Prussiate Of Copper
:
ON THE TERTIARY, OLIVE.
differs chemically from Prussian blue only in having copper instead of
iron for its basis. It varies in hue from russet to purple brown, is
transparent and deep, but, being very liable to change in colour by the
action of light and by other pigments, has never been much used, and is
now obsolete. The compound has the objection of containing free
prussiate of potash, not removable by continued washing--sometimes as
much
as five per cent.
* * * * *
There are several other pigments which enter imperfectly into, or verge
upon, the class of russet, which, having obtained the names of other
classes to which they are allied, will be found under other heads; such
are some of the ochres, as Indian red. Burnt carmine is often of the
russet hue, or convertible to it by due additions of yellow or orange;
as are burnt Sienna and various browns, by like additions of lake or
other reds.
The one pigment in this chapter known to the modern palette, Rubens'
madder, is permanent.
TTITLE TERTIARY OLIVE
Olive is the third and last of the tertiary colours, and nearest in
relation to shade. Like its co-tertiaries, citrine and russet, it is
composed of the three primaries, blue, red, and yellow; but is formed