Improvements in the Manufacture and Purification of Alkaline Cyanides.
Year: 1899

page_text: Date of Application, 6th Dec., 1899-Accepted, 6th Jan.,
1900
COMPLETE SPECIFICATION (AMENDED).
Improvements in the Manufacture and Purification of Alkaline
Cyanides.
I, THOMAS WILTON, of The Gas Light and Coke Company's Tar and Liquor.
Works, Beckton, in the County of Essex, 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:
4
My invention relates to the manufacture and purification of alkaline cyanides
such for example as cyanide of potassium, sodium and so forth, and consists
in a new or improved method whereby in the manufacture I am able to separate
or dissociate the alkaline cyanides from mixtures or compounds containing same,
and so I am able to obtain cyanides of a higher commercial purity and 'at but
little expense.
I have found that liquefied ammonia gas (NH3) has the property, when properly
applied to mixtures containing alkaline cyanides, of dissociating by dissolving
out therefrom either the cyanides or the impurities present with the same, accord-
ing to which is the most soluble. Liquefied ammonia gas is a solvent which does
not in any way injure the cyanide and has a selective action in dissolving out
certain salts, which special property I utilise. In carrying out my invention
the mixture containing the evanide or cyanides is subjected when in a reduced
or powdered condition to the action of the liquefied ammonia gas under suitable
pressure to render the process continuous the ammonia is evaporated from the
dissolved portion, whether it be the cyanide or the impurities, and then recon-
densed in a coil ready for re-use, while the separated cyanide is left in a highly
purified state.
I will describe one means of carrying my method into useful effect in refer-
ence to the accompanying drawing which shows diagrammatically in vertical
section an apparatus which I have found to give good results, and in the following
description will assume the cyanide to be the substance dissolved. The
apparatus illustrated consists of an airtight receiver a having a bottom strainer b.
The lower part of this receiver (below the strainer) is connected by a pipe c
to a lower vessel d. In order to render the process continuous I connect the
lower vessel by a pipe e to a coil-condenser f situated within a vessel
arranged at the upper part of the apparatus and connected to the receiver a
the pipe fitted with a stop cock at i.
by
In using this apparatus the mixture containing the alkaline cyanide is first
pulverised and then placed in the receiver a and the whole apparatus is made
airtight. The mixture is then subjected to the action of the solvent (N H₁₂)
by passing same therethrough in a liquid form and under sufficient pressure to
maintain liquefaction. During the process the cyanide is dissolved out of the
impurities by the selective action of the solvent and passes in liquid form through
pipe c to the lower vessel d, from which it is subsequently removed; the impuri-

page_text: ties in the mixture which are not acted upon by the solvent remain in the
vessel a and may be removed therefrom. The ammonia (NH3) when in the
lower vessel d may be evaporated by heat or otherwise from the cyanide dissolved
out the vapour of ammonia will then pass up pipe e, and being recondensed in
the coil will pass into the vessel, and thence by pipe h to the receiver a,
when the cock is opened. Thus the cyanide is left in a highly purified state
in the lower vessel and the ammonia solvent may be applied to the compound
under treatment over and over again, the required pressure being maintained
in the apparatus during the whole of the process. The process will, as above
indicated, vary according to the particular cyanide under treatment, for instance
in the treatment of potassium cyanide, when it is less soluble than the impurities
with which it happens to be mixed, the cyanide will remain in the first vessel a
whilst the impurities will be deposited in the lower vessel d, and as the solubility
of different cyanides varies it will be obvious that the same method can be used
for the purpose of dissociating or separating them from each other; for example,
cyanide of potassium may be separated from cyanide of sodium by fractional
solution, the latter being more soluble in liquefied ammonia gas. The process is
applicable to all alkaline cyanides, the above instanced being examples of the
process and the mode of application.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I wish it to be
understood that I am aware of the Specification of Letters Patent No. 5815 of 1896
granted to George Craig and that I do not claim anything described and claimed
therein, but I declare that what I claim is:
i
1. For the purpose of purifying alkaline cyanides the use of liquefied ammonia
gas substantially in the manner above described.
2. In the manufacture of alkaline cyanides the method of purification thereof
which consists in subjecting mixtures containing same to the action of liquefied
ammonia gas (NH3) under sufficient pressure to maintain liquefaction, whereby
the cyanide is separated from its impurities and obtained in a highly purified
state, substantially in the manner set forth.
Dated this 6th day of December 1899.
For the Applicant,
J. C. CHAPMAN & Co.,
Chartered Patent Agents,
70, Chancery Lane, London, W.C.,