Improvements in Incandescence Electric Lamps and Processes for the Production thereof.
Year: 1898

page_text: Date of Application, 19th Jan., 1898
Complete Specification Left, 13th Sept., 1898-Accepted, 19th Jan.,
1899
Improvements in Incandescence Electric Lamps and Processes for the
Production thereof.
I, Dr. CARL AUER RITTER VON WELSBACH, of Vienna, Austria, IV Wiedner-
Hauptstrasse, No. 69, Gentleman, do hereby declare the nature of this invention
to be as follows:-
My invention relates to the manufacture of incandescence electric lamps, in
which the metal osmium is mainly employed as incandescence material.
According to present knowledge, osmium is not volatilised even at the
volatilising temperature of iridium, whether in vacuo or in certain gases having
a reducing action. If a wire or filament of osmium has an electric current
passing through it of sufficient intensity while contained in a gaseous mixture,
such as occurs in the interior of a Bunsen flame, that is, in the presence of
aqueous vapour, or in vacuo, the wire or filament will, at about the volatilising
temperature of platinum, glow with an exceedingly bright white light of great
intensity. The filament can, in particular in vacuo, be heated considerably above
this temperature without melting. It then remains in a sufficiently dense con-
dition and almost rigid. It is only possible to heat the filament at one part
to melting point by means of an enormous increase of intensity of current rela-
tively to the capacity of the filament.
Pure osmium is probably under the above stated conditions the most refrac-
tory and unalterable body known to science, and which, at those high tempera-
tures, emits the greatest amount of light. With an increase of the light
emission, naturally the heat emission decreases in due proportion. As the osmium
preparations existing in commerce are generally of insufficient purity, they can-
not be applied directly for the above purpose. The stated properties of osmium
are not materially altered by a small addition of other platinum metals.
Next to pure osmium, the nearest in efficiency are its alloys with ruthinium.
Pure osmium, as also such containing small quantities of platinum, is, in a
dense condition in the form of a filament, tolerably elastic and it can also be
used for the production of incandescence filaments for electric lamps.
The
For the production of the filament the following process is employed:
osmium is deposited in a cohereing metallic condition upon a metallic wire.
If the wire is then gradually heated to an intense white heat, the wire core
volatilises and disappears, and the osmium remains behind as a tubular filament.
For the application of this principle, an exceedingly thin platinum wire is heated
by an electric current in a reducing atmosphere containing hydrocarbon and a
plentiful quantity of steam (in order to prevent the production of osmium car-
bide, which is easily fusible) in which, from time to time, small quantities of
volatile osmium compounds, such as osmium tetroxide, are introduced.
The coating must be formed slowly and uniformly, and the osmium wire
obtained must not show any considerable inequalities. The surface should be
smooth and of a brilliant bluish white. When obtained in this manner, the

page_text: wire is somewhat fragile, as the layer of osmium often contains a small quantity
of the lower oxides. The wire is then heated in an atmosphere of reducing
gases gradually to the volatilisation point of platinum, and afterwards some-
what above that point. The platinum is then volatilised, leaving only small
traces. The osmium wire is now somewhat elastic and almost the colour of
platinum.
This process could be modified by applying to the platinum wire, with a
brush, a dilute solution of an osmium compound which is made somewhat more
consistent by means of finely divided solid osmium or a compound of osmium,
such as the sulphide or tetrahydroxide or by leading the platinum wire through
this material and then heating it. The coating thus applied is exceedingly
thin, so that the described application must be repeated about 100 times until
a sufficiently thick coating has been obtained.
The platinum wire may also be coated with osmium or osmium oxide by means
of the electrolysis of osmium solutions; the heating of such wires can be effected
in the same manner as above described.
The process may also be carried out by coating the fine platinum wire with a
semi-liquid mass, consisting of finely divided osmium or osmium compound, or
a mixture of these bodies, with a small quantity of sugar, or other organic
binding material, and water or other medium, which allows of the formation
of a kind of emulsion, the coating thus produced being treated in the manner
above described. This last modification also allows of the application of the
osmium paste upon vegetable or animal fibres.
