Improvements in the Manufacture of Filaments for Incandescing Electric Lamps, and in Means Applicable for Use in such Manufacture
Year: 1899

page_text: Date of Application, 21st Mar., 1899
Complete Specification Left, 19th Dec., 1899-Accepted, 10th Feb.,
1900
PROVISIONAL SPECIFICATION.
"Improvements in the Manufacture of Filaments for Incandescing
Electric Lamps, and in Means Applicable for Use in such
Manufacture."
I, WILLIAM LAWRENCE VOELKER, a citizen of the United States of America,
temporarily residing at No. 38, Bernard Street, Russell Square, in the County of
London, Metallurgical Chemist, do hereby declare the nature of this invention to be
as follows:
For the purpose of my invention, I employ carbide of titanium, obtained in the
particular manner hereinafter described with the aid of a specially constructed electric
furnace. The titanium may be in combination with uranium, or with uranium and
thorium.
It is
In the production of chemically pure carbides with the aid of the electric furnace,
it is imperative that there should not be in the atmosphere of the furnace the vapours
of any substances other than those of the substances which are being treated.
also essential, in order to obtain absolutely pure products, that the substances treated
should be chemically pure. The form of electric furnace hereinafter described bas
been designed by me with the object of obtaining products of absolute purity;
particularly chemically pure carbides for use in the manufacture of filaments for
incandescing electric lamps.
In preparing the carbide, I proceed as follows:-
I take, for instance, two parts by weight of chemically pure nitrate of the earth
metal, and one part by weight of pure cane sugar, and I dissolve the same in distilled
water; taking care to use very little excess of water in dissolving the nitrate and
sugar. I then heat the solution in a suitable porcelain evaporating dish until the
boiling point is reached, whereupon the application of heat is discontinued. In a few
moments, the mass will swell to a porous body largely increased in bulk and pre-
senting a gray colour. This body spontaneously ignites, and, while burning, gives
off great volumes of nitrous fumes. When the fumes cease to be evolved, the vessel
is covered with a porcelain lid, and the mass is allowed to cool slowly. When cold, the
mass has a brownish black colour, and is soft and porous. This mass is then ground
to a fine powder in a suitable mill; and, having been transferred to a mortar and
sufficient syrup of cane sugar added, the mass is worked until it has the consistency
of putty. The mass is then pressed into cakes, slowly dried and baked hard in covered
crucibles.
The next operation consists in melting these cakes in the specially constructed
electric furnace hereinafter more particularly referred to. A cake of a size adapted to
fit the hearth of the furnace is placed therein; and, the are having been struck, the
electrodes are drawn apart until the arc covers the entire width of the cake. The

page_text: current required to reduce from 6 to 8 ounces of the compressed mass to a perfectly
fluid body in about 15 minutes should be approximately 1,000 ampères at from 75
to 100 volts. The current is cut off when the whole mass is in a perfectly fluid state,
and the furnace allowed to cool down. If sufficient care has been taken in all the
operations described, and perfect fluidity has been obtained, a reaction will have taken
place in the furnace, resulting in a carbide which, when fractured, will present a
crystalline appearance. If the heavy crystalline body resulting is to be kept for any
length of time, it should be covered with benzol to preserve it from contact with a
moist atmosphere.
To produce filaments from the carbide obtained as heretofore described, I proceed
as follows-The carbide is reduced with benzol or naphtha in a suitable air-tight
mill to an impalpable powder. The grinding surfaces, being carbide of the earth
metal employed in the preceding process, are so adjusted that the material to be
ground only comes into contact with the said grinding surfaces. The shaft that
actuates the upper grinding surface works through a stuffing-box in the top of the
mill. The impalpable powder rises to the top of the benzol or naphtha as the grinding
proceeds, and from time to time is drawn off through a suitable opening in the side
of the mill; fresh benzol or naphtha being added through an opening in the top of
the machine. When the grinding is complete, the impalpable powder is freed from
the benzol or naphtha, dried in a warm dry chamber, such as a drying oven, and then
inixed with a viscous compound composed of gun-cotton and oil of cassia. This
binding compound is prepared, by the aid of gentle heat, from one part by weight of
gun-cotton to four parts by weight of oil of cassia; sufficient time being allowed to
secure the thorough decomposition of the gun-cotton. The impalpable powder is
mixed in a mortar, or suitable mixing machine, with the gun-cotton and cassia com-
pound, and then rolled for about an hour between hard and polished steel rolls. Upon
the completion of the rolling, the mass should be smooth, glossy and tough. It is
now transferred to a strong steel cylinder, provided with a tight-fitting piston, and
having at the bottom a jewel with a polished orifice of the size required for the
filaments desired. The piston, worked by hydraulic power, a screw or other con-
venient means, is started, and the filament is expressed or squirted through the jewel-
die and wound on suitable forms made of gas carbon, the surfaces of the latter being
polished and well rubbed with graphite. The size and shape of the form should be
adapted to the length and shape of filament desired. The electrical resistance of the
finished filaments is so great that it is only necessary to have them U-shaped and
with legs much shorter than those of carbon filaments.
