A crazy thing happens when you add lithium to 7-Up

Prior to 1948, lithium was a main ingredient in 7-Up. Since the soda's recipe no longer contains the chemical, the YouTuber's behind "Periodic Videos" decided to see what happens when you add a chunk of lithium to a glass of the lemon-lime drink. 

Take a look. First up, the YouTubers drop a piece of metallic lithium into a beaker of 7-Up. 

At first, it bubbles like you might expect a freshly poured glass of soda would. This reaction is actually the lithium metal reacting with the water in the soda to form lithium hydroxide, Sir Martyn Poliakoff, the chemist narrating the video, explains. 

But as the soda continues to fizz and heat up, the lithium hydroxide reacts with the soda's other ingredients, turning it a strange shade of green. 

And as more time passes, the reaction turns the soda brown. It looks more like beer than soda, Poliakoff notes. 

For a full explanation of the experiment, you can watch the video here or below.