Spectrophotometric Determination of thorium in Monazite Sand

Thorium is very improtant in atomic energy industry. Requirements of highly pure thorium complex and metal is rapidly increasing recently with the rapid development of atomic energy industry. Thus, efficient methods for isolation and determination of thorium are required, Here, the conditions of spectrophotometric determination of thorium in monazite sand with chlorophosphonazo-m-NO_2 after PMBP-petroleum ether extraction are dealed with in this paper. Under the experimental conditions employoed, the apparent molar absorptivity of thorium at 660 nm is found to be 8.18×10_4 L.mol~(-1)·cm~(-1)·Sandell sensitivity is found to be 0.00284 μg Th·cm~(-2)·Beer's Law is obeyed for 0～20 μg of Th in 25 ml of solution at 660 nm. The coefficient of variation for the determination of 10.0 μg of thorium (10 determinations each) is 0.73%. The percentage of recovery of thorium is 97.7～105. Results obtained by using the proposed method on monazite sand samples agree well with those obtained by gravimetry. The results of determinations are satisfactory.