Improvements in the Manufacture of Hydrosulphites and the Production of Solid Sodium Hydrosulphite.
Year: 1899

page_text: Date of Application, 2nd Oct., 1899
Complete Specification Left, 30th June, 1900-Accepted, 8th Sept., 1900
TROVISIONAL
DI MUITIVATION.
Improvements in the Manufacture of Hydrosulphites and the
Production of Solid Sodium Hydrosulphite.
I, BENJAMIN WILLCOX, of 47, Lincoln's Inn Fields, in the County of London,
Patent Agent, do hereby declare the nature of this invention (which has been
communicated to me from abroad by the Badische Anilin & Soda Fabrik, of
Ludwigshafen-on-Rhine, in the German Empire) to be as follows:-
Technical sodium hydrosulphite, which is used for the reduction of indigo
for the purpose of dyeing therewith, has hitherto generally been prepared
by adding zinc-dust to a solution of sodium bisulphite, preferably
whilst keeping the solution cool, and subsequently removing the zinc compound
from the solution by means of lime. When this process is adopted only about
one-half of the sulphurous acid, and of the sodium contained in the bisulphite,
is converted into the hydrosulphurous acid salt. The remainder remains unused,
probably in the form of the sulphites of sodium and zinc. Grossman has de-
scribed a process for using up to a greater extent this unused sulphite which
consists in adding mineral acids, particularly sulphuric acid, so that some of the
sulphurous acid of the unconverted sulphite is set free, and then, by the further
addition of zinc-dust, the reduction is repeated. This process is described in
the Specification of the German Patent 84507, and, when working according
to this specification, about one-third more hydrosulphite can be obtained than
can be obtained in the usual way, but the solution obtained is less concentrated
than the usual hydrosulphite solution, and it contains a considerable quantity
of sulphates as an impurity.
My foreign correspondents have devised a process by which it is possible not
only to obtain pure, and, when desired, highly concentrated solutions of hydro-
sulphite, but also to convert practically the whole quantity of bisulphite used
into hydrosulphite. Further, my foreign correspondents have devised means of
obtaining sodium hydrosulphite in the solid state, particularly with the aid of
the concentrated solutions obtained according to the first part of the invention.
This has hitherto not been possible, although Schützenberger attempted to
obtain the body by precipitating it from solutions containing it by means of
alcohol (see also Bernthsen, Annalen der Chemie, vol. 208, p.p. 164 et seq.)
The process according to this invention for the production of the hydrosulphite
solution consists in adding sulphurous acid to the solution of sodium, potassium,
or ammonium bisulphite. The sulphurous acid may either be added in aqueous
solution, or be introduced in the form of gas. To obtain the best result accord-
ing to this invention the quantity of sulphurous acid so added is arranged to be
one-half the total quantity, otherwise contained in the bisulphite used. The
solution thus obtained is then reduced with zinc-dust. In this way not only is
the entire quantity of alkali in the bisulphite fully used, by being combined
after the treatment with lime with the hydrosulphurous acid, but also the
formation of other salts as impurities is prevented, and the solutions obtained

page_text: ->>>
are so concentrated and pure that it is possible to obtain from them solid, and,
as compared with any product hitherto obtained, very pure, hydrosulphite, by
evaporation in vacuo. The solid sodium hydrosulphite can also be obtained
from this solution by separating it by means of common salt.
The following examples will serve to further illustrate the nature of the in-
vention, but the invention is not confined to these examples:
EXAMPLE 1.
Take about twenty-five kilograms of sodium bisulphite, having a density of
40° Beaumé and to this add about fifty-four kilograms of aqueous sul-
phurous acid, containing about 6 per cent. SO₂, or prepare a similar solution by
adding to the twenty-five kilograms of sodium bisulphite of the aforesaid den-
sity, about fifty-one litres of water, and pass gaseous sulphurous acid through
the solution until the weight has been increased by about three-and-a-quarter
kilograms. Then add, slowly, about four-and-one fifth kilograms of zinc dust.
