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Viscosity measurements on Ionic liquids : a cautionary tale
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Advisor(s)
Abstract(s)
The vibrating-wire viscometer has proven to be an exceedingly effective
means of determining the viscosity of liquids over a wide range of temperature and
pressure. The instrument has a long history but a variety of technological and theoretical
developments over a number of years have improved its precision and most
recently have enabled absolute measurements of high accuracy. However, the nature
of the electrical measurements required for the technique has inhibited its widespread
use for electrically conducting liquids so that there have been only a limited number
of measurements. In the particular context of ionic liquids, which have themselves
attracted considerable attention, this is unfortunate because it has meant that one primary
measurement technique has seldom been employed for studies of their viscosity.
In the last 2 years systematic efforts have been made to explore the applicability of
the vibrating-wire technique by examining a number of liquids of increasing electrical
conductivity. These extensions have been successful. However, in the process we have
had cause to review previous studies of the viscosity and density of the same liquids
at moderate temperatures and pressures and significant evidence has been accumulated
to cause concern about the application of a range of viscometric techniques to
these particular fluids. Because the situation is reminiscent of that encountered for
a new set of environmentally friendly refrigerants at the end of the last decade, in
this paper the experimental methods employed with these liquids have been reviewed
which leads to recommendations for the handling of these materials that may have consequences beyond viscometric measurements. In the process new viscosity and
density data for 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide
[C6mim][NTf2], 1-ethyl-3-methylimidazolium ethyl sulfate [C2mim][EtSO4], and
1-ethyl-3-methylpyridinium ethyl sulfate [C2mpy][EtSO4] have been obtained.
Description
Keywords
Viscosity Ionic liquids [C2mim][EtSO4] [C2mpy][EtSO4] [C6mim][NTf2]
Citation
Diogo, João C. F. [et al.] - Viscosity measurements on Ionic liquids : a cautionary tale. "International Journal of Thermophysics". ISSN 0195-928X (Print) 1572-9567 (Online). Vol. 35, nº 9-10 (oct. 2014), p 1615-1635
Publisher
Int J Thermophys