When the filaments, wound on the form or forms, are perfectly dry, they are, either
singly or several together, placed in electrically-connected spring clips attached to
wire conductors which pass through, and are sealed air-tight in, a ground glass
stopper; the latter fitting a glass cylinder having connections to an air-pump for
exhausting the air, and to a source of supply of a purified and attenuated gas. The
stopper, with the clips holding the filament or filaments, having been fitted air-tight
into the open end of the cylinder, the air is exhausted from the cylinder, and a fairly
good vacuum created. By means of a stop-cock, the connection with the air-pump
is then closed, the gas is admitted, and the electric current turned on at a sufficiently
high voltage to cause the filament or filaments to glow bright red. The pressure
required to effect this with filaments for 100 volt lamps will be from 1000 to
1200 volts. The carbon deposited on the filament or filaments from the attenuated
gas forms a slight coating on the surface and aids conductivity; and the carboniferous
matter of the binder forms, in a few seconds, a partial union with the particles of the
carbide. When the bright red glow appears, the current is shut off, the remaining
gas is allowed to escape from the cylinder, and connection with the source of the gas
supply is closed. The filament or filaments are now removed, are joined to platinum
wires by forming suitable joints and replaced in the glass cylinder. This is then
partially exhausted, and the current again turned on until intense incandescence
results. Any uncombined carbon on the surface is hereby volatilized, and the partial
union of the carbon and carbide of the core is completed, a homogeneous structure

page_text: remaining. If it be deemed desirable to standardize the filaments, they are flashed in
a good vacuum, in a vapour of hydrocarbon and of the earth metal employed in the
filament, in a manner similar to that ordinarily pursued in normalizing carbon
filaments.
The mounted and standardized filaments are now sealed in the usual way into glass
bulbs from which the air is exhausted. The resulting finished lamps give, in com-
parison with the best carbon filament lamps, a much higher candle power with a
greatly reduced consumption of current, the electrical resistance of the carbide fila-
ments being so much higher. The carbide filaments having also greater stability at
the resulting high temperature, the economic life of the lamps is greatly lengthened..
I do not, however, restrict myself to the particular process I have described of
forming the filaments from the carbide; as they can be obtained by mixing the
powdered carbide with triturated carbon and adding a viscous mixture, such as
described above, with purified benzol, with coal tar or with pure caoutchouc. They may
also be formed by electrically heating an unbaked carbon filament, prepared from
pure powdered carbon and a suitable binding mixture, in a vapour of the particular
metal desired for forming the base of the carbide; the said vapour being produced by.
vapourizing the said metal in my improved electric furnace, there being connected to
the latter a suitable exhausted vessel wherein the filaments are set up without
contact with each other. I prefer, however, the methods hereinbefore particularly
described.
