IMPROVEMENTS IN AND RELATING TO SEPARATING FERROCYANIDES OF IRON FROM LIQUIDS CONTAINING THE SAME, ESPECIALLY APPLICABLE IN REMOVING THE BLUE COLOUR LEFT AFTER PRECIPITATING IRON FROM ALUMINOUS OR OTHER SOLUTIONS BY MEANS OF SOLUBLE FERROCYANIDES." PROVISIONAL SPECIFICATION
Year: 1880

page_text: LETTERS PATENT to William Chadwick, Thomas Chadwick, and James
"
Chadwick, all of Manchester, in the County of Lancaster, and Josiah
Wickliffe Kynaston, of Liverpool, in the same County, for an Invention of
IMPROVEMENTS IN AND RELATING TO SEPARATING FERROCYANIDES OF IRON
FROM LIQUIDS CONTAINING THE SAME, ESPECIALLY APPLICABLE IN REMOVING
THE BLUE COLOUR LEFT AFTER PRECIPITATING IRON FROM ALUMINOUS OR
OTHER SOLUTIONS BY MEANS OF SOLUBLE FERROCYANIDES."
PROVISIONAL SPECIFICATION left by the said William Chadwick, Thomas
Chadwick, James Chadwick, and Josiah Wickliffe Kynaston at the Office of
the Commissioners of Patents on the 27th August 1880.
WILLIAM CHADWICK, THOMAS CHADWICK, and JAMES CHADWICK, all of
Manchester, in the County of Lancaster, and JOSIAH WICKLIFFE KYNASTON, of
Liverpool, in the saine County. "IMPROVEMENTS IN AND RELATING TO SEPARATING
FERROCYANIDES OF IRON FROM LIQUIDS CONTAINING THE SAME, ESPECIALLY
APPLICABLE IN REMOVING THE BLUE COLOUR LEFT AFTER PRECIPITATING IRON
FROM ALUMINOUS OR OTHER SOLUTIONS BY MEANS OF SOLUBLE FERROCYANIDES."
This Invention has for its main object the more complete and rapid separation
from aluminous solutions of the blue precipitate produced by ferrocyanides in
slightly ferruginous solutions in our process for producing sulphate of alumina,
Patented No. 4078 of 1879. It will however be found useful for separating
ferrocyanides from other solutions.
We pointed out in the Specification of said Patent that the almost imponderable
precipitate of ferrocyanide of iron, or Prussian blue, which remains suspended in
these solutions after the greater part has fallen out, and is irremovable by gravitation
even when the solution is allowed to stand at rest for a considerable period, is
perfectly removed at a later stage of our process, when the arsenic present is
precipitated by means of sulphuretted hydrogen or a sulphide decomposable by the
aluminous solution. In this case the impalpable blue precipitate is completely
enveloped by the sulphide of arsenic, and the two precipitates subside together, and
the ferrocyanide so removed is irrecoverable advantageously for further use.

