Improvements in the Manufacture of Incandescent Materials and Lamps suitable for Electric Lighting.
Year: 1899

page_text: Date of Application, 6th Jan., 1899
Complete Specification Left, 5th Oct.. 1899-Accepted, 25th Nov,, 1899
Improvements in the Manufacture of Incandescent Materials and
Lamps suitable for Electric Lighting.
I, LUDWIG WILHELM GANS, of 41, Hochstrasse, Frankfort on Main, Germany,
Manufacturing Chemist, do hereby declare the nature of this invention to be
as follows:
The idea of utilizing the property of the alkaline earths and magnesia of
emitting light is not novel in the electric lighting industry.
Dating from the introduction of the electric are light many experiments which
have been partially successful have been made in this direction. The Jabloch-
koff candle and Clerc and Bureau's sun lamp brought it into a certain prominence
although these have been outstripped by the later developments in are and
incandescent lighting.
In order to counteract the competition of the Welsbach incandescent gas light,
a great many experiments have been made to utilize the rare earths, used with
such great success by Welsbach, especially thorium earth (containing a small
quantity of cerium), for the purpose of the incandescent electric light industry.
No practical result has however hitherto been obtained.
In carrying out the most obvious idea, that of coating a carbon filament with
a light emitting earth, it was found that small particles of carbon penetrated
into the coating and seriously lessened its light giving power and also rendered
the filament friable.
It was next attempted to make the core of metal, such as the infusible metals
of the platinum group. It was however found that the problem of manufacturing
a thread from the most infusible of these metals, viz. osmium, to form the core
involved great difficulties on account of the brittleness of this element.
The method invented by me for utilizing the so-called ceramic preparations of
the noble metals has led to a successful result. Application was made for a
patent for the above mentioned process on the 19th August 1898, No. 17896 which
will be here shortly epitomized as it is closely connected with the process to be
described.
The so called lustrous preparations of the noble metals in use for decorating
ceramic ware have as bases gold, silver and platinum. The sulphide compounds
or the resinous acid compounds or the sulphuretted resinous acid (thioresinous
acid) compounds of the said metals are used. These all have in common that
they are dissolved in ethereal oils. A serviceable solution may also be produced
by treating the chlorides of these metals directly with lavender oil. These pre-
parations are used in decorating ceramic ware by coating glass, porcelain and the
like with the solution and burning in, whereby a lustrous coating of the metal
in question remains behind.
The process described in the above mentioned application consists in obtaining
the skin of noble metal, produced in the usual manner by burning in, in a free
dada ka matine ower the class. Dorcelain or like backing,

page_text: By varying the shape of the coating, or by a subsequent rolling process,
various forms of core may be made such as threads, bands, strips and the like.
It will easily be seen that in this manner the brittle infusible osmium is as
easily brought to the required shape as any ductile metal. In the same way by
suitably mixing the solutions of the preparations of different metals and their
subsequent treatment as above, any desired alloy may be produced.
It is not possible either by galvanic or other methods to produce such alloys
having exactly the predetermined quantity of the several components, if osmium
form one of them.
Whilst the metallic cores of incandescent materials may be produced by the
above process, and their light emitting powers subsequently increased by a
coating of light emitting earths, it is also possible to attain the same end in the
reverse manner. This forms the object of the invention about to be described.
A small cylinder of lime, baryta, strontia, or magnesia is made in any manner,
if necessary with the addition of a small quantity of a binding material. Magnesia
is most suitable for this purpose such a cylinder being made without difficulty
by stirring with water, with the addition if necessary, of a little silicic acid,
phosphoric acid, boric acid or the like and subsequently subjecting the mass to
strong pressure. Such a cylinder gains materially in hardness and consistency
by a subsequent burning. The length of the cylinder may be from 5 to 15 milli-
metres, the thickness of its walls, 5 to 2 millimetres and its internal diameter
from 3 to 2.millimetres. The inner surface is then coated with the solution of a
preparation of a noble metal, having as basis osmium, iridium, ruthenium,
rhodium or a suitable mixture of these metals (and also if required platinum
and palladium) and the coating burnt in. This operation should, if a large
amount of osmium be present, be conducted, in the presence of a reducing or
indifferent gas such as carbonic acid, hydrogen, or illuminating gas, in a closed
chamber (muffle) in order to prevent volatilization of the osmium as osmium
tetroxide.
If the mixture contains iridium, it is preferable to burn in in a muffle filled
with hydrogen alone, and not with illuminating gas in order to prevent the
formation of iridium carbide Ir C4. Indeed it has been found preferable from
all experiments made to exclude air by filling the muffle with hydrogen.
Of course the composition of the solution of the preparation of noble metals,
is so chosen that the layer of metal remaining behind after burning in shall
possess a sufficiently high melting point not to fuse on the passage of the current.
Osmium alone, which possesses the highest melting point of the metals herein
mentioned, is not particularly suitable, because of its brittleness and it easily
developes cracks. A small admixture of another platinum metal increases its
ductility without greatly lowering its melting point.
After burning in the solution of the preparation of the noble metals the magne-
sium cylinder is supported at both ends preferably by pushing in a platinum
wire or by surrounding it with a strip of not too thin platinum foil, in which
latter case it is best to coat with the noble metal not only on the inside, but
also round about the ends of the cylinder. The copper wire of the lighting in-
stallation is connected to the platinum wire or foil by soldering or squeezing.
If a current be passed through, the layer of noble metal becomes heated, in con-
sequence of its small section and warms the cylinder, which in a heated state is
itself a conductor of electricity. After the lapse of a minute the cylinder glows
and emits a brilliant light. It is easily understood that for attaining the best
effect the dimensions of the cylinder and the strength or tension of the current
must be exactly suitable.
Data

