odourless, transparent ionic liquid (with negligible vapour
pressure) has a major health and safety advantage over the
traditional fluid. Although the ionic liquids investigated with
RI 4 1.8 are opaque to the naked eye, they do transmit near
infrared radiation; we thus continue our search for materials
with RI 4 1.8 that are transparent in the infrared.
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6 Ionic Liquids in Synthesis, ed. P. Wasserscheid and T. Welton,
Wiley-VCH, Weinheim, 2003.
7 (a) Ionic Liquids IIIA: Fundamentals, Progress, Challenges, and
Opportunities, ACS Symp. Ser., ed. K. R. Seddon and R. D.
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Society, Washington DC, 2005, vol. 902.
Conclusion
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One of the most attractive features of ionic liquids for
scientists and engineers is their potential to be tailored for
predetermined function. In the present study, the potential to
prepare ionic liquids with specific refractive indices is demon-
strated. The prediction of these values, by application of the
parachor, is described elsewhere.42
12 O. Bortolini, M. Bottai, C. Chiappe, V. Contec and D. Pieraccini,
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Although we only studied about 20 examples of neoteric
fluids, we have elaborated a design principle which will enable
these fluids to be prepared with RI in the range 1.40–2.10, at
intervals of 0.01 (either pure liquids or binary systems). Twenty
ionic liquids mixed in binary fashion generate 400 novel im-
mersion media, even with simple 1 : 1 ratios. If ratios are
changed in steps of 0.1, then 4000 new liquids will be generated.
In this work, we have potentially increased the number of RI
matching media by approximately 700 liquids. As these fluids
are ionic liquids, they have negligible vapour pressure, and, by
virtue of this physical property, are more environmentally
benign than the vast majority of existing high refractive index
immersion fluids for optical mineralogy. In this work, we have
thus not only made refractive index measurements more
precise, but have also substantially reduced health risks to
the experimental scientist.
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Acknowledgements
We gratefully acknowledge the United Institute of Geology,
Geophysics & Mineralogy (UIGGM), Siberian Branch of the
Russian Academy of Sciences at Novosibirsk for the use of the
photograph shown in Fig. 1. MD thanks QUILL and its
industrial advisory board for funding, and MS thanks J.
Webster, C. Mandeville and R. Fogel for discussions and
access to their American Museum of Natural History labora-
tories. We thank David Shara for the loan of mineral speci-
mens and for technical assistance in producing the images of
those minerals in air, water and ionic liquids. We also grate-
fully acknowledge the EPSRC National Mass Spectrometry
Service Centre at the University of Wales, Swansea for record-
ing mass spectra. MD and KRS also gratefully acknowledge
the EPSRC for funding under their Portfolio Partnership
Scheme (Grant no. EP/D029538/1).
30 N. Winterton, K. R. Seddon and Y. Patell, World Patent, WO
0037400, 2000.
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spects, ACS Symp. Ser., ed. K. R. Seddon and R. D. Rogers,
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326 | New J. Chem., 2006, 30, 317–326