Study of the fast reactions between Trilon B and the complexes formed by rare earth elements of the yttrium subgroup with Xylenol Orange

The stopped-flow method has been used to study the kinetics of the reactions of the complexes formed by the rare earth elements of the yttrium subgroup and Xylenol Orange with Trilon B. The influence of the acidity of the medium and temperature on the reaction rate has been studied. The rate constants and activation energy for the process have been determined. A reaction mechanism has been proposed.     

Study on the Spectrophotometric Determination of Rare Earths with a New Chromogenic Reagent Dibromo-p-methyl-chlorosulfonazo(DBMCSA)

IntroductionAbstract:Anewmethodforthedeterminationofceriumsubgrouprareearthswasstudiedandreportedinthispaper.ItwasfoundthaiceriumsubgrouprareearthelementsreactwithDBMCSAin0.6mol/Lhydrochloricacidmediumtol'ormstablebluecomplexes.Theabsorbancesofequalamountsofceriumsubgrouprareearthsareclosetoeachotherattheirmaximumadsorptivewavelength(641"m).Beer'slawisobeyedfor0-20igofrareearthsin25mlofsolution.Themethodhasbeenappliedtothedeterminationofthetotalamountofceriumsubgrouprareearthsinsteelandcas…     

Spectrophotometric determination of cerium subgroup rare earths in nickel-base alloys in the presence of yttrium with p-acetylchlorophosphonazo and mixed surfactants

Rare earth elements react with p-acetylchlorophosphonazo (CPApA) to form colour complexes. In the presence of emulsifier OP and cetylpyridinium chloride (CPC), the yttrium complex is not formed because of micellar masking, while the cerium subgroup rare earths give more sensitive reactions with CPApA(epsilon(Ce) = 1.16 x 10(5) 1 . mol(-1) . cm(-1)) due to micellar sensitization. Most foreign ions can be tolerated in considerable amounts. The optimum conditions of the complex formation reaction and the composition of the Ce-CPApA complex are described. A simple method is proposed for the determination of cerium subgroup rare earths in nickel-base alloys with satisfactory results.     

The influence of dissociation on simultaneous determination of zirconium and hafnium with Xylenol Orange

The molar absorptivities of the zirconium and hafnium Xylenol Orange (1:1) complexes are said to be similar in the acidity range 0.1-2.0M HCl. However, the absorbances obtained for the zirconium-Xylenol Orange complex in the acidity range 0.5-2.0M HCl are much higher than those for the same concentrations of hafnium. The absorbance differences are generally due to the higher stability of the zirconium complex at such acidities. Calculations based on the conditional stability constants of these complexes show the influence of dissociation on the results of simultaneous determination of zirconium and hafnium with Xylenol Orange.     

Simultaneous determination of lanthanum and cerium in mixed rare earths with p-acetylarsenazo by spectrophotometry

A new method has been developed for the simultaneous spectrophotometric determination of small amounts of lanthanum and cerium in the presence of large amounts of rare earth elements. Lanthanum (III) and cerium (III) were determined spectrophotometrically with p-acetylarsenazo as the color reagent in the chloroacetic acid medium at pH 3.1 by measuring the absorbances of the complexes at 670 nm. The remained rare earths were masked with ethylenediaminetetracetic acid and ethylenediaminetetracetic acid-zinc during the analysis. The optimum conditions for the simultaneous determination of lanthanum and cerium have been defined. The individual content of lanthanum (III) and cerium (III) were determined by varying the amounts of EDTA and EDTA-Zn used in the analysis and solving the simultaneous absorbance equations based on the Beer's law. The proposed method has been successfully applied to the determination of lanthanum and cerium in Longnan mixed rare earth oxides and other heavy rare earths without preliminary separation with satisfactory results. The relative errors of all analytical results of the method were not more than 2% with good precision. The procedure does not require separation of lanthanum, cerium and the other rare earth elements.     

Determination of zirconium and hafnium with xylenol orange and methylthymol blue

Both Xylenol Orange and Methylthymol Blue are highly selective and sensitive reagents for zirconium and hafnium forming intensely red complexes in an acidic medium. The factors affecting the color formation have been studied. The properties of the complexes have been determined and compared. In general, zirconium forms a more stable complex with the two dyes than hafnium, and Xylenol Orange forms a stronger complex with either zirconium or hafnium than Methylthymol Blue. Hydrogen peroxide can completely mask the zirconium complexes of either dye but only slightly affects the hafnium complex of Xylenol Orange. Zirconium and hafnium can both be determined without separation using peroxide as a masking agent and sulfate as a demasking agent. A bleaching reaction was observed when small amounts of hafnium were added to the red zirconium complex of Methylthymol Blue in 2.4 N perchloric acid or a small amount of zirconium was added to the red hafnium complex of Methylthymol Blue solution at pH 2 to 3.     

