Separation of niobium and tantalum with phenylarsonic acid

Phenylarsonic acid permits satisfactory separation of niobium and tantalum and estimation of tantalum from an oxalate solution containing sulphuric acid up to pH 5.8. For complete precipitation of niobium the pH should exceed 4.8. In mixtures, tantalum is precipitated below pH 3.0 and niobium is then precipitated above pH 5.0. When the oxalate concentration is high, recovery of niobium with cupferron is recommended. When the ratio of Nb₂O₅, to Ta₂O₅ exceeds 2:1, reprecipitation of tantalum is necessary. The effect of interfering ions is studied.     

Gravimetric analysis of tantalocolumbites by precipitation from homogeneous solution

An analysis of complex tantalocolumbites has been carried out by precipitation from homogeneous solutions. A homogeneous precipitation of tungsten, titanium, tantalum and niobium by thermal decomposition of the soluble peroxytungstates, described in previous papers, is used. Corrections for incomplete precipitation and coprecipitation phenomena are applied on the basis of the experimentally found values. Silicon and tin are separated by volatilisation as fluoride and iodide, respectively. Iron is extracted by means of isopropyl ether and the rare earth metals are precipitated homogeneously from an oxalate solution. Manganese is precipitated as the ammonium phosphate. The results are in good agreement with an independent method, the standard deviations being within 1 % for the major constituents.     

Colorimetric determination of tantalum in titanium alloys

Experimental work on tantalum-titanium alloys has been handicapped by the lack of accurate methods for the determination of the tantalum. In this paper a colorimetric procedure is proposed for the determination. The tantalum is separated completely from the titanium by two tannin precipitations with an intervening digestion with tannin. The tannin precipitate is ignited, fused with potassium bisulfate and the melt taken up with ammonium oxalate solution. Pyrogallol is then added and the intensity of the yellow color is measured. A study was made of the tantalum pyrogallol color to obtain optimum conditions. Elements that would be found in the usual tantalum-titanium alloys do not interfere with the method. More than 0.0025 gram of niobium interferes by cauaing occlusion of titanium by the tannin precipitate. This causes high results for tantalum, since titanium reacts with pyrogallol to produce a yellow color. The presence of more than 0.0050 gram of tungsten causes high results for tantalum because tungsten is partially precipitated by the tannin and reacts with pyrogallol to produce a yellow color. The proposed method is recommended for tantalum-titanium alloys containing 0.05 to 5 percent, tantalum.     

Separation of niobium and tantalum with benzo- and phenylacetylhydroxamic acids

Benzohydroxamic acid (I) or phenylacetylhydroxamic acid (II) is suggested for the quantitative separation of tantalum from niobium in an oxalate solution. The tantalum precipitate must be ignited for weighing; niobium is determined in the filtrate with another reagent. The pH range for complete separation is 4.0–6.4 for I and 4.5–6.2 for II. Single precipitation is satistactory for Nb: Ta ratios of 18 : 1 to 1 : 20 for I, and 8 : 1 to 1 : 23 for II. Titanium, zirconium, tartrate, citrate and a large excess of oxalate interfere.     

Solvent extraction separation of tantalum from niobium on macro scale using di(2-ethylhexyl) phosphoric acid as extractant

A solvent extraction procedure for the separation of niobium and tantalum has been developed. The method consists of extracting tantalum from its aqueous mixture with niobium, with the help of di(2-ethylhexyl)phosphoric acid (HDEHP) in n-heptane. The aqueous feed consists of niobium and tantalum in an aqueous medium containing hydrochloric and oxalic acids. The concentrations of niobium and tantalum were raised to 1 mg/ml in the aqueous solution. The extraction efficiency of tantalum under these conditions was found to be 85%. Effects of chloride and oxalate ions as well as those of the concentration of HDEHP on the extraction efficiency were studied and discussed in detail.     

