IMPROVEMENTS IN OBTAINING SULPHUR FROM A BYE-PRODUCT OF THE MANUFACTURE OF ALKALI
Year: 1879

page_text: LETTERS PATENT to Walter Weldon, of Rede Hall, Burstow, in the County of
Surrey, for the Invention of "IMPROVEMENTS IN OBTAINING SULPHUR FROM
A BYE-PRODUCT OF THE MANUFACTURE OF ALKALI." A communication from
abroad by Alfred Rangod Pechiney, of Salindres, in the Republic of France.
Sealed the 6th January 1880, and dated the 8th August 1879.
•
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the Office
of the Commissioners of Patents on the 8th August 1879.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey.
"IMPROVE
MENTS IN OBTAINING SULPHUR FROM A BYE-PRODUCT OF THE MANUFACTURE
OF ALKALI."
(A communication from abroad from Alfred Rangod Pechiney,
of Salindres, in the Republic of France.)
When the residue of the lixiviation of crude soda or crude potash manufactured
by the Leblanc process is exposed to the action of air and moisture, either by simple
exposure in the open air, or by more artificial and systematic treatment, a solution
is obtained which is known among alkali-makers as "yellow liquor." This solution
consists chiefly of certain sulphides of calcium. The present Invention consists in
a new method of obtaining free sulphur from the said solution or yellow liquor.
To this end the yellow liquor is partially oxidised by treatment with air, pre-
ferably by injection into it of either air alone or air and steam, the oxidation being
preferably carried to such a point that on adding hydrochloric or sulphuric acid to
a sample of the liquor which has been treated it does not evolve either sulphuretted
hydrogen or sulphurous acid. When this degree of oxidation has been reached the
addition to the liquor of hydrochloric or sulphuric acid in quantity equivalent or a
little more than equivalent to the calcium contained in the liquor precipitates the
whole of its sulphur in the free state. The process may also be performed by
oxidizing completely a portion of the liquor, and then before treating with acid
adding to the completely oxidized liquor a quantity of liquor which has not been
oxidized, the proportion of oxidized to unoxidized liquor being such that the
mixture, on, treatment with a strong mineral acid, evolves neither sulphuretted
hydrogen nor sulphurous acid. In all cases heating the liquor, by injection of steam
or otherwise, greatly facilitates the oxidation.

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 7th February
1880.
•
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey. "IMPROVE-
MENTS IN OBTAINING FREE SULPHUR FROM A BYE-PRODUCT OF THE MANUFAC-
TURE OF ALKALI." A communication from abroad from Alfred Rangod Pechiney,
of Salindres, in the Republic of France.
When the residue of the lixiviation of crude soda or crude potash manufactured
by the Leblanc process is exposed to the action of air and moisture, either by simple
exposure in the open air or by more artificial and systematic treatment, a solution
is obtained which is known among alkali-makers as "yellow liquors." This solution
consists chiefly of certain sulphides of calcium. The present Invention consists in
a new method of obtaining free sulphur from the said solution or yellow liquor.
To this end the yellow liquor is partially oxidized by treatment with air, pre-
ferably by injection into it of either air alone or air and steam, the oxidation being
preferably carried to such a point that on adding hydrochloric or sulphuric acid to
a sample of the partially oxidized liquor it does not evolve either sulphuretted
hydrogen or sulphurous acid. When this degree of oxidation has been reached the
addition to the liquor of hydrochloric or sulphuric acid in quantity equivalent or a
little more than equivalent to the calcium contained in the liquor precipitates the
whole of its sulphur in its free state. The process may also be performed by
oxidizing completely a portion of the liquor, and then before treating with acid
adding to the completely oxidized liquor a quantity of liquor which has not been
oxidized, the proportion of oxidised to unoxidized liquor being such that the
.mixture, on treatment with a strong mineral acid, evolves neither sulphuretted
hydrogen nor sulphurous acid. In all cases heating the liquor, by injection of steam
'or otherwise, greatly facilitates the oxidation.
It has been found unexpectedly that in the partial oxidation of yellow liquors
under this Invention about one-fourth of the calcium in the liquors becomes separated
it
as free lime. Before treating the partially oxidized liquor with acid
is desirable
to allow this free lime to settle out, and then to treat by acid only the liquor
decanted from above the precipitate, as the consumption of acid is reduced in
proportion to the quantity of calcium thus removed from the liquor.
The degree of oxidation of the yellow liquors necessary to yield the best results
may be indicated as follows:-If we suppose the unoxidized liquor to be a solution
of Ca S2, or bi-sulphide of calcium, it will be desirable to oxidize it so far that for
each four equivalents of Ca S, present one equivalent shall be converted into
Ca S, O. This takes place according to the equation:-
2 Ca S, +40= Ca O + Ca S, O, + 2 S.
The two equivalents of sulphur thus set free are taken up by the further two
equivalents of Ca S., in presence of which the above reaction takes place, so that the
actual result is as follows:-
4 Ca S, +40= Ca O
The Ca O having been allowed to settle
acid is,
Ca S, O₂ + 2 Ca S.
out, what remains to be treated by
Ca S. O. + 2 Ca S

page_text: Walker in 1860 (Patent No. 3038 of that year), but it was only from unoxidized
liquors that they proposed to obtain sulphur. Townsend and Walker's proposal to
oxidize solutions of sulphide of calcium was a proposal to oxidize them completely,
for the purpose of obtaining, not sulphur but hyposulphites and sulphites, to be
used as antichlor." Complete oxidation of such liquors requires days, whereas
partial oxidation, to the degree necessary for the obtainment from them by means
of an acid of the whole of their sulphur in the free state, takes place in a very few
hours. For this reason Townsend and Walker's process has not come into use for
the object for which it was proposed, that of producing an antichlor. As regards
obtaining sulphur, for which purpose however, as has been said, Townsend and
Walker did not propose to use oxidized liquors, complete oxidation would not only
be impracticably costly, but it would reduce the yield of sulphur by one-half, while
increasing the consumption of acid by one-third. Townsend and Walker's process
would convert four equivalents of Ca S, into four equivalents of Ca S, O₂, upon
which hydrocloric acid would act as follows:-
4 Ca S, O +8 H Cl = 4 Ca Cl₂+ 4 H2O + 4 SO, + 4 S.
Instead of eight equivalents, or 256 parts by weight, of free surplur being obtained
per six equivalents, or 219 parts by weight, of hydrochloric acid, as by the process
of partial oxidation, which is the subject of the present Invention, completely
oxidized liquors would thus yield only four equivalents of free sulphur, or 128
parts by weight per eight equivalents, or 292 parts by weight of hydrochloric
acid.
Having now particularly described and ascertained the nature of the said Inven-
tion, and in what manner the same is to be performed, what I claim as the Invention
to be secured to me by the hereinbefore in part recited Letters Patent is, obtaining
free sulphur from solutions such as are known to alkali-makers as "yellow liquors,"
whether such solutions be the natural drainage from waste-heaps or be obtained
artificially, substantially by the method set forth in the foregoing Specification.
In witness whereof, I, the said Walter Weldon, have hereunto set my hand
and seal, this Seventh day of February, in the year of our Lord One
thousand eight hundred and eighty.
TITAT D
TETTAV
'Tחת תמRAIT
ELDON. (LS.)
WACLE L