A new oxidimetric reagent: potassium bichromate in a strong phosphoric acid medium—IV : Titrimetric determination of uranium IV alone and in mixture with iron II, manganese II, cerium III or vanadium IV

Abstract

The potentiometric titration of uranium IV is possible at room temperature with potassium dichromate at all concentrations of phosphoric acid ranging from 3 M to 12 M. An inert atmosphere is unnecessary. The potential break at the end-point is about 70–90 mV/0.04 ml of 0.1 N potassium dichromate in the range 3 to 9 M of phosphoric acid, 140 mV in 10.5 M phosphoric arid and 180 mV in 12 M phosphoric acid. Iron II and uranium IV can be determined in the same solution if the concentration of phosphoric arid is maintained above 11.5 M at the iron II end-point. Under similar conditions a differential potentiometric titration of uranium IV and vanadium IV is possible. Uranium IV and manganese II can be determined in the same solution if the concentration of phosphoric acid is maintained between 3 M and 9 M at the uranium IV end-point, then increased so that it is 12 M at the manganese II end-point. Under similar conditions the differential potentiometric titration of uranium IV and cerium III is possible. The application of these procedures to uranium-bearing minerals is under investigation.