Remember how vinegar reacts to baking soda? Well, here is a similar one. Baking soda and citric acid (similar to vinegar but in a dry form). So that when it gets wet, poof it fizzes up. I can’t scientifically say whether it is actual deodorizing to a toilet (as toilet bombs), since the baking soda chemically reacts with the citric acid. I don’t know what you are left with after the reaction, but the kids like to use them. It’s fun to see them fizz up in the toilet.