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在聚四氟乙烯烧杯中,以过量氢氟酸和少量硝酸、盐酸,于180～220℃加热处理试样,无四氟化硅逸失。以溴甲酚紫-溴麝香草酚蓝混合指示剂,用氢氧化钠标液滴定,其终点与等当点接近,且变色较明晰。结果准确,重现性良好,适宜大量的常规例行分析。一试剂硝酸钾-乙醇洗液:每100毫升溶液中含硝酸钾10克,乙醇10毫升。溴甲酚紫指示剂:0.2%的乙醇(1+1)溶液溴麝香草酚蓝指示剂:0.2%的乙醇(1+1)溶液二操作方法称取试样0.1～0.2克(视SiO_2含量而定)于300
Teflon beaker in excess of hydrofluoric acid and a small amount of nitric acid, hydrochloric acid, heat treatment at 180 ~ 220 ℃ sample, no loss of silicon tetrafluoride. Bromocresol purple - bromothymol blue mixed indicator, titration with sodium hydroxide standard solution, the end point and the equivalent point close, and more clearly discoloration. The results are accurate and reproducible, suitable for a large number of routine routine analysis. A reagent potassium nitrate - ethanol lotion: Each 100 ml solution containing 10 grams of potassium nitrate, ethanol 10 ml. Bromocresol purple Indicator: 0.2% ethanol (1 + 1) solution Brothymol blue indicator: 0.2% ethanol (1 + 1) solution method of operation Weigh the sample 0.1 ~ 0.2 g And set) at 300