Calcium Phosphate is the calcium salt of phosphoric acid with widely used applications. This agent can be used as a countermeasure for exposure to strontium and radium radionuclides. Upon oral uptake, calcium phosphate competes for and blocks the absorption of radium (Ra-226) and strontium (Sr-90) in the gastrointestinal (GI) tract. Calcium phosphate is an odorless white solid. Sinks and mixes with water. (USCG, 1999) Tricalcium bis(phosphate) is a calcium phosphate.