Determination of micro amounts of uranium by a molybdenum blue method

A new and highly sensitive spectrophotometric method has been developed for the determination of micro amounts of uranium by a molybdenum blue method. The method is based on the observation that at low acidities uranium(IV) reduces ammonium molybdate to molybdenum blue, the absorbance of which is proportional to the amount of uranium present. The variables affecting development of the colour have been investigated and the conditions optimized. Beer's law is found to hold good for uranium concentrations between 1 and 20 ppm, with a precision of 2%. The effect of diverse ions has been studied. The method is useful for the determination of uranium present as an impurity (down to 0.1%) in plutonium, neptunium or thorium.