Precipitation and determination of tantalum and niobium from homogeneous solution with 3:3' :4' :5:7-pentahydroxyflavanone

3:3,:5:7-Pentahydroxyflavanone in fairly concentrated acidic solution (6-9N) does not precipitate tantalum and niobium ; however, on heating or boiling, in the presence of air, this flavanone is transformed into 3:3':4':5:7-pentahydroxyflavone, which precipitates any tantalum and niobium present in the solution. Under the precipitation conditions, racemisation of the flavanone also takes place. The racemised flavanone which is less soluble than the original d-form may accompany the tantalum and niobium precipitates without affecting the quantitative determination of these elements.

The precipitation of the tantalum and niobium complexes can be controlled by regulating the acidity and the duration of boiling, as well as the concentration of the flavanone. Experimental data and procedures are given for the precipitation and determination from homogeneous solution of tantalum and niobium complexes. Zirconium and molybdenum do not interfere with the determination. Titanium must be absent or present only in minute quantity.

Since the generation of the precipitating reagent, flavone, from the flavanone is comparatively slow, the precipitation of tantalum and niobium is uniform throughout the solution. By this technique, adsorption and co-precipitation of potassium and sulphate ions in the solution are shown to be negligible. This is in contrast to the less effective dropwise addition of the flavone reported by earlier investigators, in which adsorption and co-precipitation were pronounced.

In the present study, tantalum and niobium oxides were fused with potassium bisulphate. There is no necessity using hydrofluoric acid to dissolve these oxides and therefore no polyethylene apparatus is required.     

Solvent extraction and separation of zirconium,niobium and tantalum by 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone

Summary Extraction of zirconium, niobium and tantalum from oxalic and hydrofluoric acid solutions, by 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone (HA) dissolved in chloroform was studied. Extraction mechanism for the extraction of zirconium from oxalate solutions and of niobium from fluoride solutions is proposed. Separation of zirconium and niobium from oxalate solution as well as from fluoride solution and tantalum and niobium from fluoride solution is described. Back-extraction of these metals is possible by hydrofluoric and oxalic acid. Results obtained show that the efficiency of extraction by HA decreases in the sequence tantalum > niobium > zirconium.

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Zusammenfassung Die Extraktion von Zirkonium, Niob und Tantal aus oxalsauren und fluorwasserstoffsauren Lösungen mit Hilfe einer chloroformischen Lösung von 2-Carbäthoxy-5-hydroxy-(4-tolyl)-4-pyridon wurde untersucht. Ein Extraktionsmechanismus für Zirkonium aus Oxalatlösungen und für Niob aus Fluoridlösungen wurde vorgeschlagen. Die Trennung von Zirkonium und Niob aus einer Oxalatlösung oder aus einer Fluoridlösung sowie von Tantal und Niob aus einer Fluoridlösung wurde beschrieben. Die Rückextraktion dieser Metalle mit Flußsäure und Oxalsäure ist möglich. Die Ergebnisse zeigen, daß die Effizienz der Extraktion in der Reihenfolge Tantal > Niob > Zirkonium abfällt.

     

Separation of niobium and tantalum with n-benzoyl-n-phenylhydroxylamine

The use of N-benzoyl-N-phenylhydroxylamine for the separation of niobium and tantalum, allows a satisfactory estimation of niobium from a tartrate solution at an acidity of 2.0N. The pH range for complete precipitation can be extended to 6.5. For tantalum precipitation, the pH of the solution should be below 1.5 and the acidity may even be above 2.0N. At pH 3.5–6.5, niobium is completely precipitated and tantalum remains in solution; the latter is precipitated by lowering the pH. Niobium and tantalum in ratios of 1:16 to 100:1 can be separated by a single precipitation, in the case of a ratio of 1:100 precipitation must be carried out twice. Titanium, zirconium, vanadate and molybdate interfere with the determination of niobium though other ions have no effect in the presence of complexone III and tartaric acid. The precipitates are granular and easy to filter and wash. The time taken for a complete analysis is much less than that of other methods     

The precipitation of germanium by tannin

Germanium is quantitatively precipitated by tannin from oxalate solution at 0.07 N acidity, the white precipitate settles quickly, and is easily filtered and washed. Clean separations are effected in one precipitation from vanadium, ferric iron, and elements of Tannin Group B. Germanium is shown to be a member of Group A, being precipitated at an acidity below that required for tin and tantalum but above that required for titanium.Davies and Morgan's precipitation procedure in acid sulphate solution was tested. The germanium precipitate thus obtained is not quite so tractable as that produced in oxalate solution, and a separation of titanium from germanium by their method could not be effected.     

