A New or Improved Process for Making Red Oxide of Iron Pigments from Hydrated Peroxide of Iron.
Year: 1894

page_text: Date of Application, 8th Sept., 1894
Complete Specification Left, 4th June, 1895-Accepted, 13th July, 1895
PROVISIONAL SPECIFICATION.
A New or Improved Process for Making Red Oxide of Iron Pigments
from Hydrated Peroxide of Iron.
I, NORMAN MCCULLOCH, of 7 Melrose Street, Glasgow, in the County of
Lanark, North Britain, 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 a new or improved means for making red oxide of iron
pigments from hydrated peroxide of iron and consists as follows
When hydrated peroxide of iron in presence of excess water is subjected in a
closed vessel to a temperature exceeding about 340° Fahrenheit, it completely:
parts with its water of chemical combination and is converted to an aubydrous
oxide highly suitable from its colour and covering power as a pigment.
In applying this fact to the manufacture of red oxide, I proceed as follows.
I treat a solution of a persalt of iron with an amount of an oxide or carbonate of
an alkali or alkaline earth (excepting magnesia) sufficient to completely precipitate
the iron as the hydroxide. (The alkali or alkaline earth used in this operation
should preferably be one forming with the acid of the persalt a compound freely
soluble in water.) The liquor holding the iron precipitate in suspension is then
conveyed into a very strong iron boiler capable of withstanding if necessary a
working pressure of 250 lbs. to the square inch and heated therein to a temperature
of about or exceeding 340° Fahrenheit in order to dehydrate the iron hydroxide
(in this connection I may mention that it has the presence of even traces of
hydrated oxide of aluminium in the iron precipitate appreciably raises the
temperature requisite to dehydrate the iron hydroxide, and if these traces be at all
appreciable they will prevent the dehydration being effected at temperatures and
pressures convenient for practical working). The completion of this operation
may be readily ascertained by withdrawing a little of the iron precipitate from
the boiler from time to time and noting its physical appearance, for when the
critical temperature is reached at which the affinity between the oxide of iron and
the water chemically combined with it is destroyed, a few minutes heating
suffices.
The subsequent operations merely consist in running the contents of the boiler
into a collecting vat and from this the oxide of iron is taken to a filter press and
well washed to free it from soluble matter. The washed oxide of iron after being
dried. by steam, heat, or exposure to the air, is ready for use as a pigment.
Dated this 7th day of September 1894.
JOHNSONS,
115 St. Vincent Street, Glasgow, Petitioner's Agents.

page_text: A New or Improved Process for Making Red Oxide of Iron Pigments
from Hydrated Peroxide of Iron.
I, NORMAN MCCULLOCH of 7 Melrose Street, Glasgow, in the County of
Lanark, North Britain, 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 a process for making red oxide of iron pigments from
hydrated peroxide of iron and consists as follows:-
When hydrated peroxide of iron in presence of excess water is subjected in a
closed vessel to a temperature exceeding about 340° Fahrenheit it completely parts
with its water to chemical combination and is converted to an anhydrous oxide
highly suitable from its colour and covering power as a pigment.
In applying this fact to the manufacture of red oxide, I proceed as follows:-
I treat a solution of a persalt of iron with an amount of an oxide or carbonate
of an alkali or alkaline earth (excepting magnesia) sufficient to completely pre-
cipitate the iron as the hydroxide. (The alkali or alkaline earth used in this
operation should preferably be one forming with the acid of the persalt a compound
freely soluble in water.) The liquor holding the iron precipitate in suspension is
then conveyed into a very strong iron boiler capable of withstanding if necessary
a working pressure of 250 lbs. to the square inch and heated therein to a
temperature of about or exceeding 340° Fahrenheit in order to dehydrate the iron
hydroxide (in this connection I may mention that the presence of even traces of
hydrated oxide of aluminium in the iron precipitate appreciably raises the tem-
perature requisite to dehydrate the iron hydroxide, and if these traces be at all
appreciable they will prevent the dehydration being effected at temperatures and
pressures convenient for practical working). The completion of this operation
may be readily ascertained by withdrawing a little of the iron precipitate from
the boiler from time to time and noting its physical appearance, for when the
critical temperature is reached at which the affinity between the oxide of iron and
the water chemically combined with it is destroyed, a few minutes heating suffices.
The subsequent operations merely consist in running the contents of the boiler
into a collecting vat and from this the oxide of iron is taken to a filter press and
well washed to free it from soluble matter. The washed oxide of iron after being
dried by steam, heat or exposure to the air, is ready for use as a pigment.
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 :-
The process of preparing ferric hydroxide for use as a red oxide of iron pigment,
by subjecting the hydrated oxide in presence of excess water in an iron boiler or
other suitable apparatus to a steam temperature about or exceeding 340° Faht. for
such length of time as suffices for the dehydration of the iron hydroxide,
substantially as hereinbefore described.
Dated this 24th day of May 1895.
JOHNSONS,
115 St. Vincent Street, Glasgow, Applicant's Agents.