Improvements in the Manufacture of Iodine by Electrolysis.
Year: 1888

page_text: Date of Application, 9th Aug., 1888
Complete Specification Left, 9th May, 1889-Accepted, 6th July, 1889
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Iodine by Electrolysis.
We, THOMAS PARKER, Electrical Engineer, and ALFRED EDWARD ROBINSON,
Chemist, both of Commercial Road, Wolverhampton in the County of Stafford, do
hereby declare the nature of this invention to be as follows:-
This Invention relates to the manufacture of iodine by electrolysis.
According to our Invention we manufacture or prepare the iodine from a solution
of the iodides of the metals, of the alkalies, or of the alkaline earths.
The solution is subjected to the action of a current of electricity, when decomposition
of the iodide takes place, and iodine is set free at the positive pole and the metal,
alkali, or alkaline earth at the negative pole. If the solution of an iodide of a
metal is employed, no secondary reaction takes piace, but when a solution of an iodide
of an alkali or of an alkaline earth is used iodates are formed, in which cases we
prefer to mix with the iodide solution a sufficient quantity of a chloride of an alkali
which on electrolysis gives rise to freo chloring which in its turn decomposes the
iodate which has been formed. Alternatively, the electrolysis may proceed until the
solution is colourless, and the iodate is finally decomposed by any suitable oxidising
agent.
D
L A Th 1000
WILLIAM E. HEYS,
Agent for the Applicants.
COMPLETE SPECIFICATION
Improvements in the Manufacture of Iodine by Electrolysis.
We, THOMAS PARKER, Electrical Engineer, and ALFRED EDWARD ROBINSON,
Technical Chemist, both of Commercial Road Wolverhampton in the County of Stafford,
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 iodine by electrolysis.
In proceeding with the manufacture of iodine according to these Improvements,
we first prepare an acid solution (or a solution in which sulphuric or other suitable
acid will be liberated by the action of the current) containing an iodide of an alkali,
or an alkaline earth, or of a metal. It will be obvions that certain of the iodides
cannot be employed, either because they are too costly, or because they are decomposed
by water, (iodide of antimony, iodide of bismuth, etc.) or because they are insoluble
in water, (cuprous iodide, Cu, I,, iodide of sulphur, etc.). The selection of the best
iodide for use according to this Invention will therefore be governed by conditions of
local cost, and solubility in water without decomposition; iodide of sodium or of
potassium are however in all cases preferrod to be employed.
The solution should be made to a moderate degree of concentration, but it is not
necessary to provide for any precise degree of strength of the solution because this
may vary within comparatively wide limits; indeed it will be evident that when the
solution is being operated on for the reduction of the iodine, the strength of the solution
is constantly varying.
The iodide solution having been prepared is placed in a suitable electrolysing vessel
which is divided into two parts or compartments by a porous partition or septum.
In one of the divisions or cells of the electrolysing vessel there is placed a carbon,
platinum, or other suitable inoxidisable anode; in the other division, an iron or other
suitable metallic cathode is placed. These electrodes are respectively connected to the

page_text: positive and to the negative terminals of a continuous current dynamo-electric
machine capable of generating a current of more than two amperes for each square
decimeter in area of the anode.
The iodide solution is placed in that division of the electrolysing vessel in which the
positive electrode is contained the other division is filled with a (preferably caus.ic)
solution of an alkali.
Before the operation is commenced, the iodide solution may be acidified by the
addition of hydrochloric acid, or of sulphuric acid. This addition of acid (or the
hereinafter described liberation of the acid in the solution) is effected in order to
prevent the loss of iodine owing to the formation of the salts of the oxyacids of
iodine which are not readily decomposed by the action of the electric current.
The necessary acidification of the current may be ensured by adding to the iodide
solution some soluble sulphate such as, and preferably, sulphate of magnesia, of soda,
or of potash. In the electrolysis of the solution containing the soluble sulphate, the
sulphate is decomposed simultaneously with the iodide solution, thus liberating the
sulphuric acid which instantly combines with the base of the iodide, this newly formed
sulphate is in its turn decomposed, and the cycle of decompositions and recompositions is
repeated as long as the operation is continued.
The reactions are illustrated by the following formula :—
-
10 KI+5.H, SO₁=5 K₂SO₂+10 HI
and 2 KIO,+H, SO=K, SO+2 HIO,
and 2 HIO,+10 HI=6 H₂O+12 I
The above formula indicates the proportions of the constituents of the solution.
Under the action of the current, the iodine is set free at the positive pole, and the
metal, alkali, or alkaline earth which formed the base of the iodide is liberated at
the negative pole when it may be removed as required.
To make the operation continuous, it is necessary only, to add a fresh quantity of
the iodide solution, from time to time, so as to keep the solution in the electrolysing
vessel of about an average strength. The iodine which is the product of the electrolysis
is removed from the vessel ns it accumulates, is then drained and washed with cold
water, and is subsequently dried in a current of warm air.
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 :-
The manufacture or production of iodine by the electrolysis of a solution of an
.iodide containing a soluble sulphate or free acid; substantially in the manner and by
the means hereinbefore described.
1
n 1000
WILLIAM E. HEYS,
Agent for the Applicants.