A Process for the Production of Pure Double Chlorides of Aluminum.
Year: 1889

page_text: Date of Application, 4th Feb., 1889
Complete Specification Left, 4th Nov., 1889-Accepted, 7th Dec., 1889
PROVISIONAL SPECIFICATION.
A Process for the Production of Pure Double Chlorides of
Aluminum.
I, HAMILTON YOUNG CASTNER Managing Director of The Aluminium Company
Limited of 115 Cannon Street in the City of London, do hereby declare the nature
of this invention to be as follows :-
The object of this Invention is to purify the anhydrous double chlorides of
aluminium.
Although reference is only made herein to the double chloride of aluminium and
sodium it will be evident that the process is equally applicable to other double chloride
compounds of aluminium.
In the production of metallic aluminium from the double chloride (by the action
of sodium or otherwise) it is of great importance that this compound should be
pure.
The double chloride of aluminium and sodium is now generally manufactured by
passing chlorine gas over or through a highly heated mixture of alumina carbon and
salt contained in fire clay retorts. The double chloride formed by reaction being
distilled and condensed in receivers attached to the said retorts through which the
vapours are made to pass.
In manufacturing the double chloride in this manner it becomes much contaminated
with Ferrous and Ferric chloride produced by the action of the chlorine gas upon the
iron contained in the materials composing the charge and also contained in the fire
clay of which the retorts are composed.
In the subsequent treatment of this impure double chloride with sodium for the
production of aluminium both the chlorides of iron and aluminium are reduced to
the metallic state, yielding an aluminium of inferior quality due to the presence of
iron, the proportion of the same in the aluminium produced depending upon the
quantity of iron contained in the crude chloride employed.
So far as I am aware prior to my present invention no one has devised means
for eliminating the iron from the double chloride and this most desirable result is
what I effect.
To this end my invention consists in the treatment of impure double chloride by
either aluminium, sodium or potassium in such proportions as will only decompose
the chlorides of iron and precipitate the iron in a metallic form leaving the doublo
chloride pure.
To affect this purification it is generally desirable that the crude chlorides be
melted and to the molton bath sufficient aluminium (in any convenient form) be
added to combine with all the chlorine contained in the Ferrous and Ferric chlorides
in the charge.
The aluminium added reacts at a low temperature upon the iron chlorides forming
metallic iron and chloride of aluminium the metallic iron separates and settles from
the molten chloride and the pure chloride may be poured off or removed.
Instead of metallic aluminium being added to precipitate the iron either sodium or
potassium may be employed and where this is done only enough of the alkali metal
(preferably sodium) is added to combine with all the chlorine present in the iron
chlorides-The alkali metal acts partially on the iron and aluminium chlorides pro-
ducing chloride of the alkali metallic iron and metallic aluminium while the aluminium
so produced reacts on the balance of the iron chlorides producing metallic iron and
aluminium chloride.
In either case the double chloride after treatment is thoroughly purified from iron.

page_text: Other metals capable of reducing iron from its chloride may he substituted for the
precipitation of the iron but in this case the product would contain the chloride of the
melaf used.
Dated this 4th day of February 1889.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London, Applicant's Agont.
COMPLETE SPECIFICATION.
A Process for the Production of Pure Double Chlorides of
Aluminium.
I, HAMILTON YOUNG CASTNER, Managing Director of The Aluminium Company
Limited of 115 Cannon Street in the City of London, 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 :—
The object of this invention is to purify the anhydrous double chlorides of
aluminium.
Although reference is only made herein to the double chloride of aluminium and
sodium it will be evident that the process is equally applicable to other double chloride
compounds of aluminium, such for instance as the double chloride of aluminium and
potassium.
In the production of metallic aluminium from the double chloride (by the action
of sodium or otherwise) it is of great importance that this compound should be
pure.
The double chloride of aluminium and sodium is now generally manufactured by
passing chlorine gas over or through a highly heatel mixture of alumina carbon and
salt contained in fire clay retorts. The double chloride formed by reaction being
distilled and condensed in receivers attached to the said retorts through which the
vapours are made to pass.
In manufacturing the double chloride in this manner it becomes much containinated
with ferrons and ferric chloride produced by the action of the chlorine gas and carton
monoxide upon the iron contained in the materials composing the charge and also
contained in the fire clay of which the retorts are composed.
In the subsequent treatment of this impure double chloride with sodium for the
production of aluminium both the chlorides of iron and aluminium are reduced to
the metallic state yielding an aluminium of inferior quality due to the presence
of iron, the proportion of the same in the aluminium produced depending upon the
quantity of iron contained in the crude chloride employed.
So far as I am aware prior to my present invention no one has devised means for
eliminating the iron from the double chloride and this most desirable result is what
I effect.
To this end my invention consists in the treatment of impure double chloride by
either aluminium, sodium or potassium in such proportions as will only decompose
the chlorides of iron and precipitate the iron in a metallic form leaving the double
chloride pure.
To effect this purification it is generally desirable that the crude chlorides be molted
and to the molten bath sufficient aluminium (in any convenient form but proferably
in a fine state of division) be added to combine with all the chlorine contained in the
ferrous and ferric chlorides in the charge. The aluminium addod reacts at a low
temperaturo (say slightly above the melting point of the chloride) upon the iron
chlorides forming metallic iron and chloride of aluminium, the metallic iron separates
and sotiles from the molten chloride and the pure chloride may he poured off, filtered
or redistillod.
As an example may state that good results may be obtained in the following
manner. A known quantity, say 1000 pounds of the crude chloride being placed in a

page_text: large iron vessel and melted, a sample should be taken and testod as quickly as
possible to determine the amount of iron. Assuming that the test shows 5 (one half
of one) per cent. it will then at once be evident that there is a total quantity of
5 pounds of iron combined with chlorine in the form of chloride in the charge. As
the amount of ferrous chloride is usually small it may generally be taken as being
all in the form of ferric chloride and as the determined quantity of iron is 5 pounds
and this is equivalent to 14.51 pounds of ferric chloride it is at once known that there
is 9-51 pounds of chlorine to be separated or extracted from its combination with the
iron, and to effect this will require 2.44 pounds of aluminium.
The reaction may be stated thus:-
=
14:51 pounds of ferric chloride + 244 pounds of aluminium
11.95 pounds of
aluminium chloride + 5 pounds of metallic iron; or in chemical symbols :

page_text: 2. The process of purifying anhydrous double chlorides of aluminium from iron by
the addition of a metallic substance having a greater affinity than iron for chlorine
and precipitating the contained iron in a metallic state substantially as herein
described.
Dated this 4th day of November 1889.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London, Applicant's Agent.