In order to prevent a want of uniformity in the thickness of the filament,
it is, while still in a moist condition, passed through a die. It is advantageous
to twist two or three of the filaments thus produced together; inequalities in
the separate filaments are thus, to a great extent, equalised.
After drying, the filament is brought into that form which it is required to
have in the lamp and it is then slightly heated for a short time in a reducing
atmosphere. The carbonaceous skeleton of the core imparts to the osmium an
increased strength and elasticity for withstanding the subsequent manipulation,
that is to say, its introduction into lamps. The filament can, however, be fixed
into the filament-support of the lamp before the heating. The filament support
consists of two pieces of platinum wire connected to a small piece of potash
glass, which wires are formed tubular at their ends where they are to receive
the filament. In these tubular ends, the ends of the filaments are inserted,
with an application thereto of an aqueous paste, consisting of osmium and an
osmium compound, with or without a small addition of salts of the other platinum
metals mentioned above, and a binding material, such as sugar.
The filament is then heated slightly, during which time the admission of air
is not prejudicial, and after it has become fixed it is highly heated by an elec-
tric current in a reducing atmosphere containing steam. The intensity of the
current is gradually increased until a very high degree of temperature is reached.
The filaments must have the same conducting power at all parts thereof.
Should this not be the case, it must be equalised. This is effected by the first
described process of precipitating an osmium layer upon the metallic conductor.
The filament is now ready for use; the filament support is then fixed to the
wires of the lamp in a similar manner to that of ordinary glow lamps. The
globe is exhausted or is filled with the above mentioned gaseous mixtures or
neutral gases, and is closed by melting.
For the production of the osmium filaments, laminae, dises or other forms, may
also be employed the process used for the production of artificial silk. With
the collodion is mixed an intimate mixture of finely divided osmium and osmium
sulphide or osmium tetrahydroxide or of a similar compound. The addition of
these substances renders the mass viscous and prevents the emulsion from
separating, which might otherwise easily occur, owing to the great density of the
osmium. This magma is then converted into the desired form. After the deni-

page_text: tration of the mass, the filaments can be treated farther in the same manner as
above described.
When produced by either of the processes above described, the metal filament
is more or less stiff. It is, however, possible to obtain it in a soft condition,
similar to wool filaments. For this purpose, a slightly twisted thread of purified
soft vegetable fibres is taken and impregnated with a thin liquid magma, con-
sisting of an insoluble osmium compound, such as osmium sulphide, mixed
with water in a very finely divided condition together with a small quantity of
a combining material, such as sugar. After drying, the filament is heated to
redness in a reducing gas, such as coal gas.
I have also found that substances more readily fusible than osmium can also
be employed for the production of incandescence electric light. As is known,
a platinum wire, when passed through by a sufficiently intense electric current,
fuses at the commencement of a white heat; such wire behaves differently,
however, as soon as it is enclosed in a thin, cohereing, dense coating of a per-
fectly refractory body, such as thorium oxide. The intensity of the current can
now be considerably increased without causing the wire to melt.
The property of intense emission of light and heat possessed by the coating
absorbs energy from the metallic conductor. If the intensity of the current be
gradually increased, a certain part of the conductor will suddenly glow with an
intensely bright light. This will spread more or less equally, according to the
pressure of the current, over the whole length of the filament. At the same
time a small globule will exude from the filament.
During this process the platinum core will be melted within the thorium oxide
coating, which now forms a small solid tube.
The intensity of the current can now be farther increased, causing an increase
of the lighting effect without producing a melting together of the filament.
The temperature of the melted metal will gradually approach the boiling point.
The incandescent filament will now emit a comparatively small amount of heat.
As soon as the boiling point has reached the pressure necessary for bursting
the coating, the filament will be destroyed by a slight explosion.
If the metallic core is less fusible than platinum, the above described pheno-
menon of intense light will last a considerable time.
Short filaments of about a cm. in length allow of the interruption of the
current; longer filaments explode, which phenomenon is very easily explained.
The described experiments succeed best when the thickness of the thorium oxide
coating is only a few 10ths of a mm. It can, however, be decreased considerably
below this amount and can be made so thin as to become iridescent without the
experiment being materially affected thereby. For the production of the coat-
ing, any preparation of thorium can be used which will leave the oxide after
being heated to incandescence.
