Separation of uranium from vanadium by ion exchange: with special reference to the determination of small amounts of uranium

An ion exchange method has been worked out for the separation of milligram quantities of uranium from large amounts of vanadium. A solution containing vanadium and uranium and excess sodium carbonate is passed through a column filled with an anion exchanger in the chloride form. All the uranium and part ot the vanadium arc adsorbed by the resin. The adsorbed vanadium is first elutcd with 10 % sodium carbonate solution leaving uranium in the column. Uranium is then cluted with sodium chloride and estimated colorimctrically.     

Volumetric determination of small amounts of uranium : Chromous chloride as reducing agent

A volumetric method is proposed for the rapid determination of small amounts of uranium. The hexavalent uranium is reduced to the quadrivalent state by chromous chloride, the excess of which is destroyed by air oxidation. A low potential redox indicator is used to follow the reduction and air oxidation. Ferric sulphate is added to the solution and the resulting ferrous ion titrated with dichromate solution.     

Determination of uranium after its selective extraction as phenylacetate

The method described is based on the extraction of uranium with a chloroform solution of phenylacetic acid from slightly acidic solution containing nitrilotriacetic acid, which masks all interfering metals. After stripping into very dilute hydrochloric acid, uranium is reduced with ascorbic acid and determined complexometrically. The method permits reliable determination of uranium in the presence of all quadri-, ter- and bivalent metals investigated, molybdenum(VI), tungsten(VI), and vanadium(V).     

Determination of vanadium in refractory metals, steel, cast iron, alloys and silicates by extraction of an NBPHA complex from a sulphuric-hydrofluoric acid medium

A method for determining up to 0.15% of vanadium in high-purity niobium and tantalum metals, cast iron, steel, non-ferrous alloys and silicates is described. The proposed method is based on the extraction of a red vanadium(V)-N-benzoyl-N-phenylhydroxylamine complex into chloroform from a sulphuric-hydrofluoric acid medium containing excess of ammonium persulphate as oxidant. The molar absorptivity of the complex is 428 l.mole(-1).mm(-5) at 475 nm, the wavelength of maximum absorption. Interference from chromium(VI) and cerium(IV) is eliminated by reduction with iron(II). Common ions, including large amounts of titanium, zirconium, molybdenum and tungsten, do not interfere.     

Determination of small amounts of lead in uranium

Small amounts of lead in the presence of large amounts of uranium can be determined by complexing the lead with nitrilotriacetic acid in aqueous solution at about pH 6 (adjusted with hexamine)and extracting the uranium into a chloroform solution of diphenylacetic acid. The aqueous phase is then acidified the lead determined polarographically.     

Coulometric titration of uranium and uranium-vanadium mixtures with +3 titanium

Coulometric titration of + 6 uranium with electrogenerated titanous ion at a platinum cathode in 8F sulfuric acid can be performed accurately in the presence of ferrous ion as a catalyst Ampero-metric end-point detection is employed. The titration is suitable for the precise assay of uranium compounds. Mixtures of +5 vanadium and +6 uranium can be titrated, because the reduction of +5 vanadium occurs at a more oxidizing potential than the reduction of +4 vanadium and +6 uranium. Using amperometric end-point detection, two end-points are observed corresponding to the reduction of +5 vanadium to the +4 state, and to the simultaneous reduction of + 4 vanadium to the +3 state and +6 uranium to the +4 state. Errors are as small as + 0.3%, provided the uraninium/vanadium ratio is between 0.1 and 10.     

Spectrophotometric determination of tungsten in ores and steel by chloroform extraction of the tungsten-thiocyanate-diantipyrylmethane complex

A method for determining up to about 6% of tungsten in ores and mill products is described. It is based on the extraction of the yellow tungsten(V)-thiocyanate-diantipyrylmethane ion-association complex into chloroform from a 2.4M sulphuric acid-7.8M hydrochloric acid medium containing ammonium hydrogen fluoride as masking agent for niobium. The molar absorptivity of the complex is 1510 1. mole(-1).mm(-1) at 404 nm, the wavelength of maximum absorption. Moderate amounts of molybdenum and selenium may be present in the sample solution without causing appreciable error in the result. Interference from large amounts is avoided by separating these elements from tungsten by chloroform extraction of their xanthate complexes. Large amounts of copper interfere during the extraction of tungsten because of the precipitation of cuprous thiocyanate. Common ions, including uranium, vanadium, cobalt, titanium, arsenic and tellurium, do not interfere. The proposed method is also applicable to steel.     

