Improved Method of Producing Alkali Cyanides and Ferrocyanides.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improved Method of Producing Alkali Cyanides and Ferrocyanides.
I, JACOB GROSSMANN, of Harpurhey Chemical Works, Manchester, in the County
of Lancaster, Manufacturing Chemist, do hereby declare the nature of this
invention to be as follows:-
This invention relates to the production of alkali cyanides and ferrocyanides.
I have found that in the presence of and with certain sulphur compounds of
the alkalis cyanides and ferrocyanides can be produced at a red heat or there-
abouts .e. at such a comparatively low temperature as renders it practicable as
far as durability of apparatus is concerned and as obviates any serious destruc-
tion of ammonia. If, e.g. a mixture of potassium sulphide and charcoal, such
as may be obtained by heating potassium sulphate with a large excess of char-
coal until the reduction of the sulphate is sufficiently complete, is heated to
about 250° degrees Centigrade and dry ammoniagas passed over the mixture, sul-
phuretted hydrogen passes off either as such or in combination with ammonia. If
after the evolution of sulphuretted hydrogen is completed or nearly completed, the
mass is heated to red heat cyanide of potassium is formed. But the conversion
into cyanides also takes place if the mixture of sulphide and carbon is heated to
redness throughout the operation whilst dry ammoniagas is passed over.
I have found that not only are such definite compounds as the ordinary sul-
phides of the alkalis suitable for this process, but also such indefinite compounds
as polysulphides and oxysulphides. Thus even a mixture of compounds such as
come under the designation of liver of sulphur, and which contain sulphides
varying from mono to pentasulphide and their intermediates, thiosulphates and
other oxysulphides, sulphites and sulphates as well as carbonates, are suitable for
the production of cyanides by my process.
As regards the preparation of suitable sulphur compounds on a large scale,
they may be either made by the reduction of alkali sulphates or sulphites by car-
bonaceous matter by any of the well known processes, or by any other method
which produces sulphides or oxysulphides; they must naturally be as free from
water as possible. If made from sulphates or sulphites an excess of carbonaceous
matter may be used and thus the destructive action of the sulphites on appa-
ratus prevented. If liver of sulphur is used it is not even necessary to com-
plete the reaction in making it, as the heat in the apparatus which is used for
producing the cyanide is sufficiently great to finish the reaction. Thus I find
that it is sufficient to heat a mixture of carbonate of potash or soda and powered
sulphur to about 150° C. i.e. below the temperature at which sulphur volatilizes
to produce a mass which when powered and mixed with charcoal or other suit-
able carbonaceous matter yields cyanides on being treated with ammoniagas at
red heat. The proportions of sulphur to alkali may vary from one equivalent
or less to two equivalents of sulphur or even more, to one equivalent of alkali;
equal equivalents give good results;

page_text: In order to manufacture cyanide or ferrocyanide I proceed as follows. The
sulphide, oxysulphide, thiosulphate, or a mixture of either or all of these com-
pounds is ground to a powder, and if too rich in sulphur may be mixed with
carbonate of potash or soda. It should, unless suitable hydrocarbons are used in
conjunction with ammonia, contain sufficient carbon or carbonaceous matter
apart from that contained in the state of carbonate in the proportion of about
five to ten equivalents of carbon to one equivalent of alkali; and this propor-
tion should be obtained, if necessary, by adding a sufficient quantity of carbon-
neeous matter; preferably in the state of a coarse powder and of a quality which
absorbs ammoniagas such as charcoal. The mixture may be made more porous
if desired by any of the means known to chemists.
It
The mixture of the suitable alkali sulphur compound, carbonaceous matter
and if necessary of alkali carbonate or hydrate is then placed in retorts or other
suitable apparatus, and dried ammonia gas either by itself or mixed with hydro-
gen or hydrocarbons or other suitable gases is passed over it whilst the retort is
kept at red heat; several retorts may be connected so that the ammonia has to
pass them successively. The ammoniagas used need not be pure; it may con-
tain carbonate, sulphide, or other volatile ammonia compounds and may be pre-
pared from gas liquors, from sulphate of ammonia or other suitable sources.
may be passed through the retorts at ordinary, diminished or augmented pres-
sure as compared with the pressure of the atmosphere. The gases which leave
the retorts and which contain chiefly sulphuretted hydrogen and ammonia or
their combinations may be condensed" and recovered by any of the methods well
known to chemists. The red heat and the current of ammonia gas may be kept
up from the beginning to the end of the operation; or the current of ammonia
may be stopped before the maximum quantity of cyanide is formed and the
operation finished without a current of ammonia or the mass may be heated
in a current of ammonia first at a low temperature, about 300°C. and the
operation finished at a red heat by any of the variations proposed above. If it
is desired to produce ferrocyanide instead of cyanide, a suitable quantity of
iron filings may be added to the mixture of alkali sulphides and carbonaceous
matter or the process may be carried on as above for the production of cyanide
and the resulting mass after being dissolved may be treated with iron or iron
compounds to produce ferrocyanide in a manner well known to chemists. Whether
cyanide or ferrocyanide has been ultimately produced, the product may be puri-
fied by any of the means and methods which will readily occur to those conver-
sant with the subject.