The wire to be coated is drawn under high pressure between elastic cheeks,
thinly coated with the said substance, and is then slowly heated to redness. If
this manipulation be repeated about 50 times the layer will have become suffi-
ciently thick. In some cases the employment of a fritting substance may be
advantageous.
The production of a coating consisting of other refractory substances is effected
in precisely the same manner as above described.
If in this coating process considerably diluted salt-solutions are employed,
the salts of which are readily decomposed in incandescent heat, such, for instance,
as a nitrate solution, and if the moistening and heating to redness be repeated
for a hundred times, a perfectly vitreous coating will be obtained. In this way
I have obtained exceedingly tenacious coatings with a glassy lustre (actual
enamels) of thorium oxide on platinum.
The above described, many times repeated, operation can of course be carried
out by means of a small motor.
In addition to thorium oxide, probably only zirconium oxide can be used for

page_text: obtaining the coatings. The rare earths, as also magnesia, lime, alumina, and
all other oxides considered as refractory, melt at these high temperatures too
readily and become more or less volatilised to enable them to be used as per-
manent coatings. If platinum be replaced by an alloy thereof with osmium,
ruthinium, rhodium or iridium, or by means of a still more refractory alloy and
which may be easily prepared in the form of filaments or wires, according to
the above described process, bright, permanent and practically useful illumina-
ting effects can be produced. As long as the metallic core is not fused an
interruption of the current can be effected without danger to the incandescence
filament.
Dated this 19th day of January 1898.
ABEL & IMRAY,
Agents for the Applicant.
Improvements in Incandescence Electric Lamps and Processes for the
Production thereof.
I, Dr. CARL AUER RITTER VON WELSBACH, in Vienna, Austria, IV, Wiedner,
Hauptstrasse No. 69, Gentleman, 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:-
My invention relates to the manufacture of incandescence electric lamps and
has for its object the production of illuminating conductors for such lamps which
can be worked at a very high temperature and which give forth a very brilliant
light. By one part of my invention I accomplish this result by constructing
the illuminant substantially of the metal osmium a substance which when pure
can endure without melting or volatilizing a temperature as high as even the
volatilizing temperature of iridium if placed in vacuo or in certain protective
gases. It is therefore capable of being raised to so high a temperature that the
light emission bears a high rate to the consumption of energy and thus great
efficiency is obtained without destroying the durability of the filament.
There are however great difficulties in the use of this material and up to the
present time no means have been found by which it practically can be applied to
the above purpose. It is not ductile but on the contrary brittle and pulverizable.
It cannot be formed into wires either by drawing or pressure. It is necessary
therefore to devise special methods by which it can be made into filaments
suited for use in incandescence electric lamps. The methods I propose are as
follows-
FIRST METHOD.
The principle of this method is to bake a thin metallic wire (preferably of
platinum) and to coat it with osmium. The conductor thus formed is then
gradually raised to an intense heat in tacno or in a suitable protective atmos-
phere so as to gradually drive off the platinum in the shape of vapour leaving
behind the osmium as a coherent thread.
There are several methods of forming this coating of osmium. One method is
by electrically heating the platinum wire in a reducing atmosphere containing
osmium vapours such as those furnished by the volatile tetraoxide of osmium
An osmium deposit is thus formed upon the wire.
Care must however be taken in the choice of the reducing atmosphere.
Osmium is readily oxidizable if heated in an atmosphere containing oxygen.

page_text: On the other hand it appears to be able to form a carbide which is readily fusible.
I have found that the best protective atmosphere is accordingly a reducing atmos-
phere in which both water vapour and hydro-carbons are present, so that there
is an adequate supply of water vapour to prevent carbon being deposited from
the hydro-carbons and forming osmium carbide. The readiest method of obtain-
ing such atmosphere is by taking it from the interior of the Bunsen flame, that
is to say from that part which is just above the blue portion inasmuch as this
contains water vapour as well as more or less unconsumed hydro-carbons, and
at the same time it is free from oxygen. It may also be conveniently obtained
by igniting the gas at the air-inlets and taking the reducing atmosphere from
the burner tube. In such an atmosphere a filament such as described above
may safely be heated to a temperature sufficient to form a deposit of osmium in
the metallic state either directly or by first obtaining the deposit in the form of
the lower oxides of osmium and subsequently driving off the oxygen contained
therein by electrically heating it to a higher temperature in a reducing atmos-
phere such as I have described.
