Muriatic acid cleans soap scum and hard water deposits on grout and tile. To use muriatic acid as a cleaner, dilute the acid with five parts water for one part acid. Apply the mixture in small circles over the tile with a nylon scouring pad.
Muriatic acid is another name for hydrochloric acid. It is a harsh chemical and needs to be mixed outside, so that people can avoid breathing in the fumes.
Wear rubber gloves and eye protection when using the acid.
Aside from household cleaning, muriatic acid has a number of commercial and industrial uses in food production, construction, leather processing and the production of inorganic chemical compounds.