Since chemical weapon usage is banned in warfare, they have come up
with the notion that "white phosphorous is not a chemical weapon".
Note how CIA mentions white phosphorous being a chemical weapon when
Saddam Hussein used it against Kurds in 1991.
So, the definition can be changed depending on who uses it, it seems.
White phosphorous (like napalm) sticks to the skin and can burn the
flesh to the bone. It is used as an extreme terror tactic in war. An
excerpt from http://blogs.washingtonpost
On November 8, Rainews 24, an Italian satellite news channel of state
controlled RAI, aired a 20 minute documentary Fallujah: The Hidden
Massacre, reporting on the assault of Fallujah in November 2004. A
former American soldier, Army Specialist Jeff Englehart, is quoted
saying that white phosphorus was used intentionally to attack
civilians. Englehart says he "saw the burned bodies of women and
children," some melted "right down to the bone." He is quoted as
saying that he "heard the order to be careful because white phosphorus
was being used."
The documentary shows close-ups of Fallujah civilians, badly burnt,
their skin dissolved or caramelized. An Iraqi biologist in Fallujah is
interviewed, saying "a rain of fire fell on the city," burning
people's flesh, but strangely leaving "their clothes intact."