On potentiometric titration curves in complexometry

An equation is given which describes the potential change during complexometric titration of metals with potentiometric end-point detection. The potential of the indicator electrode (e.g., silver or mercury electrode) depends on the equilibrium of the reaction MY + W right harpoon over left harpoon WY + M, where W represents the indicator metal ion, and M the metal ion determined by titration with the ligand Y, forming 1:1 chelates. Introduction of the conditional stability constants and corresponding side-reaction coefficients facilitates the prediction of the limits of application of this type of titration as well as the optimum conditions for the determination.     

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.     

A new radiometric titration method based on separation by means of ion exchange

A mathematical expression is derived for the radiocomplexometric determination of a mixture of two metals with one ligand, using an anion exchanger in the solution as a phase separating system. An expression is also given for the complexometric titration of a metal, when formation of acidic or basic complexes is taken into account. In the experimental part titration procedures are proposed for determinations of nickel, copper and iron, using⁶⁵Zn as indicator. The formation of the acidic complex, ZnHY, does affect the radiometric titration curve of zinc with EDTA.     

Organic azo-dyes in quantitative analysis

Summary Chrom red brown 5RD was used as an indicator for complexometric titration of thorium. The change in the colour at the end-point was from wine-red to yellow. It is recommended that the thorium buffered aliquot should not contain less then 200 g thorium per 10 ml for a precise estimation. A range of p_H from 2.5 to 3.5 has been found satisfactory for such a titration. Ferri, ferro and zirconium ions interfere; they should be separated beforehand.Part I: Zaki, M. R., and K. Shakir: Z. analyt. Chem. 174, 274 (1960).     

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.     

Complexometric Titration of Metals Using a Lead Selective Electrode

Abstract

A solid state lead selective electrode is used satisfactorily to indicate the end point eufing the complexometric titration of Ni, Co, Zn and V (IV) with EDTA, CDTA, and DTPA, in presence of a small amount of the corresponding lead complex. The optimum pH for the titration was in the range of 4.0 to 6.0. The quantity of lead complex used was variable and should be determined in each case. The best results are obtained when the metals being determined are present in the range of 25 to 50 micromoles. Nickel, cobalt, and zinc give good results with DTPA at pH 6.0; vanadium(IV) gives excellent results with any of the three reagents in the pH range of 4.0 to 6.0.     

Photometric titration of metal ions,based on ultraviolet absorption by a lead(II) complex. I

Summary A method is described for the complexometric determination of alkaline earth metals with EDTA and EGTA by means of photometric end-point indication at 242 nm, using lead(II) as indicator ion. Determinations of 10^–5 M solutions of calcium and barium appeared to be possible with good accuracy.

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Zusammenfassung Eine komplexometrische Bestimmung von Erdalkalimetallen mit ÄDTA und ÄGTA wurde beschrieben. Die Endpunktindikation wird photometrisch bei 242 nm unter Verwendung vom Blei(II) als Indikatorion durchgeführt. Bestimmungen von 10^–5-m Lösungen von Calcium und Barium sind mit guter Genauigkeit durchführbar.

     

Evaluation of the quality of colour changes of complexometric indicators in the titration of copper (II) with EDTA by tristimulus colorimetry

The quality of colour changes of the indicators hematoxylin, 4(2-pyridylazo)resorcinol (PAR), xylenol orange, pyrocatechol violet, chromazurolS and eriochrome cyanineR in the complexometric titration of copper(II) with ethylenediaminetetraacetic acid (EDTA) were studied with the help of tristimulus colorimetry, utilising a comparative study of the parameters SCD (specific colour discrimination), CIE La^*b^* 1976 and LABHNU 1977. Hematoxylin was found to be the best indicator among those studied. A screened indicator, viz. PAR + malachite green (52), was developed to enhance the quality of colour transition at the end-point and the accuracy of the titrimetric determination.     

Application of various electrodes in potentiometric titration of calcium

In complexometric titrations various indicator electrodes may be employed for monitoring the course of titration and for detection of the end-point. Several of them, including the silver, mercury, bivalent cation membrane, calcium membrane and manganese dioxide electrodes were investigated and compared in their usefulness. As titrant, EDTA was mostly used, but results with similar chelating titrants were also obtained. The practical utility of the electrodes in titrations depends on their selectivity, magnitude of the end-point break and precision in determination of the end-point. For the electrodes studied, in some instances there is good correlation between the theoretical and experimental titration curves, but it is not always possible to predict the electrode response in the low activity range. In other cases poor correlation does not mean that reasonably good analytical results may not be obtained.     

Titration curves of compleximetric titrations of mixtures of metal ions with one ligand : Part II. Conditions for sharp end-points

Conditions are derived for sharp end-points in compleximetric titration curves for mixtures of two metals with visual or potentiometric indication. Special attention is given to end-point detection by means of a mercury or silver indicator electrode.     

