Improvements in the Manufacture of Sulphocyanides.
Year: 1894

page_text: Date of Application, 23rd July, 1894
Complete Specification Left, 22nd Apr., 1895-Accepted, 24th May, 1895
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Sulphocyanides.
We, GEORGE STACEY ALBRIGHT, of The Elms, Edgbaston, Birmingham, in
the County of Warwick, Gentleman, and JOHN JAMES HOOD, of 1 Fenchurch
Avenue, in the City of London, Chemist, do hereby declare the nature of this
invention to be as follows :-
In Specification No. 17846° a process for the manufacture of sulphocyanides
from CS, and NH, is described, whereby the whole or nearly the whole of the
ammonia and bisulphide used, are converted into a sulphocyanide and a soluble
sulphydrate of a single base, the bases which may suitably be employed being the
following, CaO, MgO, BaO, SrO, Na,O and K,O. Subsequently the soluble
sulphydrate is decomposed by CO2 gas (conveniently by lime-kiln gases) whereby
the HS, is liberated and insoluble carbonate or bicarbonate of the base is
precipitated.
Our present improvements consist in the liberation of the HS without the use
of CO2. With this object we employ magnesia as one of the bases. The magnesic
sulphydrate which is formed can be decomposed by simple boiling into magnesia
and sulphuretted hydrogen.
We proceed exactly as described in Specification No. 1784693 using MgO or
MgH,O, as the base whereby Mg(CNS), and MgH,S, are formed. The
MgHS, is then, by removing the pressure and boiling, decomposed according to
the following equation:
MgH,S, + H₂O
==
MgH2O + HS.
By the addition of calcium hydrate or other hydrate of alkali or alkaline
earth to the resulting mixture of MgH,O, and Mg(CNS), the Mg(CNS), is
converted into Ca(CNS), or sulphocyanide of other alkali or alkaline earth, and
MgH,O, is precipitated. Or we may employ in the digestor a mixture of two
bases such as MgO and CaO, the latter being in sufficient quantity to combine
with the whole of the HCNS which is formed, and the MgO sufficient to combine
with the H2S. On then removing the pressure and boiling (if lime is the second base
employed) a solution of Ca(CNS), is obtained, and the MgH,O, is precipitated.
In both cases the MgH,O, is separated from the soluble sulphocyanide by
filtration, and can be used again for a further operation.
Dated this 23rd day of July 1894.
GEO. S. ALBRIGHT.
JOHN J. HOOD.
Improvements in the Manufacture of Sulphocyanides.
We, GEORGE STACEY ALBRIGHT, of The Elms, Edgbaston, Birmingham, in
the County of Warwick, Gentleman, and JOHN JAMES HOOD, of 1 Fenchurch
Avenue, in the City of London, 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 :-
It is a well known chemical fact that carbon-bisulphide (CS,) and ammonia (NḤ,)