For producing incandescing electric lamps which yield a peculiar characteristic
light, I prefer to employ compound carbide filaments composed of titanium and
uranium. By altering the proportions in which the constituent materials are com-
bined the colour of the light may be varied from a pure white to a golden colour,
having the appearance of sunlight reflected from a polished metallic surface throwing
off golden rays. I can also vary the colour of the light by adding to the titanium
nitrate and cane sugar solution, prepared as above described, uranium nitrate, or
uranium nitrate in conjunction with thorium nitrate, preparatory to melting in the
electric furnace. Where, however, intensely white light is desired,
titanium carbide alone.
employ the
In constructing an electric furnace specially adapted for employment in the pro-
duction of chemically pure carbides intended for use in the manufacture of filaments
for incandescing electric lamps, the body of the furnace may be of limestone, cut to
the usual form; or it may be composed of suitable cohesive materials, moulded into
the required form and compressed by means of hydraulic or other power. The
channels or holes for the electrodes are several times larger than the diameter of the
carbon or other conductors employed. The furnace hearth is also several times larger
than actually required. The channels or holes for the electrodes, as also the space
for the hearth, are filled, wholly or in part, with a suitably prepared plastic. mixture
of the chemically pure oxide or oxides of the metal or metals to be treated in the
furnace. This mixture is compressed by heavy pressure, preferably by means of a
hydraulic press. A "form," of the size of the hearth and channels required, may be
employed in compressing the mixture; or it may be made solid, and the hearth and
channels subsequently cut away. Communicating with the hearth, through the side
of the furnace, is a small hole, provided with a tube, the latter being furnished with a
suitable cock and communicating with a source for the supply of hydrocarbon gas
under pressure. The cover of the furnace is of the same material as the body
thereof; and, compressed upon the under side of the cover, is a thick coating of the
oxide or oxides of the metal or metals to be treated.
The electrodes, if of carbon, must be of the purest kind; preferably derived from
pure cane sugar by decomposing it in an enclosed chamber out of contact with the
atmosphere, then heating the same red hot, passing chlorine gas over and through
the mass to further purify it, and subsequently subjecting it for some time to a very
high temperature, in order to increase its density and electrical conductivity. The
carbon thus prepared is then ground to a fine powder in such a mill as will not affect
the purity of the carbon, and mixed with a strong solution of cane sugar; the mass

page_text: being ultimately pressed through dies by hydraulic pressure. The resulting rods are
cut to suitable lengths, slowly dried and baked; the final temperature being carried
to, and maintained for a considerable time at, a very high degree.
If it be desired to produce absolutely pure carbide of any earth metal-e.g. titanium
-by the employment of compound electrodes, I first ascertain, by preliminary
tests, the percentage of water in the nitrate of the earth metal and in the sugar to be
mixed with it. This is necessary in order to make due allowance for the water of
crystallisation in proportioning the weights of the two elements to be combined.
Having thus ascertained the combining proportions, and making allowance for the
water to be added in dissolving the nitrate and sugar, the solution is evaporated in a
suitable porcelain dish until the boiling point is reached, whereupon the application
of heat is discontinued, and the mass allowed to swell and spontaneously ignite.
When nitrous fumes are no longer given off, the vessel is covered, and slow carboni-
The reaction
zation of the sugar and decomposition of the nitrate to oxide ensue.
being complete, the mass is, when cold, finely pulverized and mixed with sufficient
sugar syrup to give it the desired consistency. It is then forced through a die, dried
and baked as above described in reference to the manufacture of carbon electrodes;
the second pulverizing, remixing and rebaking, being however omitted.
When the arc is struck, these compound electrodes cominence to melt; and, as they
are fed forward by mechanism arranged to keep the arc at a constant length, the
molten particles fall into the hearth of the furnace and remain in a molten condition.
If desired, pure carbon ends, to which the electric conductors are attached, can be
welded to the compound electrodes whilst in a plastic state.
It will be evident that the whole surface of the furnace surrounding the hearth and
the electrodes becomes intensely hot while the smelting is in progress, and that more
or less volatilization takes place. When employing the compound electrodes, it is
therefore advantageous to admit a current of hydrocarbon gas as above provided for.
D 11: OLL
Ch 1000
"Improvements in the Manufacture of Filaments for Incandescing
Electric Lamps, and in Means Applicable for Use in such
Manufacture."'
I, WILLIAM LAWRENCE VOELKER, a citizen of the United States of America,
temporarily residing at No. 38, Bernard Street, Russell Square, in the County of
London, Metallurgical 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:-
For the purpose of my invention, I employ carbide of titanium, obtained in the
particular manner hereinafter described with the aid of a specially constructed electric
furnace. The titanium may be in combination with uranium, or with uranium and
thorium.
