Speciation analysis of tin at the tin side of float glass by solvent extraction combined with a stepwise etching technique

In the float process for glass making, tin penetrates the glass surface that is in contact with the molten tin. A detailed understanding of the tin penetrating the surface is required to achieve a high-quality surface. In this paper, we describe and demonstrate a novel and quantitative wet chemical analysis method for determining the concentrations of total Sn and Sn ⁴⁺ that penetrate the surface. This method consists of three steps: stepwise etching of a glass sample, separation of tin species, and determination of the total Sn and Sn ⁴⁺ concentrations. The concentration of Sn ²⁺ and the ratio of Sn ²⁺ to total Sn (Sn redox) were calculated from the total Sn and Sn ⁴⁺ concentrations. This method provides quantitative depth profiles of the total Sn, Sn ⁴⁺, Sn ²⁺, and the Sn redox. When the total Sn concentration (as SnO ₂ ) is greater than 0.2 mass%, this method has the finest depth resolution, 0.1 μm, as compared with other techniques. Moreover, it can be implemented in the laboratory because it requires only commonly used apparatus and equipment. Thus, the proposed method can be used to obtain detailed information about tin penetrating the float glass, and thereby strongly contributes to the float process for producing high-quality glass.