Chemical properties of Tri-halides - Oxidation
Phosgene is very poisonous gas. To use chloroform as an anaesthetic agent, it is required to save the reaction. The specified two precautions are taken while chloroform is stored.
(a) It is located in dark black or brown coloured bottles that are filled up to the brim.
(b) 1% ethyl alcohol is added. This retards the oxidation and transforms the phosgene formed into harmless ethyl carbonate.