Solvation is the complicated process through which a dissolved substance like salt interacts with a solvent like water – and we are closer to understanding how it unfolds at the atomic level
By Karmela Padavic-Callaghan
8 November 2023
Solvation begins after salt has dissolved in water
Pavel_dp/Shutterstock
In a world first, researchers have recorded exactly how solvents interact with dissolved materials, one atom at a time.
After a solute, such as salt, dissolves in a solvent, such as water, the two interact in a complicated way. Their interactions constitute solvation – or hydration if the solvent is water – but what exactly each solvent atom does at the start of the solvation process has eluded researchers for decades.
Now, Henrik Stapelfeldt at Aarhaus University in Denmark and his colleagues have recorded solvation atom by atom.
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Instead of water, they used a nanoscopic droplet of liquid helium cooled to -273°C as the solvent – and instead of a grain of salt, they used an atom of sodium.
The researchers embedded a xenon atom at the centre of the helium droplet, while the sodium atom sat at its perimeter. They then hit the sodium atom with an ultrashort pulse from a laser to turn it into a positively charged ion, which kicked off solvation as the helium atoms from the nanodroplet started sticking to it – just as water molecules surround sodium ions from table salt once you mix it into water.
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