Emanation indicates the general method of approach to determine Radium 226. Ra 226 decays to form Radon 222, a gas separated by aeration and measured for counting alpha disintegrations in gases. A sample is obtained in solution and radium isotopes are coprecipitated with a large amount of barium sulfate. Barium-radium sulfate is decomposed by forming with phosphoric acid, and the resulting glassy melt is dissolved by evaporation with dilute hydrochloric acid to form soluble barium-radium phosphates and chlorides. After aging, radon is removed by aeration and counted. The amount of Ra 226 is calculated from the observed counting rate and the period of ingrowth for Radon 222.