page_text: react upon each other, even at ordinary temperature to form sulphocyanic
acid (HCNS) and sulphuretted hydrogen (SH,) according to the equation NH, +
CS, HCNS + H,S.
1
These two acidic compounds, at the moment of their formation, combine with a
portion of the ammonia, forming sulphocyanide and sulphide of ammonia, so that
for a given amount of ammonia, only about one third is converted into sulphocyanic
acid.
The conversion of nearly the whole of the ammonia into sulphocyanic acid and
the effectual treatment of the sulphuretted bydrogen evolved during the reaction,
is dealt with by a process described in the Specification of a Patent No. 5354 in
the year 1891, 1 John James Hood, being one of the patentees. According to
this process the materials, carbon bisulphide and aminonia, are heated in a digestor
in the presence of the hydrated form of manganese peroxide known as Weldon
mud in conjunction with lime. The formation of sulphocyanide of ammonia is
obviated by the presence of the lime which compels the formation of calcium
sulphocyanide (Ca(CNS),) and the sulphuretted hydrogen is oxidised by the
peroxide with the formation of sulphide of manganese and free sulphur.
Another mode of dealing with the sulphuretted hydrogen evolved during the
reaction is patented by Messrs. Crowther and Rossiter No. 17846 in the year 1893.
According to this method it is dealt with not by the use of materials like Weldon
mud but by the employment of one base to form both a soluble sulphide, and. also
a sulpho-cyanide of the same base. The sulphuretted hydrogen is subsequently
expelled from the base by a second and distinct operation consisting in passing
crude carbonic acid gas, known as kiln gas, through the solution, whereby the
soluble sulphide is converted into an insoluble carbonate, and the sulphurette l
hydrogen is expelled. The Specification mentions several bases as suitable for use
in the process and amongst these are lime and maguesia.
The improvements herein described are different from those above referred to;
magnesia is used to combine with the sulphuretted hydrogen evolved during the
interaction of ammonia and carbon-bisulphide, and subsequently the sulphuretted
hydrogen is separated from the mixed product of the first operation by boiling;
by. which also magnesia is precipitated in such a form that when separated from
the sulpho-cyanide it is ready for re-use. Into a suitably constructed steam
jacketted digestor fitted with suitable stirring apparatus, we introduce the requisite
amount of carbon bisulphide, and a solution of ammonia, together preferably with
two bases, one of which is magnesia (either as oxide (MgO) or the hydrated
oxide (MgH,O,) which latter we prefer), the other is lime (CaH,O,) which we
prefer, or caustic soda, or potash, or other suitable base such as barium or
strontium hydrate. We may, however, only employ one base, namely, magnesia.
In the event of our employing two bases, the amounts of the respective bases we
add is such that the MgH,O, is slightly more than sufficient. to combine with all
the sulphuretted hydrogen, the other being sufficient or slightly less than sufficient
to combine with the sulphocyanic acid. The charge is heated by admitting steam
to the jacket. The pressure soon commences to rise; the heating is regulated to
maintain a pressure of say 50 to 90 pounds to the inch until the reaction is complete
which is ascertained by drawing samples and testing them. After the reaction has
been completed in the digestor, the sulphuretted hydrogen that has been combined
with the bases, is expelled by simple boiling under atmospheric pressure whilst a
free outlet for the gas is provided. The boiling, with a view to expulsion of the
sulphuretted hydrogen, may be effected in the digestor itself, or the solution may
be run into a separate vessel and boiled, whereby MgH,O, is precipitated, and the
sulphuretted hydrogen expelled. The sulphuretted hydrogen is cooled to condense
the steam and then conducted to suitable pyrites burners and burned to produce
sulphurous acid to be afterwards converted in the well known manner into sulphuric
acid, or the sulphuretted bydrogen gas is passed into a gas holder to be used in
the production of brimstone. The precipitated MgH,O, is removed from the
boiled solution by filtration, and is again employed in the digestor, the requisite

page_text: amount of the second base being added, together with carbon bisulphide and
ammonia, and the operation is again proceeded with. The solution of sulpho-
cyanide separated by filtration from the MgH,O, is then converted into suitable
form for the production of cyanides or ferro-cyanides. In the process above
described, if we employ lime as the second base in addition to the MgH₂O, the
reaction in the digestor may be represented by the equation:-
:-
Mg(H₂O₂) + Ca(H₂O₂) + 2 NH3 + 2 CS, = Mg(H,S₂) + Ca(CNS), + 4 H₂O.
The insoluble MgH₂O, is filtered from the soluble Ca(CNS); the latter we
can treat with the alkaline carbonate, or sulphate, so as to form a sulphocyanide of
the alkali.
If we employ caustic alkali such as potash instead of lime, we obtain in the
digestor MgH,S, + 2 KCNS which upon hoiling gives MgH₂O, + 2 H,S +
2 KCNS so that upon filtering off the magnesium hydrate we get a solution of
sulphocyanide of the alkali in one operation.
If we employ in the digestor magnesia as the only base the process yields
sulphocyanide of magnesia which we may decompose by the addition of calcium
hydrate or other hydrate of alkali or alkaline earth, obtaining thereby the
corresponding sulphocyanide and recovering the magnesia in a state fit for re-use.
We may mention that we employ magnesia in the process above described
because of the readiness with which magnesium sulphohydrate may be decomposed,
the ease with which the sulphuretted hydrogen may be expelled upon boiling, and
because when thus boiled, an insoluble substance, magnesium hydrate, is precipi-
tated, which may be readily recovered by filtration, and again employed in the
production of sulphocyanides as above described.
In carrying out the above operations the proportions of the reagents admit of
some variation. For instance we find that to destroy the last traces of sulphides
and expel SH, it is desirable to add a small quantity of sulphocyanide of magnesia.
Also that the pressure in the digestor may be maintained low by employing a
slight excess of ammonia which is afterwards given off when boiling and is
recovered.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. The process consisting in having first digested together ammonia, carbon
bisulphide and magnesia (either with or without another base), in then removing
the sulphydrate of magnesia from the mixed product by boiling whereby
sulphuretted hydrogen driven off and magnesia fit for re-use is precipitated.
2. The process, consisting, first, in digesting together ammonia, carbon bisulphide,
magnesia and a fixed alkali or alkaline earth in such manner that a mixed product
containing a sulphocyanide of the fixed alkali or alkaline earth and sulphydrate
of magnesia is obtained, and secondly in removing the sulphydrate of magnesia
from the mixed product by boiling whereby sulphuretted hydrogen is driven off
and magnesia fit for re-use is precipitated.
Dated this 20th day of Anril 1895.
GEO. S. ALBRIGHT.
JOHN J. HOOD.