In the production of chemically pure carbides with the aid of the electric furnace,
it is imperative that there should not be in the atmosphere of the furnace the
vapours of any substances other than those of the substances which are being
treated. It is also essential, in order to obtain absolutely pure products, that the

page_text: ubstances treated should be chemically pure. The form of electric furnace herein-
fter described has been designed by me with the object of obtaining products of
bsolute purity; particularly chemically pure carbides for use in the manufacture
of filaments for incandescing electric lamps.
In preparing the carbide, I proceed as follows:-
I take, for instance, two parts by weight of chemically pure nitrate of the earth
metal, and one part by weight of pure cane sugar, and I dissolve the same in distilled
water; taking care to use very little excess of water in dissolving the nitrate and
sugar. I then heat the solution in a suitable porcelain evaporating dish until the
boiling point is reached, whereupon the application of heat is discontinued. In a
few moments, the mass will swell to a porous body largely increased in bulk and
presenting a gray colour. This body spontaneously ignites, and, while burning, gives
When the fumes cease to be evolved, the vessel
off great volumes of nitrous fumes.
is covered with a porcelain lid, and the mass is allowed to cool slowly. When cold,
the mass has a brownish black colour, and is soft and porous. This mass is then
ground to a fine powder in a suitable mill; and, having been transferred to a mortar
and sufficient syrup of cane sugar added, the mass is worked until it has the
consistency of putty. The mass is then pressed into cakes, slowly dried and baked
hard in covered crucibles..
The next operation consists in melting these cakes in the specially constructed
A cake of a size adapted
electric furnace hereinafter more particularly referred to.
to fit the hearth of the furnace is placed therein; and, the are having been struck,
the electrodes are drawn apart until the arc covers the entire width of the cake. The
current required to reduce from 6 to 8 ounces of the compressed mass to a perfectly.
fluid body in about 15 minutes should be approximately 1,000 ampéres at from 75 to
100 volts. The current is cut off when the whole mass is in a perfectly fluid state,
and the furnace allowed to cool down. If sufficient care has been taken in all the
operations described, and perfect fluidity has been obtained, a reaction will have
taken place in the furnace, resulting in a carbide which, when fractured, will present
a crystalline appearance. If the heavy crystalline body resulting is to be kept for
any length of time, it should be covered with benzol to preserve it from contact with
a moist atmosphere.
To produce filaments from the carbide obtained as heretofore described, I proceed
as follows:-The carbide is reduced with benzol or naphtha in a suitable air-tight
mill to an impalpable powder. A mill adapted to the purpose of the present inven-
tion is illustrated in vertical section in Fig. 1 of the accompanying drawings. The
grinding surfaces a, b, being carbide of the earth metal employed in the preceding
process, are so adjusted that the material to be ground only comes into contact with
the said grinding surfaces. The shaft c which actuates the upper grinding surface a
works through a stuffing-box d in the top of the mill, and is rotated by means of a
worm-wheel e and worm f. The impalpable powder rises to the top of the benzol or
naphtha as the grinding proceeds, and from time to time is drawn off through a
suitable opening, such as g, in the side of the mill; fresh benzol or naphtha being
added through an opening h, furnished with a screwed stopper or plug, in the top of
the mill. When the grinding is complete, the impalpable powder is freed from the
benzol or naphtha, dried in a warm dry chamber, such as a drying oven, and then
mixed with a viscous compound composed of gun-cotton and oil of cassia. This
binding compound is prepared, by the aid of gentle heat, from one part by weight of
gun-cotton to four parts by weight of oil of cassia; sufficient time being allowed to
secure the thorough decomposition of the gun-cotton. The impalpable powder is
mixed in a mortar, or suitable mixing machine, with the gun-cotton and cassia
compound, and then rolled for about an hour between hard and polished steel rolls.
Upon the completion of the rolling, the mass should be smooth, glossy and tough.
