Improvements in Electrical Incandescence Lamps with Osmium Filaments.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in Electrical Incandescence Lamps with Osmium
Filaments.
I, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings, in the
County of London, Chartered Patent Agent, do hereby declare the nature of this
invention (as communicated to me from abroad by Oesterreichische Gasglühlicht"
and Electricitäts-Gesellschaft, of IV Schleifmuhlgasse, Vienna, Austria,) to be as
follows:-
This invention relates to the manufacture of electrical incandescence lamps with
osmium filaments described in the Specification No. 1535 of 1898.
My correspondents have found firstly, that the osmium filament occludes gases
from the atmosphere in which it is produced, to an extent equal to many times its
own weight, which gases it only gives off gradually when heated to incandescence in
vacuo.
Secondly, the osmium filament is very sensitive to the slightest quantity of gases
having an oxidising action such as steam and carbon dioxide, of which traces are
always given off by glass bulbs when heated in vacuo.
Filaments of osmium alloys such as are mentioned in the said Specification also
behave in the manner above stated.
The present invention is based on the following principles:-
1. The osmium filament when raised to an intense white heat in vacuo gives off
the gases that have been absorbed by it.
2. The gradual oxidation and disintegration of the osmium filament in vacuum
lamps at an intense white heat is prevented by the presence, even in small quantities,
of gases having a strong reducing action.
3. By continued heating to an incandescence, which is not too intense (2 to 4
Watts per candle power) at the commencement of the production of the vacuum,
the
osmium filament undergoes a peculiar process of formation.
A filament thus pro-
duced is superior to the ordinary filament both as to duration in use and as to its
power of resisting the action of incandescence.
4. The glass bulb must not contain in its composition any oxides that are easily
reducible by reducing gases under heat, such as lead oxide. The most suitable
material for the purpose is a potash-soda glass, that will not readily melt.
5. It is particularly advantageous for vacuum lamps if the osmium filament is
made to contain small quantities of substances that have a strong reducing action
and that oxidise more readily. than osmium. Such substances are: Carbon,
zirconiun, thorium, niobium, tantalium, silicon, and many others.
It should here be observed the statement contained in the said Specification No. 1535
of 1898 as to the fusibility of the osmium carbide requires some limitation, as the
compounds prepared directly from exceedingly finely divided carbon and osmium
have proved to be very refractory. They show, even with a large proportion of
osinium, the high heat emission property characteristic of carbon. The volatilisation
or disintegration of carbon-osmium filaments when heated to intense white heat
in vacuo takes place.rather easily in a similar manner to a pure carbon filament.
D
077

page_text: The production of a lamp according to the present improved method is very
simple.
After fixing the filament into the perfectly clean glass bulb by melting, the lamp
is filled with dry reducing gases, such as coal-gas or hydrogen. The lamp is left for
about 24 hours in a closed condition and the bulb is then exhausted while strongly
heated, and it is rinsed out several times with dry gas. At a pressure of about
2 millimetres the filament is heated to incandescence for a short time after which the
bulb is completely exhausted.
The filament is then heated to intense white heat, during which time it gives off
slowly the occluded gases. When this developement of gases ceases, the lamp can
be filled with a very small quantity of a strongly reducing gas or mixture of gases,
such as hydrogen illuminating gas, or the like.
The bulb is then closed by melting. After about 24 hours the filament is subjected
to the forming process. The exterior of the filament does not undergo any
perceptible change by this.
The light of such an osmium lamp is of dazzling brightness and nearly white.
If the lamp is to burn in an inclined position or to withstand concussions, the
filament may be secured to some point of the bulb in a similar manner to carbon
filament lamps for high pressures.
With osmium vacuum lamps in particular it is of advantage, as above stated, to
add to the osmium filament a small proportion of more readily oxidisable bodies,
which will not be given off from the filament at an intense white heat. Carbon is
the body which can most readily be mixed with the filament. For this purpose a
somewhat porous osmium filament is raised to incandescence in an bydrocarbon
atmosphere that will give off carbon at incandescence, preferably at low pressure;
such an osmium filament containing a small quantity of carbon is somewhat more
elastic than the pure osmium filament, otherwise it does not differ materially from
the latter. The production of osmium filaments with a proportion of other sub-
stances that do not readily volatalize, such as zirconium, can be easily effected if
the oxide or a salt of the body itself is capable of supporting incandescence. It
is effected as follows:-
:-
The somewhat porous osmium filament is lightly coated with a liquid magma, com-
posed of exceedingly finely divided oxide of the metal to be alloyed and very finely
divided carbon (or a body that will leave carbon when heated under exclusion of air,
such as sugar and the like) sufficient to reduce the oxide, these bodies being mixed
with water to form the said magma.
