Year: 1896

page_text: I. PAUL EMILE PLACET, of 18 Rue Denfert-Rochereau, Paris, France, Engineer,
do hereby declare the nature of this invention to be as follows:-
Chromium sesquioxide is one of the most refractory bodies; it is also one of
the most insoluble bodies in silicates; it consequently resists perfectly the
corrosive action of molten metals and slags.
My invention consists in employing this material for the linings of crucibles
and for smelting and other furnaces, but I do not employ the same generally in
the condition of oxide formed in advance, I have found that it is much easier
and more advantageous to employ the salts or compounds of chromium which,
in melting and decomposing under heat leave on the surface and even in the
body of the crucible and furnace walls, a very adhering and resisting chromium
sesquioxide.
I obtain this result in employing in particular bichromates of magnesia, lime,
alumina, the bichromates of potass, soda, ammonia; chromium nitrate, chromic
acid, and all the compounds of chromium which, either alone or mixed with each
other dr with reducing bodies leave as residue after calcination chromium.
sesquioxide either pure or mixed with other refractory matters.
Various modes of operating can be adopted for lining crucibles and furnaces
with salts of chromium. For example, bichromate of potass can be melted in
the crucible to be lined, and the crucible be agitated for causing the melted salt
to well line its interior, after which it is calcined at a red heat.
There is thus obtained a magnificent green coating of chromium sesquioxide,
forming a very adhering lining to the crucible; moreover, this crucible is no
longer porous, it has become impermeable, which is very advantageous in many.
cases where perfect liquid materials have to be treated in the crucible.
The crucible to be lined may also simply be heated, to a sufficient degree, and
be then rolled in powdered bichromate, after which it is calcined as above
described.
A crucible may also have the lining formed therein by employing a concentrated
solution of bichromate of magnesia, lime, alumina, chromic acid, etc. The
crucible is dipped into this solution or the solution is poured into the crucible,
a deposit is allowed to be formed during several minutes, and the excess of liquid

page_text: is then poured off. In this way a large number of crucibles may be prepared in a
very short time, which are calcined when required for use.
The powder of a bichromate or other salt of chromium can be mixed with tar,
molasses, albumen, oil, etc., to form a kind of more or less liquid paste, which is
applied with a brush or trowel on to the surfaces to be coated with sesquioxide of
chromium. This is allowed to dry and is then calcined.
Bichromates, either in the form of powder or in solution, can be mixed with
refractory materials, such as magnesia, lime, dolomite, alumina, chrome-iron,
asbestos, etc., or with solvents such as chlorides, fluorides, cryolithe, phosphates
boric acid etc. such mixtures being applied by any of the means above referred
to, after which the crucible is calcined. These mixtures can also serve as cement
in the construction and repairing of furnaces.
The crucibles previously lined with carbon, magnesia, lime, alumina etc. in
the usual manner, become much stronger and resisting when they are coated with
sesquioxide of chromium by one of the means above described.
The linings of Bessemer converters, furnaces of all kinds even electrical fur-
naces, also muffles, earthenware tubes for chemical operations, refractory bricks,
earthenware or metal objects that require to be coated with refractory material,
such as casting ladles furnace doors, firehooks, boiler tubes etc., all become much
stronger and more resisting when they are coated with a chromium salt, which
is afterwards converted into sesquioxide of chromium. Concentrated solutions
of bichromates of magnesia, lime, alumina, etc., may also be injected into the
very narrow flues of certain furnaces for rendering them more resisting.
Dated this 15th day of December 1896.
ABEL & IMRAY,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Lining of Crucibles and Furnaces.
I, PAUL EMILE PLACET, of 18 Rue Denfert-Rochereau, Paris, 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 and by the
following statement:-
Chromium sesquioxide is one of the most refractory bodies; it is also one of
the most insoluble bodies in silicates; it consequently resists perfectly the
corrosive action of molten metals and slags.
My invention consists in employing this material for the linings of crucibles
and for smelting and other furnaces, but I do not employ the same generally in
the condition of oxide formed in advance; I have found that it is much easier
and more advantageous to employ the salts or compounds of chromium which,
in melting and decomposing under heat leave on the surface and even in the
body of the crucible and furnace walls, a very adhering and resisting chromium
sesquioxide.
I obtain this result in employing in particular bichromates of magnesia, lime,
alumina, the bichromates of potass, soda, ammonia; chromium nitrate, chromic
acid, and all the compounds of chromium which, either alone or mixed with each
cher or with reducing bodies leave as residue after calcination chromium
sesquioxide either pure or mixed with other refractory matters.
Various modes of operating can be adopted for lining crucibles and furnaces
with salts of chromium. For example, bichromate of potass can be melted in

page_text: the crucible to be lined, and the crucible be agitated for causing the melted salt
to well line its interior, after which it is calcined at a red heat.
There is thus obtained a magnificent green coating of chromium sesquioxide,
forming a very adhering lining to the crucible; moreover, this crucible is no
longer porous, it has become impermeable, which is very advantageous in many
cases where perfect liquid materials have to be treated in the crucible.
The crucible to be lined may also simply be heated, to a sufficient degree, and
be then rolled in powdered bichromate, after which it is calcined as above
described.
A crucible may also have the lining formed therein by employing a concentrated
solution of bichromate of magnesia, lime, alumina, chromic acid, etc.
The
crucible is dipped into this solution or the solution is poured into the crucible,
a deposit is allowed to be formed during several minutes, and the excess of liquid
is then poured off. In this way a large number of crucibles may be prepared in a
very short time, which are calcined when required for use.
The powder of a bichromate or other salt of chromium can be mixed with tar,
molasses, albumen, oil, etc., to form a kind of more or less liquid paste, which is
applied with a brush or trowel on to the surfaces to be coated with sesquioxide of
chromium. This is allowed to dry and is then calcined.
Bichromates, either in the form of powder or in solution, can be mixed with
refractory materials, such as magnesia, lime, dolomite, alumina, chrome-iron,
asbestos, etc., or with solvents such as chlorides, fluorides, cryolite, phosphates
boric acid etc. such mixtures being applied by any of the means above referred
to, after which the crucible is calcined. These mixtures can also serve as cement
in the construction and repairing of furnaces.
The crucibles previously lined with carbon, magnesia, lime, alumina etc. in
the usual manner, become much stronger and resisting when they are coated with
sesquioxide of chromium by one of the means above described.
The linings of Bessemer converters, furnaces of all kinds even electrical fur-
naces, also muffles, earthenware tubes for chemical operations, refractory bricks,
earthenware or metal objects that require to be coated with refractory material,
such as casting ladles furnace doors, firehooks, boiler tubes etc., all become much
stronger and more resisting when they are coated with a chromium salt, which
is afterwards converted into sesquioxide of chromium. Concentrated solutions
of bichromates of magnesia, lime, alumina, etc., may also be injected into the
very narrow flues of certain furnaces for rendering them more resisting.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
Process for the lining of furnaces crucibles and similar objects of earthenware
or metal that require to be rendered refractory or unattackable by molten metals
or scoria, which consists in employing the salts of chromium, such as the bichro-
mates of magnesia, of lime, of alumina of potass, or chromic acid or other com-
pounds of chromium which in becoming fused and decomposed by the heat, leave
on the surface and even in the substance of the crucibles, furnaces etc., a sesqui-
exide of chromium which is very adherent and very refractory the said substances
being employed either alone, or mixed with refractory materials, fluxes, organic
reducing compounds, or the like, substantially as described.
Dated this 6ith day of dust 1907
ABEL & IMRAY,
Agents for the Applicant.