* Alka-Seltzer's Composition: Alka-Seltzer is a mixture of sodium bicarbonate (baking soda), citric acid, and aspirin. These components are all water-soluble, meaning they dissolve in water.

* Oil and Water Don't Mix: Oil and water are immiscible, meaning they don't mix together. They have different polarities, and water molecules are attracted to each other more strongly than they are to oil molecules.

* The Reaction: Alka-Seltzer's fizz comes from the reaction between sodium bicarbonate and citric acid, which produces carbon dioxide gas. This reaction requires water to occur.

In Summary: You won't see any fizzing or dissolving of Alka-Seltzer in oil because the ingredients need water to react and dissolve.