Spectrophotometric determination of rare earth elements by flow injection analysis based on their reaction with xylenol orange and cetylpyridinium bromide

Individual rare earth elements (REE) and their mixtures were determined by a FIA method based on the reaction with Xylenol Orange (XO) in the presence of cetylpyridinium bromide (CPB). Volumes of 30 microl of 2.5-25 microM REE solutions were injected into a carrier stream of 0.1M acetate buffer of pH 4.5 or 5.5 that was 0.06 mM in XO and 0.6 mM in CPB. At 1.8 ml/min flow rate, a sampling frequency of up to 100 samples per hour was achieved. The detection limits were in the range of 0.1-0.4 microg/ml REE and relative standard deviation of the measurement was 0.88% rel.     

Formation constants of alkaline-earth metal complexes with xylenol orange and methylthymol blue

The complexes of the alkaline-earth metals with Xylenol Orange and Methythymol Blue have been studied. Three 1:1 and two 2:1 (metal:ligand) complex species for each indicator and each element have been found to be formed in aqueous solutions, and the formation constants and the arrangements of these complexes have been determined.     

Successive determination of thorium and the rare earths with triethylenetetraminehexaacetic acid

Triethylenetetraminehexaacetic acid (TTHA) is proposed for the successive determination of thorium and rare earths in mixtures by titrating first for thorium at pH 2, then adding an excess of TTHA to complex the rare earth ions completely, and titrating the excess of TTHA with standard zinc solution. Xylenol Orange and 3',3'-bis {[N,N-bis (carboxymethy 1)amino]methyl} thymolsulphonephthalein (TMS) have been tested as indicators for the titration.     

Extraction of rare earth elements with 1-(diphenylphosphorylmethoxy)-2-diphenylphosphoryl-4-ethylbenzene with the use of 1,1,7-trihydrododecafluoroheptanol as a solvent

Extraction of rare earth elements from nitric acid solutions in a 1,1,7-trihydrododecafluoroheptanol-water system with the use of phosphoryl-containing podand 1-(diphenylphosphorylmethoxy)-2-diphenylphosphoryl-4-ethylbenzene (L) was studied. The content of metals in organic phase was shown to be negligible at nitric acid concentration lower 1 mol/L. Distribution ratio sharply increases with nitric acid concentration from 1 mol/L and reaches 5.5 for the yttrium subgroup elements at HNO₃ concentration of 6 mol/L. The rare earth elements of the yttrium subgroup were found to be extracted much better than the rare earth elements of the cerium subgroup under the same conditions, the distribution ratios in both subgroups smoothly rise with atomic number of element. It was shown using the shift of extraction equilibrium that the M: L ratio in extracted complexes is 1: 2 irrespective of the nature of rare earth element. The structure of complex {Yb[η²-(O,O′)-L]₂(η²-O₂NO)₂}(O₂NOHNO₃), whose single crystals were isolated from extraction solution, was established by X-ray diffraction study. The system can be used for the isolation and separation of rare earth elements.     

Pyrocatecholsulphonphthalein complexan as an analytical reagent

Pyrocatecholsulphonphthalein complexan (PSC) has been synthesized from Pyrocatechol Violet (PV), iminodiacetic acid and formaldehyde by Mannich condensation. Its acid dissociation equilibria have been studied potentiometrically. Some characteristic properties of Xylenol Orange (XO) and PV are found in PSC, which is slightly superior to XO and PV in sensitivity as a chromogenic reagent for bismuth. The spectrophotometric characteristics of some metal ion-PSC complexes are reported.     

Reaction of mercury(II) and xylenol orange-I Effect of the buffering media

The influence of the buffering medium on the reaction of Hg(II) with Xylenol Orange has been studied. Amine-type compounds are complexed by Hg(II)/Xylenol Orange with a sharp hyperchromic effect on the reagent itself, at 590 nm, but complex formation of Hg(II)/Xylenol Orange in non-amine-type buffer, such as citric acid-phosphate, gives a hypochromic effect on Xylenol Orange at 580 nm. Hg(II) is determined at pH 7.5 in two ranges of concentration, 2-9 ppm in citrate buffer, measured at 580 nm ( = 2.50 x 10(4)), and 6-11 ppm in hexamine buffer, at 590 nm ( = 4.18 x 10(4)).     

