Methyl isocyanate is usually manufactured by the reaction of monomethylamine and phosgene. Gases used included chlorine, mustard gas and phosgene. No antidote for phosgene oxime poisoning is known. The smoke also contains traces of organic chlorinated compounds, phosgene, carbon monoxide, and chlorine. Dimethyl carbonate is traditionally prepared by the reaction of phosgene and methanol. Sodium bicarbonate may be used to neutralise liquid spills of phosgene. Although many organic carbonates are produced using phosgene, propylene and ethylene carbonates are exceptions. Ammonia may be used to mitigate gaseous spills of phosgene. CHC(O)Cl by treatment with thionyl chloride, phosgene or one of the chlorides of phosphorus. Mustard gas was manufactured as well as chlorine, phosgene and Paris Green. The metastable dication, which is valence-isoelectronic with carbonyl fluoride and phosgene, was observed in 2010. Chloroform converts slowly in air to phosgene (COCl), releasing HCl in the process. It is prepared in the lab by treating benzyl alcohol with phosgene. Later, mustard gas, phosgene and other gases were used. The hepatotoxicity and nephrotoxicity of chloroform is thought to be due largely to phosgene.