Improvements in the Metallurgy of Metallic Sulphates.
Year: 1893

page_text: Date of Application, 28th June, 1893
Complete Specification Left. 19th Apr., 1894-Accepted, 25th May, 1894
PROVISIONAL SPECIFICATION.
Improvements in the Metallurgy of Metallic Sulphates.
I WALTER MILLS of 20 Anstey Road, Peckham, London S.E. Analyst do
hereby declare the nature of this invention to be as follows:-
Certain metallic sulphates such as sodic, potassic, magnesic, aluminic, calcic
sulphate, on being heated emit sulphuric anhydride. I take advantage of this fact
in the following manner. For example I manufacture aluminium from its sulphate
by mixing with the sulphate any one or more of the following metals viz. zinc, tin,
copper, lead, sodium, potassium, iron. I do this either by powdering the metal and
mixing it with the powdered sulphate, or by placing the sulphate and the metal in
alternate layers in a crucible; in either case I then heat the crucible. Or I may
by some convenient means bring molten metal and the heated sulphate into contact,
and in some cases I employ the vapour of the metal for the same purpose.
I thus present to the molecule of the metallic sulphate, at the moment when it
emits the anhydride, some metal or mixture of metals which will combine with the
sulphur and oxygen of the anhydride, and with the oxygen of the metallic oxide
which is left when the anhydride has been emitted. In these circumstances the
metallic sulphate is converted into metal. The heat emitted by the decomposition
of the anhydride is so intense that it enables me in some cases to mix with the
metallic sulphate, before treating it, a quantity of metallic oxide; in this case I
increase the proportion of metal or mixture of metals as aforesaid, so as to reduce
the metallic oxide which is added to the sulphate.
Thus in preparing aluminium from aluminic sulphate with tin, I am able to mix
with the sulphate almost as much alumina as is already present in the sulphate,
taking the molecule of aluminic sulphate as Al,O,.(SO,). I therefore increase
the quantity of tin I use so as to reduce the added alumina to aluminium. In like
manner and with proper adaptation of the metal or mixture of metals employed to
the heats of the various reactions I prepare sodium, potassium, magnesium, calcium,
and other metals from their sulphates.
The sulphate must always be carefully dried before using it, and this drying is
generally best performed in vacuo.
Dated this 28th day of June 1893.
COMPLETE SPECIFICATION.
Improvements in the Metallurgy of Metallic Sulphates.
I, WALTER MILLS, of 20, Anstey Road, Peckham, in the County of Surrey,
Analyst, 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 has for its object the preparation and obtaining of metals either
from their sulphates, or from mixtures of metallic salts, some of them sulphates
which bring about the same result; this depends upon the thermal value of the
re-action-

page_text: combining with the sulphur and oxygen of sulphuric anhydride emits sufficient heat
to determine the reduction of the metallic salt that is used as a source of the metal
which it is wished to prepare. The re-action in question is always powerfully
exothermal, affording heat sufficient in some cases to fuse plumbago.
Inasmuch as I employ the "reducing metal" not only to combine with the
constituents of sulphuric anhydride, but also to reduce at the same time metallic
salts, it is important to state that I find, as the result of long investigation, the
following rule applies. Where the members of a group of metals combine with
another substance to form salts, the metal which emits the greatest amount of heat
during combination has the least absolute affinity for the salt-forming substance.
The following table shews at a glance what metals may be employed in reducing
any other oxide of the series.—