The determination of zirconium in its binary alloys with niobium and tantalum

A procedure is presented for the determination of zirconium in the presence of niobium or tantalum. The bulk of the niobium or tantalum is first removed by extracting with hexone from a 10M hyclrofluoric acid, 6M sulphuric acid solution of the sample. The zirconium is then. separated from any unextractcd earth, acid element by precipitation with ammonium hydroxide followed by the addition of hydrogen peroxide. Under these conditions, both the niobium and tantalum form soluble peroxy complexes whereas the zirconium is completely precipitated from solution. After the separation of the precipitate by filtration, it is re-dissolved in hydrochloric acid and the zirconium concentration is finally determined by titration with ethylenediaminetetraacetic acid.     

Extractive Recovery of Tantalum(V) and Niobium(V) with Octanol from Hydrofluoric Acid Solutions Containing Large Amounts of Titanium(IV)

Extractive recovery with n-octanol of tantalum(V) and niobium(V) from hydrofluoric acid solutions containing large amounts of titanium (up to 2-3 M) was studied. The conditions were found for separation of tantalum(V) and niobium(V) from titanium(IV), allowing recovery of 95.7 and 84.1% of tantalum and niobium fluoride complexes, respectively, in one extraction cycle, with 2.6% recovery of titanium.     

Colorimetric determination of niobium in titanium alloys

There is need for a method for the determination of niobium in titanium alloys, since niobium-titanium alloys are becoming increasingly important. The determination of niobium in this type of alloy is an extremely difficult matter. Many approaches were tried before the problem was solved. In the method proposed in this paper the sample is dissolved in a mixture of hydrofluoric and nitric acids, the solution evaporated to a small volume, and boric acid added. Two tannic acid separations are then made to separate the niobium from the bulk of the titanium. The niobium, is determined colorimetrically by the thiocyanate method using a water-acetone medium. A study was made of the possible interference of elements that might be present in titanium alloys. It was found that the presence of tantalum causes two opposing tendencies. Tantalum can cause high results for niobium because it forms a complex with thiocyanate which is visually colorless but shows some absorption. Tantalum can cause low results for niobium by hindering the development of the niobium color. The resultant effect of the tantalum depends upon the amount of tantalum present, the amount of niobium present and the ratio of tantalum to niobium. The presence of more than one per cent. tungsten can lead to high results for niobium. Other elements that might be present in titanium alloys do not interfere with the method. The procedure is designed for titanium alloys containing 0.05 to 10 per cent. niobium. The method is reasonably rapid. Six determinations can be finished in two days. The method should be applicable to many other materials besides titanium alloys.     

Spectrophotometric determination of niobium in tantalum metal

A new method for the determination of traces of niobium in tantalum metal has been developed. The niobium is separated from tantalum by solvent extraction with hexone from hydrofluoric acid-hydrochloric acid solution, and from molybdenum and tungsten by solvent extraction with oxine-chloroform solution from ammoniacal citrate solution. The niobium is then determined by the spectrophotometric thiocyanate method.     

Separation and gravimetric determination of niobium,tantalum and titanium by precipitation with n-benzoyl-n-phenylhydroxylamine

A method is described for the separation and gravimetric determination of niobium, tantalum and titanium by precipitation with N-benzoyl-N-phenylhydroxylamine. Titanium is kept in solution with EDTA and hydrogen peroxide, and the earth acids are precipitated in 1N sulphuric acid Niobium and tantalum are separated and determined by a modification of the method of MAJUMDAR AND MUKHERJEE. All three metals are finally precipitated with N-benzoyl-N-phenyl-hydroxylamine. In the analysis of complex materials niobium, tantalum and titanium are separated from other constituents by a double precipitation with N-benzoyl-N-phenylhydroxylamine in the presence of EDTA and tartaric acid     

