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.     

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 with a dropping bismuth amalgam electrode in halide medium

The use of the dropping bismuth amalgam electrode has been investigated for the selective determination of metal ions in the presence of large concentrations of halides by means of amperometric complex-formation titrations, using normal pulse polarography. Concentrations of metal ions down to 3 x 10(-7)M have been determined with adequate accuracy in the presence of about 0.1M chloride or 0.01M bromide. Calculated and experimental current-voltage curves have been compared and found to be in reasonable agreement.     

Amperometric complex-formation titrations with a dropping indium amalgam electrode in halide medium

The applicability of a dropping indium amalgam electrode for the determination of metal ions in the presence of large concentrations of halides by means of amperometric complex-formation titrations using normal pulse polarography has been investigated. Titrations appear to be possible in the presence of 4M potassium iodide, 1M potassium bromide and 1M potassium chloride.     

Amperometric complex-formation titrations at a dropping mercury electrode, employing normal pulse polarography

Selective determinations of several metal ions by means of amperometric complex-formation titrations employing normal pulse polarography with a DME appear to be possible. Concentrations down to 3 x 10(-7)M have been determined with adequate accuracy. In alkaline medium deaeration is necessary; in acidic medium it can be omitted.     

Amperometric titrations

ln continuation of the complete review given by the author and J.J. Lingane in “Polarography”, a summary is given of the most important literature and applications of amperometric titrations since 1941.This method deserves much wider application than it has obtained up to now.     

Photometric complex-formation titrations of submicromole amounts of metals-III Back-titrations

In this paper the theoretical considerations on photometric complex-formation titrations of submicromole amounts of metals in the presence of an approximately equivalent amount of indicator are completed by considering the back-titration of a metal in the presence of another metal which is displaced by the titrant. The simultaneous formation of different metal-indicator complexes M(p)I(q) is taken into account. Titration conditions have been derived, with which optimal experimental conditions can be selected. Optimum conditions for the analysis of an indium-ytterbium alloy are deduced from the theory.     

Extractive indicators in complex-formation titrations: theory and practice

The use of conditional constants to predict the optimum conditions for titration in several complex-formation titrations, in which the end-point is detected by the formation of a coloured extractable complex, is demonstrated. The predictions have been tested by experiment. 2-(2-Pyridylazo)-1-naphthol is shown to be a useful extractive indicator for the copper-EDTA titration; dimethylglyoxine is not recommended as an extractive indicator for the nickel-EDTA titration; the titration of fluoride with aluminium, using 8-hydroxy-quinoline as an extractive indicator, is shown to be undesirable theoretically and experimentally.     

Amperometric titrations with the help of selenites

Summary A new procedure for rapid amperometric titration of cobalt based on precipitation of cobalt as the normal selenite is described. Potassium chloride (0.1 M) containing 0.01% gelatin as the maximum suppressor has been used as the supporting electrolyte. The use of 50% overall concentration of methanol was found essential for these titrations. The concentration of alcohol necessary for cobalt concentrations below 2 millimolars was 70%. The titrations have been performed at an applied potential of –1.5 volts vs. S.C.E. Effect of methanol on the equivalence point of the titration has also been studied. The procedure described gives accurate results, which agree well with the formula CoSeO₃ for the normal selenite of cobalt.     

Amperometric titrations of organolead and organotin ions

Mixtures of R₂Sn²⁺ and R₃Sn⁺ compounds can be analysed by titrating their total amount potentiometrically with alkali, and then determining R₂Sn²⁺ in another aliquot by amperometric titration with standard 8-hydroxyquinoline solution. In mixtures of R₂Pb²⁺ and R₃Pb⁺ compounds, dialkyllead ion can be titrated amperometrically with ferrocyanide solution and trialkyllead ions with tetraphenylboron solution. A potentiometric method is described for the determination of small amounts of lead chloride in the presence of any alkyllead chloride.     

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.     

Spectrophotometric extractive titrations for the determination of traces of metals

A modification of extractive titrations, spectrophotometric end-point determination, is proposed. There is no need to discard the organic layer after each extraction because specially constructed titration cells are used. Precise, rapid and selective determination of microgram amounts of single cations, and in favourable cases pairs of cations, is possible.     

Determination of traces of zinc by fluorimetrically indicated complexometric titrations

Zinc forms fluorescent complexes with 8-hydroxyquinoline-5-sulphonic acid (HQS) in the pH region 7-10. The stability of these complexes is such that two different titration procedures are possible: the titration of zinc with HQS and the titration of zinc with EDTA in the presence of HQS. For both procedures the choice of the titration conditions is described. Also two separation procedures for zinc are described, especially suitable in connection with the EDTA titration. The practical results show that zinc in concentrations larger than 10(-6)M (0.05 mug/ml) can be titrated with good precision.     

Amperometric titrations of weak acids with ethylenediamine and diethylamine in non-aqueous media

The electrochemical cell : Cu |CuSO(4) + CH(3)OH parallelKNO(3) + CH(3)OH parallelsolution to be titrated Pt was used for the amperometric determination of weak and very weak acids separately and simultaneously present in non-aqueous solvents, with diethylamine and ethylenediamine as titrants. The amperometric measurements were carried out in the presence of pyrogallol as an electrometric indicator and without an externally applied potential. Solvent mixtures such as glycerol and methanol, propanol or isopropanol (1 + 1) have been used for the determination of weak acids such as benzoic, isobutyric and salicyclic. Mixtures of methanol, propanol or isopropanol with 1-3 ml of formamide were used for the determination of very weak acids such as a-naphthol and p-nittophenol.     

Photometric complex-formation titrations of submicromole amounts of metals in the presence of an approximately equivalent amount of indicator

The photometric titration of the metal indicator complex MI with a ligand L is discussed. A tangent procedure is adopted for the determination of the end-point. From this procedure, in combination with an assumed maximum titration error, titration conditions have been derived. A procedure is introduced which, in conjunction with the derived titration conditions, permits the selection of a suitable titration medium by means of a diagram in which log K, log alpha and log chi are plotted vs. pH. The procedure is applied to determination of lead and zinc in the presence of citric acid, the medium used for their paper-electrophoretic separation. The use of citric acid introduces some limitations; it is shown that the method developed is generally applicable.     

Amperometric titration of copper in brass

A direct amperometric titration of copper is described; o-(p-tolylsulfonamido) aniline serves as titrant. The optimum conditions are discussed and the method is applied to the analysis of copper in brass alloys.

t001. IV. Analysis of various samples in which copper was determined (Values given as percentages)

     

Constituents	Thorn Smith # 30	Thorn Smith # 54	NBS # 37E	NBS # 63C
Cu present	59.30	84.04	69.61	80.48
Zn	37.81	1.452	27.85	0.093
Pb	0.1	8.590	1.00	9.35
Sn	Trace	5.737	1.00	9.03
Sb				0.52
Ni	Trace		0.53	0.32
P				0.145
S				0.060
As				0.023
Fe	1.22		0.004	0.0013
Al	1.15
Mn	0.35
Cu found	59.09	83.64	69.68a	80.54a	aAverage of 3 determinations.