Protactinium radioactivity concentration limits

An additional complication can arise in solution if the radioactive species in trace amounts react with trace concentrations of impurities. For example, in an investigation of the properties of pentavalent protactinium, Pa(V), it was foimd that the protactinium was extracted into pure xylene from 1 M HCIO4 solutions. Further experimentation showed that this extraction was due to the presence in the xylene of organic impurities at concentrations below the detectable limit of 0.01 %. Support for this interpretation was provided when the solution was made 10" M in thorium, which was expected to form complexes with the probable impurity, thereby preventing the reaction with the protactinium. In fact, no protactinium was extracted into xylene from this solution. The thorium in this case acts as a hold-back carrier. 

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See also in sourсe #XX -- [ ]

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