Quantitative precipitation of large amounts of sodium as sodium zinc uranyl acetate and its determination by an indirect complexometric method

Up to 40 mg of sodium can be quantitatively precipitated as sodium zinc uranyl acetate if enough reagent of appropriate composition is added to make the concentrations of zinc and uranium in the mother liquor at least 1.25 and 0.14M respectively. In practice, the reagent solution contains 100 g of uranyl acetate and 300 g of zinc acetate per litre and the volume added (ml) must be at least 15 times that of the solution to which it is added or 1.5 times the number of mg of sodium present, whichever is the greater. The triple salt can then be dissolved in water and the zinc selectively titrated with EDTA at pH 5.3, with Xylenol Orange as indicator. The uranium is masked with ammonium fluoride. Most constituents of ceramics and other silicates, including barium, strontium, magnesium, potassium, sulphate, phosphate and arsenate, do not interfere.