The coating should be formed slowly and uniformly so that it may be of
uniform density and cross section. prefer to admit the osmium vapours at
intervals, full time being allowed to enable them to spread themselves through-
out the receiver so that they are equally dense in all parts of the wire. This
part of the process is conducted at a comparatively low temperature. The wire
thus coated is subsequently raised gradually to a very high incandescence in a
reducing atmosphere such as described so as to reduce any of the osmium that
may be in the form of the lower oxides.
The coating may also be obtained by electro deposition in a bath containing
a salt of osmium.
The required coating may also be obtained by taking a solution of some soluble
osmium compound which has preferably been rendered more consistent by the
introduction of metallic osmium or an osmium compound in a finely divided
state. The compounds to be used are those which are not volatile and which
decompose at incandescence leaving metallic osmium or the lower oxides of
osmium. Instances of such compounds are osmium sulphide or osmium tetra-
hydroxide. The wire is then heated to drying point either electrically or other-
wise and thus a deposit is obtained and the process is then repeated. The coating
obtained by such an application is naturally very thin unless the paste be thick
and the application must be frequently repeated until a sufficiently thick coating
is obtained but this has the advantage of enabling the coating to be formed very
uniformly. I have usually repeated it about 100 times but the number must
depend upon the thickness of the coating desired and the skill of the operator.
The coating may be put on in any convenient way either by a brush or the like
or by passing the wire through the liquid or even by leading the platinum wire
through it and electrically heating the wire while it is in the mixture.
The coating may also be obtained in an analagous manner but more rapidly
by coating the wire with a semi-liquid mass consisting of finely divided metallic
osmium or osmium compound of the type above referred to or a mixture of
these bodies with a small quantity of binding material. Inasmuch as this bind-
ing material must be capable of being wholly got rid of by heating the wire it
will generally be found to be most convenient to use for the binding material
a solution of some organic substance in water or other convenient medium.
This form of the process of depositing osmium upon a platinum wire partakes
therefore of the nature of the second general method described in this specifi-
cation and I shall not further refer to it under the present head as the method of
manufacture and the precautions to be taken will readily be understood from
what is stated in that portion of the specification which relates to the second
method.
When by means of one of the above processes or an equivalent one the plat-
inum wire has been coated with metallic osmium or its lower oxides or mixtures

page_text: thereof, it is slowly and gradually heated in a protective atmosphere or a vacuum
to a temperature at which platinum volatilizes and ultimately somewhat above
that point. The platinum is thereby driven off and the osmium is left in the
form of a hollow tube not unlike platinum in color and somewhat elastic.
The inner part of the wall of the filament is usually darker than the outer and
probably contains platinum in the form of an osmium platinum alloy but this
alloy must be very stable for the behaviour of the filament shows that it is cap-
able of being raised to a very high temperature without parting with any further
amount of platinum. The melting point of the alloy so formed is probably not
much inferior to that of osmium itself. There may even be traces of platinum
throughout the filament. It will usually be found to be necessary that the
quantity of osmium deposited should exceed the amount of platinum in the wire
as otherwise there will be danger of the filament being destroyed by the melting
of the platinum.
As osmium conductor produced in this manner is coherent dense and fairly
elastic it can be used as a filament of an electric incandescence lamp if placed in
a protective atmosphere such as that already described, but it is much better to
place it in vacuo. When care has been taken to expel sufficiently the platinum
upon which the osmium coating is formed (the last portions of which go off very
slowly) in the manner described above the filament can safely be raised to a
temperature considerably above the volatilizing point of platinum. It then emits
a most brilliant light with corresponding economy of energy.
Instead of platinum other metals can be used as base for the osmium coating
provided that they can be volatilized and have a sufficiently high melting tem-
perature so that the osmium coating will be freed from all oxygen and will have
become dense and coherent before it is exposed to the strain due to the melting
of the metallic basis upon which it is formed.
