IMPROVEMENTS IN THE MANUFACTURE OF SULPHIDE OF SODIUM AND Sulphide of POTASSIUM.
Year: 1882

page_text: LETTERS PATENT to Walter Weldon, of Redo Hall, Burstow, in the County
of Surrey, for an invention of IMPROVEMENTS IN THE MANUFACTURE OF
SULPHIDE OF SODIUM AND Sulphide of POTASSIUM. A communication from
abroad by Wilhelm Helbig, Manager of the Chemical Works at Aussig, in the
Empire of Germany.
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the Office
of the Commissioners of Patents on the 13th April 1882.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey, IMPROVE.
MENTS IN THE MANUFACTURE OF SULPHIDE OF SODIUM AND SULPRIDE OF
POTASSIUM-a Communication from Wilhelm Helbig, Manager of the Chemical
Works at Aussig, in the Empire of Germany,
This invention consists in a method of manufacturing sulphide of sodium and
sulphide of potassium by the wet way.
The crude product of the manufacture of soda by the Leblanc process is known
as black-ash. It consists essentially of a mixture of carbonate of soda and sulphide
of calcium. The carbonate of soda having been separated by lixiviation, the
insoluble residue is known as alkali-waste.
My correspondent has found that when black-ash is heated with water, prefer-
ably under a pressure of from three to four atmospheres, double decomposition
takes place between the two essential constituents of the black-ash, according to
the equation:
Na, CO, Ca S = Ca CO, + Na, S.
My correspondent has also found that a portion of the carbonate of soda may
be replaced by sodium sulphate, and a portion of the black-ash by alkali-waste.
He has found that by heating alkali-waste alone with water, preferably under
pressure, the following reaction is effected:
2 Ca S+ 2 H₂O
=
Ca S, HS + Ca O.
[Price 4d.]

page_text: Ji sodium sulphate be present, the calcium sulpnyamte is decomposed by what suiv
and the results are:
2 Ca S + 2 H₂O + Na, SO, = N₁₂ S, HIS + Co. SO, + Cn O.
The sulphate of sodium is thus converted into sodium sulphydrate, and the calcium
sulphide into calcium sulphate and free lime. To convert the sodium sulphydrate
into sodium sulphide, caustic soda is required, the reaction between sodium
sulphydrate and caustic soda boing:
NS, HS + NO = 2 N₁₂S + H₂O.
My correspondent secures the passing presence of onough caustic soda by using,
instead of sodium sulphate only, a mixture of sodium sulphate and black-ash in
about equivalent proportions. The result is then the same as if the calcium
sulphide in the black-ash were converted into calcium sulphydrate and froo lime,
which last then reacted on the carbonate of soda of the black-ash to forin carbonato
of lime and the caustic soda necessary to convert into sodium sulphide the sodium
sulphydrate resulting from the reaction of the sodium sulphate on the calcium
sulphydrate which is the other product of the reaction of water on calciuin sulphide.
The proportions in which sodium sulphate and black-ash are needed for the required
reactions will be seen from the following equation:
2 Ca S+ NaCO, + N₁₂SO₁ = 2 Na,S + Ca SO, + Ca CO,.
My correspondent's invention thus consists in obtaining sulphide of sodium by
heating with water, preferably under pressure, either black-ash alone, or a mixture
of black-ash and alkali-waste, or a mixture of black-ash, alkall-waste, and sodium
sulphate; and in obtaining sulphide of potassium by similarly henting with water
either potash black-ash alone, or a mixture of potash black-ash and alkali-waste,
or a mixture of potash black-ash, alkali-waste, and potassium sulphate. My
correspondent finds that the reactions are facilitated by the presence of alkali-
waste in excess of the quantity theoretically necessary.
For the performance of his invention, my correspondent prefers to use an iron
vessel, capable of sustaining a sufficient pressure, and furnished with a mechanical
agitator, and to effect the heating of its contents by injection of stenin. When the
reactions taking place in this vessel have proceeded sufficiently far the contents of
the vessel are run off, and their liquid part separated from their solid part by any
convenient means. The liquid part is then evaporated, any impurities which fall
during the evaporation being from time to time fished out. The sulphide of
sodium or sulphide of potassium is then crystallized from the concentrated solution,
as will be woll understood.

page_text: sulphate, aro two parts by weight of black-ash to one part by weight of fresh
alkali-waste. When using sodium sulphato, proportions which give good results
are two parts by weight of black-ash, two parts by weight of fresh alkali-waste,
and one part by weight of sodium sulphato.
My correspondent employs for the performance of his invention iron vessels,
capable of withstanding the necessary pressure, and furnished interiorly with
mechanical agitators. Having charged into these vessels either alkali-waste and
black-ash, or alkali-waste, black-ash, and sodium sulphate, with a suitable quantity
of water, he closes the said vessels, and applies heat to their contents, preferably
by the injection of steam thereinto. He prefers to heat to such point that the
pressure within the said vessels used shalt amount to three or four atmospheres.
When the desired reactions have been carried sufficiently far, the contents of the
digestors are run off, and their liquid part separated from their solid part by any
convenient means. The liquid part is then evaporated until its density is about
32 degrees Beaumé. Most of the foreign salts which may at first be present in the
solution so evaporated crystallise out during the evaporation, and should bo
"fished out" from time to time as the evaporation proceeds. The concentrated
solution, on cooling, gives crystals of hydrated sodium sulphide containing nino
equivalents of water. These crystals may be purified by re-solution and
re-crystallization, as will be well understood.
What is above described is equally applicable to the manufacture of potassium
sulphide, potash black-ash and potassium sulphate being substituted for sodn
black-ash and sodium sulphate.
My correspondent's invention thus consists in obtaining sodium sulphide by
heating with water under pressure either black-ash alone, or a mixture of black-
ash and alkali-waste, or a mixture of black-ash, alkali-waste, and sodium sulphate;
and in obtaining potassium sulphide by similarly heating with water under pressure
either potash black-ash alone, or a mixture of potash black-ash and alkali-wasto
or a mixture of potash black-ash, alkali-waste, and potassium sulphate.
In witness whereof I, the said Walter Weldon, have hereunto set my hand
and seal this eleventh day of October in the year of Our Lord Ono
thousand eight hundred and eighty two.