precursor
(6) Precursor.— (A) In general .— The term “precursor” means any chemical reactant which takes part at any stage in the production by whatever method of a toxic chemical. The term includes any key component of a binary or multicomponent chemical system. (B) List of precursors .— Precursors which have been identified for the application of verification measures under Article VI of the Convention are listed in schedules contained in the Annex on Chemicals of the Chemical Weapons Convention.