Determination of silver in dore metal by weight titration with equivalence-point detection by differential electrolytic potentiometry.
Use of weight titrimetry, with differential electrolytic potentiometry for detection of the equivalence point, instead of gravimetry, has been critically tested for the determination of silver in doré metal. The electrode response in the presence of possible interferences (Sb, As, Se, Cu, Ni, Fe, Pb and Co) was studied by voltammetry. Titration curves for six different samples were obtained and their differences from those for pure silver were interpreted. Positive errors were found to occur in the presence of 0.1% Fe(III) and Se(IV) but not in the presence of 1% Cu(II). The results obtained by gravimetry and weight titrimetry were compared. The imprecision of the proposed method was between 0.03 and 0.05% (relative standard deviation); that of gravimetry was between 0.05 and 0.08%. The absolute difference from the gravimetric results was between + 0.05 and + 0.08%. The time for analysis of one sample was between 60 and 80 min.
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Facultad de Quimica, Pontificia Universidad Católica de Chile, Vicuna Mackenna 4860, Santiago, Chile.
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