page_text: selected from the table given above. I find that for many practical reasons and
having regard to economy in carrying my invention into effect it is advantageous to
use iron in a levigated or powdered condition. I remove the dried mixture of alumina
and aluminic sulphate from the vacuum pan and grind it to a fine powder. I find that
a powder which will pass through a 60 mesh sieve is well adapted for my purpose.
The sifted mixture is then intimately mixed with the iron, and the compound
rammed into a crucible made of suitable refractory material such as the well-known
"Salamander" substance, and constructed on the same plan as the pots employed
for distilling zinc. When the crucible is filled to within a distance of about three
inches from its summit the lid is luted on, and the arrangement placed in a furnace.
Before heating, I pass through the apparatus a current of coal gas or similar
reducing gas so as to expel air and prevent oxidation of the metal as it volatilises.
Heat is then applied to the crucible; when thoroughly red hot decomposition of
its contents ensues, aluminium distils over and is collected in a receptacle placed
below the orifice of the crucible. The re-action is expressed by the following
formula, which I find gives excellent results, although the proportions indicated
may be slightly modified:
It will be understood that, in preparing aluminium and other metals by my invention,
while I find it very advantageous to use iron, I do not confine myself to the use of
that metal as a "reducing metal." Other metals may be selected from the table
already given as above indicated in order to effect the same purpose. In the cases
where potassium, sodium, or zinc is used to prepare aluminium, the proportion of
alumina that is added to the aluminic sulphate may be augmented very considerably;
if tin or lead is employed as a "reducing metal" the amount of alumina that can
be added must be proportionately diminished. Iron may, as above stated, be used
with special advantage as it is difficult to distil the metals prepared by this
invention when other metals are employed as a "reducing metal," and as I find iron
the most convenient and practical "reducing metal" to employ, I have therefore
confined myself to a description of its action in this Specification.
Barium occurs in nature as an anhydrous sulphate, and may be readily precipitated
from solutions in a fine state of division. In this state 1 mix it dry with the proper
I
proportion of levigated iron, and then distil it in the same way as prepare
aluminium. A very strong heat is required to bring about the reaction-
15 and at the same time to volatilize the metal; in order to avoid the use of extreme
external temperatures I therefore add to the mixture a quantity of ferrous sulpha:e
and iron. The reaction-

page_text: the reaction expressed by the following formula is advantageous :—
BaSO, 3 FeSO4 + 17 Fe 16 FeO + 4 FeS + Ba.
.Similarly to the case of aluminium, a mixture of baric oxide and ferrous sulphate
may be used. I find that the proportions of these substances indicated by the
following formula give very satisfactory results :-
BaO+3 FeSO4 + 13 Fe = 13 FeO + 3 FeS + Ba.
The subsequent treatment of the mixed substances is the same as in the case of
aluminium and so for the other metals prepared by this invention.
In like manner to barium, and with almost the same proportions of ingredients [
prepare metallic calcium. I also prepare magnesium either from its sulphate or
oxide in a similar manner and with about the same proportions of ingredients. I
prepare potassium and sodium from their sulphates in like manner to barium, but
more easily, perhaps because these metals form sulphates which would seem to
commence to emit sulphuric anhydride at a lower temperature than the sulphates
of barium, calcium and magnesium. I find that potassium and sodium readily
volatilize at a full external red heat, using in the case of potassium about the same
proportions of the substances that I employ in making barium, and in the case of
sodium about half the quantity of ferrous sulphate and a correspondingly less
quantity of iron. Potassium and sodium may be collected and condensed in an
iron worm or tube surrounded with boiling water, as no explosive by-product is
formed in either case.
In performing the foregoing operations a quantity of ferrous sulphide is
produced, and carried by the respective metals as they volatilize to the top of the
mass of substance in the crucible. From this it may be readily separated either in
a hot or cold state. I deal with it as follows. Part of it I grind when cold to a
fine powder and mix it with finely powdered litharge. I then place this mixture
in a closed iron crucible and make the mass red hot. The following reaction
takes place :-
FeS + PbO = PbS + FeO.
The plumbic sulphide so produced is converted into metallic lead in the usual
way; the fumes of sulphurous anhydride which are given off are conducted into a
chamber where they are brought into contact with hydric sulphide, which I prepare
in the well known manner from sulphuric acid and the remainder of the ferrous
sulphide. In these circumstances the two gases are decomposed, sulphur is deposited
and water produced.
I now crush the ferrous oxide to powder and mix it intimately with finely ground
charcoal or coke. On heating this mixture to a dull red heat, out of contact with
air, the terrous oxide is reduced to metallic iron in a levigated condition, with
evolution of carbonic oxide gas.
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 method of preparing and obtaining metals by decomposing their salts in
the presence of sulphuric anhydride and a "reducing metal," substantially as
herein described.
2. The method of preparing and obtaining aluminium, barium, calcium,
magnesium, potassium and sodium by the use of sulphuric anhydride and a
reducing metal" such as iron and other metals above referred to, substantially as
herein described.
61
3. The preparation of aluminium, barium, and calcium by a process of distillation
such as is herein described.

page_text: 4. The method herein described of mixing together aqueous aluminic sulphate
and alumina and drying the same in vacuo.
5. The use of the sulphuric anhydride of a metallic sulphate in the presence of a
metal or mixture of metals, as an exothermal agent in the preparation and obtaining
of metals from their salts, as herein described.
Dated this 18th day of April 1894.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.