The formation constants of species formed in the systems H++W (VI) + nitrilotriacetic acid and H++ nitrilotriacetic acid have been determined in aqueous solution for pH=4-9 at 25oC and different ionic strengths ranging from (0.1 to 1.0) mol dm-3 (NaClO4), using potentiometric and spectrophotometric techniques. It was shown that tungsten (VI) forms a mononuclear 1:1 complex with NTA of the type (WO3L3-) at pH=7.5. The composition of the complex was determined by the continuous variations method.
The complexation of molybdenum (VI) with glutamic acid was investigated in aqueous solution ranging in pH from 4 to 9, using polarimetric, potentiometric and spectrophotometric techniques. The composition of the complex was determined by the continuous variations method. It was shown that molybdenum (VI) forms a mononuclear 1:1 complex with glutamic acid of the type (MoO3L2-) at pH=6.0. The dissociation constants of glutamic acid and the stability constants of the complex were determined at 25oC and at ionic strengths ranging from (0.1 to 1.0) mol dm3- sodium perchlorate.
In both complex formation reactions by introducing two new parameters, E and F, the dependence of the dissociation and stability constants on ionic strength is described by a Debye-Huckel type equation and the effect of the aforementioned parameters on the minimized error function is discussed. Finally, a comparison has been made between the patterns of ionic strength dependence for the two complexes and the results have been compared with data previously reported.