A selective procedure for the gravimetric estimation of uranium as oxinate using complexone as masking agent

The existing method. for the estimation of U in hexavalent condition as oxinate has been slightly modified and the scope of complexone (disodium salt of ethylenediaminetetraacetic acid) as a masking agent to develop a selective method for its estimation in presence of interfering elements has been studied. It has been found that at pH ranges from 5-9 complexone exerts no influence on the complete precipitation of uranium and that uranium can be quantitatively separated from Th, R.E., Zr, Fe⁺³, Al, Cu, Co, Ni, Zn, Cd, Pb, Bi, Mn and P₂O₅ by precipitation with oxine in a solution buffered with acetic acid and ammonium acetate (pH approximately 5.3) and also from V₂O₅, MoO₃ and WO₃ in ammoniacal medium (pH approximately 8.4).     

Gravimetric determination of beryllium with sodium oxinate

Sodium oxinate is found to precipitate Be(II) quantitatively in the pH range 7.5-8.2. The complex has the composition Be(2)O(C(9)H(6)NO)(2).2H(2)O, is stable and can be weighed directly after drying at 105-110 degrees . A method for the estimation of Be(II) and its separation from interfering elements is described. The monohydrate has been prepared from the dihydrate and characterized. The results show the presence of hydroxyl bridges in the monohydrate. Methods using various organic reagents for the direct estimation of beryllium in ores and alloys have been examined and it is found that 4-chloro-2,5-dimethoxyacetoacetanilide gives the best results. A method for the determination of be(II) in beryl without prior separation of Fe(III) and Al(III) is described.     

Complexo-titrimetric determination of mercury using hexahydropyrimidine-2-thione as a selective masking agent

A simple, rapid, accurate and selective complexometric method is proposed for the determina-tion of mercury(Ⅱ). Mercury(Ⅱ) is first complexed with a known excess of EDTA and the surplusEDTA is back-titrated at pH 5. 0--6. 0 with lead nitrate, xylenol orange being used as indicator. Hexa-hydropyrimidine-2-thione (HPT) is then added to displace EDTA from the Hg-EDTA complex quan-titatively and the EDTA released is titrated with lead nitrate. Reproducible and accurate results areobtained for 2--55 mg of mercury, with a relative error of less than 0. 5% and standard deviation ofless than 0.04.     

Dithiocarbaminoacetic acid as a masking agent in complexometry

Dithiocarbaminoacetic acid (TCA) forms very stable, water soluble complexes with a number of metal ions and is a suitable masking agent in complexometry. TCA masks from EDTA and complexometric indicators at pH 2-6 the following elements: bismuth(III), indium(III), thallium(III), cadmium(II), lead(II), mercury(II) and copper(II), thus making possible the complexometric determination of other elements in their presence.     

Gravimetric estimation of bismuth as bismuthyl dichromate

Summary Conditions are described for the quantitative precipitation of bismuthyl dichromate, (BiO)₂Cr₂O₇, and the suitability of this reaction for the gravimetric estimation of bismuth is shown. The use of arsenious oxide as a primary standard for the iodometric titration of excess chromate is emphasised.Sincere thanks of the authors are due to Prof. S. S. Joshi for research facilities and to Dr. G. S. Deshmukh for keen interest in the work.     

Selective complexometric determination of mercury using sodium nitrite as masking agent

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 sodium nitrite. Mercury and other ions are initially complexed with an excess of EDTA and the surplus EDTA is titrated with Pb(NO₃)₂ solution at pH 5.0–6.0 using xylenol orange as indicator. An excess of solid NaNO₂ is then added to decompose the Hg(II)-EDTA complex and the released EDTA is titrated with standard Pb(NO₃)₂ solution. Accurate results were obtained for 10–65 mg of mercury with relative errors <0.3% and standard deviations < 0.03 mg. Sn(IV) and Pd(II) interfere but can be easily masked. The method is applied for the determination of Hg(II) in its alloy compositions and complexes.     

Selective complexometric determination of mercury, using thiourea as masking agent

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

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.     