Analysis of rare earth sulfides, selenides and tellurides

The rare earth content of sulfides, selenides and tellurides is determined by titration with EDTA using Xylenol Orange as indicator. Sulfur is measured by titration of sulfate with lead nitrate solution after removal of rare earths on a cation exchanger. Selenium metal is precipitated from hydrochloric-sulfurous acid solution. Metallic tellurium is deposited from strongly acidic solutions containing sulfurous acid and hydrazine sulfate. An evaluation of the accuracy and precision of these methods is made.     

Spectrophotometric determination of rare earth elements and thorium with arsenazo

The simultaneous spectrophotometric determination of rare earth elements (lanthanum and gadolinium) and thorium with arsenuzo is described. In 0.05 N nitric acid, thorium alone forms a colored complex with the reagent; at PH 7.2 both thorium and the rare carths form colored complexes. Satisfactory results were obtained with weight ratios of Th/rare earths ranging from 0.2 to 10.     

Spectrophotometric study of the reaction of gallium(III) with xylenol orange

The formation of complexes between gallium(III) and Xylenol Orange at pH 2 has been studied. Complexes with the mole ratio 1:1 and 1:2 have been found and the respective formation constants determined. The latter complex, for which the absorption spectrum has been calculated, is suitable for the spectrophotometric determination of gallium, and optimum conditions for its formation have been established.     

Dynamic ion-exchange chromatography with post-column reaction detection for the determination of the rare earth elements in monazites

Summary Separation and determination of lanthanum, cerium, praseodymium, neodymium and samarium in monazites have been achieved by dynamic ion-exchange chromatography. The ore samples are decomposed by sulfuric acid and the rare earths are separated in a group as oxalates. The rare earth elements are then separated from each other on a column of bonded phase silica by gradient elution with 0.05 to 0.5 M lactic acid (pH 3.5) in the presence of 0.01 M sodium 1-octanesulfonate. Post-column reaction with Arsenazo III is used for detection and quantification of the individual rare earth elements. Results are quoted for lanthanum, cerium, praseodymium, neodymium and samarium in monazites. Detection limit is 1 μg ml⁻¹ with a S/N ratio of 3. The separation is complete within 27 min valley to valley resolution. Precision of better than 1% can usually be obtained.     

Synthesis of Fluoro-Contained Bisazo Chromotropic Acid Derivants and studies on Their Color Reactions with Rare Earth Elements

In this paper, a series of f1uoro-contained bisazo chromotropic acid derivants has been designed and synthesized. They are easily soluble in water, alcohol and acetone but insoluble in benzene, ether and chloroform. Some regularities of the effects of their molecular structure on the color reaction have also been studied. The result shows that in this series of reagents, DCF-chlorophosphonazo and DBF-chlorophosphonazo are excellent color reagents for the determination of the total amount of rare earth elements. The molar absor-ptivities of light and heavy rare earth elements are approach to each other. The tolerant quantity of Bi (Ⅲ) and Pb (Ⅱ) , Sn(Ⅳ) are larger than that of the other arsenazo or chlorophosphonazo type of color reagents. We also discover that p-fluorochlorophosphonazo can form β-type complexes with heavy rare earth elements, and p -fluoro-carboxyazo with light rare earth elements. If the reaction time is controlled, p -fluoro-carboxyao can form β-type complex only with La, and the     

Study of coordination equilibria in systems of coexisting mononuclear and polynuclear complexes by an isosbestic point-spectrophotometric method

This paper reports a method for determining the stability constants of complexes in a system of coexisting mononuclear and polynuclear complexes based on analysis of dual isosbestic points. First it is necessary to determine the dissociation degrees of either of the two complexes concerned in two directions, and then their stability constants. With this method, the conditional constant can be evaluated by appropriate treatment and selection of the proper equations for solutions. For demonstration purposes the scandium/Xylenol Orange system was used to test the model and satisfactory results were obtained.     

Semi-automated determination of aluminium with Xylenol Orange

The photometric determination of aluminium by automated colour development with Xylenol Orange is described. The reagent has been found to act faster if used in alcohol solution.     

Extractions with long-chain amines-I Extraction of some metal-xylenol orange complexes into methyltrioctylammonium chloride (aliquat 336-S)

The extraction of traces of metals forming intensely coloured complexes with Xylenol Orange in acidic medium (pH 0-3) has been studied. For such extractions in the presence of sulphates, chlorides and nitrates, a solution of methyltrioctylammonium chloride (Aliquat 336-S) in chloroform has been used. It is shown that it is possible to detect small amounts of gallium in indium and vice versa, and titanium or zirconium in thorium. These reactions should be capable of adaption to spectrophotometric determinations. The principle of the extraction of metals as their complexes with various metallochrornic indicators is briefly discussed.