This is a fascinating video that shows what happens when milk is added to a bottle of coca-cola.

After an hour, the liquid in the bottle appears to become clear, as brown sediment sinks to the bottom.

The separation, as explained by Steve Spangler Science, happens because of a reaction between phosphoric acid in the coke, and milk. Phosphoric acid molecules attach to the molecules of milk, increasing the density and separating them from the rest of the liquid.

The remaining liquids, having less density than the phosphoric acid and milk molecules, float on top.