A rapid complexometric scheme for analysis of iron, aluminium, calcium and magnesium in slags

A simple and rapid complexometric method has been developed for the simultaneous determination of iron, aluminium, calcium and magnesium in a single solution in slags. Phosphorous and small amounts of chromium (1.5 mg) and vanadium (1 mg) do not interfere in the titration. Titanium and manganese are suitably masked with lactic acid and tetra sodium pyrophosphate, respectively. In a suitable aliquot, iron is titrated at pH 2 with EDTA, using sulphosalicylic acid as indicator. To this solution, excess disodium 1,2-cyclohexane diamine tetra acetic acid (DCTA) is added and aluminium is titrated by titrating the excess DCTA with standard copper sulphate solution at pH 3.5, using 1-(2-pyridylazo)-2-naphthol (PAN) as an indicator. A known excess of EDTA is added, the pH is raised to 10 and calcium and magnesium are jointly titrated by titrating the excess EDTA with copper sulphate solution, using PAN indicator. The Ca-EDTA complex is demasked with ammonium oxalate at pH 5 and the released EDTA equivalent to calcium is titrated with copper sulphate solution at pH 10 with PAN indicator. Results of analysis compare favourably with certified values and values obtained by standard methods for BCS and other slags. A set of five samples can be analysed for iron, aluminium, calcium and magnesium in four hours as compared to three days by the classical conventional method.     

2-(3,5-二溴-2-吡啶偶氮)-5-二乙氨基苯酚作络合滴定指示剂连续测定铁和铝

对2-(3,5-二溴-2-吡啶偶氮)-5-二乙氨基苯酚作铁(Ⅲ),铜(Ⅱ)的配位滴定指示剂进行了研究.在pH1.8～2.0时用EDTA标准溶液滴定铁(Ⅲ).在滴定铁(Ⅲ)后的溶液中,加入对铝过量的EDTA标准溶液,在pH3.8～4.0煮沸下,铝(Ⅲ)与EDTA生成稳定的络合物,过量的EDTA用硫酸铜标准溶液滴定,从而测定铝(Ⅲ).     

Direct complexometric determination of aluminium in "alzinoy"

A simple and precise method for the complexometric determination of aluminium in "Alzinoy" (a binary alloy of aluminium and zinc) is described. After dissolution of the sample in hydrochloric acid, aluminium, zinc and any lead and iron are complexed with excess of EDTA. The excess of EDTA is titrated with lead solution, with Xylenol Orange as indicator. Ammonium fluoride is then added to decompose the Al-EDTA complex, and the EDTA liberated is titrated with lead solution. Four samples can be analysed in about 45 min.     

EDTA容量法快速测定酸法生产金属镓的液体物料中镓含量

建立了在酸法生产金属镓过程中,用NH4F掩蔽溶液中的铝,加入过量的EDTA标准溶液使之与镓元素完全络合,调整条件试剂硼酸溶液和无水乙醇的加入量,保证终点的准确判断,过量EDTA以PAN为指示剂用硫酸铜标准溶液回滴求得液体物料中镓含量的分析方法.实验表明,方法的相对标准偏差(RSD)为2.8％～6.5％,加标回收率为97.14％～104.0％.方法有较高的准确性和可靠性,且测定结果精密度高,可实现酸法生产金属镓液体物料中镓含量的快速检测.     

Selective masking and demasking for the stepwise complexometric determination of aluminium,lead and zinc from the same solution

Background  

A complexometric method based on selective masking and de-masking has been developed for the rapid determination of aluminium, lead and zinc from the same solution in glass and glass frit samples. The determination is carried out using potassium cyanide to mask zinc, and excess disodium salt of EDTA to mask lead and aluminium. The excess EDTA was titrated with standard Mn(II)SO₄ solution using Erichrome Black-T as the indicator. Subsequently selective de-masking agents – triethanolamine, 2,3-dimercaptopropanol and a formaldehyde/acetone mixture – were used to determine quantities of aluminium, lead and zinc in a stepwise and selective manner.     

