Thorium and yttrium oxides were recovered from siliceous ores of the Powderhorn, Colo., area. Processing comprised (1) acid curing and subsequent (2) acid baking, (3) leaching, and (4) solvent extraction of thorium, using a primary alkylamine, and yttrium, using di-2-ethylhexy1 phosphoric acid. About 95 pct of the contained thorium and yttrium was recovered from ore containing 1.2 pct ThO2 and 0.5 pct Y2O3. The thoria product was 99 pct ThO2 ; the yttria product was 77 pct Y2O3. A 150-to-1 concentration ratio was effected on the latter, but some contaminating lanthanon-group oxides remained.

Studies were made to determine the effect of the shape of a pneumatic-rock-drill exhaust muffler on its efficiency, and the origin and reduction of exit noise from the mufflers. The report describes the investigation of rock-drill noise abatement.