铌(V)的测定,常用重量法与比色法,但均较麻烦、费时。有一些间接螯合滴定铌(V)的方法也较烦琐。基于氨三乙酸(NTA)与铌(V)-过氧化氢形成三元络合物的螯合滴定则大有改进。据此,我们参考有关资料,在pH5.6附近,选用紫脲酸铵(MX)为指示剂,铜盐回滴NTA测定铌(V),效果较好。这时表观稳定常数lgK＇_(Cu-NTA) 8与与 lgK＇_(Cu-Mx) 5.8之差在2以上,因此滴定误差不超过0.2％。本法对某些铌合金及铌晶体的分析,较常法简便、快 Determination of niobium (V), commonly used gravimetric method and colorimetric method, but are more cumbersome and time-consuming. There are some indirect chelation titration niobium (V) method is more cumbersome. Chelation titration based on the formation of ternary complexes between nitrilotriacetic acid (NTA) and niobium (V) -hydroperoxide has been greatly improved. Accordingly, we refer to the relevant information, near pH5.6, the use of ammonium oxalate (MX) as an indicator, the determination of niobium (V) copper salt back to the NTA, the better. The difference between the apparent stability constant lgK ’_ (Cu-NTA) 8 and lgK’_ (Cu-Mx) 5.8 is above 2, so the titration error does not exceed 0.2%. The law of some niobium alloys and niobium crystals, the more common method is simple and fast