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Highlights in Chemical Science

News from across RSC Publishing.

Caution urged over combustible ionic liquids

20 June 2006

Leading scientists call for more care to be taken when handling ionic liquids in the laboratory following combustibility testing. 

Robin Rogers from the University of Alabama, US, and John Wilkes from the United States Air Force Academy, Colorado, together with colleagues from the US and Northern Ireland, have found that some ionic liquids (organic salts that melt below 100 degrees Celsius) can ignite and burn.  

"Our results . are not just a flash in the pan"
- Robin Rogers

'The fact that some ionic liquids are nonflammable and difficult to burn has led many to assume that this is generally true for all ionic liquids.leading to potentially unsafe working conditions,' said Rogers.  The researchers explained that ionic liquids' positive heat of formation and decomposition products formed on heating are thought to be the reasons why ionic liquids burn.

'Our results.are not just a flash in the pan', said Rogers, 'but should serve as a wake up call that ionic liquids, as a class, should not be necessarily considered safe when working with or near a heat or ignition source.'

James Davis, an expert in ionic liquids at the University of South Alabama, US, welcomed the findings of Rogers and Wilkes.  'Ionic liquids are chemicals, and should be accorded the respect which any good chemist ought to have toward any material they might be handling,' said Davis.


    Ionic liquid ignition test


However, Davis continued, 'we very much need to avoid the temptation to lurch from one overgeneralization - "ionic liquids are all sweetness and nice" to one of "ionic liquids are vile, nasty and evil".'  

'Ionic liquids hold great promise in an array of applications, some of which we are now seeing enter the marketplace, with others - of potentially enormous importance - waiting in the wings,' Davis added.

According to Rogers and Wilkes, the challenges that the introduction of ionic liquid-based technologies might confront include the 'fear of the unknown (as these are relatively new materials), resistance to change, and the perceived cost [of the compounds].'

Alison Stoddart


M Smiglak, W M Reichert, J.D Holbrey, J S Wilkes, L Sun, J S Thrasher, K Kirichenko, S Singh, A R Katritzky, R D Rogers, Chem. Commun., 2006

DOI: 10.1039/b602086k