The coated filament is then either directly fixed in the lamp by melting, or pre-
ferably, it is first gradually heated to an intense white heat by an electric current.
By this means the oxide is reduced to the metallic state and at once forms an alloy
with the osmium.
Such filaments may contain a slight excess of carbon or suboxides of the alloy
without detriment to the subsequent illuminating powers of the lamp. Such filaments
are mostly somewhat more elastic than those of pure osmium.
The rest of the process of manufacture of the lamp is the same as above described.
The elasticity of the osmium filament, which can be increased to a certain degree
by an increase. of the above described alloy, its permanent nature under incandescence
and the advantageous colour of the light which is obtained with many of the alloying
bodies will enable the said filaments to be employed with advantage in practice.
Such osmium alloys are prepared in the form of elastic incandescence filaments of
uniform thickness, in the following manner:-
The oxide-osmium filaments obtained from the paste in the manner described in
the said Specification No. 1535 of 1898, (which must contain a proportion of carbon
corresponding to the quantity of oxide to be reduced) are heated to incandescence
either under exclusion of air, or in reducing gases, and are then heated preferably in
vacuo to the temperature necessary for the reduction of the oxide. It is by no means
necessary in all cases that the amount of the substance to be mixed with the osmium

page_text: should be small and I will describe by way of example the production and behaviour
of a zirconium-osmium filament composed of about equal parts of each metal.
The filament composed of ZrO,, Os, C, is almost black. As soon as the reduction
temperature is reached, which is about that of a white heat, a rapid developement of
gases ensues. The filament sinters strongly while its conducting power rapidly
increases. The ceasing of the gas production indicates the completion of the reducing
process. The filament now composed of zirconium-osmium has become almost silvery
white, and when cold, is very elastic. It is pliable at a white heat: more so in fact
than a pure osmium filament. In vacuo or in strongly reducing gases it can be
heated to high temperatures without disintegrating or becoming deformed.
Its high resistance to chemical reagents is remarkable. Boiling water or cold
dilute acids do not attack it. This shows that the zirconium has become thoroughly
alloyed with the osmium. When highly heated in the atmosphere the filament gives
a momentary dazzling light in consequence of the combustion of the zirconium. If
the osmium be also burnt by heating in the oxidising zone of a flamé a small dense
filament of ZrO, will remain.
The other alloys behave more or less in the same way. It is obvious that other
platinum metals may be added to these alloys; the preparation of such filaments
would be effected in a precisely similar manner to that above described.
Such filaments can be secured by melting in the glass bulbs in the same way as
the osmium or carbon filaments. The fixing of the filament is effected by means of
osmium paste or osmium cement in the same way as described in the Specification
No. 1535 of 1898. The production of light with such lamps is very economical as
regards the consumption of electrical energy. The colour of the light of most of
these osmium alloys is a light yellow. An exception to this are the filaments having
a high, percentage of carbon. The colour of the light of the latter is reddish, and
they possess at a white heat, a high power of heat emission.
Dated this 15th day of May 1899
ABEL & IMRAY,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Electrical Incandescence Lamps with Osmium
Filaments.
1, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings, in the
County of London, Chartered Patent Agent, do hereby declare the nature of this
invention (as communicated to me from abroad by Oesterreichische Gasglühlicht and
Electricitäts-Gesellschaft, of IV Schleifmuhlgasse, Vienna, Austria,) and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement :-
This invention relates to the manufacture of electrical incandescence lamps with
osmium filaments as described in the Specification to Letters Patent No. 1535 of
1898 in which the filament is made to incandesce in a glass globe.
My correspondent has found in the first place that osmium, whether by itself, or
as an alloy in combination with other metals or as a mixture with oxides, has a high
capacity of absorbing gases and these occluded gases are not easily given off when
the inetal is heated. He has also found that the osmium filament is very sensitive
to even a small quantity of gases having an oxidising action, such as carbon dioxide,
of which traces are usually given off by glass bulbs when heated in vacuo.

page_text: Inese facts and cute scientific
examination of them red my correspondent to this
invention which is based on the following principles:
1. The osmium filament when raised to an intense white heat in vacuo gives off
the gases which have been absorbed by it.
2. The gradual oxidation and disintegration of the osmnium filament in lamps at
an intense white heat is prevented by the presence, even in small quantities of gases
having a strong reducing action.
