Oil and water do mix after all

19:00 19 February 03

Exclusive from New Scientist Print Edition


Oil and water do not mix - the mantra is familiar to every schoolchild. You have to shake them to overcome the forces that hold the oil together.

Now teachers may want to rewrite their lessons. If you first remove any gas that is dissolved in the water, it will mix spontaneously and even stay that way indefinitely, according to chemist Ric Pashley of the Australian National University in Canberra.

"Many scientists are going to find this very hard to believe," says colloid scientist Len Fisher of the University of Bristol in England, "but Pashley has provided very strong proof that oil and water will mix." Pashley's observation is bound to cause controversy as the reason it happens is still unclear. Chemists are waiting to see whether the experiment can be repeated.

If spontaneous emulsions can be made at will, they could have important applications in medicine and the chemical industry. Many injectable medicines are currently only soluble in oil.

An alternative might be to disperse the medicine in degassed water, which is already produced on a large scale by the oil industry. Emulsion paints, which currently use chemical stabilisers to stop them separating, could also be made more cheaply if degassed water would do the trick.

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