This webpage is maintained by the Centers for Disease Control and Prevention (CDC). The webpage provides information and resources on VX. "VX is a human-made chemical warfare agent classified as a nerve agent. Nerve agents are the most toxic and rapidly acting of the known chemical warfare agents. They are similar to pesticides (insect killers) called organophosphates in terms of how they work and what kinds of harmful effects they cause. However, nerve agents are much more potent than organophosphate pesticides. [...] VX was originally developed in the United Kingdom in the early 1950s. [...] VX is odorless and tasteless. [...] VX is an oily liquid that is amber in color and very slow to evaporate. It evaporates about as slowly as motor oil."
Centers for Disease Control and Prevention: http://www.cdc.gov/