A New and Useful Method of Manufacturing Electric Conductors and Resistances.
Year: 1899

page_text: Date of Application, 23rd Feb., 1899-Accepted, 22nd July, 1899
[Communicated from abroad by WILHELM CARL. HERAEUS, of Hanau, in the
Kingdom of Prussia.]
A New and Useful Method of Manufacturing Electric Conductors and
Resistances.
I, SAMUEL SIDNEY BROMHEAD, of 171, Queen Victoria Street, London, in the
County of London, Patent Agent, 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 ;-
It is known that from a combination of mineral substances and finely powdered
metals, an electric conducting mass may be obtained, from which electric
resistances, light bodies for aphlogistic lamps, heating bodies and the like can
be manufactured.
However, in the present known methods for manufacturing such products it
is admitted that such resistances are extraordinarily fragile, necessitating a con-
siderable use of platinum in order to preserve their metallic coherence and
conductibility and further require a strong current to reach the glowing point.
My invention however discloses a process for making rods, or filamentous bodies,
possessing great resistance, consuming but a small amount of platinum for
insuring their conductibility and which are susceptible to glow by a weak
current.
The most practical results to realize the above said invention are obtained by
using a mixture of argil and asbestos in preferably equal parts, but this will
depend on the melting capacity of the former as well as on the desired fusibility
of the finished material.
There are however, also available, natural or artificial manufactured silicato
compositions or mixtures of silicic acid with basic constituents, or with silicates
as a flux, all of which are fusible in high temperature.
These pulverulent compositions are mixed with such salts of the platinum
group which produce metal when being caused to glow. The quantity of salts
of platinum used is such that the finished material contains from 5 to 20% of
metallic platinum, according to whether it is desired to obtain more or less high
class goods.
44% of
(2H,NCIPtCl₁) which contains
Ammonia platinum chloride
platinum, is employed to great advantage for the above purpose, and about 11.5
to 40% of this is used. Proper organic substances such as gum acacia is then
added to the mixture to make it plastic, and from this are formed oblong bodies
usually circular in cross section.
After drying, these bodies are heated to a very high temperature (1300°-
1350° C.) under the simultaneous influence of reducing gases, whereby during
the smelting of the mass chemical reactions take place. The previously non-
conducting rods or wires are thus converted into conducting material.
The conditions to create the reducing gases are profitably secured by passing
hydrocarbons or hydrogen through a heated tube or muffle or by allowing them
to pass a flame, created under limited access of oxygen.

page_text: After the mass has cooled off, rods or threads of great hardness and compactness
are obtained, which have the appearance and the properties of glass or enamel.
These rods or threads by means of a blast or an oxy-hydrogen blow pipe,
can be melted or shaped into any desirable form like glass before the blow pipe.
If the heating process is interrupted at a high temperature in which no smelting
has taken place of the mineral substances, it will be observed that the rods or
threads in a practical sense are non-conductors of electric currents. They only
become useful conductors when the melting temperature has been reached. On
the other hand if the bodies are heated in a neutral atmosphere such as air or a
stream of carbonic acid, even to the melting point they nevertheless remain
non-conductors.
In order to make good conductors out of a mixture of a mineral compound
and platinum metal in a practical and useful way, the proportion of platinum
must be higher than that of mineral constituents, but with my present invention,
only from 6 to 16% of platinum metal are required. A thread or wire of
about 1 m.m. diameter, maile according to this method, in order to bring it to a
glowing point requires an extraordinary low current only, (0.3 to 0.6 ampere)
while in the old style for threads or wires of the same thickness, a considerably
more powerful current is necessary, in order to bring them to the glowing point.
The principal and extraordinary differences resulting from my method are
based on the fact that the conductibility of the threads, made by my process, is
produced by the formation of a conducting chemical platinic compound, namely,
the "platinsilicium," which, in a cohesive condition converts the threads into
conductors. This, however, can only take place by the melting of the mineral
mixture under the-reducing influence of the burning gases. When these threads
or wires are broken or ground and if this material is thus brought into new
forms, the conductibility would be lost in consequence of the limited quantity of
platinum or platinsilicium present.
Solid reducing bodies such as charcoal may be added to the mixture for making
the threads instead of heating the latter in an atmosphere or flame of reducing
power. The conduct of the electric current principally takes place on the surface
of the respective thread or wire.
This is most likely explained by the fact that the conductibility of the above
named bodies is produced under the influence of reducing gases by the formation
of platinsilicium. On the surface of the bodies, the action of the reducing media
is naturally the strongest and it follows that most of the platinsilicium is here
formed.
These observations lead to the description of the process for making resistances.
For producing the electric resistances, rods or threads from porcelain or burned
argil are made, which are coated with a paste possessing the same composition
as the foregoing mass. These rods coated with the platinous mass and the like,
are dried and then heated in exactly the same manner in a reducing atmosphere
till the melting point, viz: 1300° to 1350° Centigrade of the coating has been
reached..
This process yields a material with a non-conducting core and a conducting
surface. By these means, an important saving in the use of platinum is achieved.
Furthermore this method allows for the manufacture of flat and plane faced
bodies such as plates, cylinders and the like of considerable dimensions which
may be used as electrodes in proper cases. As soon as the temperature, caused
by the transformation of electricity into heat comes near the melting point of
the body, it may occur that the electric resisting body that does not possess a
fireproof core will, on the passing through of a current, loose their shape or form
under certain circumstances in an undesirable manner. These faulty occurrences
can be overcome in the following manner. The finished bodies, which have
been shaped as desired before the blow pipe, are coated with a fireproof mass,
such as argil, kaoline or the like by immersion or brushing over.

page_text: A very thin coating of that kind forms when heated, a stiff cover which
possesses sufficient solidity to prevent the aforesaid change of form.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
(1) An improved process or method for manufacturing electric resistances con-
sisting of mixing in certain proportions platinum or metals of the platinic group
platinic salts, or salts of metals of the platinic group with silicic materials and
heating the same to a melting point in a reducing flame or atmosphere or with
the addition of solid reducing media, substantially as described.
(2) A new method of producing electric resistances in which a saving of
platinum is effected by forming bodies made of a fireproof mass, porcelain, argil
and the like, and coating the same with a paste of the herein described
platiniferous composition, and which latter is heated to the melting point of the
coating, as set forth.
(3). A new method of producing electric resistances in the manner described,
and form desired, and coating the same with a fire-proof mass, as kaoline, argil
or the like, to retain the said resistances in their proper form when subjected to
an extra high degree of heat, substantially as described.
(4). A new method of producing flat and plane faced conducting bodies service-
able as electrodes in the manner set forth and described.
(5). A new method of producing flat or plane faced electric conducting bodies
serviceable as electrodes in which a saving of platinum is effected by forming
the bodies of a fire proof mass and coating the same at a high temperature,
with the composition set forth and described.
(6) A new method of manufacturing electric resistances in which a saving of
platinum is effected by forming the bodies of a fire-proof mass, pocelain, argil
or the like and coating the same with a composition formed by the mixture, in
the herein before described proportions of platinum, metals of the platinic group,
platinic salts or salts of the metals of the platinic group with silicic materials
heated to a melting point in a reducing flame or atmosphere, or with the addition
of solid reducing media and then properly coating the said bodies with a fire-
proof mass as kaoline or the like, to retain their desired forms, substantially as
described.
1
P
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1000