Process for the Extraction of Metallic Alloys and Pure Metals by Electric Heat.
Year: 1897

page_text: Date of Application, 12th Jan., 1897-Accepted, 27th Mar., 1897
COMPLETE SPECIFICATION.
Process for the Extraction of Metallic Alloys and Pure Metals
by Electric Heat.
I, HEINRICH ASCHERMANN of 5 Terrasse, Cassel in the Empire of Germany,
Doctor of Science 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 :-
In electric furnaces, the extraction of pure metals from their oxides presents
considerable difficulties when the metals have great affinity for carbon. There
results, in that case, a carburet or a metal containing a large proportion of carbon
and it becomes necessary in consequence, to add a very fusible metal as a flux,
which combines with the reduced metal, in the native state, and prevents it,,
accordingly, from absorbing carbon. But that alone is not sufficient. In order to
obtain a metal as nearly as possible free from carbon, it is essential that the
reduction should be effected rapidly and that it should be produced by the weakest
possible currents. That is indispensable even when no regard is paid to the
question of economy. I have never succeeded in obtaining the metal reduced to a
state of purity by the prolonged action of the voltaic arc, or by the use of more
intense currents. The flux volatilises and is immediately replaced by the carbon.
The reduced metal becomes saturated with carbon proportionately to the
volatilisation of the flux. The flux has little or no influence on the course of the
reduction; it serves simply to prevent the entry of carbon into the combination.
If, however, a metallic sulphide is taken as a flux, the reduction is effected more
rapidly and with less expenditure of thermo-electric energy. It will be seen that
it is the sulphur which favours the reaction.
If it is desired to obtain a pure metal, the sulphide of a very fusible metal is.
taken as a flux, which can easily be eliminated from the resulting alloy, by
re-heating.
Experiments have shewn that the best results are obtainable by the use of
sulphide of antimony (Sb, S3).
The mixture of the metallic oxide with the metallic sulphide is produced in
simple atomic proportions, the sulphide, however, being slightly in excess. The
mixture is interposed in the circuit of an electrical fusion-furnace, so that it forms
its kathode or negative pole. A current of from 20 to 25 amperes suffices in
any case.
By way of example, to extract metallic chromium, chromium oxide and sulphide
of antimony are mixed in the proportion of 10 to 23. The antimony is driven from
the resulting alloy by re-heating and what remains is pure chromium. For the
oxide of aluminium, the proportion is 10 for 37 of sulphide of antimony. The
mixture, being placed in iron crucible, is interposed in the electric circuit and as
soon as the fusion commences, oxide of aluminium and sulphide of autimony are
added in equal proportions.
The use of sulphide of antimony as a flux is also recommended for reducing the
greater number of metals, for the fusion of which a high temperature is necessary
because the re-action is considerably accelerated by the sulphur and the amount of
energy necessary is very considerably diminished."
The production of metallic alloys assumes still greater importance than the
extraction of pure metals, especially as concerns the combinations of iron and

page_text: copper, which are obtained in the electric furnace, in a remarkable manner, with
currents relatively weak, by melting the metallic oxide with the corresponding
metallic sulphide.
For example, ferro-chromium is prepared, in this way by melting together
10 parts of iron sulphide and 9 parts of chromium oxide; ferro-manganese, with
10 parts of iron sulphide and 11 parts of bi-oxide of manganese.
The ferro-cerium obtained by this process deserves special attention owing to its
peculiar properties; it is obtained by fusion, in the electric furnace, from 25 parts
of oxide of cerium with 10 parts of sulphide of iron.
F
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
.
A process for the extraction of metallic alloys and pure metals by electric heat,
from a mixture consisting of the oxide of a metal and the sulphide of another metal,
or composed of the oxide of a metal and the sulphide of a metalloid or again the
mixture may consist of the oxide of a metalloid and the sulphide of a metal for the
purpose of accelerating the reduction of oxides or sulphide (or both), which are
difficult to reduce, and to separate certain impurities from the metal to be obtained,
such metal, obtained first under the form of an alloy, being capable of being
delivered in this form or of being obtained in a pure state, by removing, by
distillation, the other and more fusible element, substantially as above described.
ROBERT E. PHILLIPS, Assoc. M. Inst. C.E., M.I. Mech. E.,
Consulting Engineer and Patent Agent,
70, Chancery Lane, London, W.C., Associate Agent.