Well to explain why the interest, in case it opens up some additional suggestions:
This is part of the SFX Skills series I'm working on, Hermetic Alchemy, and I'm trying to think of the various uses that players will attempt to put transmutation to. Of course, one of those would be the creation of poisonous elements. Arsenic, Antimony, and Thallium are close enough in function to just use Arsenic's stats, but Chlorine came to mind as an element that was used as a chemical weapon AND was a gas at room temperature (as opposed to the metalloids).
Of course, alot of other elements are 'poisonous', but not as commonly thought of or capable of being slipped into food or drink or released into the air.
I, personally, wouldn't even let my players go in for chemical weapons and poisons, but I figured it was responsible writing to prepare GMs out there to be able to field the things players are going to try to do when given a hammer ... everything looks like a nail. (And using alchemy to make poison is like buying an airline to get free peanuts, but somebody would want to do it.)
--fje