On the use of hydrogen peroxide as a masking agent for the determination of yttrium in uranium oxide-yttrium oxide mixture

Use of hydrogen peroxide as a masking agent for uranium during the EDTA titration of yttrium in an yttrium-uranium mixture containing large amounts of uranium has been investigated. High acetate ion concentration was necessary to keep the peroxy complex of uranium in solution during the titration. It has been observed that upto 500 mg of uranium could be tolerated in the determination of yttrium with 0.5 ml of 30% hydrogen peroxide in {lM acetate medium. The precision and accuracy of the method based on 16 determinations of yttrium at 6–16 mg level in presence of 300 mg uranium has been found to be ±0.2%.     

Gravimetric determination of carbon in uranium carbide

Summary The results of the determination of combined carbon and free carbon in uranium carbide in oxygen by a differential temperature technique suggest the pre-mature oxidation of the free carbon due to the local heating of the sample caused by the exothermic decomposition of the carbide. However, it was found possible to overcome this difficulty employing air as supporting gas at controlled heating rates.

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Gravimetrische Bestimmung von Kohlenstoff in Urancarbid

Zusammenfassung Bei der Bestimmung von gebundenem und freiem Kohlenstoff in Urancarbid bei unterschiedlichen Temperaturen ergaben sich Fehler durch vorzeitige Oxidation von freiem Kohlenstoff infolge lokaler Erhitzung der Probe durch die exotherme Zersetzung des Carbids. Diese Schwierigkeit konnte jedoch durch den Einsatz von Luft als Trägergas bei kontrollierter Erhitzungsgeschwindigkeit überwunden werden.

     

Selective non-chromatographic determination of tributyltin in sediments using EDTA and diphenylcarbazone as masking agent

Two analytical procedures based on the generation of volatile tributyltin derivatives, their separation by headspace solid-phase microextraction (HS SPME) and subsequent determination using plasma optical emission spectrometry (OES) have been developed for the selective determination of trace tributyltin (TBT) in the presence of other butyltins and inorganic tin in sediments without the use of chromatography. A microwave-assisted leaching of tin compounds from the sediment using 25%_v/v acetic acid is applied for sample pretreatment. The first method takes advantage of TBT chloride releasing from the lecheate after adding 3 M hydrochloric acid, and subsequent separation of the analyte by HS SPME using Carboxen-poly(dimethylsiloxane) (CAR/PDMS). The second method involves the use of masking agents, namely ethylenediaminetetraacetic acid (EDTA) and diphenylcarbazone (DFC), which form stable chelates with monobutyltin (MBT) and dibutyltin (DBT), respectively, followed by the ethylation of tributyltin at pH 5 using sodium tetraethylborate (NaBEt4) solution. The final concentration of NaBEt4 is 0.05%_w/v. The parameters affecting the TBT derivatisation and separation by HS SPME have been optimised including the selection of SPME fibre coating (PDMS, CAR/PDMS), the amount of masking agents and NaBEt4 added, sorption time (2–40 min) and sorption temperature (25–60°C). Higher sensitivity and robustness are attained with the method involving ethylation derivatisation, leading to the limit of detection (LOD) of 3 ng L^?1. The selective release of TBT is observed from aqueous solutions, where the concentrations of MBT and DBT were in 2–50-fold excess to TBT. The SPME-TD-MIP-OES methods have been validated against several certified reference materials (CRMs), including SOPH-1 marine sediment, PACS-2 marine sediment and BCR 646 freshwater sediment.     

Indirect complexometric determination of palladium usingl-histidine as masking agent

An indirect complexo-titrimetric method is described for the determination of palladium in the presence of other metal ions, L-histidine being used as the masking agent. Palladium(II) and other metal ions are initially complexed with an excess of EDTA and the surplus EDTA titrated with standard zinc sulfate solution at pH 4.5–5.5 using xylenol orange as indicator. An excess of 1 % L-histidine solution is then added, and the released EDTA is titrated with standard zinc sulfate solution. Accurate and reproducible results were obtained for 2–15 mg of Pd with relative errors 0.4% and standard deviations < 0.02mg. Sn(IV) and Au(III) interfere, but can be easily masked. The method is successfully applied for the determination of palladium(II) in alloy compositions.     