For the purposes of making filaments the osmium used should be as pure as
possible. It may be obtained in a relatively pure state very readily from the
tetraoxide though it may be doubted whether even in this way it can be obtained
in an absolutely pure state. Next to pure osmium the most effective is its alloys
with ruthenium, but small quantities of the other metals of the platinum group
may be present in osmium without destroying its suitability for use in the matter
described or reducing too greatly its resistent properties.
SECOND METHOD.
The principle of this method is to take a carbonaceous filament and to cover
or saturate it with an osmium compound and then by electrically heating the
conductor so formed in a suitable protective atmosphere to burn out the carbon-
aceous matter and thus to leave a coherent filament of osmium. Instead of a
carbonaceous filament being taken I may use the equivalent method of a carbona-
ceous binding material.
As the basis upon which the osmium filament is to be formed in this process I prefer
to take a slightly twisted thread of soft vegetable fibre or several such fibres
lightly twisted together and thoroughly impregnate them with a thin liquid magma
consisting of an insoluble osmium compound such as osmium sulphide or the lower
oxides of osmium or the tetrahydroxide with or without the metal itself all in
a finely divided condition together with a small quantity of binding material
such as sugar. The filament in this state may be passed through a die if desired
in order to render it uniform. It is then brought into the shape which it is
intended to have in the lamp and slightly heated in a reducing atmosphere to
fix it and to give to the filament more firmness. When it is fixed it gradually
raised to a high temperature in a reducing atmosphere containing water vapour
or hydrogen preferably of the kind before referred to which is obtained from the
Bunsen flame but mixtures of steam and hydrogen or of carbonic monoxide car-
bonic dioxide and hydrogen can also be used. The object is first to carbonize
the organic matter by destructive distillation and then to get rid of the carbon,

page_text: The function of the protective atmosphere is to oxidize the carbon of the fila-
ments without oxidising the osmium or obtaining a deposit of carbon on the
filament. Free oxygen must not be present and in fact the atmosphere should
be such as will reduce any oxides of osmium that may be present.
In such a reducing atmosphere the filament can without danger be raised to
a temperature which consolidates the osmium and forms it into a useful coherent
filament. It would be possible to burn out the carbon at a low temperature
in the presence of oxygen if care were taken to so regulate the temperature so
that when the osmium no longer received the protection of the carbon-oxides
formed during the combustion the filament was no longer at a temperature suffi-
ciently high to oxidize it but such a process would involve considerable danger
of destroying the filament or failing to render the osmium sufficiently continuous
or sufficiently consolidated and coherent for practical purposes. In practice I
keep the filament for some hours in the reducing atmosphere and raise the
temperature gradually till it incandesces strongly.
As has been already stated it is not necessary that the basis of the filaments
should be organic fibres. They may be made with any convenient carbonaceous
material which can be burnt off by the above process. Thus the method used for
the production of artificial silk may be employed. A mixture of finely divided
metallic osmium and osmium compounds such as the sulfide of tetrahydroxide is
mixed with the collodion so as to render the mixture viscous and to keep the
osmium from separating out by reason of its great density. The magma is now
formed into the desired shape as for instance by squirting it through a die. The
collodion is then denitrated and subjected to the process described above to burn
off the carbon and leave the coherent osmium filament. Other organic binding
materials can when desired be substituted for the collodion.
The filaments when finished should have the same conducting power through-
out and if this is not the case it may be remedied by heating them in atmos-
phere containing osmium vapours as described under the first method or even
by the use of the osmium cement as hereinafter described.
When osmium filaments suitable for use in electric lamps have been formed
by one or other of the above methods it is necessary to mount them so as to form
them into lamps. For this purpose the filaments are enclosed in the ordinary
way in bulbs containing a protective atmosphere as above described, or prefer-
ably a vacuum. It is very easy to mount the filaments in tubular platinum
holders by means of a magma such as I have described which may very con-
veniently be made by mixing in a finely divided state metallic osmium and an
osmium compound (which will decompose and leave osmium or one of its lower
oxides on being heated) with water and a litle sugar or other like binding
material. A small addition of salts of the other platinum metals may be made.