page_text: Improvements in the Manufacture of Incandescent Materials and
Lamps suitable for Electric Lighting.
I, LUDWIG WILHELM GANS, formerly of 41, Hochstrasse, now of 294, Gutlent-
strasse, Frankfort on Main, Germany, Manufacturing 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:-
It has been long known that certain refractory bodies such as, for example,
porcelain, magnesia, lime, zirconia, and the like, emit a brilliant light when
heated to a sufficiently high temperature.
Since the heating effect of the electric current has been known, numerous
attempts have been made to take advantage of this property and render these
bodies available for practical illumination.
The production, and introduction as a practical illuminant, by Mr. Auer von
Welsbach, of bodies which become incandescent when heated by a gas flame,
gave a new impulse to efforts in this direction, the more particularly since
through his publications the number of known "luminous earths" have been
considerably increased.
The first attempt of this kind which attracted special attention was the so-
called "Jahlochkoff lamp." But its practical defects were found to so outweigh
its merits that it soon disappeared from the field.
Walther Nernst has lately again taken up this idea, and has constructed incan-
descents, called after his name the "Nernst lamp."
With both, the Jablochkoff and Nernst lamps, the principal difficulty consists
in the initial heating of the incandescent body to a sufficiently high temperature
an initial step rendered necessary by the fact that all these "luminous earths"
conduct the electric current very poorly at normal temperatures, and only become
good conductors after their temperature has been considerably raised. It is
therefore necessary first to heat the to be incandescent body by a gas burner,
or some other extraneous source of heat or means of heating, before it will pass
the electric current and through its action become incandescent.
Jablochkoff, for example, held his incandescent body between a pair of tongs
the arms of which were connected with the conducting wires of an electric cur-
rent, connecting the said arms with the incandescent by a thin filament of a
carbon-containing material by which the current first passed. This heated the
filament, which in turn heated the to be incandescent body, until it became itself
a conductor and actually incandescent. The carbon filament was, however, des-
troyed in this operation, and had to be replaced by a new filament every time the
lamn was used.
Nernst seeks to accomplish this result by leading the electric current through
a coil of thin platinum wire, thus heating the coil which in turn heats the to he
incandescent body sufficiently to enable it to pass the current, when it becomes
incandescent and at the same time the heating coil is automatically cut out of the
circuit.
The object of my invention is to accomplish the same ultimate result in a
much more simple, effective and durable way, and at the same time dispense with
all sources and means of extraneous initial heating not so united to the incan-
descent body as to form practically an integral part thereof. Moreover my
initial heating device is not only capable of prolonged repeated use without im-
pairment, but it also dispenses with any form of cutting out device since it
remains constantly in circuit while my lamp is in operation,

page_text: To produce the conductor forming my initial heating device, I use the so-called
ceramic lustrous preparations of the noble metals" which, as well as the art
of burning them in, are well known in the art of china and glass decoration,
and are regularly made and sold for that purpose. They are organic compounds
of the noble metals, gold, silver and the metals of the platinum group (resin acid
compounds, or sulphuretted resin acid compounds, or the products of the decom-
position of metallic chlorides by heating them with lavender oil). For use in
china and glass decoration they are mixed with an ethereal oil, such as lavender
oil.
This mixture or solution is applied in a thin coat to the to be decorated glass
or china, and then burned in, leaving a thin, bright, firmly attached film of the
metal where the ceramic lustre was applied.
Generally the lustrous preparations of silver, gold and platinum are produced
and employed for decorative purposes, as aforesaid. The lustres of the other
metals of the platinum group have been little used in glass and china decoration,
since they offer no decorative advantages over the platinum preparations. But
they can be prepared and burned in, in the same manner as the platinum lustre.
The lustres which I use for my incandescents are those of the highly infusible
metals of the platinum group, such as osmium, ruthenium, rhodium and iridium.
I produce my incandescent as follows:-
With a mould, or in any other convenient manner, I form a luminous earth,
or a mixture of two or more luminous earths, into the shape I desire for my in-
candescent, preferably a hollow cylinder or similar form. I then heat it to
redness, preferably in a muffle, by which it gains materially in hardness and
consistency, if it be wanting in these respects. After cooling one of the above
described ceramic lustrous preparation of one or more of the highly infusible
metals of the platinum group, in mixture or solution with an ethereal oil, is
applied to the to be incandescent body in the form of a thin stripe, or in such
other form as is best adapted to the form of the incandescent body. If the in-
candescent body is in the form of a tube or hollow cylinder, I coat the interior
surface with the mixture or solution.
I then burn the ceramic lustrous preparation in by heating the to be incan-
descent body after the manner generally in use in the ceramic industry. Thus
I obtain upon the said incandescent body a thin firmly adherent stripe or film
of metal, which, when the incandescent is placed in electric circuit, serves in the
first instance to conduct the current and thus heat the incandescent body until
it itself becomes a conductor, when the current passes through the incandescent
and heats it to incandescence.
Owing to the highly refractory character of the metal stripe or film I employ
for the initial heating current, it is not dissipated or destroyed by the passage of
the current, nor does it require to be out out of the current when my lamp is
in operation. It takes care of itself.
The material of which my incandescent body is composed, is one of the oxides
of the earthy metals which become luminous at an elevated temperature, as for
example, lime, baryta, strontia, magnesia, the oxides of thorium, cerium, zircon-
ium, erbium, or the like, or mixtures of two or more of the same may be used.
In moulding or forming the incandescent body, if the material selected is such
as to render increased cohesion desirable, a small quantity of phosphoric, silicic,
or boric acid, or the like, may be added in admixture as a binding material.
Magnesia with a small quantity of thorium oxide, the latter containing about
one per cent of cerium oxide in admixture, I find to be well adapted for my
incandescent body. At the proper temperature, it illumines well, and, for example
a hollow cylinder may be easily made by mixing magnesia with water, adding
ten to twenty per cent. of thorium oxide containing about one per cent. of cerium
oxide and about one per cent. of silicic acid, or the like as a binder, and then

