<unk> is an organophosphate nerve agent. It was developed in the Soviet Union under the FOLIANT program and is one of the group of compounds referred to as Novichok agents that were revealed by Vil Mirzayanov. In March 2018 the Russian ambassador to the UK, Alexander Yakovenko, claimed to have been informed by British authorities that<unk> had been identified as the agent used in the poisoning of Sergei and Yulia Skripal. Vladimir Uglev, one of the inventors of the Novichok series of compounds, said he was "99 percent sure that it was<unk>  in relation to the 2018 Amesbury poisonings, noting its unusually high persistence in the environment. According to a classified report by the United States Army National Ground Intelligence Center, the agent designated as<unk> and its ethyl analog<unk>  developed under the FOLIANT program, "are as toxic as VX, as resistant to treatment as soman, and more difficult to detect and easier to manufacture than VX". Of the agent's binary versions, one is reportedly formed by acetonitrile and an organic phosphate "that can be disguised as a pesticide precursor," while for another, Bill Gertz wrote, "soldiers need only add alcohol". No certain data on toxicity exist but it is estimated that the median lethal concentration of<unk> is 7 mg/m3. This means that half of 70 kg men under slight physical activitybreathing 15 litres of air per minutewould die within two minutes of exposure. This equates to median lethal dose of 0.2 mg via respiration.
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