NPR logo A Cheap Alternative to Mentos

A Cheap Alternative to Mentos

Can you believe there's more to say on the Diet Coke and Mentos story? There is.

After the last go-round, I sent off a note to Richard Zare at Stanford University. Besides being a world-renowned chemist, Zare has a particular fascination with bubbles. He recently showed why the bubbles actually go down the side of the glass when you first pull a pint of Guinness.

So I wrote to him and asked his take on why dropping Mentos in a bottle of Diet Coke caused the bubbly liquid to shoot out. He wrote back from China to say he was sure anything with a rough edge dropped into bubbly soda would cause the geyser, including sand or salt. He recently sent this picture and caption to prove his point.

Coke Geyser

"I added salt to a bottle of Coca Cola at Huizhong University of Science and Technology, Wuhan, China. I had one of their chemistry professors (Prof. Li Guangxing) assist me. He had no idea what was going to happen and his facial expression shows that. The geyser of Coke went so high, it reached the ceiling of the lecture hall and left a stain, to the great enjoyment of the audience of about 300 undergraduates."

— Joe Palca

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