During this addition keep the solution at a temperature between 300 and 40°
· Centigrade by suitably cooling. When all the zinc dust has been added
stir for some time and then allow the mixture to stand for an hour or two.
Next treat the liquid with milk of lime, prepared from about four-and-one-fifth
kilograms of quicklime and twenty litres of water. Stir well, and finally allow
the mixture to stand for at least six hours more. Then filter through a filter-
press.
From the above mentioned quantity of twenty-five kilograms of sodium
bisulphite of 40° Beaumé according to the usual process, sufficient hydrosulphite
results to reduce rather less than 5 kilograms of indigo in the vat, whilst when
working according to this example about eighty kilograms of sodium hydro-
sulphite solution possessing a density of about 11° Beaumé are obtained, which
are sufficient to reduce twice the aforesaid quantity of indigo to indigo white in
the vat.
EXAMPLE 2.
In order to produce a highly concentrated bydrosulphite solution, mix to-
gether about twenty-eight and four-fifths kilograms of sodium bisulphite, of
about 40° Beaumé density, and thirty-four-and-a-half kilograms of concentrated
aqueous solution of sulphur dioxide (containing about 10 per cent. SO₂), or pre-
pare a similar solution by diluting the sodium bisulphite solution with about
thirty-one litres of water and causing it to absorb the corresponding quantity
of gaseous sulphur dioxide. To the solution, obtained in either of the ways
described, add, gradually, about four and four-fifth kilograms of zinc-dust, as
described, in the foregoing example. Precipitate the zinc-oxide with milk of
lime, prepared from four and four-fifth parts of quick-lime and sixteen litres of
water, and filter.
The quantities and strengths of the solutions given in this example are so
calculated that the quantity of alkali present in the sodium bisulphite is, after
the reduction, equivalent to the quantity of hydrosulphurous acid formed, so
that neutral sodium hydrosulphite is obtained. Of course if the concentration
of any of the solutions employed be varied, corresponding alterations must be
made in the quantities, or strengths, of the other ingredients in order to obtain
the best result. When proceeding as herein before described one obtains a solu-
tion of the said neutral sodium hydrosulphite, of which ten kilos are sufficient
to reduce just under two kilograms of 100 per cent. indigo.
EXAMPLE 3.
In order to produce solid aliums haluamuslakita
11:11

page_text: EXAMPLE 4.
In order to obtain sodium hydrosulphite in the solid state by precipitation
from its solution by means of common salt, prepare one hundred litres of the
concentrated sodium hydrosulphite solution according to the foregoing
Example 2, and heat the solution in a closed vessel to from about 50° to 60°
Centigrade. Then add twenty-four kilograms of common salt. Stir until the
salt is entirely dissolved. Then allow to cool. The precipitation of the hydro-
sulphite begins at once. When no further quantity separates out, collect by
filtration, and dry.
During all the operations the access of air should be avoided as much as
possible.
Dated this 2nd dox of Clotakan 1800
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.
Improvements in the Manufacture of Hydrosulphites and the
Production of Solid Sodium Hydrosulphite.
I, BENJAMIN WILLCOX, of 47, Lincoln's Inn Fields, in the County of London,
Chartered Patent Agent, do hereby declare the nature of this invention (which
has been communicated to me from abroad by the Badische Anilin & Soda
Fabrik, of Ludwigshafen-on-Rhine, in the German Empire) and in what manner
the same is to be performed to be particularly described and ascertained in
and by the following statement:-
Technical sodium hydrosulphite, which is used for the reduction of indigo
for the purpose of dyeing therewith, has hitherto generally been prepared
in solution by adding zinc dust to a solution of sodium bisulphite, preferably
whilst keeping the solution cool, and subsequently removing the zinc compound
from the solution by means of lime. When this process is adopted only about
one half of the sulphurous acid and of the sodium contained in the bisulphite
is converted into the hydrosulphurous acid salt. The remainder remains unused,
probably in the form of the sulphites of sodium and zinc. Grossman has de-
scribed a process for using up to a greater extent this unused sulphite which
consists in adding mineral acids, particularly sulphuric acid, so that some of the
sulphurous acid of the unconverted sulphite is set free, and then, by the further
addition of zinc dust, the reduction is repeated. This process is described in
the Specification of the German Patent No. 84507, and when working according
to this specification, about one-third more hydrosulphite can be obtained than
can be obtained in the usual way, but the solution obtained is less concentrated
than the usual hydrosulphite solution, and it contains a considerable quantity
of sulphates as an impurity..
