Improvements in Filaments for Use in Electric Glow Lamps.
Year: 1896

page_text: Date of Application, 25th July, 1896
Complete Specification Left. 23rd Apr., 1897-Accepted, 29th May, 1897
Improvements in Filaments for Use in Electric Glow Lamps.
1, FRÉDÉRIC DE MARE, of 6 Rue Lacroix, Paris, in the Republic of France,
Engineer, do hereby declare the nature of this invention to be as follows:-
This invention relates to an improved filament for use in electric incandescent
lamps, its object being to obtain a normal lighting effect with a reduced amount of
current.
For this purpose I utilize in the filaments of electric incandescent lamps the great
irradiating power of the so called rare earths, and I produce these filaments by
mixing oxides of such earths with carbon, so that the carbon serves as a conductor
of heat and electricity, whilst the oxides serve as irradiating bodies.
In order to produce such filaments, I take a vegetable fibre or thread, for example
a thread of linen and after the necessary cleaning operation, I impregnate the same
with a solution of an organic salt, obtained from the rare earths either alone, or in
combination with another salt.
I use an organic salt, in order that, during the carbonisation of the filament the salt,
while being decomposed, may form carbon and oxide.
The carbonized filament is soaked a second time in a concentrated solution, then
dried and annealed in vacuo under the action of the electric current.
Instead of employing the soaking process, I may utilize a mixing process; in this
case the manufacturing operation is as follows:
I grind old flax or linen paper into a fine powder and wash the product in order
to remove the sizing substances contained therein, and I subsequently reduce the
product to a pulp which, after desiccation, is mixed with the solution of organic
salts obtained from the oxides of the rare earths, then drawn out into threads and
the threads thus obtained are carbonized in a closed vessel; in the same manner
as before described, they are soaked once or several times in the saline solution
which serves to enrich them with oxides and to impart to them a higher degree of
homogeneousness; finally they are set into the bulbs, a vacuum is produced in the
bulbs and the carbonization completed.
All organic salts of the so-called group of rare metals are applicable, but
those are preferable which on the one hand contain a large percentage of carbon
and which are on the other hand the most soluble in water or other solvent
employed in the manufacture of filaments.
For these reasons I give the preference to citrates obtained by precipitating, by
citrate of ammonia, a solution composed of nitrate of thorium and nitrate of cerium,
the proportions being 99 per cent. of the oxide of the former and 1 per cent. of the
oxide of the latter. The precipitation of this mixture is complete. The precipitate
is then washed in a small quantity of water, and after the nitrate of ammonia
has been eliminated, the product is desiccated and preserved in a condition ready
for use.
In order to obtain a solution of this salt, it is placed in a solution of citrate of
ammonia, to which ammonia has been added, and is kept therein until a limpid
liquor is obtained; this solution is concentrated in a water bath until the desired
degree of concentration is obtained.
It is evident from the above, that in these filaments, each conducting molecule
of carbon, after baking and annealing, becomes intimately combined with

page_text: one molecule of non-conducting acid and that the function of the carbon is solely
to enable the electric current to heat the molecule of oxide whose light emitting
power is far superior to that of carbon at the same temperature.
Dated this 25th day of July 1896.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.
Improvements in Filaments for Use in Electric Glow Lamps.
I, FRÉDÉRIC DE MARE, of 6 Rue Lacroix, Paris, in the Republic of France,
Engineer, 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 aud by
the following statement:-
This invention relates to an improved filament for use in electric incandescent
lamps, its object being to obtain a normal lighting effect with a reduced amount of
current.
For this purpose I utilize in the filaments of electric incandescent lamps the great
irradiating power of the so called rare earths, and I produce these flaments by
mixing oxides of such earths with carbon, so that the carbon serves as a conductor
of heat and electricity, whilst the oxides serve as irradiating bodies.
In order to produce such filaments, I take a vegetable fibre or thread, for example
a thread of linen and after the necessary cleaning operation, I impregnate the
same with a solution of an organic salt, obtained from the rare earths, either alone,
or in combination with another salt.
I use an organic salt, in order that, during the carbonisation of the filament the
salt, while being decomposed, may form carbon and oxide.
The carbonized filament is soaked a second time in a concentrated solution, then
dried and annealed in vacuo under the action of the electric current.
Instead of employing the soaking process, I may utilize a mixing process; in this
case the manufacturing operation is as follows:
I grind old flax or linen paper into a fine powder and wash the product in
order to remove the sizing substances contained therein, and I subsequently
reduce the product to a pulp which, after desiccation, is mixed with the solution
of organic salts obtained from the oxides of the rare earths, then drawn out into
threads and the threads thus obtained are carbonized in a closed vessel; in the same
manner as before described, they are soaked once or several times in the saline
solution, which serves to enrich them with oxides and to impart to them a higher
degree of homogeneousness; finally they are set into the bulbs, a vacuum is produced
in the bulbs and the carbonization completed.
All organic salts of the so-called group of rare metals are applicable, but those
are preferable which on the one hand contain a large percentage of carbon and
which are on the other hand the most soluble in water or other solvent employed in
the manufacture of filaments.
For these reasons I give the preference to citrates obtained by precipitating, by
citrate of ammonia, a solution composed of nitrate of thorium and nitrate of
cerium, the proportions being 99 per cent. of the oxide of the former and 1 per cent.
of the oxide of the latter. The precipitation of this mixture is complete. The
precipitate is then washed in a small quantity of water, and after the nitrate of
animonia has been eliminated, the product is desiccated and preserved in a condition
ready for use.
In order to obtain a solution of this salt, it is placed in a solution of citrate of

page_text: ammonia, to which ammonia has been added, and is kept therein until a limpid
liquor is obtained; this solution is concentrated in a water bath, until the desired
degree of concentration is obtained.
It is evident from the above, that in these filaments, each conducting molecule of
carbon, after baking and annealing, becomes intimately combined with one molecule
of non-conducting acid and that the function of the carbon is solely to enable the
electric current to heat the molecule of oxide whose light emitting power is far
superior to that of the carbon at the same temperature.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. An improved filament for use in electric glow lamps, formed by a mixture of
carbon and oxides of rare metals, the object being to utilize the carbon as the heat
conductor and the oxide as the irradiating body.
2. The incorporation of the oxides of rare metals into the filaments, serving for
use in electric glow lamps, by employing the organic salts of these oxides which,
by their decomposition, form simultaneously carbon and the rare oxides.
3. The method of preparing filaments for use in electric glow lamps, either by a
soaking or impregnating, or by a mixing process, substantially as, and for the
purpose, specified.
Dated this word day
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.