Samples Containing Thorium or Uranium

Catalysts

Zeolites and to a lesser extent silica gel are common supports for the REEs. The following procedure may prove useful:

1. Weigh 0.1 to 0.5 grams of sample into a Pt crucible or dish.
2. Add 20 mL of HClO₄ and 20 to 50 mL of HF depending upon sample size.
3. Heat on a hot plate to the dense white fumes of HClO₄.
4. Cool and add 15 mL of a 4% H₃BO₃ solution.
5. Quantitatively transfer to a quartz or Vycor beaker and heat to heavy dense fumes.
6. Transfer to a volumetric flask (250 to 1000 depending), add dilute with DI water and HCl to 10% v/v HCl.

The above procedure is presented only as a guide into the basic theory behind the acid digestion of silica containing catalysts where HF is used to break apart and dissolve the entire zeolites, heating to fumes of HClO₄ then ridding the sample of excess HF, and very importantly, the addition of boric acid and heating to fumes results in the dissolution of any insoluble RE fluorides. Si is lost during the preparation.

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