Improvements in the Manufacture and Production of Polysulphides of Potassium and Sodium.
Year: 1895

page_text: Date of Application, 17th June, 1895-Accepted, 3rd Aug., 1895
COMPLETE SPECIFICATION.
Improvements in the Manufacture and Production of Polysulphides
of Potassium and Sodium.
I, BERNHARD VON SCHENK of 1 Lauerstrasse Heidelberg in the Empire of
Germany Manufacturing Chemist do hereby declare the nature of this invention
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
The mono-sulphide of sodium generally known as sulphide of sodium, has, for a
long time, been used commercially for manufacturing purposes.
This compound or combination has powerful corrosive properties, while, as a
dilute solution, it exhibits highly efficient purifying and dissolving properties.
The idea of reducing or neutralizing these corrosive properties and of thereby
obtaining a substance having a milder action would therefore, naturally suggest
itself, and with this object in view it has been proposed to introduce an increased
proportion of sulphur into each one molecule of the said compound.
In point of fact I found that the reaction of the pure polysulphides was
practically neutral, and that they possessed none of the corrosive properties of the
mono-sulphides.
Polysulphides of metals of the alkalies have been obtained by boiling
monosulphides with a quantity of sulphur in excess. Whilst this reaction takes
place, however, it is accompanied by certain additional or secondary processes,
which do not offer the least guarantee that the whole of the monosulphide shall
be converted into polysulphides. A uniform compound product is not therefore
obtainable by this method.
I have succeeded in obtaining according to my invention liquors or lyes,
- absolutely free from any monosulphide, by the process hereinafter described, which
consists in bringing about a reaction between the soluble polysulphides of calcium
and the carbonates or sulphates of either potassium or sodium, the reaction taking
place in accordance with the following equations.
CaS + Na2SO =
CaSO4 + Na2S,
CaS+ Na2CO3 = CaCO3 + Na,S.
Sulphide of calcium or, to be strictly accurate, monosulphide of calcium is a
product insoluble in water, and one which can only be obtained by a pyro-chemical
process whereas polysulphides of calcium, which are readily soluble, may be
obtained without difficulty by boiling hydrate of lime in the presence of an excess
of sulphur.
By mixing the calcium polysulphide lyes, after cooling, with a quantity of soda
5 or potash, predetermined by calculation, the product immediately resulting will be
polysulphide of sodium or potassium (as the case may be) which may then be
decanted off from the underlying precipitate of carbonate of lime.
The following is the process I prefer to employ for preparing these polysulphides
but I do not limit myself to the precise details.
PROCESS OF PREPARATION.
30 kilogrammes of flowers of sulphur (or sublimed sulphur) are thoroughly
mixed with 20 kilogrammes of hydrated lime, the whole being then ground and
sifted through a sieve having say 4000 meshes per square centimetre, after which
it is placed in a boiler containing about 110 litres of water. The three ingredients

page_text: are boiled together for two and a half hours and in the course of the first hour of
ebullition while the boiling liquor still retains its yellow colour and frothy
condition, further small quantities of water, amounting to ten litres altogether, are
added, so as to prevent the mixture from boiling over.
The lye obtained after the boiling has been continued for about 24 hours will be
of a muddy greyish green colour and of 48° Beaume specific gravity.
This lye is further diluted with boiled water until its specific gravity is reduced
to 10° Beaume and then allowed to rest for 12 hours, whereupon the clear sulphur
lye, which, by that time, will have assumed a deep yellow colour, should be
decanted.
By a further addition of water, its specific gravity is then reduced to 5° Beaume.
Of the sulphur lye thus obtained, 50 litres are again poured into a boiler, with
an addition of 100 kilogrammes (95 per cent.) of soda, or the same amount of
calcined potash, as the case may be, the whole being well stirred, decanted and
then allowed to evaporate until it is dry.
r
After evaporation, the contents of the boiler are discharged and cooled by
exposure to the atmosphere, the product obtained as a result being a yellow,
consistent granular mass, partly in lumps.
After cooling the material is sent through a mill, wherein it is ground down to
a state of fine division, and then it is passed through a sieve having about
3000 meshes per square centimetre. The ground and sifted substance is finally
placed in tightly closed receptacles of wood.
This article of manufacture in the final condition assumes a pure white colour
with a yellowish shimmer, and, is then ready for use.
With this product which I term "polysulphine," lyes or solutions of different
degrees of concentration are prepared, suitable for washing, boiling, bleaching, and
cleaning purposes, they are also particularly serviceable for washing or scouring
raw wool, half wool and textile fibres generally, and constitute a novel bleaching
agent for vegetable fibre.
The specific gravity of a solution of 15° concentration should not exceed 1.158 or
19 Beaumé.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed, I declare that what
I claim is:
1. The improved process for the manufacture of polysulphides of potassium and
sodium substantially as herein before described.
2. As an article of manufacture the new substance which I term polysulphine
produced in the manner herein before described.
Dated this 17th day of June 1895.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.