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方硼石含大量硼、锰、氯及少量铁、钙、镁、硅、钾、铝和钛,难溶于一般矿物酸中,故采用熔融。由于其中所含的锰在熔融时被空气氧化为锰酸盐,而在提取酸化时,高价锰将氯离子氧化成氯气挥发,有时损失高达90%以上,因此严重干扰氯的测定。本法采用氢氧化钠熔融分解试样,用乙醇溶液提取,在提取熔融物的同时Mn~(6+)被还原为Mn~(4+),保证了氯根的定量提取。但MnO_2沉淀存在影响滴定终点的观察,在酸性溶液中,用亚硝酸钠将其还原溶解。然后加入过量硝酸银,以硫酸高铁铵为指示剂,用硫氰酸铵返滴测定氯根。相对误差≤±0.5%。
Boronite contains a large amount of boron, manganese, chlorine and a small amount of iron, calcium, magnesium, silicon, potassium, aluminum and titanium, insoluble in common mineral acids, so the use of melting. Since the manganese contained therein is oxidized by the air to manganese oxide when melted, the high-valent manganese oxidizes the chloride ions to form chlorine gas when the acid is extracted and volatilizes, sometimes losing as much as 90% or more, thereby seriously interfering with the determination of chlorine. This method uses sodium hydroxide to dissolve the sample and extract it with ethanol solution. At the same time, Mn 6+ is reduced to Mn 4+, which ensures the quantitative extraction of chloride. However, the presence of MnO 2 precipitation titration end point observation, in acidic solution, with sodium nitrite reduction and dissolution. Then add excess silver nitrate to ammonium ferric sulfate as an indicator, with ammonium thiocyanate back drop determination of chloride. Relative error ≤ ± 0.5%.