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试样用酸或碱分解,以碳酸钡沉淀分离铁、铝、钙和镁,硼则以偏硼酸钡留在溶液中,用甲基红作指示剂,准确中和,加入甘露醇或转化糖等多元醇使硼酸定量的转变为具有环状结构的离解度较大的络合酸,因而可用酚酞作指示剂,用氢氧化钠标准溶液滴定。其反应式如下:C_3H_5(OH)_3+H_3BO_3→C_3H_5OH·HBO_3+2H_2O;C_3H_5OH·HBO_3+NaOH→C_3H_5OH·NaBO_3+H_2O。本法可测定0.2%以上的三氧化二硼。
The sample was decomposed with acid or alkali to separate iron, aluminum, calcium and magnesium with barium carbonate precipitation. Boron was retained in solution with barium metaborate and accurately neutralized with methyl red as an indicator, adding mannitol or invert sugar Such as polyhydric alcohols to quantitative boric acid into a cyclic structure with greater dissociation complex acid, which can be used as a phenolphthalein indicator, titration with sodium hydroxide standard solution. The reaction is as follows: C_3H_5 (OH) _3 + H_3BO_3 → C_3H_5OH · HBO_3 + 2H_2O; C_3H_5OH · HBO_3 + NaOH → C_3H_5OH · NaBO_3 + H_2O. This method can be determined 0.2% more than three boron oxide.