where it is used for suppressing radical formation, emulsion stabiliser and viscosity control. While etidronic acid has not been limited from inclusion in cosmetics and does have legitimate uses, it is recommended that, as with most cosmetic products (particularly soaps), the product should be thoroughly rinsed from the skin after use. Etidronic acid is also included among swimming pool chemicals. It is used as a stain inhibitor to prevent metal ions coming out of solution and staining the sides of swimming pools. Etidronic acid is used in bars of soap. Pharmacology Synthesis Etidronic acid can be prepared by reaction of Phosphorus trichloride with acetic acid in a tertiary amine, or by reaction of an acetic acid/acetic anhydride mixture with phosphorous acid. References Bisphosphonates Chelating agents