Process for the Separation and Precipitation of Salts of Iron and Zinc from Solutions Containing both.
Year: 1894

page_text: Date of Application, 8th Mar., 1894 Accepted, 13th Oct., 1894
Process for the Separation and Precipitation of Salts of Iron and
Zinc from Solutions Containing both.
A communication from EMILE WARZEE, Ex-Receveur de l'Enregistrement et
des Domaines (pensioned), 42, Rue Metseys, Brussels, in the Kingdom of
Belgium.
I, Alfred JULIUS BOULT of 323 High Holborn in the County of Middlesex,
Chartered Patent Agent, 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 separation and precipitation of salts of zinc and iron from a solution in
which both are contained has hitherto been practicable only by the employment of
costly reagents (hydrogen-sulphide, ammonium-sulphide, etc.) so that these
processes of recovery have been practically applied solely in analyses in laboratory
work, and possessed no industrial value.
As an example, I will take a solution constituted as follows:-
FeCl + FeCl2 + 2 ZnCl2 + aq.
1
The solution therefore consists of a mixture of ferric chloride, ferrous chloride, and
zinc chloride.
The problem of the separation of zinc and iron depends thereon, that all zinc is
obtained in the form of soluble zinc-chloride, and all iron in the form of insoluble
ferroso-ferric oxide.
In order to initiate the process, this mixed solution must have added to it just so
much of the more electro-positive metal (Zn) as corresponds to the electro-positive
salt so that the more electro-negative salts-in this case the ferric and ferrous
chlorides may be decomposed and converted to the ferroso-ferric oxide (black
oxide of iron Fe,O₁) an oxygen compound which is here insoluble and is at once
precipitated.
By this preliminary addition of metallic zinc a solution is formed which
essentially contains zinc-chloride; but which nevertheless is of a strong green
colour, an indication that a certain quantity of the ferrous-chloride is still present
in the zinc-chloride solution.
At the bottom of the vessel used for the process a quantity of the brownish-
black ferroso-ferric oxide Feз, O, is found, which represents the remainder of the
iron-salts, so far decomposed, and is their equivalent.
Zinc must now be added in excess to the solution which is then brought to the
boiling-point, being meanwhile subjected to the action of a strong air-current
blown into it.
After boiling, under these conditions for a period of from 12 to 20 hours, the
solution previously green (as stated) becomes colourless, i.e., the green colour of the
ferrous-chloride disappears, which is a sure proof that the zinc-chloride is now
entirely freed from iron-salts.
The process which is the basis of this change may be expressed in the following
chemical equation ;-

page_text: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is ;-
A process for the separation and precipitation of iron salts and zinc salts from a
solution which contains an admixture of both consisting in
1. The addition of such a quantity of the more electro-positive metal zinc (i.e. the
metallic base of the electro-positive salts) as will suffice to bring out the
decomposition and the reduction of the electro-negative or iron salts with
the consequent formation and deposition of a new and insoluble oxygen compound.
2. Submitting the solution thus transformed into a mixture of zinc-chloride and
ferroso-ferric oxide and after a further addition of zinc in suitable quantity to a
process of boiling in the presence of a strong current of air blown through it for a
period of from 12 to 20 hours in order to liberate by decomposition and precipitation
the last remaining particles of ferrous-chloride, yet remaining with the zinc
chloride.
Dated this 8th day of March 1894.
W. P. THOMPSON & BOULT,
Agents for the Applicant.