The commercial powder is a mixture of
phases which melts at ~130 °C. DPPH-I (m.p. 106 °C)
is orthorhombic, DPPH-II (m.p. 137 °C) is amorphous and
DPPH-III (m.p. 128–129 °C) is triclinic (Kiers et al., 1976)
DPPH is a well-known radical and a trap ("scavenger") for other
radicals.