Richard,
"I think that counts as a chemical weapon."

You are entitled to your opinion but it is diametrically opposed to the understanding of every government in the world, every military in the world and every treaty, protocol and agreement that has ever been stated.
It does not act by toxicity, so it is not a chemical weapon according to the universally accepted definition of a chemical weapon.

McGrath, your information is correct.
WP smoke munitions are designed to contain the WP so as to minimise casualties.
WP anti personnel weapons blast it over a wide area.
British forces do not use such things.
They do use smoke WP munitions as does every military in the world.
The munitions used in Gaza were smoke not anti personnel.