This Is The World’s Purest Water Drop

This Is The World’s Purest Water Drop
Image: TU Wien / EurekaAlert

You might think glacial water melted by a virgin flame (whatever that is) would give you the purest H2O. Not quite. In fact, it’d be utter bilge compared to this delicious, laboratory-made dew, created using a combination of a vacuum chamber, titanium dioxide and a “cold finger”.

The trick is to start with a very clean surface and pure ice, according to Professor Ulrike Diebold of Vienna University of Technology’s Institute of Applied Physics. You also need a vacuum, as contact with air introduces impurities:

“In order to avoid impurities, experiments like these have to be carried out in a vacuum,” [says Diebold]. “Therefore, we had to create a water drop that never came into contact with the air, then place the drop on a titanium dioxide surface that had been scrupulously cleaned down to the atomic scale.”

This task was made even more difficult by the fact that water drops evaporate extremely quickly in a vacuum, regardless of the temperature.

In order to get the water to stick around for a while, researchers came up with something called a “cold finger”. No, it’s not what you think, you dirty, dirty people:

The tip of this metal finger is cooled to around -140°C and ultra-pure water vapour is then allowed to flow into the chamber. The water freezes on the tip of the cold finger, producing a small, ultra-clean icicle. The titanium dioxide sample is then placed beneath the finger. When the icicle melts, ultra-pure water drops on to the sample.

So, what’s the point of doing all this? Are they releasing a brand of bottled water so clean it’ll put Evian and Fiji out of business? Actually, it was to figure out where “molecular dirt” — a layer of acetic and formic acid that forms on a surface when it touches air — comes from.

Using this ultra-pure water (and one made from soda water), there was no “dirt” to be found:

The surface was then investigated using high-powered microscopes, but the scientists saw no traces of the unknown molecules … This means that the molecules must come from something other than water or carbon dioxide.

Cool. I’d still like a sip, though.