Document Type


Date of Award


Degree Name

Master of Science in Chemical Engineering - (M.S.)


Chemical Engineering

First Advisor

Michael Frederick

Second Advisor

James A. Bradley

Third Advisor

C. L. Mantell


Two methods of analysis to determine thoria (thorium oxide, ThO2) content of thoriated tungsten electrodes are investigated.

Chlorination methods are shown to leave thoria residues contaminated with tungstic oxide which may not be removed by extended chlorination. Ignition of the sample in air before chlorination increases contamination. A correction for the tungstic oxide in the residue is obtained colorimetrically.

The classical hydrofluoric-nitric mixed acid method is modified and shown to be equally as accurate, less exposed to operator's error, and more rapid than chlorination methods. Thin-walled polyethylene beakers are preferable to platinum ware for dissolving the sample, and quartz crucibles may re-place platinum for ignitions. Tungstic oxide contamination of the thoria residue is much less than with chlorination methods.

When purity of the thoria is questioned, thorium is isolated from the common elements by precipitation as the fluoride in preferance to the oxalate, and from the rare earths and uranium by precipitation with benzoic acid.



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