A rapid method for the estimation of radium and radon in water samples with activity levels more than 1–2 pCi/l. is described. Radium and daughter products of radon are precipitated with more than 95% efficiency in the presence of ZnS (Ag) scintillation powder giving a composite scintillator-sample combination. Apart from being rapid and inexpensive, the method is suitable for field use as it requires very little apparatus and does not involve laborious chemical analysis. Effects of temperature, pH and amount of ZnS (Ag) were studied and conditions for optimum yield were determined experimentally. Results of radium and radon levels in some thermal springs measured in the field using this method, are also presented in the paper. © 1969 Health Physics Society.