This gives a most convenient material not only for mounting the filaments in
their tubular holders but also for joining broken fragments of filaments or even
for strengthening weak places in them inasmuch as on heating in the manner
above described the carbon can be got rid of and osmium is left in a firm coherent
form.
The osmium filaments thus prepared can be worked at a very high tempera-
ture and thus form lamps of great efficiency. Filaments can also be formed
according to the second method of the other metals of the platinum group and
of mixtures of the same especially rhodium and ruthenium but with the excep-
tion of the alloys of osmium as above referred to they do not bear so high a
temperature so as to enable them to compete with osmium in practical working.
This method as well as the first method may however be employed to form fila-
ments of highly resistent metals of the platinum group and their alloys for the
purpose of being used in the way hereinafter set forth in connection with the
bortion of my invention that relates to the use of refractory oxides.
Having now described that portion of my invention which deals with the
oduction of illuminating conductors which are wholly metallic in their com-

page_text: position I will now describe that portion of my invention which deals with the
production of illuminating conductors which have a metallic core but are exter-
nally covered with a refractory oxide or oxides.
If a filament or a wire or a highly resistent metal such as osmium or an alloy
of osmium with platinum or a metal of the platinum group be enclosed in a
thin cohering dense coating of a highly refractory body such as thorium oxide
it will endure a very high temperature and give out a very brilliant light. In
this way filaments can be made of metals which of themselves would not be
serviceable to a like extent as illuminating conductors the effect of the thorium oxide
at this high temperature being apparently to draw off energy from the metallic
core and use it to sustain its large light emission as well as to confine the metal
in a tube which prevents it so readily breaking down either by melting or
volatilizing. In addition to this the coating of refractory oxide itself takes part
in the conduction of the electric current and is heated thereby. The combined
effect of these causes is to render it possible to work the illuminating conductor
at a very high temperature and to obtain a brilliant light with a comparatively
small expenditure of energy that is to obtain a filament of high efficiency which
is durable.
The above described effect of a thin coating of thorium oxide can be observed
for instance in the case of platinum wire. Such a wire used alone would fuse at
the commencement of a white heat. But when a similar wire coated with
thorium oxide approaches such a temperature the thorium oxide undergoes
a change by which it is converted into a tube of dense and coherent
character like a coating of enamel of an exceedingly refractory character.
The temperature of the platinum can now be raised. The conductor will
glow with an intensely brilliant light and if pushed far enough the
metal will melt usually exading in some part of the filament in the
form of a small globule. In this way the temperature of the filament can be
further raised without breaking it down even to a point approaching the boiling
point of the metal. The coating of thorium oxide may be extremely thin and
yet able to produce the effects above described of forming a tube and enabling
the metal to be raised to such a temperature that a more brilliant light and
higher efficiency can be obtained I prefer the thickness to be a few tenths of a
millimetre but I have obtained practical results even with a thickness that showed
the optical effects of thin plates.
The best practical results are obtained by using the most resistent metals for
the body of the filament. Osmium is the best and it can be made into the
required shape by the processess given in the earlier portions of this specifica-
tion. Its alloys with ruthenium rhodium iridium and platinum may also be
used with advantage. But easily fusible metals will not answer the purpose
because they melt before the temperature has become sufficiently high to vitrify
the thorium oxide in the way I have described.
Zirconium oxide may be substituted for thorium oxide. The rare earths (other
than thorium) as well as other oxides that are usually called refractory melt
too readily and become more or less volatilized to enable them to be used with
nearly the same advantages that are given by thorium or zirconium from the point
of view of luminous effect and durability.
For the production of the coating any preparation can be used that will leave
the oxide after heating to incandescence. Thus nitrate of thorium can be to
form a coating of thorium oxide on the metallic filament. If the metallic fila-
ment be in the form of a wire with uniform surface it can be coated by being
drawn under considerable pressure between elastic pads thinly coated with the
substance and the wire is then slowly heated to redness and the process is
repeated. This must be done until the coating is sufficiently thick. Or solutions
may be used with which the wire is moistened and then heated as before. The
number of times that this process should be repeated must depend on the density
of the solution but it will be readily ascertained by a little practice.

