IMPROVEMENTS IN THE TREATMENT OF COMPOUNDS OF ALUMINIUM FOR THE PURPOSE OF OBTAINING THEREFROM ALUMINIUM OR ALUMINIUM BRONZE AND IN THE MEANS EMPLOYED IN THE SAID TREATMENT
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by John Henry Johnson at the Office
of the Commissioners of Patents on the 9th June 1883. Communicated to
him from Julien Varin a person residing at Paris in the Republic of France.
JOHN HENRY JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex,
Gentleman "IMPROVEMENTS IN THE TREATMENT OF COMPOUNDS OF ALUMINIUM
FOR THE PURPOSE OF OBTAINING THEREFROM ALUMINIUM OR ALUMINIUM BRONZE
AND IN THE MEANS EMPLOYED IN THE SAID TREATMENT a communication to me
from Julien Varin a person residing at Paris in the Republic of France
"
This Invention relates to an improved process and means for the production of
Aluminium on a large scale with facility and economy by the employment of
electricity applied as hereinafter described.
According to this invention electric currents generated by magneto or dynamo
electric machines are employed to decompose compounds of aluminium such for
example as the double chloride of Aluminium and sodium in a state of fusion. It
is evident that if chloride of Aluminium alone were simply decomposed by means
of electricity Aluminium would be deposited at the negative electrode whilst
chlorine would be liberated at the positive electrode but as chloride of Aluminium
volatilises before melting it cannot be employed alone and requires to be
combined with other elements as hereinafter explained. It is also desirable to
maintain the bath of fused materials constant. This result is obtained according
to this invention by means of soluble positive electrodes prepared as hereinafter
explained
The aluminiferous bath that is subjected to the action of electrolysis is preferably
composed of the double chloride of aluminium and sodium which is perfectly fluid
when melted and presents but slight resistance to the passage of electricity but
other similar compounds of aluminium such as the Buoride bromide and the like
may also be employed being rendered more fusible if necessary by a suitable
addition of Chloride. The bath may be readily purified from any foreign metallic
matter which it may contain by the action of the same current these matters being
deposited with the first layers of Aluminium so that it is simply necessary to employ
a tempory negative electrode at first and to exchange it for a fresh one directly the
aluminium is deposited in a condition of purity.
1
In order to preserve the constancy of the bath chloride alone may be introduced

page_text: from time to time in order to replace that which has been decomposed by the
current. In this case a closed vessel must be employed in order to enable the
chlorine liberated to be collected and conducted to the retort in which the supply
of chloride is prepared but it is preferred to employ a positive electrode composed
of an intimate mixture of carbon and alumina so that the chlorine in place of
escaping combines with the aluminium of the alumina and regenerates the
decomposed chloride whilst the oxygen resulting from the reduction of the alumina
unites with the carbon causing a regular production of oxide of Carbon which may
be got rid of without difficulty.
The alumina employed in the preparation of these electrodes should be as pure as
possible and is mixed with about ten per cent of its weight of purified wood
charcoal in powder together with a small quantity of water.
Sufficient tar or
bitumen is then added to agglomerate the ingredients and this mixture is triturated
and pugged so as to obtain a perfectly homogeneous mass. This is then moulded
into rectangular plates under a powerful pressure so as to expel nearly all the
water. After drying, the plates are set on end in pots such as blacking pots, being
separated from each other by powdered charcoal to prevent them from adhering or
becoming distorted. These pots are covered and placed in a reverberatory furnace.
The aluminous carbon thus obtained is hard sonorous and an excellent conductor
but is highly hygrometric so that it is adviseable to use it directly it is removed
from the pots and while it is yet hot.
The negative electrodes upon which the metal is deposited may be made of any
suitable materials such as retort charcoal or of thin plates of aluminium roughly
rolled which latter need not be separated from the metal deposited thereon being
melted down with the same.
By employing a sheet of copper as the negative electrode which is melted with
the deposited aluminium, aluminium bronze may be obtained.
The bath of the double chloride is maintained in a state of fusion in troughs
preferably constructed of sheet iron enamelled internally and maintained at a
suitable temperature by the flame of a special furnace supplementing the heat
afforded by the waste gases from the reverberatory furnace herein before referred to
or otherwise. These troughs are closed by suitable covers so as to keep the
contents clean and collect the oxide of carbon and enable it to be conducted to the
furnace.