Improvements in the Electrolytic Separation of Zinc from Zinc Oxide.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Electrolytic Separation of Zinc from Zinc Oxide.
We, OSCAR JULIAN STEINHART and JULIUS LEONARD Fox VOGEL, both of
91, Blackfriars Road, in the County of Surrey, Electro Chemists, and HENRY
ERNEST FRY, of 5, Laurence Pountney Hill, in the City of London, Mineral Mer-
chant, do hereby declare the nature of this invention to be as follows:-
The object of this invention is to enable zinc oxide to be reduced electrically
into metallic zinc by dissolving the zinc oxide in fused zinc chloride or other
suitable salt capable of acting in like manner and passing an electric current
through the molten bath so that oxygen is evolved at the anode and zinc is
deposited in a molten state at the cathode.
The zinc oxide which is an infusible salt is capable of being held in a fused
condition in a bath of molten zinc chloride or it may be said to form a basic
chloride or oxychloride of zinc. When an electric current of low voltage is passed
through such a fused salt or mixture of salts so long as there is present any
oxide of zinc that oxide is decomposed in preference to the chloride and oxygen
free from chlorine is given off. Thus by continually feeding fresh supplies of
oxide into the bath a continuous reduction is obtained the zinc chloride present
only acting as a solvent.
Dated this 19th day of September 1898.
0. J. STEINHART,
JULIUS L. F. VOGEL,
HENRY E. FRY.
Improvements in the Electrolytic Separation of Zinc from Zinc Oxide.
We, OSCAR JULIAN STEINHART and JULIUS LEONARD Fox VOGEL, both of
91, Blackfriars Road, in the County of Surrey, Electro Chemists, and HENRY
ERNEST FRY, of 5, Laurence Pountney Hill, in the City of London, Mineral Mer-
chant, 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:―
The object of this invention is to reduce zinc oxide electrically into metallic zinc.
This we effect by dissolving zinc oxide in zinc chloride kept fused in an externally
heated vessel in which the reduction is to be effected and by passing an electric
current through the molten bath so that oxygen is liberated at the anode and
zinc is deposited in a molten state and joins the cathode which is formed of a
laver of molten zinc at the bottom of the vessel.
Zinc oxide although being of itself an infusible compound at the temperature at
which zinc fuses can be dissolved in a bath of molten zinc chloride and forms
with it a readily fusible compound which when acted upon by an electric current

page_text: is decomposed in such manner that no chlorine is evolved so long as zinc oxide
is present.
Thus by continually feeding fresh supplies of oxide into the bath of molten
zinc chloride a continuous reduction of the oxide is obtained, the zinc chloride
present only acting as a solvent.
To the zinc chloride may be added some sodium chloride which will render it
less hygroscopic.
We effect the reduction of zinc oxide in the above manner in any suitable
vessel formed of or lined with refractory material. We prefer to use a vessel with
carbon blocks projecting downwards from the cover into the vessel at a distance
apart from one another to form the anode a layer of molten zinc at the bottom
of the vessel serves to form the cathode. An opening or openings by which zinc
oxide may from time to time be fed into the vessel and a suitable gas outlet .are
also provided in the cover.
The vessel is externally heated by a fire sufficiently to keep the layer of zinc at
the bottom of the vessel in a fused state.
A channel leading upwards from the bottom of the vessel for a short distance
to an overflow spout allows molten zinc to flow off whereby the layer of molten
zinc at the bottom of the vessel is always kept approximately at one uniform level.
When commencing to work sufficient zinc is first placed in the vessel to form
when fused a layer of about one inch deep and then zinc chloride previously
dehydrated is introduced in sufficient quantity to form when melted a layer say of
about two inches deep which floats on the top of the zinc or if the zinc chloride
is not previously completely dehydrated it will be dehydrated by the current
at starting.
The carbon plates which form the anode are made of such a length that their
lower ends are immersed about an inch and a half in the zinc chloride and are con-
sequently distant about half an inch from the surface of the molten zinc. A
quantity of zinc oxide previously purified is now introduced into the cell and
some of it becomes dissolved in the chloride the remained being held in suspen-
sion. Afterwards electric current of suitable voltage say of about 3 volts is passed
through the molten chloride, the molten zinc at the bottom of the vessel forming
the cathode and the carbon plates the anode, the oxide dissolved in the molten
chloride is decomposed, oxygen being evolved at the anode and zine in a molten
state deposited at the cathode. As the zinc oxide fed into the vessel becomes
gradually dissolved in the molten chloride fresh zinc oxide is from time to time
added and in this way a continuous reduction is obtained.
By keeping the vessel heated externally just sufficiently to keep the zinc at the
bottom of the vessel in a fused state we are able to use an electric current of lower
voltage than would otherwise be practicable if the required heat were to be applied
by the current passing and can so ensure that the oxide only shall be decom-
posed and not the chloride whilst at the same time the carbons are not materially
heated by the passage of the current and are not so quickly consumed as they
otherwise would be.
Having now particularly described and ascertained the nature of our said in-
vention and in what manner the same is to be performed, we declare that what
we claim is:-
1. The separation of zinc from zinc oxide by dissolving or suspending zinc
oxide in molten zinc chloride and by passing an electric current through the
molten mixture substantially as described.
Dated thin 12th day of T 1000
O. J. STEINHART,
JULIUS L. F. VOGEL,
HENRY E. FRY.