Determination of thorium in the parts per million range in rocks

Abstract A procedure is presented for the determination of thorium in the concentration range of 0·2 to 10 parts per million ThO 2 in felsic or mafic rocks. Thorium is extracted by mesityl oxide and purified by iodate precipitation from nitric acid medium containing tartaric acid and hydrogen peroxide. The thorium is determined spectrophotometrically with thoron from meso-tartaric acid medium.