Thermometric Titration of Copper and Zinc in Copper-Based Alloys with Triethylenetetramine

Abstract

The thermometric titration of copper(II) ions with triethylenetetramine was investigated. The apparent enthalpy change of the titration reaction varied over a wide range, even from exothermic to endothermic, depending on the reaction conditions, such as pH of sample and titrant solutions, species of buffer and coexistence of auxiliary reagent. In acetate buffer solution, this reaction was endothermic, and copper(II) ions could be titrated with error less than 0.5% of RSD even in the presence of other heavy metal ions. Furthermore, the sequential titration of copper(II) and zinc(II) ions was possible with error less than 0.7% of RSD when tartrate was added as an auxiliary reagent to get sharp end points. The methods were applied to the analysis of four samples of copper-based alloy. The analytical results agreed closely with those obtained by the JIS (Japanese Industrial Standard) method based on electrogravimetry.