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在EDTA的络合滴定中,因EDTA为多元弱酸的盐,滴定剂的有效成分受溶液酸度的影响很大,即存在酸效应;在不同PH时,它的有效成分的浓度不同,在高的PH时,酸效应较小,甚致不存在。另外,滴定中对共存其它离子的影响,通常要加入其它络合剂进行掩蔽,加入掩蔽剂后,掩蔽剂或多或少地也会与被滴定离子反应,生成络合物、而减少溶液中自由存在的被测离子的浓度,即存在有络合效应;当溶液PH较高时,被测离子(尤其是高价重金属离子)又会因水解(水解效应)而降低浓度等。因此,络合滴定和其它滴定分析法相比,关系较为复杂。滴定曲线的计算就此其它滴定复杂了。
In the complexation titration of EDTA, because EDTA is a salt of a plurality of weak acids, the active component of the titrant is strongly affected by the acidity of the solution, that is, there is an acid effect; at different pHs, the effective concentrations of the active ingredients are different, PH, the acid effect of small, very non-existent. In addition, the impact of titration on the coexistence of other ions, usually with the addition of other complexing agent masking, masking agent added, the masking agent will be more or less react with the titration ions to form a complex, and reduce the solution There is a complexing effect for the freely existing concentration of the ion to be measured. When the pH of the solution is high, the measured ion (especially the high-valent heavy metal ion) will have a lower concentration due to hydrolysis (hydrolysis effect). Therefore, complexometric titration and other titration analysis compared to the relationship is more complicated. Titration curve calculation Other titrations thus complicated.