Solvent extraction-absorptiometric determination of niobium in steels with bromopyrogallol red

A simple and rapid method is described for the determination of niobium in steel with Bromopyrogallol Red. After dissolution of the sample, niobium is extracted along with iron from concentrated hydrochloric acid into isopentyl acetate. Niobium and iron are stripped into an aqueous solution containing sodium acetate, and EDTA, ammonium chloride, tartaric acid, and Bromopyrogallol Red are added to complex the niobium. The niobium-Bromopyro-gallol Red complex along with excess of reagent is extracted into isopentyl acetate containing di-n-octylmethylamine, and measured at 610 nm. The molar absorptivity is 2.50 x 10(4) and Beer's law is obeyed up to 27 mug of niobium. The method is free from interferences and can be applied to the analysis of samples containing as little as 0.01 % niobium.     

Extractive spectrophotometric method for the determination of niobium in steels

A strongly coloured complex of niobium with PAR is formed in oxalate solutions and at pH 7.4 can be extracted into nitrobenzene as an ion-association complex with xylometazolonium ion (XMH), with a molar absorptivity of 46300 1 mol^–1 cm^–1 at 545 nm. In contrast to cationic extractants such as tetraphenylphosphonium or tetraphenylarsonium chloride, XMH is an effective extractant over a wide concentration range without any difficulties in either the separation of the phases or the absorbance of the reagent blank. Job's method of continuous variations revealed that the composition of the extracting species as 1 1 1 1 for niobium oxalate PAR XMH. Based on this extraction, a highly sensitive and selective spectrophotometric method for the determination of niobium in various steels, after prior separation of iron, is described. 4-(2-Pyridylazo)resorcinol (PAR) reacts with the niobium tartrate complex in nearly neutral medium to form a red, water-soluble 1 1 anionic complex [1]. PAR is an unselective reagent and one way of improving selectivity is by ternary and ion-association complex formation. The extraction of some highly coloured metal-PAR complexes with tetraphenylarsonium or tetraphenylphosphonium ion has been described [2, 3]. The PAR complex of niobium, which is formed in oxalate solutions has been shown to be extractable by chloroform using tetraphenylarsonium and phosphonium salts [4, 5]. However, in many of these extraction spectrophotometric procedures difficulties arise due to the delay in the separation of the two phases and significant absorbance of the reagent blank solution, particularly when concentrated solutions of reagents are used.The extraction of anionic complexes of Pd, V, and Cr with xylometazolonium (XMH) cation has been reported elsewhere [6–9]. In the present study we have tried to extract Nb(V) and it is observed that 1 1 oxalatoniobium-PAR complex can be extracted with XMH. A method is proposed for the determination of niobium in standard steels.     

Determination of niobium in zirconium-niobium alloys

A rapid control determination of niobium in 50% zirconium/50% niobium master-alloy is described; it is a direct spectrophotometric procedure, based on the reaction of niobium ions with hydrogen peroxide in concentrated sulphuric acid. The procedure is suitable for the examination of zirconium alloys containing niobium in the range 0.1 to about 60%. At least 1% of chromium, cobalt, copper, manganese, nickel or tantalum, does not interfere. Interference due to optical absorption by the peroxy-complexes of titanium, tungsten, molybdenum and vanadium is not significant in the determination of niobium above about 1%, provided that these metals are not in excess of about 0.5%, 0.25%, 0.1% and 0.02%, respectively. To compensate for optical absorption due to iron(III), a solution of the sample, not treated with peroxide, is used.     

Determination of zirconium in steels

The determination of zirconium in the range 0.01-0.20% is required for some special alloy steels. A method has been developed, based on initial removal of iron as its chloro-complex by extraction with methyl isobutyl ketone, followed by further extraction after addition of potassium thiocyanate, and determination of the zirconium left in the aqueous phase, with Arsenazo III. The absorbance is measured at 665 nm.     

Determination of carbidic carbon in steels

An attempt has been made to develop a simple analytical technique that can readily be used in an industrial laboratory to isolate and quantify the precipitated carbides in steel samples. Attempt has also been made to correlate this value with the thermodynamically predicted values. There is good agreement between the predicted and experimental results. More work is in progress to develop this technique for the preparation of Certifed Reference Materials with dissolved and precipitated carbon in steels.     