Synthesis of calcium metaniobate by thermal decomposition of a coprecipitation product

The paper presents a new, nonconventional method, based upon coprecipitation, for the synthesis of niobium oxidic compounds. The coprecipitation product of niobic acid with calcium oxalate was used as precursor. Calcium metaniobate was obtained by appropriate thermal treatment of the coprecipitate. The coprecipitation mechanism was studied and the optimal conditions for quantitative precipitation of niobium and calcium were established. The mechanism of thermal decomposition of the coprecipitate was investigated by means of differential thermal analysis and X-ray powder diagrams. The final product of thermal decomposition, calcium metaniobate, is formed at 730°C.     

Spektrophotometrische Bestimmung von Tantalspuren in Niob mit Malachitgrün

Traces of tantalum are separated from niobium by extraction from hydrofluoric acid solution with methylisobutyl ketone. The determination of the separated trace amounts of tantalum is based upon their conversion to a complex with malachite green, the absorbance of which is measured at 635 nm. 0.2 μg of tantalum can be determined in 0.5 g of niobium metal.     

Synthesis of lead metaniobate by thermal decomposition of a coprecipitation product

The paper reports a new, nonconventional method for the preparation of oxygen-containing niobium compounds, based upon coprecipitation. The coprecipitation product of niobic acid with lead oxalate was used as precursor. Lead metaniobate was obtained by proper thermal treatment of the coprecipitate. The coprecipitate mechanism was studied and the optimal conditions for quantitative precipitation of niobium and lead were established. The mechanism of thermal decomposition of the coprecipitate was investigated by differential thermal analysis and X-ray powder diagrams. The final product of thermal decomposition, lead metaniobate, is formed at 850°C.     

Smart optical probe for ‘equipment-free’ detection of oxalate in biological fluids and plant-derived food items

A reversible ‘turn-on’ sensor has been designed for ‘naked-eye’ detection of oxalate at nanomolar concentration (～12.5?nM) at pH 7.4. The sensory system shows a highly specific response towards oxalate among a wide range of antinutrients and biologically relevant anionic species. Mechanistic investigations indicate that oxalate can turn the pink-colored solution colorless by dissociating the preformed metal complex. Additionally, high specificity and good accuracy with recovery values ranging from 93.3 to 105.0% were obtained during oxalate estimation in spiked water and human urine samples, confirming the suitability of the present method in estimating trace-level of oxalate in complex matrices. With these results, quantitative estimations of endogenous oxalate were achieved in more than twenty-five different agricultural crops. Finally, low-cost, portable paper strips were developed for on-site detection of oxalate.     

Gravimetric separation of titanium and zirconium from Niobium with Phenylacetylhydroxamic acid

Phenylacetylhydroxamic acid is used to separate titanium and zirconium from niobium in an oxalate medium at pH 6.5–7.5 in presence of ammonium chloride at room temperature. The method is accurate when the ratio of (TiO₂ + ZrO₂) : Nb₂O₅ is 10 : 1 to 1 : 1 ; when the niobium concentration is higher, reprecipitation is necessary. Tantalum, citrate, tartrate, lactic acid, EDTA, and a large excess of oxalate interfere.     

电感耦合等离子体原子发射光谱法测定钛合金中钨、铌、钽

采用电感耦合等离子体原子发射光谱法（ICP-AES）法测定钛合金中W,Nb,Ta元素的含量。样品采用盐酸、氢氟酸和硝酸溶解,并对仪器工作参数和试验条件进行了优化试验,确定了仪器最佳工作条件,考察了钛合金基体和共存元素对待测元素的影响,确定了各待测元素谱线为W207．911nm,Nb309．418nm,Ta240．063nm。选定的待测元素分析线不受合金基体和共存元素的干扰,通过基体匹配消除基体的影响。加标回收率在98％104％之间,测定结果的相对标准偏差为0．3％～2．4％（n=8）,方法的检出限为0．003-0．013μg／mL。进行了标准物质对照试验,试验结果与标准值相符。