE."
Great nuisance is occasioned, as is well-known, by the waste-product which
accumulates in the neighbourhood of many soda-works, and great nuisance is also
occasioned by the residual solution of chloride of iron and other bodies, which is
sent into the water-courses by the manufacturers who extract copper from the
cinders, which are the residue of the manufacture of sulphuric acid from the
sulphur of cupreous pyrites. The object of this Invention is to obtain useful
products from these residues. In one method of carrying out this Invention the
residual chloride of calcium of the Weldon chlorine process is utilized also.
Soda-makers' waste, after exposure for a certain time to the atmosphere, gives
off what are known as " yellow liquors." Liquors of similar constitution are
obtained in what is known as Mond's process, and in other similar processes by
artificial treatment of soda-makers' waste. In what follows the term yellow
liquors will be used to include all solutions containing sulphur obtained from soda
waste, whether by natural means or by artificial means.
Copper-extractors' residual liquors contain chiefly chloride of iron and sulphate
of sodium.
The first part of the present Invention consists in treating copper-extractors'
residual liquors by a solution of chloride of calcium, which solution of chloride of

page_text: calcium may be the residual product of the Weldon chlorine process. The sulphate
of soda of the copper-makers' residual liquor is thereby decomposed with formation
of practically insoluble sulphate of calcium. The resulting mixture of sulphate of
calcium with mixed solution of chloride of sodium and chloride of iron is thrown
on a filter and allowed to drain, or else is filtered by means of a centrifugal hydro-
extractor or other adequate appliance. The sulphate of calcium so separated after
being suitably washed will be available for various industrial applications. The
liquor from which it has been separated can be used with advantage for precipitating.
sulphur from yellow liquors.
The second part of this Invention consists in adding either lime or oxide of iron
to the liquor which has been filtered from the sulphate of lime formed by adding
chloride of calcium to copper-extractors' residual liquor, and then treating yellow
liquors by the resulting mixture of oxide of iron with solution containing chloride
of iron. A mixture of free sulphur with sulphide of iron and possibly other
metallic sulphides precipitates, and chloride of calcium and chloride of sodium
remain in solution. The magma of precipitate and solution is drained or filtered,
and the precipitate is then washed and dried, when it is ready to have its sulphur
burnt off from it as sulphurous acid for use in the manufacture of sulphuric acid,
or otherwise. Or before having its sulphur burnt off from it, the precipitate may
be exposed to the action of the air for the oxidation of its sulphide of iron into
oxide of iron and free sulphur. The liquor from which the precipitate was
separated may be used instead of solution of chloride of calcium from the Weldon
chlorine process for decomposing the sulphate of soda in the copper-extractors'
residual liquor under the first part of this Invention. The copper-extractors'
residual liquor used under the present Invention may or may not have previously
been treated for the separation from it of a portion of its sulphate of soda as such.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Walter Weldon in the Great Seal Patent Office on the 6th February
1882.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey. " IMPROVE-
MENTS IN UTILIZING CERTAIN RESIDUES OF THE MANUFACTURE OF SULPHURIC
ACID AND ALKALI, PARTLY APPLICABLE ALSO TO THE UTILIZATION OF A
RESIDUE OF THE MANUFACTURE OF CHLORINE."
Great nuisance is occasioned, as is well known, by the waste product which
accumulates in the neighbourhood of many soda works, and great nuisance is
also occasioned by the residual solution of chloride of iron and other bodies, which
is sent into the water-courses by the manufacturers who extract copper from the
cinders, which are the residue of the manufacture of sulphuric acid from the
sulphur of cupreous pyrites. The object of this Invention is to obtain useful
products from these residues. In one method of carrying out this Invention the .
residual chloride of calcium of the Weldon chlorine process is utilized also.
Soda-makers' waste, after exposure for a certain time to the atmosphere, gives
off what are known as "yellow liquors." Liquors of similar constitution are
obtained in what is known as Mond's process, and in other similar processes, by
artificial treatment of soda-makers' waste. In what follows, the term "yellow
liquors" will be used to include all solutions containing sulphur obtained from
soda waste, whether by natural means or by artificial means.
Copper extractors' residual liquors contain chiefly chloride of iron and sulphate
of sodium.
The first part of the present Invention consists in treating copper-extractors'
residual liquors by a solution of chloride of calcium, which solution of chloride of
calcium may be the residual product of the Weldon chlorine process. The sulphate
of soda of the copper-makers' residual liquor is thereby decomposed with formation
of practically insoluble sulphate of calcium. The resulting mixture of sulphate of
calcium with mixed solution of chloride of sodium and chloride of iron is thrown
on a filter and allowed to drain, or else is filtered by means of a centrifugal hydro-
extractor or other adequate appliance. The sulphate of calcium so separated after
being suitably washed will be available for various industrial applications. The
liquor from which it has been separated can be used with advantage for precipitating
sulphur from yellow liquors.