Potentiometric and Coulometric Determination of Carbimazole

ABSTRACT

A method for the determination of carbimazole involving its reaction with iodine in an alkaline medium is presented. In volumetric titration with potentiometric end-point detection the range of determination is 30–500 μmol (5.6–93 mg). In coulometric titration using biamperometric end-point detection, 0.5–20 μmol (0.09–3.7 mg) of carbimazole was successfully determined. The coulometric titration was applied to the determination of carbimazole in tablets.     

Indirect Complexometric Determination of Aluminium using a Solid-Membrane Cupric Ion-Selective Electrode

Abstract

Indirect complexometric determination of 0.4–4 mg of A1 in 0.2 M solutions of NaNO₃, NH₄NO₃ and 0.01 M Mg(NO₃)₂ or 0,01 M Ca(NO₃)₂ was studied. The solid membrane cupric-ion selective electrode was used for end-point detection in back‐titration of DCTA (added in excess) with a cupric standard solution.     

Organic azo-dyes in quantitative analysis

Summary Eliamina blue FFL is used as indicator in the complexometric titration of thorium in the p_H range 2.5–3.5. The end-point is sensitive, sharp and obvious. Solutions containing from 20 g to 20 mg thorium — in the nitrate form — per 10 ml aliquot can be easily titrated. Fe³⁺, Zr, Cu²⁺, Ni and Al interfere while Sb⁵⁺, Sn⁴⁺, As⁵⁺, Ce⁴⁺, U⁶⁺, Ca, Pb, Cd Na, K, Co, Mn²⁺ and Cr⁶⁺ do not.     

Potentiometric Determination of Potassium in Seawater and Interstitial Water

Abstract

A method is described for the determination of potassium in seawater and marine sediment porewater. After precipitation of the halogen ions with AgNO₃, potassium is precipitated with sodium tetraphenylborate. The excess tetraphenylborate is then determined by AgNO₃ titration, using a silver electrode for end-point detection. Application of this method to seawater samples as small as 1 cm³, gave accuracy and precision of better than 1%.     

Simple test kit based on colorimetry for quantification of magnesium content in natural rubber latex by miniaturized complexometric titration without using masking agent

A simple, low-cost and portable field test kit based on colorimetry with detection by naked eye was developed for determination of magnesium content in natural rubber latex (NRL). The miniaturized complexometric titration between Mg²⁺ and EDTA without any masking agent was a key reaction in this development, which was designed according to the concept of green chemistry by reduction of waste generation and chemical and time consumption. The system enabled quantification of magnesium content in NRL at low concentration with the detection limit being <50 mg L⁻¹, small sample volume uptake (0.18 g, sampling by a small spoon) and use of <1.5 mL reagent volume which was >70 times less than that applied in the conventional method. Moreover, with the presence of potential interference ions, greater selectivity towards magnesium was observed. Furthermore, the reagents used in our developed test kit were stable for >6 months at room temperature. The results obtained on real samples were in agreement with those obtained from the conventional complexometric titration (ISO 17403: 2014(E)) method. The proposed technique provides a low-cost, rapid, simple, selective and on-site analysis of magnesium content in NRL.     

Graphite-silver diethyldithiocarbamate as a new potentiometric sensor for titration of some metals,halides, thiols,and sulfonamides

A new simple potentiometric sensor based on the precipitation of AgDDC within a graphite rod is described. The electrode is sensitive for both DDC and silver ions down to 10^?5M and can be used as an indicator electrode for complexometric titration of metallic ions with NaDDC and argentimetric titration of some organic and inorganic compounds. Accurate results are obtained for microdetermination of some metal ions singly or simultaneously (in binary and tertiary mixtures and alloys) and thiols, sulfonamides, and halides in organic compounds.     

Coulometric titration of salts of strong mineral acids in acetic anhydride by application of a hydrogen/palladium electrode

The application of H₂/Pd electrodes as generator and indicator electrodes is described for coulometric titrations of alkali metal halides and trivalent metal sulphates in acetic anhydride with potentiometric end-point detection. In acetic anhydride, sodium fluoride is a strong enough base to be titrated directly with H⁺ ions obtained by anodic oxidation of hydrogen dissolved in palladium. Other halides (NaCl, KCl, LiCl, KBr and NaBr) can be determined, after reaction of halides with mercury (II) acetate, by coulometric titration of the liberated base. Potentiometric end-point detection with a H₂/Pd-mercury(I) acetate electrode pair is satisfactory. Sulphates of Fe(III), Cr(III) and Al(III) are determined by back-titrating the excess of barium acetate after precipitation of barium sulphate. The errors in these determinations are < 1% for concentrations ranging from 0.001 to 0.003 M.     

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.     

Complexometric and spectrophotometric determination of thorium(IV), cerium(III), and uranium(VI), using quinizarin sulphonic acid after separation with ion-exchange resins

A method is described for the complexometric EDTA-titration and spectrophotometric determination of Th⁴⁺ Ce³⁺, and UO₂²⁺ in binary or ternary mixtures after primary separation with ion-exchange resin. As indicator or coloring agent, quinizarin sulphonic acid is used. The EDTA titration gives accurate results with Th⁴⁺ and Ce³⁺ only, but the spectrophotometric method proved to be suitable for determination of small quantities of the metal ions.