Improvements relating to the Manufacture of Paris Blue, or Berlin Blue, and of Berlin Green by Electrolysis.
Year: 1893

page_text: Date of Application, 20th July, 1893-Accepted, 20th July, 1894
COMPLETE SPECIFICATION.
Improvements relating to the Manufacture of Paris Blue, or Berlin
Blue, and of Berlin Green by Electrolysis.
1, Dr. HUGO GOEBEL, of Garzweiler, Rhenish Prussia, in the Empire of
Germany, Chemist, 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 :—
This invention relates to the manufacture of Paris blue (Berlin blue) and of
Berlin green by ozone produced by electrolysis.
The white bluish precipitate which is obtained when yellow prussiate of potash
or potassium ferro cyanide is precipitated by a solution of ferrous salt which may
also contain iron oxyde; for instance ferrous sulphate, or green vitriol produces in
the electrolysis at the anode, if suspended in water, which is changed into a
conductor of electricity, for instance, by acids, salts or the like, a Paris blue or
Berlin blue of an extremely vivid violet reflex, so called copper lustre. The
cathode is, in this case, only surrounded by water which has been rendered
conductive. The water may also contain, substances which combine with the
hydrogen produced by the electrolysis. The water in which the white or bluish
precipitate is suspended, may be changed into a conductor by adding sulphuric acid,
muriatic acid, nitric acid or phosphoric acid. These substances may be added in
such quantities as the liquid contains from 1-20% acid.
During the electrolysis it is expedient to continually stir the contents of the
anode cell. In case the cathode cell should contain the above mentioned substance,
the contents of this cell must also be constantly stirred. Periodically a sample of
the anode liquor is filtered for the purpose of enabling an interruption of the
electrolysis to take place as soon as the filtered sample shows a deep fiery violet
tint.
When the electrolytic action is continued too long, the blue becomes more and
more faint, ultimately changes to dark Berlin green, which when moist, or in the
moist air reverts to blue.
The above described manufacture of Paris blue can be accomplished by the
apparatus heretofore employed in electrolysis. Some substances which may be
combined with hydrogen are: superoxides (for instance: superoxide of manganese:
MnO2), organic nitro derivatives and the like. The quantity of the added
substances may be calculated theoretically from the quantity of the hydrogen
produced by the process. A smaller quantity of the substances may be used
without disadvantage, but it is preferable to add a quantity larger than is required
by the produced hydrogen.
The production of the white or bluish precipitate is known, as well as the
acidification of the water for the purpose of changing the same into a conductor.
I do not therefore claim these processes, but only the production of. Paris blue and
Berlin green from the white or bluish precipitate.
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 :-
A process of manufacturing Paris blue or Berlin blue and Berlin green by ozone
produced by electrolysis, this process consisting in the precipitating of a solution of

page_text: yellow prussiate of potash by means of a ferrous salt, such as green vitriol,
suspending this precipitate in water and subjecting it to electrolysis.
Dated this 14th day of February 1894.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.