OSCILLOPOLAROGRAPHIC TITRATION OF COPPER IN ALUMINUM ALLOYS

Oscillopolarographic titration was applied to the determination of copper in aluminum alloys.In a weakly acidic solution of the sample,Cu(Ⅱ) ion was reduced to Cu(Ⅰ) by ascorbic acid,and a definite amount of standard sodium tetraphenyl borate solution was added to precipitate Cu(Ⅰ) quantitatively.Excess of the tetraphenylborate solution was backtitrated with standard solution of tetraethyl ammonium chloride until the incision at the lower part of the oscillopolarogram of tetraphenyl borate instantly disappeared,indicating the approach of end-point of titration.Mass of copper found was calculated by the given formula.Test for precision with an aluminum alloy of known copper content (wCu 1.33%) for 5 successive determinations,the RSD found was 0.19%.Results of test for recovery by standard addition method were found in the range of 98.7%-102.0%.