Muriatic acid is another name for hydrochloric acid (HCl). It is a hazardous material for skin and eye contact and produces dangerous vapors. It must be used with proper protective equipment and adequate ventilation or acid gas respirator.

It is an effective cleaner and will remove grout haze on many sufaces. It can also etch surfaces so be careful where you put it. I have used the acid on bricks and dilute the acid just enough so it fumes when applied, dilution instructions are usually included. You will see it sizzle and fume on grout. It can be applyed with a stiff nylon brush or broom from a bucket. Allow the acid to work, agitate and rinse completely. Acid can be neutralized with an alkaline cleaner, lime, or enough rinsing. Lime is also a good first aid precaution if you get acid on your skin.