It is now transferred to filament forming apparatus of the ordinary type, such, for
5 example, as illustrated in vertical section in Fig. 2, comprising a strong steel
cylinder i, provided with a tight-fitting piston k, and having at the bottom a
perforated jewel 7, the orifice therein being.polished and of a diameter corresponding

page_text: with that desired for the filaments. The piston k, worked by hydraulic power, by a
screw m and worm-gear nor by other convenient means, is started, and the filament
is expressed or squirted through the jewel-die land wound on suitable forms such as
shown at o made of gas carbon, the surfaces of the latter being polished and well
rubbed with graphite. p is a loop or suspended guide for the filament on its passage
to the form. The size and shape of the form should be adapted to the length and
shape of filament desired. The electrical resistance of the finished filaments is so
great that it is only necessary to have them U-shaped and with legs inuch shorter
than those of carbon filaments.
When the filaments, wound on the form or forms, are perfectly dry, they are, either
singly or several together, placed in electrically-connected spring-clips attached to wire
conductors which pass through, and are sealed air-tight in, a ground glass stopper;
the latter fitting a glass cylinder having connections to an air-pump for exhausting
the air, and to a source of supply of a purified and attenuated hydrocarbon gas. The
stopper, with the clips holding the filament, or filaments, having been fitted air-tight
into the open end of the cylinder, the air is exhausted from the cylinder, and a fairly
good vacuum created. By means of a stop-cock, the connection with the air-pump
is then closed, the gas is admitted, and the electric current turned on at a sufficiently
high voltage to cause the filament or filaments to glow bright red. The pressure
required to effect this with filaments for 100 volt lamps will be from 1,000 to 1,200
volts. The carbon deposited on the filament or filaments from the attenuated gas
forms a slight coating on the surface and aids conductivity; and the carboniferous
matter of the binder forms, in a few seconds, a partial union with the particles of the
carbide. When the bright red glow appears, the current is shut off, the remaining
gas is allowed to escape from the cylinder, and connection with the source of the gas
supply is closed. The filament or filaments are now removed, are joined to platinum
wires by forming suitable joints and replaced in the glass cylinder. This is then
partially exhausted, and the current again turned on until intense incandescence
results. Any uncombined carbon on the surface is hereby volatilized, and the partial
union of the carbon and carbide of the core is completed, a homogeneous structure
remaining. If it be deemed desirable to standardize the filaments, they are flashed
in a good vacuum, in a vapour of hydrocarbon and of the earth metal employed in
the filament, in a manner similar to that ordinarily pursued in normalizing carbon
filaments.
The mounted and standardized filaments are now sealed in the usual way into glass
bulbs from which the air is exhausted. The resulting finished lamps give, in com-
parison with the best carbon filament lamps, a much higher candle power with a
greatly reduced consumption of current, the electrical resistance of the carbide fila-
ments being so much higher. The carbide filaments having also greater stability at
the resulting high temperature, the economic life of the lamps is greatly lengthened.
I do not, however, restrict myself to the particular process have described of
forming the filaments from the carbide; as they can be obtained by mixing the
powdered carbide with tritarted triturated carbon and adding a viscous mixture,
such as described above, with purified benzol, with coal tar or with pure caoutchouc.
They may also be formed by electrically heating an unbaked carbon filament, pre-
pared from pure powdered carbon and a suitable binding mixture, in a vapour of the
particular metal desired for forming the base of the carbides; the said vapour being
produced by vapourizing the said metal in my improved electric furnace, there being
connected to the latter a suitable exhausted vessel wherein the filaments are set up
without contact with each other. I prefer, however, the methods herein before par-
ticularly described.
For producing incandescing electric lamps which yield a peculiar characteristic
light, I prefer to employ compound carbide filaments composed of titanium and
uranium. By altering the proportions in which the constituent materials are com-
bined, the colour of the light may be varied from a pure white to a golden colour
having the appearance of sunlight reflected from a polished metallic surface throwing
off golden rays. I can also vary the colour of the light by adding to the titanium

page_text: nitrate and cane sugar solution, prepared as above described, uranium nitrate in
conjunction with thorium nitrate, preparatory to melting in the electric furnace.
Where, however, titanium carbide is employed alone, the light yielded is intensely
white in consequence of the high electrical resistance offered by that substance.