Spectrophotometric determination of niobium in steels with 4-(2-pyridylazo)-resorcinol

A direct method is presented for the spectrophotometric determination of niobium with PAR in mild and alloy steels. Interference is caused only by tantalum and large amounts of copper. A compensating solution is used to correct for coloured ions and for the copper-PAR complex. The method covers the range 0–100 mg of niobium, and Beer's law is obeyed from 0 to 2.0μg Nb/ml. A molar absorptivity of 14,400 at 536 nm was found for the niobium-PAR complex, with a relative standard deviation of ±0.6%.     

Optimal reaction conditions for the direct spectrophotometric determination of niobium in steels with sulphochlorophenol s

Optimal reaction conditions for the direct spectrophotometric determination of niobium in steels are described. Conditions for the formation of the niobium—sulphochlorophenol S complex are defined, and the effects of many alloying elements are discussed. Niobium can thus be determined in all types of steels in the range of 0.002–3%Nb.     

Determination of niobium and tantalum with quinaldinohydroxamic acid

Summary A new method has been described for the gravimetric estimation, from a tartrate solution, of niobium and tantalum by quinaldinohydroxamic acid. In theph range of 5.0 to ammoniacal, both the elements are quantitatively precipitated from an ice-cold solution in presence of ammonium chloride and can be separated from quite a large number of ions using EDTA as a masking agent.Niobium complex can be dried at 110 C and weighed for the direct determination of niobium or the complex can be ignited to pentoxide. Tantalum complex, however, needs ignition to pentoxide.

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Zusammenfassung Es wird eine Methode zur gravimetrischen Bestimmung von Niob und Tantal beschrieben. Hierbei werden beide Elemente im Gebiet zwischenph 5 und ammoniakalischem Medium aus eisgekühlter, ammoniumchloridhaltiger Lösung mit Hilfe von Chinaldinhydroxamsäure ausgefällt. Eine größere Zahl von Fremdionen stört nicht, wenn man der Lösung Tartrat und äDTA zusetzt. Der Niobkomplex kann entweder bei 110 C getrocknet und anschließend ausgewogen oder auch zum Pentoxid verglüht werden. Tantal kann nur durch Verglühen bestimmt werden.

     

Determination of niobium in pyrochlore ore by differential pulse polarography

A differential pulse polarographic method has been developed for the quantitative determination of niobium in pyrochlore ore. One-step polarographic curves were obtained in 0.01 mol L(-1) EDTA as supporting electrolyte. Analytical curves indicated that response was linearly dependent on Nb(V) concentration between 1.6 and 8.6 mg L(-1) in the pH range 2-5. The system is quasi-reversible and controlled by diffusion in 0.01 mol L(-1) EDTA as supporting electrolyte; the electrode process involves one-electron reduction of Nb(V) to Nb(IV). The results obtained so far for niobium in pyrochlore ore were comparable with those obtained by X-ray fluorescence determination. Ions such as Fe(III), Cr(III), As(III), Cu(II), Ni(II), Co(II), Mn(II), Sn(IV), Zn(II), V(V), Ta(V), W(VI), Ce(IV), and Ti(IV) did not interfere. Possible interference from Pb(II) can be avoided by complexation with the supporting electrolyte in the pH range 3.5 to 4.6; Mo(VI) ions can be tolerated when their concentration is one-tenth that of Nb(V).     

Determination of molybdenum in steels by flow-injection spectrophometry

A flow-injection procedure is proposed for the determination of molybdenum in steels based on the thiocyanate method. Effects of iron(III), acidity, reagent concentration and interfering species were investigated by using flow-injection systems with the merging zones approach which reduced drastically the number of standard solutions to be prepared. Full details of system design are given. The procedure can be applied to several types of steel samples of industrial relevance. After dissolution of the steels in aqua regia, molybdenum can be determined in the range 0.10–4.00% (w/w) at a rate of up to 270 samples per hour with relative standard deviations less than 2%. The results agree with those obtained by atomic absorption spectrometry with the standard addition method and by plasma atomic emission spectrometry, and with certified values of standard reference samples.     

