Titrimetric Determination of Tin(II, IV) in Electrolytes Used in Electroplating for the Deposition of Sn, Cu–Sn, and Ni–Sn Coatings

A procedure is developed for the separate determination of the Sn(II) and Sn(IV) in the range of 0.05–0.25 M in acidic aqueous and ethylene glycol solutions in the presence of Ni(II), Cu(II), F–, a surfactant (OS-20), and citric or oxalic acids. The direct iodatometric titration of Sn(II) is used before and after the reduction of Sn(IV) with aluminum. The procedure is applicable to the analysis of electrolytes for the deposition of tin and Ni–Sn and Cu–Sn alloys and can be used to monitor changes in the concentrations of Sn(II and IV) as a result of redox processes in electrolytes and the hydrolysis of tin compounds. The interfering effect of copper consists in the interaction of Cu(II) with Sn(II) and Al with the formation of Cu(I) ions, reacting with iodate ions, and is eliminated by the introduction of oxalic acid. The relative error in determining the concentration of tin in the absence of copper(II) ions and in the presence of other components does not exceed 2.2%, and in the presence of Cu(II) the error is 4.3%.