Determination of uranium in seawater samples by liquid chromatography using mandelic acid as a complexing agent

The determination of uranium at different stages of the recovery process as well as in seawater is important in its recovery study. A previous study developed a high-performance liquid chromatography (HPLC) method for uranium determination in seawater using α-hydroxy isobutyric acid as a chelating agent. However, this method causes turbidity in process samples containing high amounts of iron, resulting in the clogging of the HPLC column. In the present work, use of mandelic acid as a chelating agent for uranium has been explored. Elution conditions were optimized for the separation of iron [Fe(III)] and uranium [U(VI)] by studying the effect of an ion interaction reagent, the concentration of mandelic acid, and methanol content in the mobile phase. Different parameters were optimized to develop off- line pre-concentration of uranyl-mandelate on the reversed stationary phase. The method offers quantitative recovery of uranium and linearity in the U(VI) concentration range of 0.5 ppb to 500 ppb and can be used for the determination of U(VI) in process samples with Fe/U amount ratios up to 3,000. The method has been successfully used for the determination of U(VI) in seawater samples and process samples. The developed methodology was validated by comparing the results with those of isotope dilution-thermal ionization mass spectrometry.     

Partitioning of plutonium and uranium in aqueous medium using hydroxyurea as reducing agent

A new process for the partitioning of plutonium and uranium during the reprocessing of spent fuel discharged from fast reactor was optimised using hydroxyurea (HU) as a reductant. Stoichiometric ratio of HU required for the reduction of Pu(IV) was studied. The effect of concentration of uranium, plutonium and acidity on the distribution ratio (Kd) of Pu in the presence of HU was studied. The effect of HU in further purification of Pu such as solvent extraction and precipitation of plutonium as oxalate was also studied. The results of the study indicate that Pu and U can be separated from each other using HU as reductant.     

Indirect complexometric determination of cadmium(II) using 1,10-phenanthroline as selective masking agent

An indirect complexometric method is described for the determination of cadmium(II), 1,10-phenanthroline being used as masking agent. Cadmium(II) in a given sample solution is 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 indicator. An excess of 1,10-phenanthroline is then added and the EDTA released from the Cd-EDTA complex is titrated with standard lead nitrate solution. Results are obtained for 1.5–57 mg of Cd with relative errors 0.90% and standard deviations 0.06 mg. Cu(II), Co(II), Hg(II), Ni(II), Zn(II), Pd(II), Tl(III), Au(III) and Sn(IV) interfere, but can be easily masked. The method is applied for the determination of cadmium in synthetic alloy solutions.     

Gravimetric determination of molybdenum and tungsten using pyridoin as a reagent

Summary Pyridoin has been used as a reagent for the gravimetric determination of molybdenum and tungsten. The reagent quantitatively precipitates molybdenum from ammonium molybdate solution at p_H 2.0–9.5 and tungsten from sodium tungstate solution at p_H 2.0–4.5. The precipitate in each case is ignited to the oxide and weighed.

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Zusammenfassung Zur gravimetrischen Bestimmung von Molybdän und Wolfram wird Pyridoin als Reagens empfohlen. Molybdän wurde aus Ammoniummolybdatlösung bei p_H 2,0–9,5 quantitativ ausgefällt, Wolfram aus Natriumwolframatlösung bei p_H 2,0–4,5. Die Niederschläge wurden jeweils zum Oxid verglüht und dieses ausgewogen.

     

Selective complexometric determination of palladium with thiosulphate as masking agent

A selective complexometric method is suggested for the determination of palladium, sodium thiosulphate being used as releasing agent. To a solution containing palladium and other cations, excess of EDTA is added and the surplus is back-titrated with lead nitrate solution at pH 5-5.5 in sodium acetate buffer with Xylenol Orange as indicator. EDTA equivalent to palladium is then released quantitatively with sodium thiosulphate and is titrated with the lead nitrate solution. The interference of various cations has been studied and the method applied for the analysis of alloys.