Contributions to the basic problems of complexometry—X: Determination of nickel and cobalt in the presence of iron, copper and some other metals

A complexometric determination of nickel and cobalt in the same solution has been devised. It is based on the determination of the sum of nickel and cobalt by back-titration of added excess EDTA in a strongly alkaline medium with calcium chloride using Fluorexon (Calcein) as indicator. After oxidation of cobalt with hydrogen peroxide to form the cobalt^III- EDTA complex and screening of nickel by potassium cyanide, the liberated EDTA corresponding to the amount of nickel present is titrated with further calcium chloride. High concentrations of iron and aluminium are screened with triethanolamine. Copper and other heavy metals are screened with thioglycollic acid.     

Use of nitrosochromotropic acid as a metal indicator

Summary Nitrosochromotropic acid and copper give a purple coloured complex in the pH range 5.8–6.5, which is less stable than Cu(II)-EDTA complex. When milligramme quantities of copper solution containing few drops of nitrosochromotropic acid were titrated with EDTA the colour changes to light green or colourless. Copper can be titrated from 15–30° C, but at higher temperature low results are obtained due to dissociation of copper complex. Alkaline earths do not interfere in the titration of copper, but zinc, cadmium, nickel, cobalt, aluminium and iron(III) interfere. The interference of aluminium and iron(III) is masked by sodium fluoride. Microtitration can be carried out using nitrosochromotropic acid screened with xylene cyanol FF as metal indicator.     

Complexometric determination of palladium(II) using thioacetamide as a selective masking agent

A simple, rapid and accurate complexometric method for the determination of palladium(II) is proposed, based on the selective masking property of thioacetamide towards palladium(II). In the presence of diverse metal ions, palladium(II) is complexed with excess of EDTA and the surplus EDTA is back titrated at pH 5-5.5 (acetic acid-sodium acetate buffer) with standard lead nitrate solution using xylenol orange as indicator. An excess of a 0.5% aqueous solution of thioacetamide is then added to displace EDTA from Pd(II)-EDTA complex. The released EDTA is titrated with the same standard lead nitrate solution as before. Reproducible and accurate results are obtained in the concentration range 0.5 mg - 17.80 mg of palladium with relative error of +/- 0.16% and coefficient of variation not exceeding 0.26%. The effect of diverse ions is studied. The method is used for the determination of palladium in its complexes, catalysts and synthetic alloy mixtures.     

Selective complexometric determination of mercury with sulphite as indirect masking reagent

A complexo-titrimetric method for the determination of mercury(II) in the presence of other metal ions is described, based on the selective masking ability of sulphite ion towards Hg(II). Mercury in a given sample solution is initially complexed with a known excess of EDTA and the surplus EDTA titrated with zinc sulphate solution at pH 5.0–6.0 (hexamine), using xylenol orange (or methylthymol blue) as indicator. An excess of solid sodium sulphite is then added to decompose the Hg(II)-EDTA complex and the released EDTA is titrated with standard zinc sulphate solution. Reproducible and accurate results are obtained for 9.9–99 mg Hg with relative errors < 0.35% and standard deviations < 0.05 mg. The effects of various cations and anions are studied.     

Rapid chelatometric determination of bismuth, titanium and aluminium using Semi-Xylenol Orange with visual end-point indication

