The Production of Incandescent Materials Suitable for Use in Electric Lighting.
Year: 1898

page_text: Date of Application, 19th Aug., 1898
Complete Specification Left, 19th May, 1899-Accepted, 8th July, 1899
PROVISIONAL SPECIFICATION.
The Production of Incandescent Materials Suitable for Use in Electric
Lighting.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, do hereby
declare the nature of this invention (which has been communicated to me from
abroad by The Pharmaceutisches Institut, Ludwig Wilhelm Gans, of Frankfort-
on-Main, in the Empire of Germany, Manufacturing Chemists,) to be as follows:-
Incandescent materials consisting of an inner conductor having an outer
covering of metallic oxides are known. Their manufacture however presents
great difficulties.
Neither galvanic nor mechanical coatings give satisfactory
results. Above all attempts to produce an even but sufficiently thin coating
have not been successful.
The object of this invention is to obviate these difficulties.
In this process the so called lustrous preparations of the noble metals which
are already on the market, are used. Hitherto they have served for the decoration
of glass and porcelain, by coating the object with a suitable preparation (gold,
silver and platinum) and then burning in.
In a similar manner the lustres (also commercial products) which are organic
compounds of metallic oxides soluble in ethereal oils, serve for like purposes, thus
for example resinous acid compounds, sulphuretted resin compounds, or again
the products of decomposition of metallic chlorides in solution in lavender oil.
At present they are only used for producing a lustre upon glass or porcelain, by
coating the glass or porcelain in a similar manner to that employed for the pre-
parations of the noble metals then burning in.
Small rods, tubes or discs of glass or porcelain which have been treated with
the preparations of the noble metals and the lustres serve for the production of
the incandescent bodies. As the glass must be eliminated it is dissolved in
hydrofluoric acid or special glasses easily dissolved by hydrochloric acid may be
employed. The most suitable noble metals are those of the platinum group
which possess a high melting point such as ruthenium, rhodium, osmium and
the like. Lustrous preparations of these metals may be prepared in an analogous
manner to those of gold, silver and platinum. The small glass rods, tubes,
discs and the like are coated in straight or curved lines with the preparation
which is then burnt in. Mixtures also of different metals are suitable and form
alloys which are produced in the manner above described. When necessary the
strips are strengthened by electro-deposition.
A second coating is now applied by laying on the lustre. For this purpose the
known luminous earth metals (thorium, didymium, cerium, erbium, zirconium and
the like) either alone or in combination are suitable. Incandescent light practice
shows that a mixture of 99% thorium and 1% cerium is especially advantageous,
as is confirmed by this invention. The metal strips obtained in the first operation
are provided with a coating of illuminating earths by dusting with thorium
resinate containing about 1% of cerium in powder or laying on in ethereal oil

page_text: solution (by dipping, brushing and the like) and subsequently burning in. The
great difference between these resin compounds and the usual soluble salts
(nitrates, acetates) lies in the fact that with the latter on firing the oxide is
left behind as a raw powder which has little adhesion, whilst with the former
a very adherent glass like coating is produced.
To make the strips the glass rod or the like must be removed. Preferably
this is done after it has been coated with the noble metals and before being
coated with the illuminating metal oxides. The removal of the glass may how-
ever be the last operation, after both coatings are complete.
The strips may also be produced by first coating the glass rod with a thin
layer of silver placing upon this latter a layer of alumina or other refractory lustre
which need not consist of an illuminating earth, and finally treating with the
lustrous noble metals and the illuminating lustre.
described be dissolved with hydrochloric or hydrofluoric acid, and the silver.
The glass may then as
layer with nitric acid.
The finished incandescent bodies, are connected with metal or carbon contacts
either by soldering or pinching if necessary after previously coppering the ends.
These incandescent bodies which are very durable emit a brilliant light with a
current of suitable strength and may be used for lighting either exposed to the
air or in an exhausted bulb. As they always contain pure metal they possess
sufficient conductibility.
Dated this 1011
COMPLETE SPECIFICATION.
The Production of Incandescent Materials Suitable for Use in Electric
Lighting.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, do hereby
declare the nature of this invention (which has been communicated to me from
abroad by The Pharmaceutisches Institut Ludwig Wilhelm Gans, of Frankfort-
on-Main, in the Empire of Germany, Manufacturing Chemists,) and in what
manner the same is to be performed to be particularly described and ascertained
in and by the following statement:-
outer
Incandescent materials consisting of an inner conductor having an
covering of metallic oxides are known. Their manufacture however causes
great difficulties.
Neither galvanic nor mechanical coatings give satisfactory
results. However all attempts to produce an even but sufficiently thin coating
have been unsuccessful. The object of this invention is to remove these diffi-
culties.
In this process the so-called lustres or lustrous preparations of the metals are
used, which hitherto sold and used for the decoration of porcelain, glass etc., are
organic compounds of metals (resin acid compounds, or sulphuretted resin com-
pounds, or products of the decomposition of metallic chlorides produced by heat-
ing them with lavender oil), mixed in their application with an ethereal oil,
such as lavender oil.
Such lustres of many of the metals are well known, but there is a
remarkable difference between those which have for basis the so-called noble
very
metals, i.e. gold, silver and all the metals of the platinum group, and those,
which have for basis the common " unnoble" metals.
applied upon porcelain, glass or metal, and then heated to a high temperature,
The first ones when

