Improvements in the Manufacture of Incandescing Bodies or Mantles for Lighting Purposes.
Year: 1896

page_text: Date of Application, 30th June, 1896-Accepted, 12th Sept., 1896
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Incandescing Bodies or
Mantles for Lighting Purposes.
We, NIкODEм CARO, Ph.D. and Analytical Chemist, of 1 Roonstrasse, and
WILLY SAULMANN, Ph.D. and Analytical Chemist, of 26 Potsdamerstrasse,
both in Berlin, in the German Empire, 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, that is to say :-
Incandescing bodies, or mantles, as heretofore used, are produced by saturating
a fabric of organic or vegetable fibre with a solution of nitrate of thorium and
nitrate of cerium, and then calcining them. In this way a molecular mixture of
oxide of thorium and oxide of cerium is formed which, when heated to incan-
descence, possesses great power of emitting light. The incandescing bodies or
mantles produced in this way have, however, the defect that their power of
coherence is very small, as the powdery oxides do not give great strength to the,
mantles. Therefore, when used, the mantles get out of shape, and portions of the
powdery oxides break away, together with the gases, whereby the light emitting
power of the mantles is injured.
Our aim has been to find means which render it possible to produce durable
fabrics or mantles, without impairing the light emitting power of the same.
In the first instance, we would say that experiments have proved that the
emitting capacity of the mantles is not based on the existence of a compound of
cerium-thorium oxide, but that the presence of cerium, in other than oxide form, is
capable of bringing the oxide of thorium, which in itself does not emit light, to
incandescence.
If, for example, silicate of cerium is suspended in a solution of nitrate of
thorium, and the fabrics for the mantles be impregnated therewith, then, after
calcination, a skeleton will remain which is of great incandescing power, although
the nitrate of thorium alone, applied in the same manner, did not give an incan-
descing. body. As it is obvious that silicate of cerium will not become decomposed
on incandescence, this proves that the presence of a compound of cerium is capable
of imparting incandescing power to the thorium skeleton, even when it does not
form oxide after having been calcined.
But the application of silicate of cerium is impracticable, as, by the mere
suspension of the same in a solution of nitrate of thorium, it is impossible to obtain
uniformity, which is indispensible for the manufacture of incandescing bodies.
The production of silicates upon vegetable fibre itself is not practicable, because
of the presence of alkalis, which has to be avoided.
Now, according to our invention, we employ compounds of cerium which are
durable when incandescent, and yet can be obtained by solution in a crystalline
form upon the fibre itself. The compounds consisting of trivalent elements, such
as arsenic, antimony, bismuth, boron, vanadium, have been found suitable.
For example, if a solution of nitrate of cerium be mixed with a solution of
arsenic acid, the mixture will remain clear. If, however, it is boiled, or steamed,
the cerium arsenate will separate as a white crystalline precipitate.
With arsenic, the production of the incandescing bodies is as follows: The
fabric for the mantle is saturated with a solution of arsenic acid and nitrate of
cerium, and dried, whereby the arsenate of cerium separates in an insoluble form.

page_text: After this, the fabric is saturated with thorium nitrate, dried, and calcined, so that
a mantle is obtained which consists of thorium oxide and cerium arsenate.
If boric acid, or acids of the other bodies mentioned, be employed, the treatment
is the same:
Instead of boric acid, arsenic acid, etc., other compounds of these elements may
be taken, if these have the property of depositing from solutions in a crystalline
form.
The mantles produced according to this method or process are very durable, as
the arsenate, borate, etc., contained therein; being of crystalline form, renders them
more cohesive than the amorphic powdery oxides. For the same reasons, they
are much less influenced in their incandescing power than those produced as
heretofore:
Instead of the arsenates, borates, etc., basic compounds may be employed,
although they do not produce such durable fabrics as the cerium arsenate; and
instead of cerium, other rare earths, or their mixtures, may be employed.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. The improved method or process of producing incandescing bodies or mantles,
which consists in substituting for amorphous cerium oxide, compounds of cerium,
or other rare earths of trivalent elements which deposit upon the fabric in a
crystalline form, whereby greater durability and duration of the incandescence is
obtained, substantially as described.
2. Our improvements in the manufacture of incandescing bodies, or mantles, for
lighting purposes, substantially as hereinbefore described.
Dated this 30th day of June 1896.
ERNEST DE PASS,
Chartered Patent Agent;
78; Fleet Street, London, and 54, Market Street, Nottingham,
Agent for the Applicants.