Improvements in the Manufacture of Artificial Cryolite and similar Compounds.
Year: 1888

page_text: Date of Application, 22nd Aug.. 1888
Complete Specification Left, 2nd May, 1889-Accepted, 22nd June, 1889
PROVISIONAL SPECIFICATION.
[Communicated from abroad by Professor CLEMENS WINKLER, of Friesberg,
Germany.]
Improvements in the Manufacture of Artificial Cryolite and
similar Compounds.
I, Professor CURT NETTO, of The Alliance Aluminium Company, 1 Tokenhouse
Yard, in the City of London, Engineer do hereby declare the nature of this invention
to be as follows:-
My invention relates to the manufacture of artificial cryolite.
In extracting the aluminium from the mineral cryolite (6 Nu F1 + Al Fl) by
means of metallic sodium there are formed scoria or slags consisting in Na Fl
together with the flux applied at the melting.
The chief object of my invention is to provide an improved process for transforming
these slags into artificial cryolite or a double compound of sodium fluoride and
aluminium fluoride which may be employed for the production of metallic aluminium)
as well as for other purposes.
In carrying my said invention into practice I proceed in the following manner that
is to say melt the slags in proper proportion with sulphate of alumina (which for
convenience is first freed of the water it contains by previous heating).
1 then tap or remove in any other convenient way the molten mass from the
furnace or smelting vessel. This mass consists now of a mixture of a double fluoride
of sodium and aluminium which compound is not soluble in water, and of sulphate
of soda which easily dissolves in water.
In order to separate the compounds above mentioned I lixiviate or wash the
mass with hot water until a sample of the washing water shows no trace of sulphuric
acid.
The sulphate of soda contained in the water may be employed for any suitable
purpose. The solid residue consists of a crystalline powder which resembles the
mineral cryolite in its chemical composition.
un
This residue may be used for the production of metallic aluminium while the slag
of this operation may be transformed again into artificial cryolite and so
ad infinitum. The flux mixed with the cryolite on the extraction of the aluminium
usually consists of sodium or potassium chloride and does not interfere with the
process, and is washed out by water simultaneously with the soda sulphate.
In extracting the aluminium from the natural or artificial cryolite, a part of the
said cryolite remains undecomposed. This part is not altered by the regenerative
process, but remains at the end of the operation together with the recently produced
artificial cryolite.
If potassium is used for the extraction of the aluminium from the cryolite a double
compound of fluorine with potassium and aluminium is formed by the regenerative
process, which as well as the double compound of fluorine with sodium and aluminium
may be used for the extraction of metallic aluminium.
Instead of employing cryolite slags for starting the process. I can use artificial
sodium fluoride, which upon being melted with sulphate of alumina. gives rise to
the production of the double-salt of fluorine of sodium and aluminium and
sulphate of soda which therefore could also be used for the manufacture of artificial
cryolite.
111 00
1
J
21000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Artificial Cryolite and
similar Compounds.
1, Professor CURT NETTO, of 16 Lindenaustrass, Dresden, in the Empire of
Germany, 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 :-
In the extruction of aluminium from the mineral cryolite or from aluminium
fluoride by means of metallic sodium, there are formed scorice or slags which consist
chiefly of sodium fluoride together with the flux employed.
My invention is designed to provide for regenerating these slags or transforming
them into artificial cryolite, that is to say, into a double compound of sodium fluoride
and aluminium fluoride, which may be employed for the production of metallic
aluminium as well as for other purposes.
:
In carrying my said invention into practice, I proceed in the following manner,
that is to say I melt the slags with a suitable proportion of sulphate of alumina,
which for convenience is, by previous heating, freed from the water which it
contains. For this purpose I prefer to mix about 100 parts of slag with about
32 parts of dehydrated sulphate of alumina, when the following reaction will take
place :-
After the mass has been fully heated and liquefied, I remove the same in any
convenient manner from the furnace or smelting hearth. This mass consists of a
mixture of double fluoride of sodium and aluminium (which compound is not soluble
in water) with sulphate of soda, which easily dissolves in water.
In order to separate the compounds above mentioned, 1 lixiviate or wash the
mass with hot water until a sample of the washing water shows no trace of sulphuric
acid.
The sulphate of soda contained in the water may be disposed of in any suitable
manner. The solid insoluble residue consists of a crystalline powder which resembles
the mineral cryolite in its chemical composition.
This residue or artificial cryolite may now be used for the production of metallic
aluminium in the same manner as ordinary natural cryolite, and the slag resulting
from the process may be transformed into artificial cryolite, which may also be used
in the manufacture of metallic aluminium, and so on. The flux mixed with the
cryolite in the extraction of the aluminium usually consists of sodium or potassium
chloride, and does not interfere with the process, being washed out by the water
simultaneously with the soda sulphate.
In extracting the aluminium from the natural or artificial cryolite, a part of the
said cryolite may remain in excess and undecomposed. This excess will not be
affected by the regenerative process, but will pass through the same and be found at
the end of the operation together with the newly formed artificial cryolite.
If potassium instead of sodium is used for the extraction of the aluminium from
the cryolite, a double compound of fluoride of potassium and aluminium is formed
by the regenerative process, which, like the double compound of fluorine with sodium
and aluminium, may be used for the extraction of metallic aluminium.
Instead of commencing the process with slags obtained in the treatment of cryolite,
I can take sodium noride obtained from other sources, which, upon being melted
with sulphate of alumina, gives rise to the production of the double salt of fluoride
of sodium and aluminium on the one hand and sulphate of soda on the other hand, as
above mentioned. This double salt may then be used for the manufacture of
aluminium after the sulphate of soda has been washed out.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed as communicated to me by my
foreign correspondent I wish it understood that I claim
First: The process herein described of producing artificial cryolite by the treatment
of slag obtained in the manufacture of metallic aluminium from mineral or artificial
cryolite or from aluminium fluoride.
Second-The treatment of fluoride of sodium by the improved process herein
described.
Dated this 1st day of May 1889
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.