Tin(II) oxidation by oxygen and formation of Sn(IV)-Sn(II) colloid

Sn(IV) compounds, formed by a slow oxidation of Sn(II) by air in HC1 or H2S O4 solutions, take part in formation of non-stable colloid particles, which coagulate rather quickly. Introduction of additional amount of Sn(IV) to t he solutions of Sn(II) in HC1 or H2SO4 or formation of Sn(IV) during high-r ate catalytic oxidation of Sn(II) by oxygen results in formation of yellow- coloured stable colloid solutions. The colloid particles formed in HC1 solu tion are charged positively, while formed in H2SO4 solution they are charge d negatively. Sn(IV)-Sn(II) colloid particles act as an inhibitor of the pr ocess of Sn(II) oxidation by oxygen in both I-ICI and H2SO4 solutions. Howe ver, the colloid particles do not change the rare of Sn(II) oxidation in th e H2SO4 solution with addition of Cu(II), catalyzing this reaction.