Anion exchange separation of tin and zinc from copper and its application to copper-alloy analysis

Abstract

A method was described for the determination of tin and zinc in copper alloys. After the sample had been dissolved in a mixture of nitric and hydrochloric acids together with a small amount of hydrogen peroxide, the obtained solution was treated with sulfuric acid to remove lead by filtration. The filtrate was diluted to a definite volume with water and adjusted to 3N in sulfuric acid. An aliquot of the solution was taken and placed on the top of an ion exchange column of strong basic anion exchanger Dowex 1-X8 in a thiocyanate form. Metal ions such as nickel, aluminum, manganese were first removed with 30ml of 0.5N sulfuric acid, while tin, zinc and copper were retained on the column. Both tin and zinc were subsequently eluted with 15ml of 0.5M NaCl-0.5M NaOH solution. Small amounts of copper tended to contaminate the fraction of tin and zinc and interfered with the determination of both metals. However, this difficulty could be effectively eliminated by masking the copper with thiourea. Tin in effluent was determined photometrically with dithiol and zinc was titrated chelatometrically with EDTA using xylenol orange as an indicator.