Use of complexones in chemical analysis. XVa. The amperometric determination of bismuth and certain other metals

Chelon approach to analysis: I. Survey of theory and application

“…This approach is by far the most popular at the present time and has served to focus considerable favorable attention on the practicality of the chelon approach to the titration of metal ions. NaOH or (Et)r-NH; 12.5 NaOH; [12][13][14] NH3; 10 NH,; 10 NH,; 9-10, Asc.…”

The Versene complexes

“…(8) Colorimetric procedures: (a) the versene complexes are more intensely colored than the corresponding aquo ions (21)(22)(23)(24), and (b) versene can eliminate interferences by sequestering unwanted ions in the aqueous phase while the desired element is extracted into an organic solvent as another colored complex (25). ( 9) Amperometric titrations at the dropping mercury electrode to the disappearance of the diffusion current of the metal in question (26). The potential of the electrode is maintained at a value yielding a diffusion current for the uncomplexed metal but not sufficiently negative to cause reduction of the complex formed.…”

Amperometric Titration of Two- and Three-Component Mixtures of Metal Ions with (Ethylenedinitrilo)-tetraacetic Acid

“…The general electrode reaction for the anodic wave of EDTA is Eg + HnY""4 HgY-+ nH+ + 2e~ ( 7) when n depends upon pH and varies between 0 and 4. The halfwave potential for the anodic wave of EDTA then becomes Em = E°Us -0.0295 log KnJ (8) neglecting activity coefficients and assuming that the diffusion coefficients of the mercury-EDTA chelate and the various forms of EDTA (H4Y, H3Y-HsY-, HY-, Y"4) are equal to one another. The term, Kus, corresponds to the stability constant of the mercury-EDTA complex and 1/ to the fraction of the EDTA which is in the Y-4 form:…”