Aluminum ions in water produce an acid solution. To demonstrate the acidity of a solution containing aluminum ions, grind 7.0 grams of aluminum sulfate hydrate with a mortar and pestle. Into a 250-mL beaker add 1 g of laundry detergent and 50 mL of water plus the ground up aluminum sulfate. Into a second beaker prepare a 50-mL solution containing 5 grams of baking soda (NaHCO₃). Pour the contents of the detergent solution into the bicarbonate solution. This mixture causes a reaction that generates CO₂ gas which is trapped into a foam due to the presence of the detergent. This demonstration can be performed without foam; a burning splint can be extinguished in the CO₂ produced. Bicarbonate will decompose to water and carbon dioxide when mixed with an acid. From a practical point of view, some baking powders [local] contain sodium aluminum sulfate and a newer product, sodium aluminum phosphate.

Baking soda, NaHCO₃, is used when the mixture is somewhat acidic. In this case, rather than using a hydrolyzing metal to bring about the CO₂ producing reaction, a direct reaction with H⁺ takes place.