Etidronic acid is a chelator that can also be found in soaps, moisturizers and tooth whitening products. The word chelator (pronounced "key-lay-tor") comes from the Greek word chele, or claw. Think of a chelator as a tiny claw that reaches out and grabs the minerals in soap scum or soils, to keep them from depositing on a surface. We use etidronic acid in products to remove soap scum and mineral deposits that are caused by hard water. By binding to the soap scum or deposit, it allows them to be rinsed away.