Electrolytic conductivity of four imidazolium-based room-temperature ionic liquids and the effect of a water impurity

Published

April 9, 2005

Author(s)

Jason A. Widegren, Eric M. Saurer, Kenneth N. Marsh, Joe W. Magee

Abstract

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 = (κ_wet ¿ κ_dried)/ κ_dried}. This work illustrates the importance of measuring the water content in RTILs before and after measurements of κ.

Citation

J. Chem. Thermodynam.

Volume

37

Pub Type

Journals

Download Paper

Local Download

Citation

Widegren, J. , Saurer, E. , Marsh, K. and Magee, J. (2005), 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 March 13, 2025)