page_text: subjecting the mass to strong pressure in a mould. Incandescent bodies of other
suitable materials may be made in the same manner.
As to the form of my incandescent, the hollow cylinder is perhaps the most
convenient and useful form, since it is easy to make and has a large lighting
surface; and it is the form I prefer. But I do not restrict myself to that precise
form, since it is obvious that other forms will answer the purpose more or less
perfectly.
If the hollow cylinder be used, the following dimensions will be found gener-
ally useful, though the size, of course depends largely on the amount of light
desired and the strength and voltage of the electric current used. Length of
cylinder from five to fifteen millimetres; thickness of wall, one to five milli-
metres; internal diameter, from two to three millimetres.
Having formed my incandescent body, if of hollow form I coat the inside of the
hollow, if not hollow, I apply a small stripe on the side of the body, using for this
purpose the mixture or solution with an ethereal oil of a ceramic lustre having
as its basis osmium, iridium, rhodium, ruthenium, or a mixture of two or more
of these metals, and then burn suid lustre in as is done in the decoration of
china, glass, &c., when these lustres are used for that purpose.
if the ceramic lustre contains much osmium, or other oxidizable metal, the
operation of burning in should be conducted in a closed muffle in the presence
of a reducing or neutral gas, such as carbonic acid, hydrogen, or illuminating
gas, as is well known. If the mixture contains iridium, it is preferable to burn
it in a closed muffle filled with hydrogen alone, and not with illuminating gas,
in order to prevent the formation of iridium-carbide (Ir. C). Indeed in any
case it is safer, and therefore preferable to burn in in a closed muffle in the
presence of hydrogen alone, since this method is adapted to all lustres. Of
course such a ceramic lustre should be chosen as will, after burning in, leave a
metallic film of a sufficiently high melting point not to fuse on the passage of the
electric current.
Generally, a single application and firing of the lustre gives sufficient thick-
ness. But where the solution or mixture of the lustre is so poor in lustre as to
give too thin a coating in one operation, the operation of coating and firing may
be repeated until a satisfactory coating has been obtained.
I have obtained my best results with a hollow cylinder of magnesia, mixed with
about twenty per cent. of oxide of thorium containing about one per cent. of
cerium, coated within with osmium. But instead of the magnesia, lime, baryta,
or any of the hereinbefore mentioned earths may be used, or the coating may be
of ruthenium or rhodium, and good results may be obtained.
My incandescent operates as follows:
-
When a suitable electric current is passed through the metallic coating of the
incandescent body, which we will assume is in the form of a hollow cylinder,
the coating becomes heated because of its thinness and consequent resistance
to the current. This in turn heats the cylinder, which when so. heated is a con-
ductor of electricity. The cylinder then speedily begins to glow and emits a
brilliant light.
My incandescent body may be used as an illuminant in the open air provided
the metallic coating consists of a highly inoxidizable metal. But if it contains
any material quantity of osmium, the incandescent body should be protected by
a bulb that is exhausted or filled with a neutral or reducing gas.
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:
The herein described method of making incandescents adapted to incandescent
electric lighting, which consists in first forming a body of the desired shape from
an oxide of one or more of those earthy metals which become luminous at elevated
temperatures; second, applying to the surface of the body so formed a partial

page_text: coating of a ceramic lustrous preparation of one or more of the highly infusible
metals of the platinum group; and lastly, burning said ceramic preparation in
to reduce the same to a metallic form and cover the coated portion of said body
with a superficial adherent film-like deposit of such metal or metals.
Dated this 4th day of October 1899.