Year: 1889

page_text: Date of Application, 22nd Jan., 1889
Specification Accepted, 23rd Mar., 1889
I EUGÈNE AUGE, of 6 rue Barraleric, Montpellier, in the Republic of France, Civil
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 :-
My Invention of improvements in the manufacture of salts of alumina has for its
object obtaining these salts freed from iron by means of an improved method of
treatment as hereinafter described. The direct treatment of aluminous minerals
such as kaolin clay and proferably bauxite with sulphuric acid yields a product
containing an objectionable per centage of iron. Many attempts have been made to
discover efficaceous and economical means for separating the aluminic salts from the
salts of iron with which they are associated and which render them unfit for certain
purposes.
The desired result is obtained according to this invention by means of a process
which is carried out in practice as hereinafter described.
About one hundred and sixty parts by weight (or say 1600 kilos for example) of
sulphuric acid at about 50 degrees Beaumé from the acid chambers are placed in a
tank lined with lead and of relatively large capacity (about 9 or 10 cubic yards).
About ten parts by weight (or 100 litres) of water being preferably water resulting
from previous operations are added so as to reduce the density of the acid to about
45 degrees Beaumé after which the acid is heated by means of a jet of free steam
and when the temperature has been raised to at least about 90 degrees Centigrade
about seventy parts (or 700 kilos) of the aluminous mineral such as finely pulverised
bauxite are thrown in, care being taken to stir the mixture for some minutes. After
a short interval a violent reaction takes place and the mixture increases considerably
in volume and would overflow the sides of the tank if the precaution were not taken
to make it of the large capacity hereinbefore indicated. The mixture afterwards
gradually resumes its original volume and from this time the mass must be allowed
to remain for about five hours in the same tank after which water being preferably
water from previous operations is added to the product now composed of sulphate of
alumina solution and such bauxite as the acid has not acted on. The solution is then
run off into a settling tank.

page_text: If the whole of the iron originally contained in the bauxite is not converted¡ to
the condition of peroxide some oxidising agent such as nitric acid, a nitrate, or the
like, must be added during the reaction in order that the iron may be thoroughly
peroxidised.
The quantities specified in this example are merely given for the sake of explaining
how the proportions are to be regulated in working the invention in practice on a
large scale. Both the foregoing and the following proportions may be varied
according to circumstances. For example the quantity of bauxite must be regulated
according to its richness and the degree or fineness of the pulverisation. In certain
cases sixty parts (or 600 kilos) or even less of bauxite may be employed with the
hundred and sixty (or 1,600 kilos) of acid hereinbefore specified but it is indispensable
to cause the whole of the iron to be peroxidised and that in the solution obtained
there are no traces of free sulphuric acid.
When the solution of sulphate of alumina is introduced into the settling tank its
temperature is from about 40 to 60 degrees Centigrade. About eight and a half
(85 kilos) parts of bauxite such as that employed in the first stage is then introduced
and then a potassic salt, sulphate, oxide, carbonate, or potash, alum or the like, is
added. Alum being usually produced in sulphate of alumina works, impure or
refuse alum is preferably employed for this purpose the quantity being regulated
according to the quantity of iron to be precipitated. In the case of bauxite containing
from four to five per cent. of peroxide of iron for example from about 5 to 6 parts
by weight (50 to 60 kilos) is a suitable quantity to employ for the proportions
hereinbefore specified.
The solution is energetically stirred and then allowed to stand for a time. The
iron is eliminated slowly. At the end of a fortnight the per centage of iron
represented at first by 0-80 per cent. of peroxide of iron is reduced to less than 0.00015
and after 25 days it is quite inappreciable.
In place of the 85 kilos of bauxite (which are not wasted being put in the reaction
tank in a subsequent operation) a corresponding quantity of pure hydrate of alumina
may be employed.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The employment of a potassic salt and hydrate of alumina or bauxite in order
to precipitate the iron in a solution of sulphate of alumina containing no free acid
the said iron having been previously peroxidised substantially as hereinbefore
described.
2. The improvements in the manufacture of salts of alumina substantially as heroin-
before described.
Dated this 0-1
T
1000