page_text: Our present improvement in carrying out this process consists in adding to the
blue mixture a minute proportion of a metallic salt, such as the sulphate of copper
or zinc.
We find that the addition of not exceeding three pounds of either of
these salts to the ton of hydrated sulphate of alumina contained in the solution is
sufficient, without producing chemical decomposition of the ferrocyanide, to produce
an aggregation of the previously imponderable particles of blue, and that which
prior to the addition of the copper or zinc salt has the appearance of a blue
solution is afterwards seen to be a colourless solution with the blue particles
floating in it. The blue precipitate now rapidly subsides, is collected, washed, and
by treatment with lime reconverted into ferrocyanide of calcium for subsequent
use for the removal of a further quantity of iron.
We prefer to use in this improved process the sulphate of copper for the reason
that the trace of copper thus introduced into the aluminous solution is perfectly
removed again in the subsequent treatment of the solution for the removal of
arsenic by means of sulphuretted hydrogen or other sulphide.
A similar course to the above is adopted in removing the ferrocyanides of iron
from other solutions not aluminous.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Chadwick, Thomas Chadwick, James Chadwick, and
Josiah Wickliffe Kynaston, in the Great Seal Patent Office on the 25th
February 1881.
WILLIAM CHADWICK, THOMAS CHADWICK, and JAMES CHADWICK, all of
Manchester, in the County of Lancaster, and JOSIAH WICKLIFFE KYNASTON, of
Liverpool, in the same County. "IMPROVEMENTS IN AND RELATING TO SEPARATING
FERROCYANIDES OF IRON FROM LIQUIDS CONTAINING THE SAME, ESPECIALLY
APPLICABLE IN REMOVING THE BLUE COLOUR LEFT AFTER PRECIPITATING IRON
FROM ALUMINOUS OR OTHER SOLUTIONS BY MEANS OF SOLUBLE FERROCYANIDES."
This Invention has for its main object the more complete and rapid separation
from aluminous solutions of the blue precipitate produced by ferrocyanides, or
double cyanides of iron and another base, in slightly ferruginous solutions in our
process for producing sulphate of alumina Patented No. 4078 of 1879. It will
however be found useful for separating ferrocyanides from other solutions. In our
process in cases where we find proto-salts of iron present we find it advantageous
to oxidize by means of chlorine the yellow prussiate or ferrocyanide ordinarily
used so as to convert it partially into the red prussiate.
We pointed out, too, in the Specification of said Patent, that the almost
imponderable precipitate of prussiate of iron or Prussian blue which remains
suspended in these solutions after the greater part has fallen out, and is irremovable
by gravitation even when the solution is allowed to stand at rest for a considerable
period, is perfectly removed at a later stage of our process when the arsenic present
is precipitated by means of sulphuretted hydrogen or other sulphide.
In this case
the impalpable blue precipitate is completely enveloped by the sulphide of arsenic,
and the two precipitates subside together, and the ferrocyanides so removed are
irrecoverable advantageously for further use.
In some cases however there is not sufficient arsenic left in the solution to form
a precipitate, and in other cases where arsenic is not used a precipitation of finely
suspended ferrocyanide of iron is required. In these cases we add a small quantity,
a little at a time, of sulphate of copper or sulphate of zinc. These have apparently
no chemical action on the ferrocyanide of iron, as iron will actually take ferrocyanic
acid from copper when finely suspended ferrocyanide of copper is shaken up in a
liquid containing soluble salts of iron, yet the action of sulphate of copper is
equally effective when there is free soluble iron in the liquid. It has however a
wonderful molecular action on the ferrocyanide of iron, causing its particles to
have a magnetic or other attraction for each other, so that they unite or coagulate
together, and thus from being practically imponderable become ponderable in the
liquid and very speedily subside in flakes. We now concentrate the clear solution
till it solidifies on cooling, as before mentioned. The result is a hydrated sulphate
of alumina almost chemically pure, which may be used for almost any purpose for
which the crystallized potash or ammonia alums are now requisite. We take the
precipitate of ferrocyanide of iron, or Prussian blue, obtained as before described,
and after washing it slightly with water we add to it milk of lime in sufficient
quantity to entirely destroy the blue colour. We boil the mixture well with
steam and allow it to deposit the insoluble matter and then draw off the clear
solution. We thus again obtain the ferrocyanide of calcium required for the
precipitation of iron, as described in the aforesaid Patent.
It will be seen that the action of sulphide of arsenic, and still more that of the
sulphate of copper or zinc, on the ferrocyanides of iron is apparently mechanical
rather than chemical. In the one case the sulphide of arsenic in precipitating
envelopes the particles of the ferrocyanides of iron and carries them down; in the

page_text: other the sulphate of copper appears to cause a molecular change in the
ferrocyanides. This action is not confined to sulphate of copper and sulphate of
zinc; other salts will do it to some extent, but the other soluble salts of copper or
zinc are undesirable adulterations to the sulphate of alumina, and all other kindred
salts that will perform the action are cither much more expensive or much slower
in their action.
If sulphate of copper be used however the copper is entirely precipitated by the
sulphuretted hydrogen when completing the process.
Having now described our Invention, and the best mode known to us of carrying
it into effect, we wish it to be understood that what we believe to be new and
desire to protect under the herein before in part recited Letters Patent is,―
First. The herein described process of separating finely suspended ferrocyanides
of iron by causing a molecular change in their particles by the addition to the
solution containing them of a small quantity of a salt or mixture of salts, such as
sulphate of copper, capable of effecting that change.
Second. The application of sulphate of zinc or sulphate of copper for the purpose
of throwing down ferrocyanides of iron when suspended in liquids.
In witness whereof, I, the said Josiah Wickliffe Kynaston, on behalf of myself
and the said William Chadwick, Thomas Chadwick, and James Chadwick,
have hereunto set my hand and seal, this Twenty third day of February,
in the year of our Lord One thousand eight hundred and eighty one.
Witness,
W P. THOMPSON,
Patent Agent,
Liverpool & London.
J. W. KYNASTON. (L.S.)