My foreign correspondents have devised a process by which it is possible not
only to obtain pure, and when desired, highly concentrated solutions of hydro-
sulphite, but also to convert practically the whole quantity of bisulphite used
into hydrosulphite. Further, my foreign correspondents have devised means of
obtaining alkaline hydrosulphites in the solid state, particularly with the aid of
the concentrated solutions obtained according to the first part of the invention.
This has hitherto not been possible, although Schützenberger attempted to
obtain the body by precipitating it from solutions containing it by means of
alcohol, (see also Bernthsen, Annalen der Chemie, volume 208, pages 164 et seq.).

page_text: "
The process according to this invention for the production of the hydrosulphite
solution consists in adding sulphurous acid to the solution of sodium, potassium
or ammonium bisulphite. The sulphurous acid may either be added in aqueous
solution, or be introduced in the form of gas. To obtain the best result accord-
ing to this invention the quantity of sulphurous acid so added is arranged to be
one-half the total quantity, otherwise contained in the bisulphite used. The
solution thus obtained is then reduced with zine dust. In this way not only is
the entire quantity of alkali in the bisulphite fully used, by being combined
after the treatment with lime with the hydrosulphurous acid, but also the
formation of other salts as impurities is prevented, and the solutions obtained
are so concentrated and pure that it is possible to obtain from them solid, and,
as compared with any product hitherto obtained, very pure, hydrosulphite, by
evaporation in часно. The solid hydrosulphite can also be obtained,
as my foreign correspondents have found, particularly from the solutions so
obtained, by salting it out by means of common salt.
The following examples will serve to further illustrate the nature of the
invention, and the manner in which it can be carried into practical effect, but
the invention is not confined to these examples.
EXAMPLE 1.
Take about twenty five kilograms of sodium bisulphite, having a density of
40 degrees Beaumé and to this add about fifty four kilograms of aqueous sul-
phurous acid, containing about 6 per cent. SO, or prepare a similar solution by
adding to the twenty-five kilograms of sodium bisulphite of the aforesaid den-
sity, about fifty one litres of water, and pass gaseous sulphurous acid through
the solution until the weight has been increased by about three and a quarter
kilograms. Then add, slowly, about four and one fifth kilograms of zinc dust,
During this addition keep the solution at a temperature between 30 degrees and
40 degrees Centigrade by suitably cooling. When all the zinc dust has been added
stir for some time and then allow the mixture to stand for an hour or two.
Next treat the liquid with milk of lime, prepared from about four and one fifth.
kilograms of quicklime and twenty litres of water. Stir well, and finally allow
the mixture to stand for at least six hours more. Then filter through a filter
press.
From the above mentioned quantity of twenty five kilograms of sodium
bisulphite of forty degrees Beaumé according to the usual process, sufficient
hydrosulphite results to reduce rather less than five kilograms of indigo in the
vat, whilst when working according to this example about eighty kilograms of
sodium hydrosulphite solution, possessing a density of about eleven degrees
Beaumé, are obtained which are sufficient to reduce twice the aforesaid quantity
of indigo to indigo white in the vat.
EXAMPLE 2.
In order to produce a highly concentrated hydrosulphite solution, mix to-
gether about twenty eight and four fifths kilograms of sodium bisulphite, of
about forty degrees Beaumé density, and thirty four and a half kilograms of
concentrated aqueous solution of suphur dioxide (containing about ten per cent.
SO), or prepare a similar solution by diluting the sodium bisulphite solution
with about thirty one litres of water and causing it to absorb the corresponding
quantity of gaseous sulphur dioxide. To the solution, obtained in either of the
ways described, add, gradually, about four and four-fifths kilograms of zinc dust,
as described in the foregoing example. Precipitate the zinc-oxide with milk
of lime, prepared from four and four-fifth parts of quicklime and sixteen litres
of water, and filter.
