Studying ionic liquids' thermal stability is important, claim chemists in Australia.

Janet Scott and colleagues at Monash University wanted to find out how stable ionic liquids actually were when heated to a high temperature for several hours. These potentially greener solvents are used for high temperature experiments because they emit very little vapour when heated.

Scott's group heated ionic liquids made up of different anions and cations and measured the weight lost over time. The results from these isothermal experiments gave them an upper operational temperature at which only a small amount of decomposition occurred within ten hours.

The team developed a simple equation that gives the highest temperature to which the ionic liquids should be heated. Scott said that the rule 'allows estimation of real upper operational temperatures without requiring the researcher to resort to the rather long and tedious isothermal experiments that we had to do'.

They also found that certain combinations of anions and cations led to polymeric products when they decomposed, and were not suitable for high temperature experiments. 'This could have implications for various high temperature applications and reactions carried out in such ionic liquids,' said Scott.

According to Kenneth Seddon, an expert in ionic liquids at the Queen's University of Belfast, UK, Scott's work 'is a model template for how a study of thermal stability should be performed. It should be compulsory reading for all workers in the field.'

Rachel Warfield