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铌(V)在溶液中容易水解聚合,致使其螯合滴定的方法受到限制。最初,人们使铌(V)与锌或钙在一定条件下共沉淀,利用铌(V)与这些金属的固有组成比,用EDTA滴定其中的锌或钙,来换算出铌量。这不但难于控制确定的组成,且操作也比较烦琐。 1963年,Lassner提出,在pH 5.0～5.5,铌(V)与过氧化氢及氨三乙酸(NTA)生成稳定的Nb∶NTA=1∶1的Nb(V)-H_2O_2-NTA三元络合物,用甲基钙黄绿素作指示剂,以硫酸铜回滴法测定铌(V)。
Niobium (V) in the solution easily hydrolyzed polymerization, resulting in its chelation titration method is limited. Initially, niobium (V) was coprecipitated with zinc or calcium under certain conditions. The amount of niobium was converted from the intrinsic composition of niobium (V) to these metals by titrating the zinc or calcium with EDTA. This is not only difficult to control the determined composition, and the operation is more cumbersome. Lassner proposed in 1963 that a stable Nb (V) -H 2 O 2 -NTA ternary complex with Nb: NTA = 1: 1 be formed at pH 5.0-5.5 with niobium (V) and hydrogen peroxide and nitrilotriacetic acid (NTA) Material, with calcein methyl indicator, copper sulfate back drop method for the determination of niobium (V).