Watch the video all to the end – it starts off a bit slow, but it gets pretty rad towards the end. I’m not sure what I was expecting to happen… but it clearly wasn’t this:

Image credits: Steve Spangler.

So what’s happening here? Well, it’s plain to see that a bunch of dark particles precipitate at the bottom of the bottle, while the rest of the remaining light liquid rises to the top. But why? Well, the chemistry behind it is actually quite interesting: there is a reaction between the phosphoric acid in the Coke and the milk, especially the proteins in the milk. The phosphoric acid attaches itself to the proteins in the milk, they become heavier, and sink to the bottom, while the rest of the liquid, stripped of its heavier elements, rises to the surface.

You can easily replicate this experiment at home. Here’s what you should do:

  • Get a small bottle of brown soda – coke works great, but basically any dark soda works fine. Throw away just a bit of it.
  • Fill the rest of the bottle with milk – any milk works here, be it whole milk, skimmed milk or something in the middle
  • Mix them gently and wait.
  • Observe the chemistry in action.

I wouldn’t recommend drinking the mix, but if you do conduct this experiment, upload it to Youtube and share it with us in the comment section! We’d be more than happy to share your take on this milk and soda experiment.

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