Viscosity of 1-Hexyl-3-methylimidazolium Hexafluorophosphate and 1-Octyl-3-methylimidazolium Hexafluorophosphate at High Pressure Tomida, D.; Kumagai, A.; Kenmochi, S.; Qiao, K.; Yokoyama, C.; Journal of Chemical & Engineering Data 2007, 52, 577-579