Extraction titration of silver(I) and copper(II) by the ion exchange with lead(II) ethylxanthogenate

Abstract

A selective and simultaneous determination of silver(I) and copper(II) was performed by ion-exchange extraction with lead(II) ethylxanthogenate in chloroform. The procedure is as follows: Transfer the prepared sample solution containing silver(I) {(0.2~8.8)mg} and copper(II) {(0.1~2.2)mg} to a separating funnel, dilute to (20~40) cm3 with water, and adjust the pH to 3~5 with acetate buffer. Extract the solution with 1 cm3 (or less) portions of 10-3 mol dm-3 lead(II)ethylxanthogenate-chloroform solution, draining off each extract until its color changes to brown for the end point of silver (I), and further extract until its color turns colorless for the end point of copper(II). The behavior of silver (I) and copper (II) in the procedure above was examined by atomic absorption spectrometry, and from the results the reaction in the first process is that 2Ag++Pb(EtX)2(0)= 2Ag(EtX)(0)+Pb2+, and the second one is Cu2++Pb(EtX)2(0)=Cu(EtX)2(0)+Pb2+. Most cations and anions do not interfere. This method is applicable to the direct determination of (40~0.2)% silver and (15~0.1)% copper in silver brazing filler metals or other alloys after dissolving of them with nitric acid. © 1978, The Japan Society for Analytical Chemistry. All rights reserved.