As a Bunsen burner heats the bottom of this glass tube, a thin layer of potassium—called a potassium mirror—grows along the tube’s inner wall. Chemists like Andryj Borys, who is a researcher at the University of Kent, use these sealed tubes to keep chemicals away from the oxygen and moisture in air to prevent unwanted reactions. As an added precaution, before putting his water-free hexane in the tube, Borys first placed a bit of potassium metal at the bottom and vacuum sealed the tube. At the low pressure created by the vacuum, the potassium didn’t melt when heated; instead, it turned directly into a gas and deposited onto the cooler walls above. The coating kept his hexane water-free because the metal rapidly reacts with any water present.
Credit: Andryj Borys
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