Oxidation of sulphides with alkaline potassium permanganate

Summary Sulphides are oxidised with potassium permanganate in alkaline medium to give dithionate. A method based upon this reaction is proposed for the determination of sulphides. The method consists in mixing the sulphide solution with an excess of permanganate in presence 1–2 M NaOH and 0.2 g telluric acid. The excess permanganate is then treated with ferrous ammonium sulphate in acid medium and the excess ferrous titrated with permanganate.     

Extractive separation of lower valent vanadium by complexation with picolinic acid

Summary Vanadium (III), obtained by sodium dithionite reduction of vanadium (V), forms a coloured complex with picolinic acid which is extracted into chloroform from slightly acidic medium. The method is free from interference by relatively high concentrations of analytical important elements such as iron, cobalt, nickel, zinc, copper, titanium, aluminium, chromium, molybdenum, tungsten and uranium. The proposed method of separation is simple and rapid and its applicability has been tested by the satisfactory recovery of vanadium from a variety of synthetic and natural samples.     

Precise and accurate determination of chromium in steel

Determination of chromium(VI) by addition of weighed amounts of solid ammonium ferrous sulfate in excess and back-titration with permanganate, using spectrophotometric end-point detection, is applied to the determination of chromium in steel. Except in the case of vanadium. and especially of vanadium + tungsten, very high selectivity and precision are claimed. Relative standard deviations of the order of 0.05% to 0.15% were found. Recoveries in excess of 99.95% were obtained in most cases. Results for the determination of chromium in standard samples of steel are given.     

Extraction of bivalent vanadium as its pyridine thiocyanate complex and separation from uranium, titanium, chromium and aluminium

A simple method is described for the extraction of V(II) as its pyridine thiocyanate complex. Vanadate is reduced to V(II) in 1-2N sulphuric acid by zinc amalgam. Thiocyanate and pyridine are added, the solution is adjusted to pH 5.2-5.5 and the complex extracted with chloroform. The vanadium is back-extracted with peroxide solution. Zinc from the reductant accompanies the vanadium but alkali and alkaline earth metal ions, titanium, uranium, chromium and aluminium are separated, besides those ions reduced to the elements by zinc amalgam. The method takes about 20 min and is applicable to microgram as well as milligram amounts of vanadium.     

Extraction with long-chain amines-II Extraction and colorimetric determination of chromate

Highly selective extraction of chromate from slightly acidic solutions (0.1-0.2M sulphuric acid) with a chloroform solution of trioctylamine (Alamine 336-S) or trioctylmethylammonium chloride Aliquat 336-S) is described. Many metals such as iron, nickel, cobalt, copper, alluminium, zinc, are not extracted, even if present in large concentrations. Coextraction of vanadium(V) and uranium(VI) is prevented by addition of sodium chloride. Traces of extracted molybdenum are scrubbed with ammonium oxalate. Final determination of chromium is based on measurement of the absorbance of the extract at 445-450 nm.     

Anion-exchange separation of beryllium, vanadium and other elements from large amounts of uranium

A method is described for the anion-exehange separation of small quantities of beryllium, vanadium, magnesium, calcium, aluminium, gallium and indium from gram-amounts of uranium. For this purpose, a medium consisting of 95 % methanol and 5% 5M nitric acid is passed through a resin bed of Dowex 1, X8. By subsequent washing of the resin with a methanol-nitric acid mixture of the same composition, these metal ions are preferentially eluted from the column, whereas uranium is still retained by the anion exchanger. In the eluates the elements are determined by means of spectrophotometric or titrimetric procedures.     

