In this report, a method for chelometric determination of lead(II) in a standard solution of lead tetraacetate is investigated. The difference between the total amount of lead(II) measured by the chelometric determination after the reduction of lead(IV) with sodium oxalate, and the amount of lead(IV) measured separately by the potentiometric determination with sodium oxalate standard solution, is used for the determination.
The procedure of this method is as follows:
Into a 300 ml tallbeaker containing 50 ml of 0.05 M lead tetraacetate standard solution, 0.1 N sodium oxalate standard solution is added until its amount reaches(12)% excess to reduce lead(IV) to lead(II). This solution, after evaporated almost to dryness on a water bath, is treated with 5 ml of conc. HNO
3 and again evaporated to dryness. The white residue is dissolved in 2 ml of 1 N HNO
3 and diluted up to 250 ml. The resulted sample solution of lead(II) is titrated with a standard solution of EDTA at pH 5 using Xylenol Orange as an indicator. The concentration of lead(II) as an impurity is calculated from the difference between the total amount of lead(II) and the amount of lead(IV) measured by the potentiometric determination with sodium oxalate standard solution.
By this procedure, it was found that (1.41.7)% of lead(II) in mole fraction was contained as an impurity in a freshly prepared standard solution of lead tetraacetate. These results agree with the amount of lead(II) found by the polarographic method in the previous paper.
This method is simpler than that reported in the previous paper and is applicable over a wide range of impurity content of lead(II) in a standard solution of lead tetraacetate.
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