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本文试验了用氨水、过氧化氢沉淀分离铁、锰、钛、稀土等干扰元素后,在pH=10的氨性缓冲溶液中,以酸性铬蓝K-萘酚绿B为指示剂,用EDTA滴定钙镁合量,然后调至pH≥12.5,用钙标液回滴释出的EDTA(相当于镁量),以差减法求得钙量。本文还改进了溶样方法以及在回滴前加入甘露醇、补加钙指示剂以改善终点观察等。本法具有稳定性好、快速、准确、消除了公害等优点。分析时间约20分钟。分析手续:称取试样(160目)0.05克于铂坩埚中,逐滴加入浓硝酸10滴、氢氟酸12滴,反应平稳后加浓硫酸3滴,摇匀。加热蒸发至烟冒尽,取下。加盐酸(1+1)10毫升,加热至盐类
In this paper, ammonia, hydrogen peroxide precipitation after the separation of iron, manganese, titanium, rare earth and other interfering elements, pH = 10 in ammonia buffer solution, acid chrome blue K-naphthol green B as an indicator, with EDTA Titration of calcium and magnesium, and then adjusted to pH ≥ 12.5, with calcium standard solution of EDTA released back (equivalent to the amount of magnesium), calculated by subtractive calcium content. This article also improved the method of lysing and adding mannitol before the drop back, adding calcium indicator to improve the end point of observation. This law has a good stability, fast, accurate, eliminating the advantages of pollution. Analysis time is about 20 minutes. Analysis procedures: Weigh the sample (160 mesh) 0.05 g In a platinum crucible, 10 drops of concentrated nitric acid and 12 drops of hydrofluoric acid are added dropwise. After the reaction is stabilized, 3 drops of concentrated sulfuric acid are added and the mixture is shaken. Heat and evaporate till fumes, remove. Add hydrochloric acid (1 + 1) 10 ml, heated to salt