An electric furnace specially adapted for employment in the production of chemic-
ally pure carbides intended for use in the manufacture of filaments for incandescing
electric lamps, is illustrated in Figs. 3, 4, 5 and 6 of the accompanying drawings; Figs. 3
and 4 being respectively a longitudinal and a transverse section of a furnace wherein
the carbons are carried in supports detached from the furnace and Figs. 5 and 6 respec-
tively similar views of a furnace wherein the carbons are carried in tubes inserted in
the ends of the furnace. In constructing the furnace, the body A may be of lime-
stone, cut to the usual formn; or it may be composed of suitable cohesive materials,
moulded into the required form and compressed by means of hydraulic or other power.
The channels or holes B B for the electrodes are several times larger than the
diameter of the carbon or other conductors CC employed. The furnace hearth A¹ is
also several times larger than actually required. The channels or holes B B, as also
the space for the hearth, are served wholly or in part with a coating or filling A² of a
suitably prepared plastic mixture of the chemically pure oxide or oxides of the metal
or metals to be treated in the furnace. This mixture is compressed by heavy
pressure, preferably. by means of a hydraulic press. A form," of the size of the
hearth and channels required, may be employed in compressing the mixture; or it
may be made solid and the hearth and channels subsequently cut away. Com-
municating with the hearth, through either or both sides of the furnace as also the
bottom, is a small hole D, provided with a tube D', the latter being furnished with a
suitable cock and communicating with a source for the supply of hydrocarbon gas
under pressure. The cover A³ of the furnace is of the same material as the body A;
and, compressed upon the under side of the cover, is a thick coating lining A2* of
the oxide or oxides of the metal or metals to be treated. In Figs. 5 and 6, E E are
tubes of metal through which the carbons C C pass and by which they are supported ;
in Figs. 3 and 4 the carbons pass directly through the linings Hning A2 A2x.
mode of construction will however be found satisfactory in practice.
Either
The electrodes, if of carbon, must be of the purest kind; preferably derived from
pure cane sugar by decomposing it in an enclosed chamber out of contact with, the
atmosphere, then heating the same red hot, passing chlorine gas over and through the
mass to further purify it, and subsequently subjecting it for some time to a very high tem-
perature, in order to increase its density and electrical conductivity. The carbon thus
prepared is then ground to a fine powder in such a mill as will not affect the purity
of the carbon, and mixed with a strong solution of cane sugar; the mass being ulti-
mately pressed through dies by hydraulic pressure. The resulting rods are cut to
suitable lengths, slowly dried and baked; the final temperature being carried to, and
maintained for a considerable time at, a very high degree.
If it be desired to produce absolutely pure carbide of any earth metal-e.g., titanium
-by the employment of compound electrodes, I first ascertain, by preliminary tests,
the percentage of water in the nitrate of the earth metal and in the sugar to be mixed
with it. This is necessary in order to make due allowance for the water of crystallisa-
tion in proportioning the weights of the two elements to be combined. Having thus
ascertained the combining proportions, and making allowance for the water to be
added in dissolving the nitrate and sugar, the solution is evaporated in a suitable
porcelain dish until the boiling point is reached, whereupon the application of heat
is discontinued, and the mass allowed to swell and spontaneously ignite. When
nitrous fumes are no longer given off, the vessel is covered, and slow carbonization of
the sugar and decomposition of the nitrate to oxide ensue. The reaction being com-
plete, the mass is, when cold, finely pulverized and mixed with sufficient sugar syrup
to give it the desired consistency. It is then forced through a die, dried and baked
as above described in reference to the manufacture of carbon electrodes; the second
pulverizing, remixing and rebaking, being however omitted.
When the arc is struck, these compound electrodes commence to melt; and, as they

page_text: are fed forward by mechanisin arranged to keep the arc at a constant length, the
molten particles fall into the hearth of the furnace and remain in a molten condition.
If desired, pure carbon ends, to which the electric conductors are attached, can be
welded to the compound electrodes whilst in a plastic state.
