Up until the 1948, the lemon-lime soda 7-Up contained lithium salts, a substance most commonly known for its medical qualities used in the treatment of major depressive disorders.

While the additive has long since been removed from 7-Up, the scientists from the YouTube channel Periodic Videos thought it would be interesting to drop a piece of lithium into the current day recipe for the soda.

Initially, the results were as expected: nothing special. But after a few more seconds, the solution began transforming from its clear, bubbly state to a dark, sludgy brown. Watch as Sir Martyn Poliakoff explains the unexpected phenomena.