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在有氯化物和溴化物存在下,碘化物的含量测定,按《成药分析》(皮列里曼等著,中譯本296頁)記載是用三价铁氧化碘离子,过量的鉄离子用磷酸除去。析出的碘加入碘化鉀溶解后,用标准硫代硫酸鈉液滴定。但在我們測定过程中发現有两个問題:1.测得的含量往往偏低;2.滴定終了时继續有碘析出,因此滴定終点很难确定。針对这两个問題我們进行了試驗,得到了解决。 1.測得結果偏低的原因,我們认为是由于氧化剂浓度不够高,致使氧化不完全。經过試驗,并从文献方面得到証实,把三价鉄的浓度由約10%提高到1M以上,可使氧化較完全。 2.过量的三价铁,虽用磷酸絡合和大量水
The iodide content in the presence of chloride and bromide is reported as iodide ionization by ferric iron as measured by the “Assay Analysis” (Pletchman et al., P. 296), with an excess of phosphonium ion Remove. Precipitation of iodine dissolved in potassium iodide, with standard sodium thiosulfate solution titration. However, we found two problems in our determination: 1. The measured content tends to be low; 2. Iodine precipitation continues at the end of the titration, so the titration end point is difficult to determine. In response to these two issues we conducted a test, has been resolved. 1. The reason for the low measured results, we believe that due to the oxidant concentration is not high enough, resulting in incomplete oxidation. After testing, and confirmed from the literature, the trivalent tin concentration from about 10% to 1M above, can make the oxidation more complete. Excess ferric iron, although complexed with phosphoric acid and a large amount of water