It will be evident that the whole surface of the furnace surrounding the hearth and
the electrodes becomes intensely hot while the smelting is in progress, and that more
or less volatilization takes place. When employing the compound electrodes, it is
therefore advantageous to admit a current of hydrocarbon gas as above provided
for.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I claim :
1. In the manufacture of incandescing electric lamp filaments containing titanium
carbide, the herein described method of producing carbides of the earth metals, con-
sisting in taking two parts by weight of chemically pure nitrate of the earth metal
and one part by weight of pure cane sugar, dissolving the same in a minimum
quantity of distilled water and heating the solution in a suitable evaporating dish to
boiling point, then withdrawing the source of heat and allowing the mass to assume
the condition at which spontaneous combustion takes place, and then, the evolution
of nitrous fumes having ceased and the resulting black porous mass having cooled,
compressing the same into cakes of a size to fit the hearth of an electric furnace, and
there reducing the same to a molten fluid by a large volume of current at a relatively
low pressure, substantially as set forth.
2. The herein described method of producing incandescing electric lamp filaments
containing titanium carbide, consisting in reducing to impalpable powder the carbide
of the earth metal or earth metals employed by grinding same in a suitable mill
under benzol or naphtha, between grinding surfaces of the like carbide, separating
the powder from the benzol or naphtha, mixing the former with a viscous compound
of gun-cotton and oil of cassia, rolling the mass between hard polished rollers,
squirting the same through jewel-dies, drying the filaments so formed, heating the
latter to a bright red colour, by means of an electric current of high voltage, in
an atmosphere of a purified and attenuated gas, then volatilizing at a very high
temperature and in vacuo the surface carbon deposited from the gas, and finally
completing the union of any uncombined carbon with the carbide in the core of
the filaments by bringing them to their highest degree of incandescence, substantially
as set forth.
3. In the manufacture of incandescing filaments from carbides of the earth metals,
the employment of grinding surfaces composed of the same carbide as that in
course of being ground, the material treated being meanwhile covered with benzol,
naphtha or like fluid hydrocarbon, deterioration by contamination with impurities
and by oxidation being thereby prevented.
4. In the manufacture of filaments for incandescing electric lamps from carbide
of titanium, the herein described means for varying the colour of the light emitted
by the filament; same consisting in adding to the titanium nitrate and cane sugar
solution a suitable proportion of uranium nitrate, or uranium nitrate in conjunction
with thorium nitrate, the mass being ultimately reduced in the electric furnace,
substantially as set forth.
5. The manufacture of filaments for incandescing electric lamps from carbide of
titanium, the reduction to carbide being ultimately effected in the electric furnace,
substantially as herein described and whereby high electrical resistance and an
intensely white light are obtained.
6. The herein-described-method-of-producing-filaments for--ineandeseing--electric
lumps, consisting in heating-oxide of titanium-ton-high temperature-in-the-presence
of-carbon, producing a viscons-mass-of-the-resultant-carbide and an agglutinating
agent, forming-filaments-from-the-mass, and exposing-the-same-to-a-high-tempera
ture, substantially-as-set ferth.
7. In-the-manufacture of incandeseing-electric-lamp filaments-from-the-earbide-or

page_text: arbides-of earth-metal-or-metals, mixing the powdered--carbide-with--triturate.!
carbon-and-adding-a-viscous-mixture-of-the-character-herein-described-with-purified
benzol-with-eoal-tar-or-with-pure-enontehone,-substantially-as-set-forth.
S.-In-the-manufacture-of
incandeseing-electric-lamp-filaments-from-carbide-or
filament
in-n-vapour of
earbides-of-earth-metal-or-metals,-electrically-heating-an--unbaked--carbon
prepared from-pure-powdered-carbon-and-a-suitable-binding-mixture,
the-earth-metal desired to form-the-base of-the-carbide, substantially us-set-forth.
9. An-electric furnace-whereof-the-parts-exposed-to-the-direct-nation of-the--heat
are-composed of the oxide-or-oxides-which-by-means-of-the-electric-current;-is-or
are to-be-decomposed, substantially us and for the purpose-set-forth.
10. For use-in-an-electric furnace, electrodes-compesed-of-carbon-and-of--the--oxide
or-oxides-of-the-metal-or metals to-be-combined-therewith in their chemically-com-
bining-weights, substantially-as-and-for-the-purpose-set-forth.
ed this tu day
For the Applicant,
G. G. M. HARDINGHAM,
Chartered Patent Agent, Clun House, Surrey Street, London, W.C.