Mercury beater

Poisonous mercury in thermometers has been replaced by harmless and better performing ionic liquids, according to European and US researchers writing in the Royal Society of Chemistry's journal Green Chemistry.

Ionic liquids (ILs) are salts in liquid form and already have a wide range of applications, from use in drug delivery to fuel cells and batteries.

Robin Rogers of Queen's University Belfast and his colleagues have now found another role for them. 'We have known the basic properties of ILs and have thought for some time that they should make a great thermometer fluid,' said Rogers. 'We simply had to prove it!'

ILs offer several advantages for thermometers: they have a faster temperature response time compared with mercury and operate over a wider range of temperatures compared with many molecular liquids, including ethanol.

Their low volatility also reduces their ability to escape into the environment, giving an additional environmental advantage over mercury, which needs to be carefully disposed of if a thermometer is broken.