Phosgene oxime, or CX, is an organic compound with the formula Cl2CNOH. It is a potent chemical weapon, specifically a nettle agent. The compound itself is a colorless solid, but impure samples are often yellowish liquids. It has a strong, disagreeable odor and a violently irritating vapor. Phosgene oxime, or CX, is an organic compound with the formula Cl2CNOH. It is a potent chemical weapon, specifically a nettle agent. The compound itself is a colorless solid, but impure samples are often yellowish liquids. It has a strong, disagreeable odor and a violently irritating vapor. Phosgene oxime can be prepared by reduction of chloropicrin: The observation of a transient violet color in the reaction suggests intermediate formation of trichloronitrosomethane (Cl3CNO). Early preparations, using stannous chloride as the reductant, also started with chloropicrin.