Electrolytic conductivity of four imidazolium-based room-temperature ionic liquids and the effect of a water impurity
Jason A. Widegren, Eric M. Saurer, Kenneth N. Marsh, Joe W. Magee
The electrolytic conductivities (κ) of four hydrophobic room-temperature ionic liquids (RTILs) were measured at temperatures from 288.15 K to 323.15 K. The measurements were made with a commercial conductivity cell with platinum black electrodes. In order to exclude atmospheric moisture, the conductivity cell was modified so that it could be sealed during measurements. The RTILs studied were 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 1-butyl-3-methylimidazolium hexafluorophosphate. The RTILs were dried under vacuum until the mass fraction of water (w2) was less than or equal to} 10-5. Coulometric Karl Fischer titration was used to determine w2 in each RTIL before and after measurements of κ. Most measurements were made on dried RTILs, but some measurements were purposely performed at higher w2 in order to study the effect of a water impurity on κ. For water + 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide}, κ was found to increase dramatically with increasing w2; for example, in going from w2 = 10-5 to w2 = 10-2, the fractional increase in κ was 0.36 = (κwet ¿ κdried)/ κdried}. This work illustrates the importance of measuring the water content in RTILs before and after measurements of κ.
, Saurer, E.
, Marsh, K.
and Magee, J.
Electrolytic conductivity of four imidazolium-based room-temperature ionic liquids and the effect of a water impurity, J. Chem. Thermodynam., [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=50045
(Accessed December 8, 2023)