A rapid and simple general complexometric method was presented for the determination of bismuth, titanium and aluminium in laboratory synthesized alloys similar to those of some bauxites, clay, ilmenite, Portland cements and ceramic products. The precision and accuracy attainable in successive titrations of Bi(3+), Ti(4+) and Al(3+) with 0.01 and/or 0.001M solutions of disodium ethylenediaminetetraacetate (Na(2)EDTA) and standard ZnCl(2) of the same concentration, using Semi-Xylenol Orange (SXO) as a metallochromic indicator with visual end-point indication were studied. For one aliquot Bi(3+) was at first directly titrated at pH 1-2 (HNO(3)) with Na(2)EDTA using SXO as indicator in the presence of L-ascorbic acid to reduce Fe(3+) to Fe(2+). At the bismuth end-point, an excess of Na(2)EDTA was added, the pH was adjusted with hexamine buffer (pH 5) and the excess of Na(2)EDTA was back-titrated with solution of standard zinc(II) chloride for both the simultaneous and consecutive titrations in the presence of (SXO) as indicator. For the simultaneous titration, fluoride was added to release the Na(2)EDTA combined with both Al(3+) and Ti(4+). For the consecutive titration, phosphate was added to release the Na(2)EDTA combined with Ti(4+) and then fluoride to release the Na(2)EDTA combined with Al(3+). The interference of various anions and cations in the determination of Bi(3+), Ti(4+) and Al(3+) was studied. A comparison of the accuracy of both the simultaneous and consecutive titration was also carried out. The proposed methods were applied successfully to some real samples of bauxites, clay, ilmenite, Portland cements and ceramic products and the results were satisfactory.     

Selective complexometric determination of copper in ores and alloys using 2,2′-bipyridyl as masking agent

An EDTA titration method is described for the determination of copper(II) in the presence of other ions based on the selective masking ability of 2,2′-bipyridyl. Copper and other ions in a given sample solution are initially complexed with an excess of EDTA and the surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamine), using xylenol orange as an indicator. A known excess of 2,2′-bipyridyl solution (1% in 50% alcohol) is then added, the mixture is shaken well and the released EDTA from the Cu–EDTA complex is titrated against standard lead nitrate solution. The interference of various ions are studied and the method is applied to the determination of copper in its ores and alloys. Reproducible and accurate results are obtained for 2.54–25.40 mg of copper with S.D. values <0.04 mg.     

The rapid determination of silica in rocks and minerals

A method is described for the rapid determination of silica in various substances by precipitation of potassium fluorosilicate ; calcium ions are used. to repress coprecipitation of aluminium and titanium. Solubility is reduced by low pH and excess potassium chloride. The separated precipitate is titrated with standard sodium hydroxide solution using phenolphthalein as indicator.     

Automatic derivative spectrophotometric titration of iron and/or aluminum with edta

Automatic derivative spectrophotometric EDTA titration procedures for the determination of iron and/or aluminum are described. Iron is automatically titrated in the presence of aluminum at pH 1.8–3.0 using 3,5-dinitrosalicylic acid as indicator. Total iron and aluminum, or aluminum alone, are determined by adding a small excess of standard EDTA, as visually indicated by the fluorescence of calcein W, with subsequent automatic titration of excess EDTA. The intense color of the iron-EDTA complex causes no difficulty in the automatic method, and macro as well as micro quantities of iron and/or aluminum can be determined with relative errors of 0.3% or less, even when the amount of aluminum is 4 times that of iron.     

Selective complexometric determination of mercury with thiocyanate as masking agent

A method is proposed for selective complexometrie determination of mercury, thiocyanate being used as masking agent. An excess of EDTA is added and the surplus is back-titrated at pH 5-6 with lead nitrate, Xylenol Orange or Methylthymol Blue being used as indicator. Thiocyanate is then added to decompose the mercury-EDTA complex and the liberated EDTA is titrated with lead nitrate. The interference of various cations has been studied.     

Determination of palladium(II) using thiosemicarbazide as a replacing reagent

A simple, rapid, accurate, and selective complexometric method is proposed for the determination of palladium(II). Palladium(II), with associated diverse metal ions, is first complexed by adding a known excess of EDTA, and the uncomplexed EDTA is back titrated with lead nitrate solution in acetic acid-sodium acetate buffer (pH 5.0–6.0) until the end-point. Thiosemicarbazide (1%) solution in water is added to displace EDTA from the Pd-EDTA complex. The released EDTA is then titrated with the lead nitrate solution. Reproducible and accurate results are obtained in the concentration range of 1–10 mg of palladium with a relative error of less than 0.4% and a standard deviation of less than 0.02. The interference of many commonly associated metal ions was also studied. Advantages of this method over other complexometric methods of palladium determination are high-lighted.     

