1.1 ,This test method covers the separation of dissolved radium from water for the purpose of measuring its radioactivity. Although all radium isotopes are separated, the test method is limited to alpha-particle-emitting isotopes by choice of radiation detector. The most important of these radioisotopes are ²²³Ra, ²²⁴Ra, and ²²⁶Ra. The lower limit of concentration to which this test method is applicable is 3.7 ×, 10^-2 Bq/L (1 ,pCi/L).