Amperometry with two polarisable electrodes-XI Determination of bismuth by EDTA titration

Optimum conditions have been found for a highly selective determination of bismuth via EDTA titration with biamperometric indication of the end-point. The influence of the applied potential, pH and stirring on the accuracy and selectivity of the determination has been studied. In a medium of 0.4M nitric acid only high concentrations of iron(III) and copper(II) interfere with the determination of bismuth. Zirconium, thallium(III) and indium interfere even in small concentrations. The average error of the determination of 5-100 mg of bismuth (when titrated with 0.05M EDTA solution) is +/-0-1 % rel. and for the determination of 0.5-10 mg it is +/-0.3% rel. (0.005M EDTA). The method has been verified by the analysis of a Wood's metal of known composition.     

Specification of colour changes of metallochromic indicators in the titration of bismuth with EDTA

The quality of the colour changes at the end-point in the complexometric titration of bismuth(III) with EDTA, using the indicators Hemotoxylin, PAN [1-(2-Pyridylazo)-Naphthol-2], PAR [4-(2-Pyridylazo)-Resorcinol], Xylenol Orange and Thoran is studied by means of the CIE 1931 trichromatic system, using specific colour discrimination (SCD) and colour difference (DeltaE*). The indicators are arranged in order of colour change quality. Of the indicators studied, Hemotoxylin is recommended as the most suitable for this titration.     

EDTA titration of bismuth(III) in ores and concentrates with biamperometric indication

Summary A method is described for the chelatometric titration of bismuth(III) with biamperometric indication. It is applied to ores and concentrates and can also be used in presence of interfering elements (as Zr, Tl, In, Mo, Cu, Fe).

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Zusammenfassung Ein Verfahren wird beschrieben zur chelatometrischen Titration von Wismut(III) mit biamperometrischer Endpunktsanzeige. Es wird auf Erze und Konzentrate angewendet und kann auch in Gegenwart störender Elemente (wie Zr, Tl, In, Mo, Cu, Fe) benutzt werden.

     

Spectrophotometric determination of bismuth and EDTA by means of the reaction of bismuth with pyrocatechol violet in the presence of septonex

The reaction of bismuth(III) with Pyrocatechol Violet in the presence of the cationic surfactant Septonex was studied and the optimal conditions for its analytical use were found (lambda = 612 nm, pH = 3.1, C(PV) = 4 x 10(-5)M, C(Sept), = 5 x 10(-4)M). The Lambert-Beer law is obeyed over the bismuth range 0.1-7.5 mug/ml. Decomposition of the Bi-PV-Septonex complex was utilized for indirect determination of ethylenediaminetetra-acetic acid at concentrations of 0.3-7.4 mug/ml.     

Chelatometric titration of bismuth with hedta

A new chelatometric method for the determination of Bi in bismuth-base alloys, low-melting alloys and reagent-grade bismuth salts is proposed. It is based on the chelation of Bi(III) with HEDTA, which is added in substoichiometric amount in perchloric acid medium to eliminate the interfering side-reactions of olation and oxolation, followed by pH adjustment and titration at pH 2 with Semi-Xylenol Orange as indicator. It is more selective than the classical EDTA method, and the accuracy and precision are enhanced. The coefficient of variation was found to be ˜ 0.1%.     

Spectrophotometric study of the reaction of bismuth with bromopyrogallol red in the presence of tensides: The determination of bismuth and EDTA

The formation of the complex between bismuth and bromopyrogallol red in the presence of cationogenic tensides CPB or Septonex was studied. Optimal conditions for this reaction were found and a new spectrophotometric method was developed for determining bismuth in the concentration range 0.2–5.5 μg · ml^?1. On the basis of the reaction of Bi with EDTA, a new method was developed for the indirect determination of EDTA in the concentration range 0.2–6.0 μg · ml^?1.     

复杂高铋物料中铅的Na2EDTA滴定法测定

复杂高铋物料中,铋、砷、锑、锡四元素含量高且共存时会影响铅的测定。特别是铋含量高时对铅的测定影响大。实验用EDTA—酒石酸联合掩蔽铋、砷、锑、锡,在稀硫酸介质中以硫酸钾为沉淀剂,使铅生成硫酸铅钾复盐沉淀而与铋、砷、锑、锡、铁、铜、锌、铝、钴、镍等干扰离子分离,沉淀以乙酸-乙酸钠浸取,二甲酚橙为指示剂,Na2EDTA滴定法测定铅。试验进一步优化了测定条件,确定最佳条件：硫酸（1 1）加入量为7mL、硫酸钾用量为5g、煮沸时为5min、沉淀陈化时间为2h、EDTA 50g/L 加入量为10mL、酒石酸用量为0.5g,铅的回收率99.70% ～100.65%。将实验方法应用于测定复杂高铋物料中铅,标样BY0111-1与给定值一致,相对标准偏差（n=11）RSD 0.20%～0.23%,满足生产测试要求。     

Spectrophotometric determination of EDTA

Both iron(III) and its EDTA complex in 0-1N H(2)SO(4) medium absorb in the ultraviolet region of the spectrum, with absorption maxima at 305 and 258 nm respectively. EDTA can thus be determined by addition of excess of Fe(III) and measurement of the absorbance at the two wavelengths. An EDTA concentration as low as 10(-6)M can be determined with a fair degree of accuracy. The method is free from interferences from most common metal ions, and is simple and rapid.     

Spectrophotometric determination of bismuth with diethylenetriaminepenta-acetic acid

Diethylenetriaminepenta-acetic acid is used for spectrophotometric determination of bismuth (at 270 nm) in 1.6 M perchloric acid. The system obeys Beer's law in the range 1–40 μg/ml. The method has been tested for the determination of bismuth in pure lead and polymetallic ores.     

Consecutive indirect titration of periodate and iodate with EDTA

Periodate and iodate (μmol amounts) are determined successively in the same solution by their selective oxidation of iron(II) at pH 2.0 and in acetic acid, respectively. The resultant iron(III) is titrated with EDTA solution to a sulphosalicylic acid end-point. Bromate—iodate mixture can be titrated similarly.     

Indirect complexometric titration of sodium and potassium with EDTA

Summary Sodium is precipitated as sodium zinc uranyl acetate, filtered and dissolved in water, and zinc is titrated with EDTA using eriochrome black T as indicator. Potassium is precipitated as potassium sodium cobaltinitrite and dissolved in hot water containing little hydrochloric acid. The blue colored solution produced by cobalt in solution, with ammonium thiocyanate and acetone was titrated with EDTA until colorless. The results are good.The author is grateful to Prof. Philip W. West, Boyd Professor of Chemistry, Louisiana State University, for kindly providing the facilities to carry out the investigation.     

EDTA titration of calcium and magnesium with a calcium-selective electrode

Direct semi-automatic and automatic derivative potentiometric EDTA procedures for the determination of calcium and/or magnesium with a calcium-selective electrode are described. Calcium is titrated in the presence of magnesium at pH 12.0 and the total calcium and magnesium is determined at pH 9.7. Calcium in the range 1-8 mg and magnesium in the range 0.7-5 mg are determined semi-automatically with average errors of about 0.2 and 0.3% respectively and automatically with average errors of 0.4 and 0.7%. Titration times vary from a few seconds to a few minutes.