Simultaneous determination of gallium and aluminium in biological samples by conventional luminescence and derivative synchronous fluorescence spectrometry

The simultaneous determination of gallium and aluminium by using conventional fluorimetry and derivative synchronous fluorescence spectrometry has been studied. These determinations are based on the formation of fluorescent complexes of gallium and aluminium with salicylaldehyde carbohydrazone (SACH). In the conventional method, two samples are analysed under different analytical conditions, and the results are evaluated by solving a system of two simultaneous equations. In the derivative synchronous method (at pH = 2.6, in an ethanol-water medium containing 72% of ethanol), the following conditions are used: a constant wavelength difference of 20 nm between the monochromator settings, a time-constant of 1.5 sec, a scan-speed of 120 nm/min, and a derivative wavelength difference of 10 nm; gallium can be determined in the range 7-38 ng/ml, and aluminium between 6 and 45 ng/ml. The synchronous method shows more advantages, and has been used in the determination of both metal ions in diverse biological samples (animal tissues and human serum) with good results.     

Contributions to the complexometric determination of cation mixtures: Simultaneous titration of iron(iii) and aluminium in the presence of ammonium thiocyanate as indicator

With thiocyanate as indicator iron(III) and aluminium(III) can be titrated simultaneously if [Fe⁺³]/[Al⁺³] ? $\text{1}\text{4}$; iron(III) is titrated directly with EDTA, and aluminium(III) is determined by back-titration of the excess of EDTA with cobalt nitrate solution in an acetone-water medium.     

Complexometric Determination of Zinc(II) Using 2,2′-Bipyridyl as Selective Masking Agent

 An indirect complexometric method is described for the determination of zinc(II) using 2,2′-bipyridyl as masking agent. Zinc(II) in a given sample solution is initially complexed with an excess of EDTA and surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamine), using xylenol orange as indicator. An excess of 2,2′-bipyridyl is then added, the mixture shaken well and the EDTA released from the Zn-EDTA complex is titrated with standard lead nitrate solution. Results are obtained for 3–39 mg of Zn with relative errors ≤ 0.5% and standard deviations ± 0.06 mg. The interference of various ions are studied. The method is applied for the determination of zinc in its alloys and ores. Received October 27, 1998. Revision June 10, 1999.     

Complexometric determination of aluminium in iron ore,sinter, concentrates and agglomerates

A method for the complexometric determination of aluminium in iron ore, sinter, concentrates and agglomerates encountered in international trade is described. The sample is fused in a zirconium crucible with a mixed flux of sodium carbonate and sodium peroxide. The fused mass is completely soluble in hydrochloric acid. The R₂O₃ oxides are then precipitated with ammonia and redissolved in hydrochloric acid. Elements such as iron, titanium and zirconium are separated from aluminium by solvent extraction with cupferron and chloroform. After removal of traces of organic matter from the aqueous phase, the solution is treated with an excess of EDTA, which is then back-titrated with zinc solution (Xylenol Orange as indicator). Addition of ammonium fluoride then releases EDTA equivalent to the aluminium and this is titrated with zinc solution. The method is rapid. The precision and accuracy are excellent, and the results comparable with those obtained by the referee method.     

Selective complexometric determination of bismuth with mercaptans as masking agents, and its estimation in alloys

A method is proposed for selective complexometric determination of bismuth. To a solution containing bismuth and other cations, excess of EDTA is added and the surplus is back-titrated at pH 5-6 with lead nitrate (Xylenol Orange as indicator). Thioglycollic or mercaptopropionic acid is then added to decompose the bismuth-EDTA complex and the liberated EDTA is titrated with lead nitrate. The interference of various cations has been studied and the method employed to determine bismuth in a variety of alloys.