F. Freese

Compleximetric titrations based on 1:2 complex formation: Part I. Mathematical expressions

Summary Mathematical expressions are given for the titration curves of compleximetric titrations of a metal M with a ligand L, resulting in 1:2 complexes of the type ML 2 . A few examples illustrate the practicability of these titrations.

Amperometric complex-formation titration of traces of alkaline earths.

Alkaline earth metals were determined in microgram quantities by complexometric titration with EDTA, EGTA and DTPA. The end-point was detected by following the anodic wave of the chelating agent at the rotating mercury electrode. All the alkaline earths can be titrated at the microgram level with reasonable accuracy, and calcium may be titrated with EGTA in the presence of a 1000-fold excess of magnesium.

Amperometric complex-formation titrations of traces of copper

Copper has been determined in the submicrogram range by means of a eomplexometric titration with triethylenetetramine (TRIEN), the end-point being detected by following the anodic wave of the chelating agent at a rotating mercury electrode. The influence of the presence of other metals has been investigated both from the theoretical and the experimental point of view. Because of its higher selectivity TRIEN is preferred to other reagents of the EDTA group. The results show that copper can be determined in the presence of large amounts of most other metals.

Amperometric complex-formation titration of traces of thorium

Thorium has been determined in the microgram range by complexometric titration with EDTA. The end-point was detected by following the anodic wave of EDTA at a rotating mercury electrode. It has been shown that thorium can be titrated in the presence of large amounts of other metals. Following electrolysis at a mercury pool electrode the titration is selective for thorium.

Amperometric complex-formation titration of traces of cations.

The amperometric titration of cations with chelating agents can be extended to the microgram range by using a rotating mercury anode.

The influence of halides on amperometric complex-formation titrations with the rotating mercury electrode.

The interference of halides with complexometric titrations, indicated by means of the anodic wave of the ligand at a rotating mercury electrode, has been studied theoretically. The effect of halides strongly depends on the pH of the solution. In alkaline solutions there appears to be no interference by chloride at all. A critical value for the halide concentration can easily be found for any medium. The theoretical predictions have been verified experimentally.

Polarographic determination of NTA in the presence of metal ions

ZusammenfassungDie quantitative Bestimmung von Nitrilotriessigsäure, NTA, in wäßrigen Lösungen, die große Mengen Metallionen enthalten, die mit NTA auch in saurer Lösung stabile Komplexe bilden, ist nach Entfernung dieser Metallionen durch Elektrolyse an einer Quecksilberelektrode möglich. Nach der Elektrolyse kann NTA nach einer der üblichen voltammetrischen Methoden bestimmt werden. In dieser Arbeit wurde dazu die Wechselstrompolarographie angewendet.SummaryThe determination of NTA in water containing large amounts of metal ions strongly complexing with NTA, even in acid solution, appears to be possible after removal of the metal ions by electrolysis at a mercury pool electrode. After the electrolysis NTA can be determined in the usual way by a suitable voltammetric method, which in the present work was a.c. polarography.

Titrimetric applications of complexes with 1:2 metal-ligand ratios in the determination of ligands and in back-titrations

Abstract The conditions for suitable end-point determination in linear compleximetric titrations of a ligand L with a metal M, resulting in a ML 2 complex, are given. The determination of 8-hydroxyquinoline-5-sulphonic acid with copper(II), and back-titrations of copper(II) and cobalt(II) involving pyridine-2,6-dicarboxylic acid as the ligand, are given as examples.

Compleximetric titrations based on 2:1 metal-ligand complex formation

Abstract Mathematical expressions are given for the titration curves of compleximetric titrations of a metal M with a ligand L, resulting in 2:1 complexes of the type M 2 L. The theory is illustrated with the titration of copper(II) with DTPA.

Photometric or fluorimetric titration of small amounts of acids or bases

ZusammenfassungWesentlich kleinere Mengen Säuren und Basen können oft bestimmt werden, wenn anstelle logarithmischer Indikationsmethoden lineare Methoden angewendet werden. Falls nicht die linearisierten pH-Kurven verwendet werden, sondern die Indikation über eines der anderen an der Reaktion teilnehmenden Teilchen verläuft, gelten andere Bedingungen. Diese Bedingungen werden abgeleitet und anhand einiger Titrationen substituierter Phenole geprüft.SummarySmaller amounts of acids and bases can often be determined when instead of logarithmic methods linear ones are used. If not linearized pH-curves are employed, however, but one of the other species participating in the reaction is measured, more strict conditions have to be fulfilled. The applicability is illustrated for the case of the titration of some substituted phenols.