page_text: leave behind a thin skin of metal, whilst the lustres of the baser metals, when
treated in the same manner, form a skin of metallic oxide.
The completed incandescent body consists of a core or interior of one of the
highly infusible metals of the platinum group. such as osmium, rhodium,
ruthenium or iridium, or alloys of the same, covered by an adhesive coherent
coating of the oxide of one of the luminous earthy metals such as thorium.
didymium, cerium, erbium, zirconium and the like. A mixture of 99% of
thorium oxide and 1% of cerium oxide seems best adapted for this purpose, as far
as my correspondents are at present informed.
The two phases of the process will now be described, first the preparation of
the core, and secondly the applying of the coating to the core.
PRODUCTION OF THE CORE.
Upon small rods, tubes or discs of glass or porcelain there is spread a solution
of a ceramic lustre of a highly infusible metal of the platinum group such as
ruthenium, rhodium, osmium, iridium. Lustrous preparations of these metals
may be prepared in an analogous manner to those of gold, silver and platinum.
The small rods, tubes or discs, and the like, are coated in straight or curved lines
or in any other form with the preparations and then burned in. Mixtures also of
different metals are suitable and form alloys which are produced in the manner
above described. When necessary the skin of metal thus formed can be
strengthened by electro-deposition.
Though known in the art, it may not be amiss to mention, that while the
lustres of the non oxidizable noble metals may be burned in without precaution
against oxidation, the lustres of the oxidizable metals, such as osmium, should
be burned in in a reduction flame, or better still in a closed muffle in the presence
of a reducing or neutral gas, such as illuminating gas, hydrogen or carbonic acid.
The next step is to detach the skin of the noble metals. In order to do that,
the glass or the porcelain must be removed, which is done very easily by treating
it with hydrofluoric acid, or even with hydrochloric acid (supposing that a
special kind of glass soluble in this acid has been used).
In doing so, it is not at all necessary that the whole glass, porcelain, etc., be
dissolved before one is able to draw the metal-strip off, but generally one
succeeds after short treatment with the hydrofluoric acid in taking the metal-
skin away just as easily, as for instance a postage stamp stuck on paper can
be removed from the latter by dipping it into water.
It is easily to be comprehended that the shape for the core of the incan-
descent bodies is determined by the design in which the lustrous preparation is
spread upon the foundation.
One applies the lustrous preparation in the shape of straight or curved lines
or ribbons and may avail one's-self of the skins after detaching either directly in
the shape obtained or for instance by producing previously a broader strip which
may be folded thus obtaining a smaller ribbon.
The finished incandescent bodies are connected with metal or carbon contacts
either by soldering or pinching if necessary after previously coppering the ends.
These incandescent bodies which are very durable, emit a brilliant light with a
current of suitable strength and may be used for lighting either exposed to the
air or in an exhausted bulb. As they always contain pure metal, they possess
sufficient conductibility.
APPLYING OF THE COATING TO THE CORE.
This core, produced as described, may be used in this form as incandescent body.
In order to strengthen its illuminating power, it may be coated with luminous
earthy metal oxide. This second step of the invention is carried out as follows:
Upon the core, formed as herein before described, of one of the highly infusible
metals of the platinum group, is applied a coating of a ceramic resin lustre of
the desired luminous earthy metal oxide such as a mixture of 99% thorium

page_text: oxide and 1% cerium oxide by dusting it on in the form of a powder, or by
painting on, or dipping into, or otherwise applying a solution or mixture of
said resin ceramic lustre with an ethereal oil, such as lavender oil. It is then
fired in the usual manner, and the result is an incandescent body adapted to
incandescent electric lighting, which consists of a core of one of the highly
infusible metals of the platinum group, covered with an adherent glass-like
coating of the oxide of luminous earthy metal.
A great practical difference is found in the behaviour of these resin com-
pounds of the luminous earthy metals and that of their usual soluble salts-
nitrates, acetates etc.-since with the latter when fired, the oxide is left behind as
a raw powder which has little adhesion, whilst with the resin compounds a very
adherent glass-like coating of oxide is produced.
The incandescent body can then be introduced into an electric circuit in the
usual manner and may be used as a substitute for the ordinary carbon filament
in a bulb, which in the case, that the core contains one of these metals of the
platinum group, which are oxidizable in the air, such as osmium, can be evacuated
or filled with a reducing or neutral gas, such as illuminating gas, hydrogen, or
carbonic acid. The core is heated by the electric current, and heats in its turn
the exterior coating of the luminous earthy metal oxide to incandescence.
The temperature to which the electric incandescent bodies are heated by the
current, being far higher than that reached by Auer's incandescent light, even
those kinds of earths for instance lime, magnesia, etc. can be employed of which
the power of light-emission is still trifling at the temperature of Auer-light,
but increases considerably at a higher temperature.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. The within described process of producing bodies suitable for incandescent
electric lighting, which consists: first, in wholly or partially covering a plate or
matrix of glass, porcelain, earthenware or the like with a lustrous preparation
of one or more of the highly infusible metals of the platinum group and burning
the same in; second, detaching the resultant metallic film from the plate or
matrix by the action of solvents which will attack the plate or matrix and not
the film; and third, forming the said metallic film into the desired shape.
2. The within described process of producing bodies suitable for incandescent
electric lighting, which consists: first, in wholly or partially covering a plate or
matrix of glass, porcelain, earthenware or the like with a lustrous preparation
of one or more of the highly infusible metals of the platinum group and burning
the same in; second, detaching the resultant metallic film from the plate or matrix
by the action of solvents, which will attack the plate or matrix and not the
film; third, forming the said metallic film into the desired shape; and fourth,
coating said so formed metallic film with ceramic resin lustre of one or more of
the luminous earthy metals and burning the same in.
1011
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