Volumetric and Speed of Sound of Ionic Liquid, 1-Butyl-3-methylimidazolium Hexafluorophosphate with Acetonitrile and Methanol at T = (298.15 to 318.15) K Zafarani-Moattar, M.T.; Shekaari, H.; Journal of Chemical & Engineering Data 2005, 50, 1694-1699