page_text: The coating can also be done by the use of a magma of the finely divided oxide
made with water alone or with some binding substance which will be dissipated
at incandescence the process being otherwise the same as before. Other equi-
valent processes may be used to effect the object which is to cover the metallic
filament with a thin coating of oxide which is vitrified and rendered dense and
coherent by heating the filament to a suitable temperature. The results will
be better if the coating is put on in several successive layers instead of at one
operation as the coating can thus be made more uniform. Each layer is dried
before the next is applied.
It will be obvious that by whatever methods the filaments are constructed the
osmium paste herein before described can be used as a cement to mount them,
or, if needed to repair weak places or fractures. This is of great importance
in the practical manufacture of lamps as it gets over the difficulties that would
otherwise arise as to making joints which would stand the extremely high tem-
peratures at which the lamps burn.
Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed, I declare that what I
claim is
1. An illuminating conductor for an electric incandescence lamp consisting of
a filament composed substantially of osmium.
2. The herein described process of forming an illuminating conductor for elec-
tric incandescence lamps by coating a filament of platinum or other suitable
metal with osmium and driving off the platinum or other metal forming the
core by electrical heating so as to produce a filament of osmium or osmium alloy
substantially as described.
3. In the process claimed in the Second Claim, the formation of the coating
by means of deposition by heat from an atmosphere containing vapours of
osmium substantially as described.
4. In the process claimed in the Second Claim the formation of the coating
by means of electric deposition.
5. In the process claimed in the Second Claim the formation of the coating
by means of a solution of an osmium compound (preferably rendered more con-
sistent by the introduction of metallic osmium in a finely divided state) substan-
tially as described.
6. In the process claimed in the Second Claim the formation of the coating by
means of a magma containing finely divided osmium or osmium compound with
a binding material substantially as described.
7. The herein described process of forming osmium filaments for use in elec-
tric incandescence lamps by impregnating or coating a carbonaceous base and
subsequently burning out the carbon in a protective atmosphere substantially
as described.
8. In the process claimed in the Seventh Claim the use of vegetable fibre
(preferably slightly twisted together) as the carbonaceous basis of the filament
substantially as described.
9. In the process claimed in the Seventh Claim the use of collodion to form
the carbonaceous basis of the filament and subsequently denitrating it and burn-
ing it out substantially as described.
10. In the production of filaments for electric incandescence lamps the use of
a magma consisting of finely divided osmium or osmium compounds with a little
binding material out of which filaments are shaped by squirting or otherwise
which after electric heating produce coherent metallic osmium conductors sub-
stantially as described.
11. An illuminating conductor for electric incandescence lamps consisting of
a metallic core of a metal or metals of the platinum group (preferably osmium
or osmium alloys) coated with a coherent covering of thorium oxide or other
refractory oxide or oxides substantially as described.

page_text: 12. The herein described process of manufacturing illuminating conductors
for electric incandescence lamps by coating with thorium oxide or other refrac-
tory oxide or oxides a wire of osmium or other metal or alloy of sufficiently high
fusing point to convert the oxide or oxides into a coherent covering substantially
as described.
13. In the processes hereinbefore claimed the substitution of alloys of osmium
with other metals of the platinum group (and preferably ruthenium) for osmium
so as to produce metallic filaments suitable for use as the illuminating conductors
of incandescence electric lamps either alone or after being coated with refractory
oxide or oxides substantially as described.
14. In the processes hereinbefore claimed the substitution of ruthenium or other
of the more infusible metals of the platinum group or alloys formed of mixtures
thereof for osmium or osmium alloys so as to produce metallic filaments suitable
for use as the illuminating conductors of incandescence lamps either alone or
after being coated with a refractory oxide or oxides substantially as described.
15. In the processes hereinbefore claimed for the manufacture and mounting of
illuminating conductors for incandescence electric lamps the use of a protective
atmosphere containing free water vapour (and preferably derived from the
Bunsen flame) or a mixture of carbon monoxide carbon dioxide and hydrogen
substantially as described.
16. In mounting and repairing illuminating conductors for incandescence elec-
tric lamps the use of a magma of osmium or osmium compounds or mixtures
thereof and the requisite binding material substantially as described.
17. The improved illuminating conductors for incandescence lamps herein-
before described.
Dad this 1941
J
1000