The sample is dissolved in hydrochloric acid in the presence of a small amount of fluoride. Thorium and zirconium are separated from the magnesium by precipitation with ammonia and the zirconium is then separated from thorium by extraction into chloroform as the cupferrate. Finally the thorium is co precipitated on ferric hydroxide and is determined spectrographically by the iron flux method using a Jarrell-Ash grating instrument.
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