Butyl-3-methylimidazolium hexafluorophosphate, also known as BMIM-PF6, is a viscous, colourless, hydrophobic ionic liquid. Together with 1-butyl-3-methylimidazolium tetrafluoroborate, BMIM-BF4, it is one of the most widely studied ionic liquids and is commercially available from most of the major international suppliers of chemicals. It is known to very slowly decompose in the presence of water.R.P.