3. By continued heating to an incandescence which is not too intense (2 to 4
Watts per candle power) in a partial vacuum, the osmium filament undergoes a
peculiar process of formation. A filament thus produced is superior to the ordinary
filament as regards duration of burning and as to its power. of resisting the action of
incandescence.
4. The glass bulb should not contain in its composition any oxides that are so.
easily reducible by reducing gas under heat that at the working temperature they
will be affected. The most suitable material for the purpose is a potash-soda glass
that will not readily melt.
5. It is in some cases particularly advantageous for vacuum lamps with filaments
containing osmium if the filament is made to contain small quantities of substances
that have a strong reducing action and which become oxidised more readily than
osmium. Such substances are carbon, zirconium, thorium, niobium, tantalium.
silicon and the metals of the rarer earths and many others.
It should be here observed that the statement contained in the said Specification
No. 1535 of 1898 as to the fusibility of the osmnium carbide requires some limitation
as the compounds prepared directly from exceedingly finely divided carbon and
osmium have proved to be very refractory. They shew even with a large proportion
of osmium the high heat emission which is the characteristic property of carbon.
But the volatilisation or disintegration of carbon-osmium filaments when heated
to intense white heat in vacuo takes place rather easily in a similar manner to that
of a pure carbon filament.
The production of a lamp according to the present improved method is very simple.
After the filament has been fused into the perfectly clean glass bulb, the lamp is
filled with dry reducing gases such as illuminating gas or hydrogen. The lamp may
be left for about 24 hours in a closed condition, but this is not essential. The hulb
is exhausted while heated to a considerable temperature and is rinsed out with dry
gases several times. At a pressure of about 2 m/m the filament is heated to
incandescence for a short time and then the bulb is completely exhausted.
The filament is now heated to intense white heat during which time it gives off
slowly occluded gas. When the filament ceases to give off gas the lamp is sealed,
previous to which a very small quantity of a strong reducing gas or mixture of gases,
such as hydrogen, illuminating gas or the like, may be introduced, the vacuum being
thus rendered partial.
After about 24 hours the filament is subjected to the forming process of continued
heating at a moderate incandescence temperature. The exterior of the filament is
not altered by this in any noticeable manner.
The light of these osmium lamps is of dazzling brightness and nearly white. If
the lamp is to burn in an inclined position or to be subjected to strong vibrations
the filaments may be secured to some point of the bulb in a similar manner to carbon
filament lamps for high pressure.
In the case of osmium vacuum lamps in particular it is an advantage to give as
above stated to the osmium filament a small proportion of more readily oxidisable bodies
which will not be given off by the filament at intense white heat. Carbon is the
substance which can be most readily mixed with the filaments.
For this purpose a
somewhat porous osmium filament is raised to incandescence in a hydro-carbon
atmosphere which gives off carbon at incan lescence, preferably at low pressure.
Such an osmium filament containing a small quantity of carbon has a little more
elasticity than the pure osmium filaments, otherwise it does not differ materially
from the latter.

page_text: The production of osmium filaments with a proportion of other substances that do
not readily volatilise, such as zirconium, can be easily effected when the oxide or
some salt of the body itself is capable of supporting incandescence. It is effected as
follows:-
-
The somewhat porous osmium filament is lightly covered with a liquid magma
composed of exceedingly finely divided oxide of the metal to be alloyed and very
finely divided carbon (or some other body that will leave carbon when heated under
exclusion of air, such as sugar and the like) sufficient to reduce the oxide; these bodies
being mixed with water to form the said magma. The coated filament is then
directly fixed in the lamp by melting or preferably is first gradually heated to an
intense white heat by an electrical current. These operations taking place either in
a vacuum or in an atmosphere having a reducing action, by this means the oxide is
reduced to the metallic state and at once forms an alloy with the osmium. Such
filaments may contain a slight quantity of carbon or sub-oxides of the alloying metal
without interfering with the subsequent illuminating powers of the lamp.
The rest of the process of manufacture of the lamp is the same as above described.
According to what has been stated at the commencement, gases of reducing
character occluded and subsequently driven out from the osmium may be used for
the purpose of effecting the reduction. The resulting filament is in this case
exactly the same as above described.
The elasticity of the osmium filament which may be increased to a certain degree
by an increase of the above described alloy, its permanent character under incandes-
cence and the advantageous colour of the light which it obtained with many of the
alloying bodies will enable the said filaments to be employed with advantage in
practice.
Such osmium alloys are prepared in the form of elastic incandescent filaments of
uniform thickness in the following manner :-
.