The quantities and strengths of the solutions given in this example are so
calculated that the quantity of alkali present in the sodium bisulphite is, after
the reduction, equivalent to the quantity of hydrosulphurous acid formed, so that

page_text: best result if the concentration of any of the solutions employed be varied,
corresponding alterations must be made in the quantities, or strengths, of the
other ingredients. By proceeding as herein before described a solution of the
said neutral sodium hydrosulphite is obtained, of which ten kilos are sufficient
to reduce just under two kilograms of 100 per cent. indigo.
EXAMPLE 3.
In order to produce solid sodium hydrosulphite, the highly concentrated solu-
tion described in the foregoing Example 2 is prepared and then this is evaporated
to dryness in vacuo.
EXAMPLE 4.
In order to obtain sodium hydrosulphite in the solid state by precipitation
from its solution by means of common salt, prepare one hundred litres of the
concentrated sodium hydrosulphite solution according to the foregoing
Example 2, and heat the solution in a closed vessel to from about fifty to sixty
degrees Centigrade. Then add twenty four kilograms of common salt. Stir
until the salt is entirely dissolved. Then allow to cool. The precipitation of
the hydrosulphite begins at once. When no further quantity separates .out,
collect by filtration and dry.
During all the operations the access of air should be avoided as much as
possible.
EXAMPLE 5.
Sodium hydrosulphite can also be precipitated in the solid state by means of
common salt from ordinary solutions of sodium hydrosulphite prepared in the
usual way. For instance prepare a sodium hydrosulphite solution in the manner
described on pages 83 and 84 of the treatise on indigo by Georg von Georgiewics,
namely: Fill a vessel which can be hermetically sealed, with strips of zinc and
then with a solution of sodium bisulphite of 31 to 32 degrees Baumé which has
a strong odour of sulphurous acid, and stir the contents occasionally. In about
an hour the reaction is finished. Pour off the liquid from the excess of zinc,
treat the solution thus obtained with milk of lime, so that to every litre of hydro-
sulphite of 34 degrees Baumé about four hundred and fifty grams of milk of
lime (containing about four hundred grams of calcium oxide in a litre) are added.
Filter from the precipitate which forms. Heat one hundred parts of the solu-
tion so obtained, to about fifty degrees Centigrade and add twelve parts of
common salt whilst thoroughly stirring or shaking. Collect the sodium hydro-
sulphite and work up in the manner described.
EXAMPLE 6.
Solid ammonium hydrosulphite can be obtained as follows:-Take one
hundred parts of ammonium hydrosulphite solution, of such concentration that
eight parts of it serve to reduce one part of indigo, and heat the solution to
about fifty degrees Centigrade. Then add twenty six parts of common salt and
stir thoroughly. Collect the hydrosulphite by filtering and dry.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is:―
1. In the manufacture of hydrosulphites the improvement which consists in
adding sulphurous acid to the solution of the bisulphite treated, and reducing
this mixture, substantially as herein before described.
2. In the manufacture of hydrosulphites the improvement which consists in
adding to the bisulphite solution to be treated, a quantity of sulphurous acid,
that is one half of the quantity otherwise contained in the bisulphite used, and
reducing this mixture, all substantially as hereinbefore described.

page_text: 3. The production of solid alkaline hydrosulphites by evaporating in vacuo the
very pure and concentrated solutions of hydrosulphite obtained substantially as
herein before described and claimed, substantially as hereinbefore described.
4. The production of solid alkaline hydrosulphites by salting them out of their
solutions by the addition of common salt, or the like, substantially as herein-
before described.
5. The manufacture of solutions of sodium hydrosulphite in the manner de-
scribed in the foregoing Examples 1 and 2.
6. The manufacture of solid hydrosulphite in the manners described in the
foregoing Examples 3, 4, 5 and 6.
7. As a new article of manufacture commercially pure solid alkaline hydro-
sulphite such as can be obtained, substantially as herein before described.
Dated this 29th day of June 1900.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.