Determination of niobium and tantalum in binary alloys and zirconium alloys

Recent developments in the metallurgy of niobium, tantalum and zirconium have necessitated provision of analytical procedures for determining niobium and tantalum in the presence of each other and in the presence of zirconium. For this purpose, absorptioinetric procedures based on the formation of yellow coloured complexes, between pyrogallol and niobium or tantalum, have been critically examined. Direct absorptiometric procedures are described, which are suitable for determining niobium or tantalum in the range 2 to 7%; when either of these metals exceeds 7%, differential absorptiometric procedures are recommended. Corrections must lie made for absorption due to the presence of other metals which form complexes with pyrogallol. In tlie determination of niobium or tantalum up to 5%, the precision of the method is about ±0.05%. About 12 determinations can be made in a day, by one analyst.     

Determination of chromium in low-alloy steels by atomic-absorption spectrophotometry

Iron causes severe depression of the signal in determination of chromium by atomic-absorption spectrophotometry in an air-acetylene flame. This effect can be eliminated by addition of hydroxylamine hydrochloride and use of a fuel-rich flame. Addition of iron to the standard solutions is not necessary for up to 300 ppm of iron in the test solution.     

Determination of vanadium in high alloy steels by isotope-dilution

An isotope-dilution method has been developed for the determination of vanadium in high-alloy steels. Vanadium is titrated amperometrically after removal of chromium as chromyl chloride. Vanadium losses due to adsorption were corrected for radiometrically. The procedure was tested on N.B.S. steel samples and showed good precision and accuracy.     

近场激光热透镜光谱分析法测定铌

采用氦-氖激光器(632．8nm)观测了铌(V)与2-(5-溴-2-吡啶偶氮)-5-二乙氨基苯酚(5-Br-PADAP)和酒石酸所形成的紫蓝色三元配合物的激光热透镜效应，建立了近场激光热透镜光谱分析法测定铌的新方法。铌(V)质量浓度在0-500ng/mL范围内与热透镜信号强度呈良好的线性关系，检出限为5ng/mL。该方法已应用于钢样及铌矿样中铌的测定。     

Determination of niobium in rocks, ores and alloys by atomic-absorption spectrophotometry

Niobium, in concentrations as low as 0.02% Nb(2)O(5), is determined in a variety of materials without separation or enrichment. Chemical and ionization interferences are controlled, and sensitivity is increased, by maintaining the iron, aluminium, hydrofluoric acid and potassium content within certain broad concentration limits. There is close agreement with the results of analyses by emission spectrographic, electron microprobe and X-ray fluorescence methods.     

Determination of impurities in niobium metal by a radiochemical neutron activation analysis

A radiochemical separation method using an anion exchange resin has been applied to 3N grade Nb for determining nine impurity elements. Five elements (Cr, Fe, Co, Zn and Se) were separated in 2M HF, three elements (Mo, W and Hf) in 32M HF, Nb in 0.5M HF/3M HCl, and Ta in 1M NH₄F/4M NH₄CCl. The contents of the elements were calculated by a single comparator method using two monitors of Au and Co. The main impurity was revealed to be Ta with a content of over 160 ppm.     

Determination of phosphorus in steels by radiochemical neutron activation analysis

The viability of radiochemical neutron activation analysis as a method for certification of phosphorus in steels was tested by analysis of SRM low alloy steels. Preliminary results are generally in agreement with certified values. The limit of detection, as defined by Currie¹, was determined to be 5 μg/kg.     

Determination of phosphorus in low-alloy steels by alpha-particle activation analysis

Determination of phosphorus in low-alloy steels by alpha-particle activation analysis has been studied in detail. After thick target yield curves of main interferences produced from the sample were measured as a function of alpha energy, the working standard for the present experiments was provided by applying the internal standard method coupled with the standard addition method under the most suitable bombarding conditions. Using the above working standard, it was demonstrated that the concentration of phosphorus in several low-alloy steels can be determined accurately and precisely by ordinary alphaparticle activation analysis.