Oil and water may mix under extreme pressure

August 28, 2017, University of Edinburgh

They say that oil and water do not mix … but now scientists have discovered that – under certain circumstances – it may be possible.

A new study suggests that some oily – which normally repel water – can be forced to dissolve in water when the two substances are squeezed together under extreme pressure. Researchers at Edinburgh applied high pressure to tiny containers filled with water and methane, creating conditions similar to the intense pressure found on the ocean floor or inside the planets Uranus and Neptune.

Water-repelling substances

By compressing water and methane together, scientists have been able to gain insights into how the chemicals interact. Methane is often used in experiments to study the properties of substances like oil that repel water – called hydrophobic molecules. The new findings suggest it may be possible to mix other hydrophobic molecules with water in a similar way.

The study is published in the journal Science Advances.

The team squeezed methane and water molecules between two ultra-sharp diamonds and compressed them by bringing the two anvil points together. The diamond anvil was used to apply pressures of up to 20,000 Bars – 20 times greater than the pressure at the bottom of the Mariana trench, the deepest part of the world's oceans.

Compacted molecules

Under a microscope, methane – much like oil – appears as large droplets in water at normal pressure, demonstrating that the substances do not mix. However, the team found the droplets disappeared at high pressures, indicating that the methane had dissolved.

Researchers think this happens because methane molecules shrink as is increased, while water molecules stay largely the same. This could allow compacted to fit between the much larger , enabling them to mix, the team says.

Useful applications

Understanding the mixing properties of water and could help researchers find ways of replacing expensive and hazardous solvents used in industry.

It could also help provide new insights into conditions at the bottom of the ocean or in the outer solar system. The study was supported by the Engineering and Physical Sciences Research Council and European Research Council.

"These exciting findings shed light on how -repelling substances behave under high pressures, such as those found at the or inside planets. This could have a huge range of applications, from replacing expensive and environmentally hazardous industrial solvents to modelling planetary bodies like Saturn's largest moon, Titan," says Dr John Loveday.

Explore further: Study finds hydrate gun hypothesis unlikely

More information: Ciprian G. Pruteanu et al. When immiscible becomes miscible—Methane in water at high pressures, Science Advances (2017). DOI: 10.1126/sciadv.1700240

Related Stories

Study finds hydrate gun hypothesis unlikely

August 23, 2017

Clathrate (hydrate) gun hypothesis stirred quite the controversy when it was posed in 2003. It stated that methane hydrates—frozen water cages containing methane gas found below the ocean floor—can melt due to increasing ...

Probing methane's secrets: From diamonds to Neptune

September 12, 2013

Hydrocarbons from the Earth make up the oil and gas that heat our homes and fuel our cars. The study of the various phases of molecules formed from carbon and hydrogen under high pressures and temperatures, like those found ...

Scientists predict Neptune's chemical make-up

August 11, 2017

Scientists have helped solve the mystery of what lies beneath the surface of Neptune – the most distant planet in our solar system. A new study sheds light on the chemical make-up of the planet, which lies around 4.5 billion ...

Newly discovered methane consumers in lakes

June 7, 2017

When decaying organic matter sinks to the bottom of a lake or ocean, methane is produced as the biomass is broken down. Some of the methane is released from the surface into the atmosphere, where it acts as a potent greenhouse ...

Recommended for you

Ancient enzymes the catalysts for new discoveries

October 22, 2018

University of Queensland-led research recreating 450 million-year-old enzymes has resulted in a biochemical engineering 'hack' which could lead to new drugs, flavours, fragrances and biofuels.

New algorithm can more quickly predict LED materials

October 22, 2018

Researchers from the University of Houston have devised a new machine learning algorithm that is efficient enough to run on a personal computer and predict the properties of more than 100,000 compounds in search of those ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.