Sulphocyanides may also be used in place of the sulphur compounds mentioned
above. In some cases the preparation of the sulphur compounds and their con-
version into cyanides may be carried on in one operation.
Dated this t
1800
Improved Method of Producing Alkali Cyanides and Ferrocyanides.
I, JACOB GROSSMANN, of Harpurhey Chemical Works, Manchester, in the County
of Lancaster, 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:-
This invention relates to the manufacture of alkali cyanides and ferrocyanides.

page_text: I have found that if ammonia gas be passed over a red hot mixture of potas-
sium sulphide and carbon, or of liver of sulphur and carbon, a reaction takes
place in which the principal product formed is potassium cyanide; sulpho-
cyanide being only formed in quite negligeable quantities. The greater part of
the sulphur passes away as sulphuretted hydrogen or ammonium sulphide
respectively ammonium cyanide can hardly be shown to exist in the gases
which are evolved.
In order to work this process on a large scale I proceed as follows: -
The sulphide of an alkali or its liver of sulphur is intimately mixed with
ground or rasped charcoal. This mixture is placed in retorts which are arranged
in such a manner that several retorts are connected together into one set or
system; so that the gas or gases which are used in the process, that is to say
ammonia by itself or mixed with other gases, pass from one retort into another
and so on into each retort of the set, the temperature in all retorts being kept
at red heat; a heat of between 700° C. to 800° C. is sufficient.
Thus, when the contents of the retorts have attained red heat, the ammonia
gas in excess is passed from a suitable ammonia still or from a gasometer over
the mixture which is contained in the first retort. The excess of the ammonia
mixed with other gases which are evolved the first retort during the process
pass into the second retort and so forth. The gases which leave the last retort
of the set are condensed in the usual manner and reconverted into ammonia gas
according to methods well known. The ammonia used in the process is dried
by dephlegmation; it is not necessary to use chemical agents for drying the
same. After a sample taken from the first retort shows that the reaction has
proceeded sufficiently, as far as the formation of cyanide is concerned, the first
retort is disconnected from the system and emptied. Air is excluded during the
emptying process or the retorts may be emptied in an atmosphere of a non-
oxidising gas. The second retort now becomes the first in the system, whilst
the first retort after being charged becomes the last retort of the set and is
exposed to the action of the gases last; but it is not coupled into the system
again, until its contents have reached a temperature of about 700° C.
As regards the charge for the retorts the quantities are chosen in such a way
that the mass does not cake at red heat; if sulphide is used about equal parts
of sulphide and charcoal may be taken; if working with liver of sulphur a good
proportion will be to take on every 100 parts of potassium carbonate about 120 to
140 parts of charcoal and 24 parts of sulphur. In either case the quantity of char-
coal may be reduced. If sodium compounds are used the proportions may he
altered accordingly: mixtures of potassium and sodium compounds may also be
used in this process
The ammonia may be prepared by any of the known methods; compressed
ammonia may also be used. The ammonia gas need not be pure, it may con-
tain other volatile non oxidizing ammonia compounds, hydrogen, hydrocarbons
or other gases of a non-oxidising nature and it may be passed through the
retorts at ordinary, diminished, or augmented pressure, as compared with the
pressure of the atmosphere.
It
If it is intended to manufacture ferrocyanides, iron filings may either at the
beginning or at the end of the reaction be added to and mixed with the mass.
contained in the retorts. It is, however, advantageous even in working for the
production of ferrocyanide compounds to effect the conversion into ferrocyanide
outside the retorts from the alkali cyanide which is in the resulting mass.
is therefore more advantageous to lixiviate this mass .e. the drawn charge,
systematically after it has been cooled in suitable apparatus. From the liquor
thus obtained alkali cyanide may either be separated as such or after treatment
with suitable ferrous compounds, as ferrocyanide. The mother liquid may be evapo-
rated in vacuum pans or in other suitable manner and the residue returned into
the process.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is
1. A process for the manufacture of alkali cyanides consisting in passing pure
ammonia gas, or ammonia gas mixed with volatile non-oxidising ammonia com-
pouls or mixed with hydrogen, hydrocarbons or other non-oxidizing gases over
a mixture of carbon or carbonaceous matter, and a sulphide of an alkali, or liver
of sulphur or ingredients forming an alkaline sulphide at red heat, substantially
as described.
2. A process for the manufacture of ferrocyanides consisting in passing pure
ammonia gas or ammonia gas mixed with volatile non-oxidising ammonia com-
pounds or mixed with hydrogen, hydrocarbons or other non-oxidising gases over
a mixture of carbon and a sulphide of an alkali or liver of sulphur or ingre-
dients forming an alkaline sulphide, at a red heat and adding to the products
of the reaction either at the beginning or at the end of the reaction iron filings
for the purpose of converting the cyanides first formed into ferrocyanides, sub-
stantially as described.
.
1000