Improvements in the Mantles or Hoods of Incandescent Gas Burners.
Year: 1894

page_text: Date of Application, 6th Mar., 1894-Accepted, 7th Apr., 1394
COMPLETE SPECIFICATION.
Improvements in the Mantles or Hoods of Incandescent Gas
Burners.
We, LUDWIG KARL BÖHM Ph.D., Chemist, of 81, Nassau Street, in the City
of New York, and THERON CLARK CRAWFORD, Gentleman, of 17, Lenox Place,
New Brighton, in the County of Richmoud, and State of New York, United States
of America, 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 :-
Our invention relates to the mantles, hoods, or like devices used in connection with
gas and rendered incandescent by the combustion of the gas to increase the
illuminating effect. Such incandescent devices, to be successful, must be light and
at the same time durable and of sufficient substance and cohesion to stand
transportation and ordinary handling.
Our invention relates particularly to a composition of matter which, used in the
manufacture of such incandescent devices, produces an article having the qualities
above indicated. In this composition we employ magnesium oxide as the so-called
incandescent material or base. It is this material which, when heated, emits the
light but used alone it lacks cohesion so that there must be combined with it
another substance or substances for the purpose of making the hoods, mantles, or
other articles durable in use and reasonably strong for the necessary handling
incident to transportation and use. This substance, or these substances, are designed
to form a supporting skeleton of non-incandescent material and, obviously, in order
not to impair materially the incandescence these substances should constitute
as small a percentage of the mass as possible and at the same time secure reasonable
strength and durability.
It is the object of our present improvement to reduce the non-incandescent
material in hoods for incandescent gas lighting to a minimum and at the same time
secure sufficient strength in the hoods to make them suitable for transportation
and use.
This we accomplish by the use of a composition which we will now
describe.
The new composition material consists of magnesium oxide, silicic acid, and
preferably an alkali. In forming the composition we use of the first ingredient
about 90% of the second about 10%, and of the third from one to two per cent.,
but we do not limit ourselves to these exact proportions. For the third ingredient
-alkali-
i-we prefer potassium, either hydrate or carbonate. The silicic acid may
be replaced partly by phosphate of calcium or phosphate of magnesium which
would result in a mass containing magnesium oxide, silicic acid, alkali, and
phosphate of lime or phosphate of magnesium. The phosphate of calcium or
magnesium adds to the strength of the hoods made from this composition. These
substances help to build up the supporting skeleton in the hood and thereby
strengthen the same; in this result their action is similar to that of borax, but
they are preferable to the latter because they make a mixture not so easily fusible
by heat as with borax. The inaterial obtained by the described composition is
mixed with a suitable organic glutinous substance, in order to obtain a plastic mass,
and the hoods, mantles, or other articles are then shaped or moulded from this mass
and baked in suitable ovens.
The alkali may be added in solution to the glutinous substance and the latter
may be molasses or any like material. This modification in the manipulation, of

page_text: course contemplates no alkali in the first composition and is especially suitable in
case potassium hydrate is employed. When carbonate of potassium is used it may
be preferable to add it, in the form of dry powder, to the magnesium oxide.
The carbonates will then be reduced to potassium oxide during the process of
baking and, as such, it will combine with the silicic acid and magnesium oxide to
form a supporting skeleton in the greater mass of the magnesium oxide which is left
uncombined and which is the incandescent material emitting light. The composition
of silicic acid and potassium is silicate of potassium, but as such it is not found in
the finished article. Silicic acid forms with magnesium oxide, silicate of magnesium
and when some potash is present a more complicated silicate or compound silicate
is formed. This compound of silicate constitutes the supporting skeleton in the
greater portion of the magnesium oxide which is the incandescent material.
To form this composition which makes the supporting skeleton, only a small
percentage of the entire quantity of magnesium oxide is utilized only such a small
quantity of alkali being used as is necessary to combine with this small percentage
of the said oxide. By far the greater portion of the magnesium oxide is left free
and is the material which becomes incandescent in the practical use of the hood.
It will be understood of course that the proportion of silicic acid and alkali used is
sufficient to unite with only a comparatively small proportion of the magnesium
oxide, thus leaving a large percentage of the latter uncombined, as already
. stated.
Clays have been used for similar purposes. They contain silicic acid in
: combination with aluminum oxide and in a free condition as a mechanical mixture.
Uncombined silicic acid is found in clays in various quantities and, as silicic acid is
the principal substance which forms the supporting glazy skeleton in the mantles or
incandescent articles, these various quantities of said acid in the clay give burners
of various strength. For this reason pure silicic acid is more desirable as a mineral
binder for this structure. It forms, when precipitated by well known methods and
after complete drying, a dust-like powder and can in this condition be easily mixed
with magnesium oxide and the proportionate quantities thereof can always be
determined with accuracy. In our composition we are also relieved from the
presence of silicate of aluminum and other undesirable substances contained in the
clays. Furthermore, the presence of a small percentage of alkali serves to
strengthen the hood. It helps to build up a harder skeleton. This results from
the complicated or compound silicate mentioned above, which is formed by the use
of alkali and which has great power in resisting the destructive effect of a high
degree of heat.
We find that on using this composition for the manufacture of incandescent hoods
or mantles, we obtain an article having a strong, durable skeleton composed of a
simple or compound silicate of magnesium which holds and supports a comparatively
large mass of magnesium oxide. We therefore obtain a hood sufficiently strong
for practical purposes in transportation and use, of great durability in use in
connection with a suitable gas burner, and of great illuminating power owing to the
presence of so large a quantity of the incandescent material, which is magnesium
oxide. This large quantity of free magnesium oxide results from the manipulation
above described; as explained, silicic acid forms with magnesium oxide silicate of
magnesium, but if there is only a small quantity of silicic acid and a large excess of
magnesium oxide, as herein specified, the silicic acid cau form a combination with
only a small quantity of magnesium oxide while the remainder of the latter
substance remains free or uncombined. Of course the whole quantity of magnesium
· oxide can be combined with silicic acid if a sufficient quantity of the latter is
employed, but, as distinctly set forth above, this is not done, only so much of the acid
being used as will combine with a small percentage of the magnesium oxide. For
this reason a large quantity of magnesium oxide is present in the finished article
as such, free and uncombined, only enough of other substances, such as named, is
added and is necessary to form the chemical combination which provides a desirable
- material for a supporting skeleton.

