IMPROVEMENTS IN THE MANUFACTURE OF BICHROMATES OF POTASH AND SODA
Year: 1883

page_text: "
LETTERS PATENT to John Henry Johnson of 47 Lincolns Inn Fields in the
County of Middlesex, Gentleman, for an Invention of "IMPROVEMENTS IN
THE MANUFACTURE OF BICHROMATES OF POTASH AND SODA Communicated
to him from Otto Neuhaus, Adolf Neuliaus, and Albert Neuhaus all residing
at Elberfeld in the Empire of Germany
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at
the Office of the Commissioners of Patents on the 10th February 1883.
JOHN HENRY JOHNSON, of 47 Lincolns Inn Fields, in the County of Middlesex,
Gentleman, "IMPROVEMENTS IN THE MANUFACTURE OF BICHROMATES OF POTASH
AND BODA a communication to me from Otto Neuhaus Adolf Neuhaus and
Albert Neuhaus all residing at Elberfeld, in the Empire of Germany,
The Invention consists in the manufacture of Bichromates of Potash (or Soda)
by acting with Carbonic Acid upon the melts; these melts are obtained by treating
a mixture of Chrome Ore with Lime and Carbonate (or caustic) Potash (or Soda)
in a furnace until the process is considered complete.
By preference the mixture of the melt is regulated in such a manner that the
half of the oxide of chromium, which is set free in the furnacing process, is
obtained as Chromate of Calcium and the other half as Chromate of Potash (or
Soda).
The melt thus obtained is treated in a boiler which is sufficiently strong to stand
a pressure of five or more atmospheres and which contains a stirrer or agitator.
Water ie added to the melt, sufficient in quantity to obtain a thin paste. This
paste is well stirred and heated up to about 130° Celsius, or more, and Carbonic
Acid passed or pumped into the boiler, until the process is found to be completed.
The melt, which is used by preference in a mixture as above stated, contains
about one half of the Chromate in the form of Chromate of Potash (or Soda), which
is converted by the action of the Carbonic Acid into bichromate of potash (or Soda)
.

page_text: and Carbonate of Potash (or Soda). The other half of the Chromate contained in
the melt is in the form of Chromate of Calcium, which is converted by the action
of the Carbonic Acid into bichromate of Calcium and Carbonate of Calcium; the
bichromate of Calcium is by the action of the Carbonate of Potash (or Soda), set
free as above stated, first into Chromate and then into bichromate of Potash (or
Soda).
The whole of the Chromate, when the operation has been properly conducted, is
thus contained in the form of bichromate of potash (or Soda) in solution.
The contents of the boiler are then thrown on a filter and washed in the usual
manner. The Bichromate of Potash in solution, thus obtained is then concentrated
by evaporation and crystallized in the usual way.
When Soda instead of Potash, has been employed in the melt, the liquor
containing the Bichromate of Soda, is concentrated, and calcined if necessary.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Henry Johnson in the Great Seal Patent Office on the
9th August 1883.
JOHN HENRY JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex
Gentleman "IMPROVEMENTS IN THE MANUFACTURE OF BICHROMATES OF POTASH
AND SODA" a communication to me from Otto Neuhaus, Adolf Neuhaus, and
Albert Neuhaus all residing at Elberfeld in the Empire of Germany.
The Invention consists in the manufacture of Bichromates of Potash or Bichro-
mates of Soda by acting with Carbonic acid upon the melts. The said melts are
obtained by treating a mixture of Chrome Ore with Lime and Carbonate or caustic
Potash (or soda) in a furnace until the process is considered complete.
By preference the mixture of the melt is regulated in such a manner that the
half of the Oxide of Chromium which is set free in the furnacing process is
obtained as Chromate of Calcium and the other half as Chromate of Potash (or
Soda).
The melt thus obtained is treated in a boiler which is sufficiently strong to stand
a pressure of five or more atmospheres and which contains a stirrer or agitator.
Water is added to the melt sufficient in quantity to obtain a thin paste. This
paste is well stirred and heated to about 130° Celsius or more if necessary and
Carbonic acid is passed or pumped into the boiler until the process is found to be
completed. The melt which is used by preference in a mixture as above stated
contains about one half of the Chromate in the form of Chromate of Potash (or
soda) which is converted by the action of the Carbonic Acid into Bichromate of
Potash (or Suda) and Carbonate of Potash (or Soda). The other half of the
Chromate contained in the melt is in the form of Chromate of Calcium which is
converted by the action of the Carbonic acid into bichromate of Calcium and
Carbonate of Calcium; the bichromate of Calcium is by the action of the Carbonate
of Potash (or Soda) set free as above stated first into Chromate and then into
bichromate of Potash (or Soda).
The whole of the Chromate when the operation has been properly conducted is
thus contained in the form of bichromate of Potash (or Soda) in solution.
The contents of the boiler are then thrown on a filter and washed in the usual
manner. The bichromate of Potash in solution thus obtained is then concentrated
by evaporation and crystallized in the usual way.
When soda instead of Potash has been employed in the melt the liquor containing
the bichromate of Soda is concentrated and calcined if necessary.
Having now described and particularly ascertained the nature of the said
Invention and the manner in which the same is or may be used or carried into
effect I would observe in conclusion that what I consider to be novel and original
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is:-
The manufacture of Bichromate of Potash or of bichromate of Soda by adding
under pressure and heat if necessary Carbonic acid to the Chrome melt obtained by
furnacing a mixture of Chrome Ore with Lime and Carbonate (or Caustic) Potash
(or Soda) as hereinbefore described.
In witness whereof I the said John Henry Johnson have to this my
Specification set my hand and seal this eighth day of August One thousand eight
hundred and eighty three.
J. HENRY JOHNSON
(L.S.)