IMPROVED MEANS FOR OBTAINING ELECTRIC LIGHT
Year: 1878

page_text: LETTERS PATENT to John Scudamore Sellon, Metallurgist, of Hatton Garden,
in the County of Middlesex, William Ladd, and Henry Edmunds, both of
Beak Street, in the same County, Engineers, for the Invention of "IMPROVED
MEANS FOR OBTAINING ELECTRIC LIGHT."
Sealed the 13th May 1879, and dated the 15th November 1878,
PROVISIONAL SPECIFICATION left by the said John Scudamore Sellon,
William Ladd, and Henry Edmunds at the Office of the Commissioners of
Patents on the 15th November 1878.
JOHN SCUDAMORE SELLON, Metallurgist, of Hatton Garden, in the County of
Middlesex, WILLIAM LADD, and HENRY EDMUNDS, both of Beak Street, in the same
County, Engineers. "IMPROVED MEANS FOR OBTAINING ELECTRIC LIGHT."
"
This Invention relates, firstly, to a novel construction of electrode to be used in
electric lamps. It is well known that the electrodes at present in use burn away
more or less rapidly. Now the object of the first part of this Invention is to remedy
this defect. To this end we employ as one of the electrodes iridium in a practically
pure state.
The iridium in any suitable shape to form a
"point we fix in a
metallic setting, preferably platinum, and this platinum setting we affix to a plug of
copper. This arrangement ensures the rapid diffusion of the heat produced by the
electric arc, the iridium (which is practically indestructible) giving off its heat to
the metal setting, which, yielding the same to the copper plug, ensures the rapid
diffusion of the heat.
We have stated that the iridium which we employ is in a practically pure state.
Iridium, therefore, which contains what are known as the platiniferous metals, will
not serve our purpose. The chief present source of iridium is from the insoluble
residues resulting from the ordinary refining of platinum ores.
This residium
usually contains besides iridium the so called platiniferous metals, rhodium, palla-
dium, osmium, and ruthinium, and in addition frequently the baser metals, such as
[Price Bd21

page_text: iron in a state of chromate, the association of which with the iridium would render
it useless as an electrode.
We therefore select for our purpose iridium which is free from these impurities,
and this iridium, mounted as above described, we use as one electrode, employing
carbon as the other electrode. By this combination we are enabled to obtain a better
result than has heretofore been secured, the iridium point being practically permanent.
Instead of employing rods or wires of platinum in a closed circuit for emitting
light we propose to use alloys of this metal with iridium in order to enable the rods
or wires the better to resist the action of heat. The proportion of iridium to the
platinum may vary from 5 per cent. to 95 per cent., according to the position in the
circuit in which the bars or wires are intended to be placed, and the amount of
resistance required.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Jolin Scudamore Sellon, William Ladd, and Henry Edmunds in the
Great Seal Patent Office on the 15th May 1879.
JOHN SCUDAMORE SELLON, Metallurgist, of Hatton Garden, in the County of
Middlesex, WILLIAM LADD, and HENRY EDMUNDS, both of Beak Street, in the same
County, Engineers. "IMPROVED MEANS FOR OBTAINING ELECTRIC LIGHT."
This Invention relates, firstly, to a novel construction of electrode to be used in
electric lamps. It is well known that the electrodes at present in use burn away
more or less rapidly. Now the object of this Invention is to remedy this defect.
To this end we employ as one of the electrodes iridium in a practically pure state.
The iridium in any suitable shape to form a "point" we fix in a metallic setting,
preferably platinum, and this platinum setting we affix to a plug of copper. This
arrangement ensures the rapid diffusion of the heat produced by the electric arc, the
iridium (which is practically indestructible) giving off its heat to the metal setting,
which, yielding the same to the copper plug, ensures the rapid diffusion of the
heat.
The Figure in the accompanying Drawing shews our new compound electrode in
section and in full size. a is a bead of iridium, set in a holder b of platinum. This
holder is threaded and screwed into a copper block c, which is intended to be fitted
to a metal holder connected with a wire leading to the electric generator. The
surfaces of the three metals are so proportioned as to insure a rapid diffusion of the
heat generated at the "point" a. Thus whatever may be the energy of the current
the iridium point will remain unaffected by the heat. We have stated that the
iridium which we employ is in a practically pure state. Iridium, therefore, which
contains what are known as the platiniferous metals will not serve our purpose.
The chief present source of iridium is from the insoluble residues resulting from the
ordinary refining of platinum ores. This residuum usually contains besides iridium
the so-called platiniferous metals, rhodium, palladium, osmium, and ruthinium, and,
in addition, frequently the baser metals, such as iron in a state of chromate, the
association of which with the iridium would render it useless as an electrode. We
therefore select for our purpose iridium which is free from these impurities, and
this iridium, mounted as above described, we use as one electrode, employing
carbon as the other electrode. By this combination we are enabled to obtain a
better result than has heretofore been secured, the iridium point being practically
permanent.
The Invention relates, secondly, to an improvement applicable to closed circuit
lamps.
Instead of employing rods or wires of platinum in a closed circuit for emitting
light we propose to use alloys of this metal with iridium, in order to enable the rods
or wires the better to resist the action of heat. The proportion of iridium to the
platinum may vary from five per cent. to ninety-five per cent., according to the
position in the circuit in which the bars or wires are intended to be placed, and the
amount of resistance required.
Having now set forth the nature of our Invention of “ Improved Means for
Obtaining Electric Light," and having explained the manner of carrying the same
into effect, we wish it to be understood that under the above in part recited Letters
Patent we claim,-
.
First. Constructing iridium electrodes in the manner and for the purpose above
described.

page_text: Second. The use in closed circuit lamps of rods or wires composed of an alloy of
platinum and iridium, for the purpose above set forth.
In witness whereof, we, the said John Scudamore Sellon and Henry Edmunds,
have hereunto set our hands and seals, the Fifteenth day of May, in the
year of our Lord One thousand eight hundred and seventy nine.
JOHN S. SELLON.
(L.S.)
HENRY EDMUNDS. (L.S.)