Spectrophotometric determination of small amounts of tellurium with bismuthiol II

A spectrophotomeiric method of determining small amounts of tellurium in acidic media with Bismuthiol II has been studied. The tellurium complex with bismuthiol II is extracted almost quantitatively with chloroform from a 3M hydrochloric acid solution or from a solution buffered at pH 3.5. Up to 25 mug of tellurium can be determined by measuring the absorbance of the yellow complex in the chloroform phase at a wavelength of 330 mmu, after washing the chloroform extract with a buffer solution (pH 7.5) to remove the excess reagent from the organic phase. The effects of diverse ions on the determination of tellurium have also been examined. This method is more simple and more sensitive than the methods proposed by Jankovsky et al. and by Cheng.     

The determination of uranium in alloy systems

A procedure is described for the determination of the uranium content of metallurgical alloys containing this element as a minor constituent. The uranium is first separated from the sample solution by precipitation as uranyl ammonium phosphate in the presence of ethylenediamine-totra-acetic acid. By this means the uranium is separated from many elements including iron, chromium, copper, nickel, vanadium, cerium, ncodymium and bismuth. Tho uranyl ammonium phosphate precipitate is dissolved in hydrochloric acid and the resulting solution is passed through a lead reductor. The tetravalent uranium is titrated with a standard cerie sulphate solution, using ferroin as the indicator. This procedure has proved very suitable for the analysis of bismuthuranium binary alloys containing uranium in amounts up to approximately 20%.     

Determination of micro amounts of uranium by a molybdenum blue method

A new and highly sensitive spectrophotometric method has been developed for the determination of micro amounts of uranium by a molybdenum blue method. The method is based on the observation that at low acidities uranium(IV) reduces ammonium molybdate to molybdenum blue, the absorbance of which is proportional to the amount of uranium present. The variables affecting development of the colour have been investigated and the conditions optimized. Beer's law is found to hold good for uranium concentrations between 1 and 20 ppm, with a precision of 2%. The effect of diverse ions has been studied. The method is useful for the determination of uranium present as an impurity (down to 0.1%) in plutonium, neptunium or thorium.     

Dosage rapide du chrome et du vanadium

The two elements are supposed to be in solution in their maximum value. The total chromium + vanadium content is determined by direct titration in 23̄ 3 N sulphuric acid solution with a ferrous solution in the presence of sulphonated diphenyl amine as an oxydo-reduction indicator. Vanadium is titrated in the same solution after bringing it into its highest valence state by means of a slight excess of permanganate. After the destruction of the excess of oxidizing agent with sodium azide, the titration is completed with the ferrous solution in the presence of the same indicator.     

Spectrophotometric determination of molybdenum by extraction of a green molybdenum(v) species

A simple method is described for the rapid spectrophotometric determination of molybdenum in samples containing 1-60% Mo, with satisfactory accuracy. Molybdenum is reduced with excess of hydrazine sulphate in boiling 5.5M hydrochloric acid and extracted with isoamyl acetate from 7M hydrochloric acid. The green colour is measured at 720 nm against a reagent blank. Beer's law is obeyed over the range 0.08-5.4 mg of molybdenum per ml. Interference from iron and copper is removed by adding stannous chloride and thiourea respectively in slight excess. Titanium, vanadium, niobium, chromium, tungsten, nickel, uranium, and antimony do not interfere even in large amounts. Only cobalt interferes seriously.     

An improved titrimetric method for the determination of oxygen to metal ratio in uranium oxide

A new method for determining the O/U ratio in uranium oxide is described. The method consists of dissolving an accurately weighed sample in a known excess of ceric ammonium nitrate in 2N perchloric acid at room temperature and estimating the unreacted Ce/IV/ with benzohydroxamic acid. A standard deviation of 0.0016 for ten estimations is observed.     

Volumetric Studies In Oxidation-Reduction Reactions: Oxidation with ceric sulphate ferrous ethylenediamine sulphate method

Ceric sulphate has been used as an oxidizing agent in acid medium for the indirect volumetric determinations of ferrous ammonium sulphate, cuprous chloride, potassium thiocyanate, sodium thiosulpliate, sodiuin nitrite, hydrogen peroxide, sodium oxalate, hydroquinone and pyruvic acid. The excess of ceric sulphate added to each of the substances in acid medium was titrated with standard ferrous ethylenediamine sulphate solution using ferroin as an indicator.