IMPROVE- MENTS IN PIGMENTS
Year: 1871

page_text: LETTERS PATENT to Thomas Rowan, of Glasgow, in the County of
Lanark, North Britain, Chemist, for the Invention of "IMPROVE-
MENTS IN PIGMENTS."
Sealed the 4th August 1871, and dated the 8th February 1871.
PROVISIONAL SPECIFICATION left by the said Thomas Rowan at the
Office of the Commissioners of Patents, with his Petition, on the
8th February 1871.
I, THOMAS ROWAN, of Glasgow, in the County of Lanark, North
Britain, Chemist, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN PIGMENTS," to be as follows, that is to say:—
This Invention consists in obtaining improved pigments of good
shades, permanent character, and easy application, by suitably treating
manganese carbonate and manganese chloride. The manganese carbonate
is economically and easily obtainable by precipitation by a carbonate
from manganese chloride, a bye product of the manufacture of chlorine.
In carrying out the Invention according to one modification the
manganese carbonate is heated in a vessel having an outlet for gas or

page_text: vapor, but in which the presence of air or active oxygen is prevented in
any convenient way. Thus if coal or carbonaceous matter is placed at
the inner end of the vessel the heat applied will cause a stream of gas to
issue from it, which will keep air out of the vessel. The manganese
carbonate treated in this way is converted into a beautiful green oxide
in the state of an impalpable powder, admirably suited for a pigment.
By a second modification the manganese carbonate is strongly heated
in an open vessel with free access for air, and a beautiful brown oxide is
formed, also suitable as a pigment.
By a third modification a gentler heat is applied than is requisite for
obtaining the brown oxide, and the result is a black oxide, which being
in the form of an impalpable powder is much more suitable for a black
pigment than the natural black oxide of manganese, which ordinary
grinding cannot reduce to so fine and uniform a state, and which is
not nearly so pure as that obtained from the carbonate in the manner ]
indicated.
The Invention also comprises the obtaining of the brown and black
pigments from manganese chloride without first converting it into
carbonate, but by adding lime or other alkaline earth or alkali to the
solution, whereby black manganese oxide is precipitated. This black 2
precipitate is converted into the brown pigment by heating it in a dry
state with free access of air or by blowing cold or hot air or steam
through it in its freshly precipitated condition.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas Rowan in the Great Seal Patent Office 2
on the 8th August 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
ROWAN, of Glasgow, in the County of Lanark, North Britain, Chemist,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her 30
Letters Patent, bearing date the Eighth day of February, in the year of
our Lord One thousand eight hundred and seventy-one, in the thirty-
fourth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Thomas Rowan, Her special licence

page_text: that I, the said Thomas Rowan, my executors, administrators, and
assigns, or such others as I, the said Thomas Rowan, my executors,
administrators, and assigns, should at any time agree with, and no
others, from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
PIGMENTS," upon the condition (amongst others) that I, the said Thomas
Rowan, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, should particularly
describe and ascertain the nature of the said Invention, and in what
manner the same was to be performed, and cause the same to be filed
in the Great Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
NOW KNOW YE that I, the said Thomas Rowan, do hereby declare
the nature of my said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and
by the following statement in writing, that is to say :—
My said Invention consists in obtaining improved pigments of good
shades, permanent character, and easy application, by suitably treating
manganese carbonate and manganese chloride. Manganese chloride is,
as is well known, a bye product of the manufacture of chlorine, and
manganese carbonate is economically and easily obtainable from the
chloride by precipitation by a carbonate, such as chalk, being thereby
got as a fine or impalpable powder peculiarly suitable for the purposes
of my present Invention.
In practically carrying out my said Invention, according to one
modification, I heat the manganese carbonate in a vessel or retort of
iron, fire-clay, plumbago, or other suitable material, such vessel having
an outlet for gas or vapor, but having the presence of air or active
oxygen prevented in any convenient way. Thus if coal or carbonaceous
matter is placed at the inner end of the vessel or retort the heat applied
will cause a stream of gas to issue from it which will keep air out of the
vessel. Or the same end may be attained by closing the vessel all but
a small outlet barely sufficient for the escape of the carbonic acid gas
evolved by the heating of the material, when such gas issuing at the
outlet will prevent the ingress of air. The manganese carbonate is, by
being treated in this way converted into a beautiful green oxide in

page_text: the state of an impalpable powder admirably suited for a pigment.
The heat employed should be about what is known as a red heat, and
after all the carbonic acid gas appears to be evolved the vessel should
be closed and kept heated for at least an hour, whereby the color is
rendered more permanent.
By a second modification the manganese carbonate is strongly heated
in an open vessel with free access of air and a beautiful brown oxide is
formed, also suitable as a pigment. The heat employed in this case
should range from a red heat to a bright red heat, according to the
desired shade, the higher heat giving the brighter shade.
By a third modification a gentler heat, say from 300 to 450 degrees
Fahrenheit, is applied, and the result is a black oxide, which artificial
oxide being in the form of an impalpable powder is much more suitable
for a black pigment than the natural black oxide of manganese, which
ordinary grinding cannot reduce to so fine and uniform a state, and
which is not nearly so pure as that obtained from the carbonate in the
manner indicated.
My Invention also comprises the obtaining of the brown and black
pigments from manganese chloride without first converting it into
carbonate, but by adding lime or other alkaline earth or alkali and forcing
air through, whereby black manganese oxide is precipitated. This black
precipitate may have any traces of lime separated from it by dissolving
them out with the aid of carbonic acid or by a solution of chloride of
calcium, and it may be dried and sifted and applied as a black pigment.
Or the black precipitate may be converted into the brown pigment by
heating it in a dry state with free access of air or by blowing cold or
hot air or steam through it in its freshly precipitated condition.
I am aware that the ordinary manganese chloride usually contains
iron chloride which can be precipitated as carbonate along with man-
ganese carbonate by adding chalk, but it is not necessary to separate
such iron carbonate even although present in larger proportion than the
manganese chloride, as the mixture of the two may be treated as herein-
before described and utilised as a pigment.
Having thus particularly described my said Invention, and the manner
in which the same is to be performed, I have to state that I do not
restrict myself to the precise details herein described or delineated, but
that what I believe to be novel and original, and claim as the Invention
secured to me by the herein-before in part recited Letters Patent is,

page_text: the applying of artificial oxides of manganese prepared substantially
as herein-before described as pigments.
In witness whereof, I, the said Thomas Rowan, have hereunto
set my hand and scal, this Fifth day of August, in the year of
our Lord One thousand eight hundred and seventy-one.