Improvements in the Manufacture or Production Electrolytically of Coatings Composed of Earthy Oxides.
Year: 1895

page_text: Date of Application, 21st Dec., 1895
Complete Specification Left, 19th Sept., 1896-Accepted, 5th Dec., 1898
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture or Production Electrolytically of
Coatings Composed of Earthy Oxides.
I, RUDOLF LANGHANS, of 12 B, Elisabeth Strasse, Berlin, in the German Empire,
Electrical Engineer, do hereby declare the nature of this invention to be as
follows:-
:-
This invention relates to the production, by the aid of electrolysis and subsequent
calcination, of coatings composed of earthy oxides which are dense as well as perfectly
cohesive and adhesive; and it consists in an improvement whereby, on the one hand,
the preparation of the electrolytic bath is essentially simplified, and, on the other
hand, the hydroxide deposit is enabled to separate out under the action of currents
of weak density.
The invention is based on the fact that the aqueous solutions of the earthy water-
soluble hydroxides, on being subjected to the action of the electric current, behave in
a different manner according to the degree of their concentration. When the solution
is concentrated, it constitutes an electrolytical conductor which is so extremely
efficaceous that no deposit will be formed upon the negative electrode, whether the
current density employed be high or low, owing to the violent evolution of hydrogen
at said electrode. On the contrary, when a dilute solution is employed, a deposit of
insoluble hydroxide will be formed at once on the negative electrode, even with the
aid of a current of low density; the deposit thus produced constituting a uniform and
dense coating which is perfectly cohesive and adhesive of itself.
This discovery I make use of for coating bodies or foundations of any shape with
earthy oxides, for instance cone-shaped bodies constructed of platinum wire gauze or
of carbonised fibre for use as incandescent bodies with gas and other burners.
In the production of the coating, supposing the body to be coated to consist of a
platinum wire gauze cone, I proceed as follows:-I take a dilute solution of the
selected water-soluble hydroxide, for instance, the water-soluble hydroxide of thorium ;
in this solution, I dip the said platinum wire gauze cone, using the same as the
negative electrode and using as the anode an insoluble electrode, and I then subject
the said solution to the action of a current preferably of weak density, allowing the
deposit to assume such thickness as is required without filling the interstices of the
body. The coated cathode is thereupon removed from the bath, disconnected from
the negative pole of the source of electricity, dried and finally calcined.
The best results have hitherto been obtained by using a solution which contains
about 3 per cent. of the water-soluble earthy hydroxide-for instance, that of
thorium and treating it with a current the density of which is about 3 ampères per
100 square centimetres.
I wish it to be understood that in the foregoing the term "earth hydroxides and
oxides" is intended to cover the hydroxides and oxides of both the earth metals proper
and the earth alkali metals, as they manifest, in the form of their water-soluble
hydroxides, the same behaviour on being treated electrolytically.
To prevent the coating cracking or crazing in the calcining stage, and for imparting
porosity to the same, I dissolve in the watery solution of the water-soluble hydroxide
an organic base as such, that is to say, not in the form of a salt-for instance, opium,
morphine, quinine, cinchonine, bases of the veratrine class, strychinine, brucine,
piperine, bases of the pyridine class, &c., whereby in the electrolysing stage the negative
electrode is coated with an intimate mixture composed of insoluble earthy hydroxide
O