The second part of this. Invention consists in adding either lime or oxide of iron
to the liquor which has been filtered from the sulphate of lime formed by adding
chloride of calcium to copper-extractors' residual liquor, as aforesaid, and then
treating yellow liquors by the resulting mixture of oxide of iron with solution
containing chloride of iron. A mixture of free sulphur with sulphide of iron, and
possibly other metallic sulphides precipitates, and chloride of calcium and chloride
of sodium remain in solution. The magma of precipitate and solution is drained
or filtered, and the precipitate is then washed and dried, when it is ready to have
its sulphur burnt off from it as sulphurous acid for use in the manufacture of
sulphuric acid or otherwise. Or before having its sulphur burnt off from it the
precipitate may be exposed to the action of the air for the oxidation of its sulphide
of iron into oxide of iron and free sulphur. The copper-extractors' residual liquor
used under the present Invention may or may not have previously been treated
for the separation from it of a portion of its sulphate of soda as such.
The quantity of lime or of oxide of iron to be added to the solution of chloride
of iron and chloride of sodium obtained as above, before employing that solution
to decompose yellow liquors, will depend on the constitution of the yellow liquors

page_text: Yellow liquors are a mixed solution of sulphydrate of calcium and of a
polysulphide or several polysulphides of calcium. Chloride of iron reacts on the
former of these bodies as follows:-
Ca SH, S+Fe Cl, = Ca Cl, + Fe S + H₂ S;
while its reaction on polysulphides will be understood from the following equation,
which represents the reaction of chloride of iron on bisulphide of calcium :-
Ca S, + Fe Cl, = Ca Cl, + Fe S + S.
The quantity of lime or of oxide of iron to be added to the solution of chloride of
.iron and chloride of sodium must thus depend upon the proportion of sulphydrate
in the yellow liquors. If lime be used the quantity employed need be only very
slightly in excess of the quantity chemically equivalent to the sulphydrate in the
yellow liquors. If oxide of iron be used it will usually be best to employ a
quantity of it appreciably greater than the quantity simply equivalent to the
quantity of sulphydrate in the yellow liquors. In either case the quantity of lime
or of oxide of iron used must be sufficient to prevent all evolution of sulphuretted
hydrogen during the treatment together of the yellow liquors, and the solution of
chloride of iron and chloride of sodium.
The operations to be performed in carrying this Invention into effect will be
essentially two, and they may be performed as follows:-Firstly, copper-extractors',
residual liquor, and solution of chloride of calcium should be pumped into a large
wooden or other suitable vessel furnished with a mechanical agitator, and then
when the right proportion of each liquor has been pumped in and the contents of
the vessel have been sufficiently agitated, the resulting mixture of solution of
chloride of sodium and chloride of iron with suspended sulphate of lime should be
run on to a filter-bed, from which the filtrate should flow to a second similar
vessel also furnished with a mechanical agitator. In this second vessel there should
be added to the said filtrate either the quantity of lime necessary to decompose a
part of the chloride of iron in it so as to produce a quantity of protoxide of iron
equivalent to the quantity of sulphuretted hydrogen, which would otherwise be
evolved on the addition of yellow liquors to the filtrate, or there should be added
to the filtrate, instead of lime, a suitable quantity of finely divided oxide of iron,
which may conveniently be some of that remaining after the combustion of the
sulphur of a previous quantity of final product. The second operation will then
consist simply in pumping into this second vessel yellow liquor as long as it
continues to be decomposed, the agitator being of course kept in motion while the
yellow liquor is being pumped in. The contents of the second vessel should now
be run on to a filter-bed or other equivalent appliance, and there washed, after
which the precipitate, consisting of a mixture of sulphide of iron and free sulphur
should be exposed to the action of the air, preferably under cover, until the sulphide
of iron in it has become wholly or partly oxidized into oxide of iron and free
sulphur. When dry it can then have its sulphur burnt off from it, as will be
well understood; or it may be treated for the separation of its sulphur from it in
any other way.
..
What I claim as my Invention consists in obtaining useful products from waste
liquors, substantially as is above described.
In witness whereof, I, the said Walter Weldon, have hereunto set my hand
and seal, this Fourth day of February, in the year of our Lord One
thousand eight hundred and eighty.two.