It's Teribus who is disputing that internationally agreed definition, Keith. It includes precursors. The convention was deliberately drafted so as to prevent the stockpiling of ingredients for CWs. Whoever drew up the brief description I quoted from must have had the dissembling defence of CWs coming from the likes of Teribus in mind.
Two quotes, the first from Teribus on 6 September :
"If US arms manufacturers sold weapons and exported WEAPONS to Saddam Hussein please provide details. You have specifically stated that chemical weapons were sold - please don't give a long list of component parts and materials which through some convoluted process might possibly be used as part of a weapon (Making chemical agents is easy, any facility that makes fertilizer can do it - weaponising those agents thankfully is extremely difficult)"
The second quote from the internationally recognized description of a CW :
"The term chemical weapon is applied to any toxic chemical or its precursor that can cause death, injury, temporary incapacitation or sensory irritation through its chemical action. Munitions or other delivery devices designed to deliver chemical weapons, whether filled or unfilled, are also considered weapons themselves."
The Halabja chemical attack occured on March 16, 1988 ,towards the end of the Iraq -Iran war . Iraqi chemical weapons killed between 3,200 and 5,000 Kurds and injured 7,000 to 10,000 more, most of them civilians.
According to the wiki entry on the attack:
"Among the chemical precursors provided to Iraq from American companies such as Alcolac International and Phillips was thiodiglycol, a substance needed to manufacture mustard gas, according to leaked portions of Iraq's "full, final and complete" disclosure of the sources for its weapons programs."