Improvements in and relating to a Process of Making Green Oxide of Chromium.
Year: 1894

page_text: COMPLETE SPECIFICATION.
Improvements in and relating to a Process of Making Green Oxide
of Chromium.
We, FRANK LEROY SLOCUM, Chemist, and CHARLES YANDES WHEELER,
Manufacturer, both citizens of the United States of America, and residing
respectively at the corner of Linden Avenue and Reynolds Street in the City of
Pittsburgh, and at 237 Western Avenue in the City of Allegheny, County of
Allegheny and State of Pennsylvania, one of the United States of America, 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 :-
Our invention relates to the manufacture of green oxide of chromium, this green
oxide being employed in paints or for coloring purposes, as well as in the chemical
arts for the making of metallic chromium, and in the treatment of metals. The
object of the invention is to provide a cheap and rapid method of forming
the same.
To these ends the invention consists, generally, in wetting a powdered chromate
and powdered carbon with hydrochloric acid and subjecting the same to heat,
resulting in a metallic chloride and green oxide of chromium, the latter being this
way very cheaply produced. It also consists in the steps above iudicated, and the
further steps of moistening the resultant mass with hydrochloric acid and
dissolving out the salt from the oxide with boiling water.
To enable others skilled in the art to practice our invention, we will describe the
same more fully.
We may employ for the manufacture of the green oxide any suitable chroinate, such
as the bi-chromate of soda, (Cr2Na207), or the bi-chromate of potash (Cr²K207).
These salts should be finely powdered and mixed with about one tenth part of
powder carbon, it being preferred that the chromate shall be first moistened with
strong hydrochloric acid, as the combination of the carbon with the chromate in
its dry state forms an explosive from which accident might occur. We prefer to
employ finely divided wood charcoal for the carbon element. The whole mass is
then wetted again with hydrochloric acid until brought to a paste, the proportion
of acid employed in the entire wetting of the mass being about one part acid to
three of chromate, by weight. This paste is then charged into a suitable furnace,
and is allowed to burn without admission of air, the chromate providing the
oxygen for the combination with the carbon of the mixture, the furnace being
heated to a cherry red. The combustion takes place in a slow form, like the
burning of saltpetre paper.
In order to insure the reaction of practically all the particles, while it is still
hot, we wet it again with hydrochloric acid by one or more treatments until brought
to about the state of mortar. The mass then consists of the green oxide of
chromium and the chloride of sodium or potassium, with a small trace of the
original salt, which should not be over one or two per cent.
The mass is then heated with boiling water in which the chloride of sodium or
potassium, and the original chromate, if any be present, are soluble, and these
substances are then separated from the green oxide of chromium by a mechanical
process, such as by the filter press. The green oxide of chromium is obtained
from the filter press in the form of a hard moist cake.
It is found by the process above described a pure green oxide of chromium can
be obtained which is suitable for use for any of the purposes to which this
material has been previously applied, and that it may be obtained at ahout

page_text: one-half the cost of producing the green oxide by methods heretofore employed
for that purpose.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what
we claim is :
1. The herein-described process of forming green oxide of chromium, consisting
in wetting a powdered chromate with hydrochloric acid, mixing therewith a
powdered carbon, again wetting the mass with hydrochloric acid and subjecting
the same to heat, then further wetting the mass with hydrochloric acid and
dissolving out the resultant chloride and any remaining chromate with boiling
water, substantially as set forth.
2. The herein-described process of forming green oxide of chromium, consisting
in wetting a powdered chromate and powdered carbon with hydrochloric acid and
subjecting the same to heat, then further wetting the mass with hydrochloric acid and
dissolving out the resultant chloride and any remaining chromate with boiling
water, substantially as and for the purpose set forth.
3. The herein-described process of forming green oxide of chromium consisting
in wetting a powdered chromate and powdered carbon with hydrochloric acid and
subjecting the same to heat, and then further wetting the resultant mass with
hydrochloric acid, substantially as set forth.
4. The herein-described process of forming green oxide of chromium, consisting
in wetting a powdered chromate and powdered carbon with hydrochloric acid and
subjecting the same to heat, substantially as set forth.
Doted this 14th dow of Aumont 1904
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.