Journal of Radioanalytical and Nuclear Chemistry, Articles, VoL 134, No. 1 (1989) 45-51 POTENTIOMETRIC DETERMINATION OF FREE ACIDITY AND URANIUM IN URANYL NITRATE SOLUTIONS M. ANWAR, D. MOHAMMAD Pakistan Institute of Nuclear Science and Technology, Islamabad (Pakistan] (Received April 12, 1989) Free acid and uranium in uranyl nit.rate solutions have been determined potentio- metrically using Na2SO, - NaOH, Na, SO 4 - Na, CO 3 and (NH4)2 SO 4 - NaOt'I complexant-titrant combinations. The overall recovery of nitric acid varies in the range of 95.25 to 118.5%, depending upon the acid as well as the total uranium present, while that of uranium always a positive bias ranging from 100.2 to 106.4%. The results have been discussed in light of recent available data, It has been conclud- ed that all the complexant-titrant combinations studied provide similar results. Introduction Determination of free acid in the presence of large amounts of heavy metal ions, especially uranium, has been a subject of continued interest) ,2 Reliable anal3,sis methods for rapid and accurate determination of both the free acid and uranium simultaneously present in the same sample over extreme ratios, are still desirable. 3 Such methods may be applied for efficient and safe running of uranium processing plants, solvent extraction systems, ion-exchange, precipitation, complex formation, neutralization and polymerization studies involving heavy metal ions. Accurate ana- lyses have been approached by first following separation of both the species, i.e. acid and the heavy metal and then individual analysis. 3,4 For routine process control analysis, generally, the simultaneous analysis of both of these species is followed employing different complexing agents followed by pH titration, s ,6 first end-point indicating the free acid present and the second end-point being reached after breaking the complex, represents the heavy metal present. In the recent study AHMED et at.1 have determined free acid and uranium with relatively good precision and accuracy using Na2 SO4 complexing agent and Na2 CO3 as titrant and have mentioned certain advantages of using this combination. However, the authors analyzed samples containing < 70 mg of uranium with the acid amount ranging, from 0.036 to 1.46 mequiv, only. We have, in our laboratories, simultaneously Elsevier Sequoia S. A., Lausanne Akaddmiai Kiad6, Budapest