A simple and efficient method to isolate228Ra from natural thorium oxalate was developed. It consists in the coprecipitation of radium by hydrolysis of saturated solutions
of ammonium thoroxalate followed by ion-exchange chromatography on Amberlite IR-120. The final product is carrier-free and
pure enough for the preparation of thin sources for alpha and conversion electrons spectrometry. The radium coprecipitation
utilized in the first step of this method, could be used to separate thorium from most of its radioactive daughters, decreasing
the hazards of manipulation of large quantities of thorium.