Two poisonous gases that can be prepared with chlorine gas are:

(i) Phosgene(COCl₂)

This is how phosphene is formed:

CO + Cl₂→ COCl₂(in presence of sunlight)

(ii) Mustard gas(Cl-C₂H₄-S-C₂H₄-Cl)

(iii) Tear gas(CCl₃NO₂)