page_text: and organic base, the latter being destroyed by the action of the heat in calcining,
so as to leave a coating of pure oxide in a perfectly porous state. Or I may proceed
as described in the specification appended to my Application filed 3rd Dec., 1895,
No. 23,137, that is to say, by covering the body with combustible fibres previous to
electrolysing, or transforming the hydroxide deposit, previous to drying and calcining,
into such salts as are capable of parting with their acid under the action of heat.
Dated this 19th day of December 1895.
Improvements in the Manufacture or Production Electrolytically of
Coatings Composed of Earthy Oxides.
I, RUDOLF LANGHANS, of 12 B, Elisabeth Strasse, Berlin, in the German
Empire, Electrical 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 :-
This invention relates to the production, by the aid of electrolysis, and sub-
sequent calcination, of coatings composed of earthy oxides, which are dense as well
as perfectly cohesive and adhesive; and it consists in an improvement whereby, on
the one hand, the preparation of the electrolytic bath is essentially simplified, and,
on the other hand, the hydroxide deposit is enabled to separate out under the
action of currents of weak density.
The invention is based on the fact that the aqueous solutions of the earthy
water-soluble hydroxides, on being subjected to the action of an electric current,
behave in a different manner, according to the degree of their concentration.
When the solution is concentrated, it constitutes an electrolytical conductor, which
is so extremely efficaceous that no deposit will be formed upon the negative
electrode, whether the current density employed be high or low, owing to the
violent evolution of hydrogen at said electrode. On the other hand, when a dilute
solution is employed, a deposit of insoluble hydroxide will be formed at once on
the negative electrode, even with the aid of a current of low density; the deposit
thus produced constituting a uniform and dense coating which is perfectly cohesive
and adhesive of itself.
I make use of this discovery for coating bodies or foundations of any shape with
earthy oxides; for instance, cone-shaped bodies constructed of platinum wire
gauze or of carbonised fibre for use as incandescent bodies with gas and other
burners.
In the production of the coating, supposing the body to be coated to consist of a
platinum wire gauze cone, I proceed as follows:-I take a dilute solution of the
water-soluble hydroxide, for instance, the water-soluble hydroxide of thorium. In
this solution, I dip the said platinum wire gauze cone, using the same as the
negative electrode, and using as the anode an insoluble electrode. I then subject
the said solution to the action of a current, preferably of weak density; allowing
the deposit to assume such thickness as is required without filling the interstices
of the body. The coated cathode is thereupon removed from the bath, disconnected
from the negative pole of the source of electricity, dried and finally calcined.
Instead of forming the mantle or other body to be coated of platinum or gold, it
may be made of vegetable fibre, parchmentised, carbonised and then electro-plated
to increase its conductivity.
The best results have hitherto been obtained by using a solution which contains

page_text: about 3 per cent. of the water-soluble earthy hydroxide-for instance, that of
thorium and treating it with a current the density of which is about 3 ampères
per 100 square centimetres.
The water-soluble form of the earthy hydroxide may be prepared in the following
manner :-Oxide of thorium, obtained by calcination of the oxalate, is heated on a
water bath with excess of nitric or hydrochloric acid. On the excess of acid being
expelled, a residue which dissolves in water is obtained.
"
I wish it to be understood that in the foregoing, the term "earth hydroxides
and oxides is intended to cover the hydroxides and oxides of both the earth
metals proper and the earth alkali metals; as they manifest, in the form of their
water-soluble hydroxides, the same behaviour on being treated electrolytically.
To prevent the coating cracking or "crazing" in the calcining stage, and for
imparting porosity to the same, I dissolve in the aqueous solution of the water-
soluble hydroxide an organic base, as such; that is to say, not in the form of a
salt for instance, opium, morphine, quinine, cinchonine, bases of the veratrine
class, &c., whereby in the electrolysing stage, the negative electrode is coated
with an intimate mixture composed of insoluble earthy hydroxide and organic base,
the latter being destroyed by the action of the heat in calcining, so as to leave a
coating of pure oxide in a perfectly porous state. Or I may proceed as described
in the specification filed in pursuance of my Application for Letters Patent of the
United Kingdom, dated 3rd December, 1895, No. 23,137; that is to say, by
covering the body with combustible fibres previous to electrolysing, or by trans-
forming the hydroxide deposit, previous to drying and calcining, into such salts as
are capable of parting with their acid under the action of heat.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I claim :-
1. The manufacture of bodies adapted for use as incandescent mantles for gas-
burners and otherwise, by immersing, in an electrolyte, formed of a dilute solution
of a water-soluble hydroxide of an earth metal, a foundation composed of platinum,
gold, carbon or other suitable electro-conductive material, passing an electric
current of low density through the electrolyte, and depositing upon the foundation,
as a cathode, a coating of earthy hydroxide, which, by means of heat, is subsequently
converted into an earthy oxide.
2. In the production, by electrolysis and subsequent calcination, upon an electro-
conductive foundation and with the aid of a weak current, of coatings composed of
oxides of the earth metals, the employment of a dilute solution of a water-soluble
hydroxide of an earth metal, the body to be coated being immersed therein and
used as a cathode, whilst an insoluble electrode forms the anode, substantially as
herein described.
3. In the production by electrolysis and subsequent calcination upon an electro-
conductive foundation of coatings composed of oxides of the earth metals, the
herein described method of rendering the coating porous and of preventing
cracking, consisting in dissolving in an electrolyte of the character herein referred
to, an organic base or alkaloid, which, under the influence of the electric current
becomes deposited jointly with the hydroxide of the earth metal upon the negative
electrode, the former being destroyed upon the body being subjected to calcination,
substantially as herein described.