The oxide osmium filaments which have been produced from the paste in the
manner described in the said Specification No. 1535 of 1898 and which must contain a
proportion of carbon corresponding to the quantity of oxide to be reduced, are heated to..
incandescence but not to a temperature sufficient to reduce the oxide, either under ex-
clusion of air or in a reducing atmosphere thus driving off the occluded gases and are then
heated preferably in vacuo to the temperature necessary for the reduction of the oxide.
It is by no means necessary in all cases that the amount of the substances to be mixed
with the osmium should be in small quantities and I will describe by way of example
the production and behaviour of a zirconium osmium filament composed of about equal:
parts of each metal.
The filament which consists of ZrO2 + 0,+C, is almost black.
3
As soon as the
reduction temperature is reached, which is about that of a white heat, a rapid
developement of gases ensues. The filament sinters strongly whilst its.conductivity
increases rapidly. The cessation of the gas production indicates the completion of
the reducing process. The filament is now composed of zirconium and osmium and
has now become almost as white as silver and when cold, is very elastic. It is flexible
at white heat; more so in fact than a pure osmium filament. In vacuo or in strongly
reducing gases it can be heated to high temperatures without disintegration or
becoming deformed. Its high resistance to chemical reagents is peculiar. It is not."
affected by boiling water or by dilute acids in the cold. This shews that the
zirconium has become completely alloyed with the osmium. When highly heated
in the atmosphere the filament gives momentary dazzling light in consequence of the.
combustion of the zirconium. If the osmium is also burnt by heating in the
oxidising zone of a flame a small dense filament of ZrO, will remain. The other alloys
behave more or less in the same way.
It is obvious that other platinum metals may be added to these alloys. The
production of such filaments would be effected in precisely the same manner to that
above described.
Such filaments can be secured by melting in the glass bulbs in the same way as
osmium or carbon filaments. The fixing of a-filament is effected by means of osmium
:

page_text: paste or osmium cement in the same way as described in the Specification No. 1535
of 1898.
The production of light in such lamps is very economical as regards consumption of
electrical energy. The colour of the light of most of these osmium alloys is a light
yellow, but an exception to these are the filaments having a high percentage of
carbon, the colour of the light of which is reddish. They possess at a white heat a
high power of heat emission.
It will thus be seen that in the compound osmium filaments for incandescent lamps
herein referred to, the other elements inay be present in the form of a metal such as
zirconium or the bases of the rare earths or there may be a certain portion of the
oxide also present. On the other hand a small proportion of carbon may also be
present in an osmium filament as and with the results above set forth.
It is probable that in the best forms of filaments containing oxides of zirconium or
the rare metals the oxygen is present wholly or partially in the form of a sub-oxide
which protects the osmium from the action of small quantities of gas such as steam
which have a direct oxydising action. These oxide-osmium filaments as they may be
termed can also be produced by using for the purpose of the necessary partial
reduction of the oxide, the occluded gases that are given off from the osmium itself
preferably in a commencing vacuum. It is evident that filaments prepared by the
means and in the way set forth in this Specification may subsequently be coated
with refractory oxides as described in the Specification of the main patent above
referred to.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, I declare that what I
claim is :-
1. In the preparation of filaments wholly or partially consisting of osmium for
electric lamps, the process of taking all or nearly all the occluded gas out of the
filament in a vacuum at a white heat.
2. Osmium filaments for electric incandescent lamps containing small proportions
of carbon or hydrocarbon substantially as described.
3. Compound osmium filaments for incandescent lamps containing a proportion
of zirconium, thorium, niobium, tantalium, silicon or metals of similar behaviour or
of the rare earth metals substantially as described,
4. A process for the manufacture of the illuminating filaments from oxide-osmium
filaments, characterised by having the oxides of the filament partially reduced in a
white heat.
5. Compound osmium filaments for incandescent lamps containing the substances
mentioned in the preceding claim wholly or partially in an oxidised state
substantially as described.
6. In the preparation of filaments for incandescent electric lamps of osmium and
osmium alloys the process of formation by long continued glowing in a partial
vacuum.
7. The preparation of filaments consisting of osmium and the substances referred
to in Claim 3 by the partial or complete reduction of the oxides by means of carbon
or of the gases occluded in the osmium itself, substantially as described.
8. In the manufacture of filaments for electric incandescent lamps, in which
oxides are present, the process of heating them in a vacuum or any suitable gases
below the temperature of reduction of the oxide filament until the occluded gases
are driven out prior to heating them to the temperature necessary for the reduction
of the oxide.
9. Filaments prepared by the processes herein described and claimed with or
without an external covering of resistant oxides.
Dated this 14th day of February 1900.