Improvements in Process for the Production of Chemical Compounds by Electrolysis.
Year: 1898

page_text: Date of Application, 26th Apr., 1898-Accepted, 11th June, 1898
COMPLETE SPECIFICATION.
Improvements in Process for the Production of Chemical Compounds
by Electrolysis.
We, JOSEPH WILLIAM RICHARDS, a subject of the Queen of Great Britain, resid-
ing at Bethlehem, in the State of Pennsylvania, United States of America,
Electrical Chemist, and CHARLES WILLIAM ROEPPER, a citizen of the United
States, residing at Bethlehem aforesaid, Electrical 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:→→
Our invention relates to those processes in which a desired compound is obtained
by the electrolysis of a solution containing one or more of the elements necessary
to form the compound, in connection with electrodes which, under the electro-
lytic attack, supply the remaining element or elements, the resultant compound
being insoluble in the electrolyte. The invention consists in the employment,
under these conditions, of an alternating current.
We will illustrate our invention by explaining its application to a process which
we have also invented for the production of metallic sulphides, by employing as an
anode, the metal whose sulphide it is desired to obtain, in the electrolysis of a
solution containing a hyposulphite salt, the sulphide sought for being thus formed
at the anode and precipitated therefrom.
Thus, for example, in the formation of cadmium sulphide, we prepare two
electrodes of metallic cadmium and employ as electrolyte a solution of sodium
hyposulphite, say ten per cent. An alternating current is then passed through
the solution, with the electrodes as poles. As a result at each electrode, while it
is acting as an anode, there is formed an insoluble sulphide of cadmium, while at
the same electrode, when acting as a cathode, hydrogen is set free.
Important advantages result from our invention. The production of the in-
soluble precipitate and the hydrogen in alternating succession at the electrodes
facilitates the loosening of the precipitate from the metal pole by reason of the
mechanical action of the bubbles of hydrogen, so that the sulphide is disengaged
as it is formed, falling to the bottom of the vessel and thus enabling the electrodes
to constantly present a clean metal surface to the attack of the electrolyte.
Another advantage is the substantially uniform consumption of both electrodes
and the consequent avoidance of unnecessary resistance, such as occurs when there
is any unequal or unilateral attack. It is to be understood in this connection that
by an alternating current we mean one in which the poles are systematically
reversed at short intervals, either as an incident to the production of the current,
or otherwise.
It is a necessary limitation of our process that it can only be used where as a
esult of the electrolysis an element is liberated, or a compound derived at one
f the poles, which under the conditions designated is inert with respect to the
elements or compounds liberated or formed at the other. These conditions usually
exist wherever gases are liberated, or insoluble precipitates are formed at one
ole. Under these conditions the precipitate formed when the current passes in
ne direction is not decomposed or dissolved, but is simply mechanically dis-

page_text: lodged, when the current passes the other way. Subject, however, to this limita-
tion, our invention is applicable to all processes for the electrolytic production of
precipitated compounds formed by the combination of one or more elements from
an electrolyte with one or more elements from the electrodes.
Thus far we have described our process as applied to the production of simple
compounds by the use of electrodes of similar composition, whereby the same pro-
duct results at both electrodes. Our invention, however, has a further applica-
tion, in that a double or mixed compound may be obtained by it by the employ-
ment of properly chosen dissimilar electrodes. Thus, for example, if electrodes
are employed one of which is of zinc and the other of cadmium, in connection with
the same hyposulphite solution which has been referred to, there will be produced
at the cadmium electrode, whenever it is an anode, cadmium sulphide, and like-
wise at the zinc electrode, whenever it is an anode, zinc sulphide. The resultant
precipitant will therefore be a mixture of these two salts. In all other respects
the effect and operation of the process, and the advantages which flow from it,
are as before, with the additional advantage that by properly varying the alter-
nation of the current so as to regulate the length of time during which the
cadmium electrode is an anode in relation to that during which the zinc electrode
is an anode, a corresponding variation in the proportions of the resultant mixture
can be obtained.
It is to be understood that in instancing the production of sulphides by electro-
lysis of a hyposulphite salt, we have merely chosen a convenient example, and
that our process is not limited to the production of sulphides, but is applicable to
the manufacture of all precipitated compounds, subject to the limitations which
have been above explained.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed we declare that what
we claim is:-
1. The process of obtaining compounds electrolytically, which consists in
passing an alternating current through electrodes immersed in an electrolyte,
one or more of whose constituents forms alternately at each electrode by electro-
lytic attack thereon a compound or compounds partially derived from the con-
sumption of that pole, and which are insoluble in either the electrolyte or the pro-
ducts formed at the opposite pole for the time being, and which compound or
compounds are precipitated from the electrode of consumption, substantially as
described.
2. The process of obtaining compounds electrolytically, which consists in
passing an alternating current through electrodes immersed in an electrolyte, one
or more of whose constituents forms alternately at each electrode by electrolytic
attack thereon a compound or compounds partially derived from the consumption
of that pole, and which are insoluble in the electrolyte, and which are precipi-
tated from the electrode of consumption, while one product of the electrolysis, at
the opposite pole for the time being, is a liberated gas, substantially as described.
Dated this 25th day of March 1898.
CARPMAEL & Co.,
Agents for the Applicants.