tailieunhanh - Volume 10 - Materials Characterization Part 5

Tham khảo tài liệu 'volume 10 - materials characterization part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | forms during titration using iodine. Antimony may be determined similarly although tartrate is added to prev precipitation of the analyte. Reduction of selenium to the elemental form with potassium iodide followed by titration of the iodine that forms w standard sodium thiosulfate solution may be used but tellurium must be absent. The solution is titrated until the s blue color disappears. Similar analytical techniques are used to determine c C10g J bromate Pr 3 and iodate anions the free halogens GBr2 and b ozone Q and NQ in gases . Numerous indirect iodimetric methods are also used. Lead is precipitated first as the sulfate the filtered residi dissolved and the lead precipitated a second time as the chromate. The filtered residue is dissolved and potassium is added. Iodine is liberated in stoichiometric proportion to the lead content and is titrated using standard SO thiosulfate solution. Similarly mercury is precipitated as the periodaỉe l0 ầ 2 which is filtered then dissolved in potassium iodide which reacts to produce iodine. This is then titrated using sodium thiosulfate solution. Copper can be determined by first separating it as the sulfide dissolving the filtered residue then reacting the broi oxidized slightly acid solution with potassium iodide. Copper ll reacts to form copper l iodide which precipitates b iodide anions are oxidized to iodine. The iodine is titrated using sodium thiosulfate solution. Alternately copper ma precipitated as copper ll thiocyanate then the filtered residue dissolved in hydrochloric acid and titrated using star potassium iodate. The disappearance of iodine color due to the formation of ICI in a large drop of chloroform is US detect the endpoint. Miscellaneous Redox Titrations. Most volumetric methods in routine use fall under this general heading. Table 1 summarizes the most commonly used volumetric procedures. In most cases endpoint detection can be accomf potentiometrically or by use of an appropriate redox indicator. Table