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准确测定存在大量硝酸根时的小量硫酸根是项比较困难的分析课题。采用不预先分离的比浊法,误差较大;采用硫酸钡沉淀法使硫酸根与硝酸根分离,则分离速度较慢。 Schwab曾提出在活性氧化铝上,SO_4~(2-)的亲和力大于NO_3~-,但未见用活性氧化铝分离SO_4~(2-)与NO_3~-的报道。我们做了用小型氧化铝柱从存在大量硝酸根的溶液中选择性地分离小量硫酸根的实验。起初用NO_3~-型Al_2O_3进行分离,发现硫酸根不能定量吸附,后改用ClO_4~-型Al_2O_3,分离获得成功。分离后的SO_4~(2-)用Pb(NO_3)_2滴定,并以铅离子选择性电极为指示电极进行了测定,由于滴定终点的电位突跃非常明显,所以分析方法有较高的精密
Accurate determination of a small amount of nitrate in the presence of a small amount of sulfate is a more difficult analytical task. With no pre-separation turbidimetric method, a larger error; the use of barium sulfate precipitation sulfate and nitrate separation, the separation speed is slower. Schwab proposed that the affinity of SO_4 ~ (2-) is higher than that of NO_3 ~ - on activated alumina, but there is no report on the separation of SO_4 ~ (2-) and NO_3 ~ - with activated alumina. We have done an experiment using a small alumina column to selectively separate a small amount of sulfate from a solution that contains large amounts of nitrate. At first, NO_3 ~ - type Al_2O_3 was used for separation, and it was found that sulfate could not be adsorbed quantitatively, but later changed to Cl__4 ~ -type Al_2O_3, the separation was successful. The separated SO_4 ~ (2-) was titrated with Pb (NO_3) _2, and the lead ion selective electrode was used as the indicator electrode. Because the potential jump of titration end point was very obvious, the analytical method was more precise