page_text: The process for making incandescent hoods or mantles, consists in the mode of
preparing the plastic mass from which the hoods or mantles are to be made. In
the composition hereinbefore described, the incandescent material-magnesium
oxide is mixed with silicic acid and alkali. In this composition the pure silicic
acid in the form of dry dust-like powder, is used as the mineral binder for forming
the supporting skeleton. This powder is obtained by precipitating silicate of sodium
or potassium, or, as it is called "water-glass," by hydrochloric acid in the usual
way and then carefully washing out and drying the precipitate. This precipitate
is the anhydrous silicic acid (SiO2) which is dried at 120° centigrade, and is no
longer soluble in water or dilute acids and if heated more highly it becomes
insoluble in aqueous alkali. It therefore differs from the gelatinous silicic acid
(SiO³H2) not only in composition but also in quality and effect, as herein further
explained. The precipitated mass is at first in a gelatinous condition and it
requires several days to dry this mass so that it will form a dry dust-like powder
suitable for use.
From experiment and test we have discovered that the silicic acid may be used
in the gelatinous condition in which it is found when precipitated and that when so
used it presents a great practical advantage over the employment of silicic acid as
a dry dust-like powder. To carry out this part of our improvement we prepare a
saturated sugar solution and to about one part, by weight, of said solution add
about one quarter part of gelatinous silicic acid as it is obtained by precipitation
described above and without any drying; these ingredients are rubbed together
until a uniform product is obtained, and there is then added in small quantities
successively about one part of magnesium oxide and some alkaline element or
phosphate, as before described. The mass is rubbed together after the addition of
each quantity of magnesium oxide. The result is a plastic mass which gives
about 90% of magnesium oxide and 10% of silicic acid in the finished article
when the moisture and organic substances are burned out in baking ovens. This
mixture forms a plastic composition in which the silicic acid is evenly distributed
forming a continuous frame or skeleton and which is ready to be made up into
hoods or mantles without further manipulation and the hoods or mantles are
prepared therefrom either by spinning threads which form the hood, or by moulding
it into the required shape. The hoods or mantles are then baked in suitable ovens.
The sugar solution is highly saturated and prepared in a pure condition, so as to
avoid discoloration of the light by salts which are found in commercial molasses.
Organic substances are used as binders for making the mass plastic, as heretofore
described. Sugar solution has been described as the organic binder, but other
organic glutinous substances may be used in the place of sugar solution.
There is an important practical advantage in the use of silicic acid in a gelatinous
condition instead of a dry powder. A plastic substance is formed at once by the
mixture of the original elements, and this plastic mass will remain in a uniform
plastic condition for a considerable time. As already stated, it requires several
days to dry the precipitated silicic acid; if employed in the gelatinous condition, as
described, it requires a correspondingly long time to dry and consequently the mass
retains its plastic character longer than is necessary to work up any convenient
quantities in practice. In the use of the dry silicic acid, only a small quantity of
the plastic material can be made and utilized at once, for the mass hardens quickly,
so that it will soon become difficult to shape the hoods and after some time
impossible to do this. The hardened mass then has to be reduced to fine powder
and as such mixed with fresh powders to form a new mass. This difficulty is
completely overcome by the use of the silicic acid in gelatinous condition, because
it remains in a plastic state a much longer time; this permits a large quantity of
the material to be made up at once and then entirely worked up into hoods before
hardening prevents. The use of the acid in this gelatinous condition therefore
effects some saving in expense and also greatly facilitates the manipulation of the
compound in making hoods, and renders their production simpler and more practical
in a commercial way.

page_text: :
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that
what we claim is :-
1. A composition of matter for incandescent hoods, consisting of magnesium
oxide, silicic acid, and an alkali, substantially as described.
2. A composition of matter for incandescent hoods, consisting of magnesium
oxide, silicic acid, alkali, and phosphate of lime or magnesium, substantially as
-described.
3. The herein described process for making a composition for incandescent
hoods, the same consisting in first mixing gelatinous silicic acid, as it is formed by
precipitation, with a sugar solution and rubbing well together, and then adding
successive quantities of magnesium oxide and rubbing together until the mass is
uniform, the ingredients being in proportion substantially as specified.
4. In a process for forming a composition for incandescent hoods composed of
magnesium oxide, silicic acid, and an organic binder, the use of silicic acid in a
.gelatinous condition as formed by precipitation, substantially as described.
Dated this 6th day of Manah 1001
L. K. BÖHM,
T. C. CRAWFORD,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.