Chemical
Properties
This black oxide, with nominal composition Pr6O11,
is the stable oxide formed when any Pr salt is calcined
in air. It is hygroscopic, absorbing moisture and
carbon dioxide from the atmosphere onto its surface;
it dissolves in mineral acids to form green solutions
of Pr3+ salts. [Pr(IV) salts are too strong oxidizers
to exist under normal conditions.] Like other Ln(III)
salts, the carbonate, hydroxide and oxalate are
insoluble in water whereas the chloride and nitrate
are soluble.
