Spectrophotometric determination of traces of gallium and indium with 1-(2-pyridylazo)-2-naphthol

1-(2-Pyridylazo)-2-naphthol (PAN) reacts with either gallium or indium at pH 5–6 giving a red complex in an aqueous medium in the presence of N.N-dimethyl-formamide. The maximum absorption of both PAN complexes of gallium and indium in an aqueous solution is at 545 mμ. The gallium-PAN complex shows a characteristic enhancement of color by addition of small amounts of ethers. Based on this selective enhancement reaction, gallium can be determined in the presence of other metals without separation. The results of determining gallium and indium in the presence of each other are reported. Both gallium and indium form M₂(PAN)₃; but in the presence of certain organic solvents, a different gallium complex, Ga(PAN)₅, and the same indium complex, In₂(PAN)₃, are formed. The reaction of PAN with cadmium can be masked by iodide; an example of determining indium in the presence of cadmium is given. The PAN method has a sensitivity of 0.003 μg/cm² for gallium and 0.005μg/cm² for indium and an absorptivity of 24,900 for the Ga-PAN complex and of 24,500 for the In-PAN complex, respectively. The methods have been successfully applied to the determination of both gallium and indium in germanium thin films.     

Solvent extraction of rare earth metal ions with 1-(2-pyridylazo)-2-naphthol (PAN)

The formation of the Tm(III) complex with 1-(2-pyridylazo)-2-naphthol (PAN or HL) in aqueous-methanol mixtures (50 and 75%v/v) was studied by a spectrophotometric method. The equilibrium constant for the complexing reaction and the stability constant of the complex TmL ²⁺ were calculated. The solvent extraction of Tm(III) byPAN in carbon tetrachloride from aqueous and aqueous-methanol phase was investigated. The extraction equilibrium constants and two-phase stability constants for the TmL ₃ and the TmL ₃(MeOH)₃ complexes were evaluated. It was confirmed that the addition of methanol to the aqueous phase (above 25%v/v) causes a synergistic effect.

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Extraktion von Ionen der Seltenerdmetalle mit 1-(2-Pyridylazo)-2-naphthol (PAN), 5. Mitt.: Komplexbildung und Gleichgewichtsverteilung von Thulium (III) mitPAN

Zusammenfassung Die Bildung des Komplexes von Tm(III) mit 1-(2-Pyridylazo)-2-naphthol (PAN oder HL) in Wasser-Methanol Mischungen (50 und 75%v/v) wurde mit einer spektrophotometrischen Methode untersucht. Die Gleichgewichtskonstante für die Reaktion der Komplexbildung und die Stabilitätskonstante des Komplexes TmL ²⁺ wurden berechnet. Die Extraktion von Tm(III) mittelsPAN in Kohlenstofftetrachlorid aus Wasser oder Wasser-Methanol wurde untersucht. Die Werte der Extraktionsgleichgewichtskonstante sowie der zweiphasigen Beständigkeitskonstante für die Komplexe TmL ₃ und TmL ₃(MeOH)₃ wurden berechnet. Es wurde festgestellt, daß die Zugabe von Methanol zur wäßrigen Phase (25%v/v) einen synergistischen Effekt hat.

     

Solvent extraction of rare earth metal ions with 1-(2-pyridylazo)-2-naphthol (PAN)

The solvent extraction of Yb(III) and Ho(III) by 1-(2-pyridylazo)-2-naphthol (PAN or HL) in carbon tetrachloride from aqueous-methanol phase has been studied as a function ofpH ^× and the concentration ofPAN or methanol (MeOH) in the organic phase. When the aqueous phase contains above ～25%v/v of methanol the synergistic effect was increased. The equation for the extraction reaction has been suggested as: $$\begin{gathered} Ln(H_2 0)_{m(p)}^{3 + } + 3 HL_{(o)} + t MeOH_{(o)} \mathop \rightleftharpoons \limits^{K_{ex} } \hfill \\ LnL_3 (MeOH)_{t(o)} + 3 H_{(p)}^ + + m H_2 0 \hfill \\ \end{gathered} $$ where:Ln ³⁺=Yb, Ho; $$\begin{gathered} t = 3 for C_{MeOH in.} \varepsilon \left( { \sim 25 - 50} \right)\% {\upsilon \mathord{\left/ {\vphantom {\upsilon \upsilon }} \right. \kern-\nulldelimiterspace} \upsilon }; \hfill \\ t = 0 for C_{MeOH in.} \varepsilon \left( { \sim 5 - 25} \right)\% {\upsilon \mathord{\left/ {\vphantom {\upsilon \upsilon }} \right. \kern-\nulldelimiterspace} \upsilon } \hfill \\ \end{gathered} $$ . The extraction equilibrium constants (K _ex ) and the two-phase stability constants (β ₃ ^× ) for theLnL ₃(MeOH)₃ complexes have been evaluated.     

Solvent extraction of rare earth metal ions with 1-(2-pyridylazo)-2-naphthol (PAN)

Extraction of lutetium(III) and erbium(III) with 1-(2-pyridylazo)-2-naphthol (PAN or HL) in carbon tetrachloride from aqueous solutions was examined. The composition of the complex extracted was determined and it was found that the extraction process can be described by the following equation (Ln ³⁺=Lu, Er): $$Ln(H_2 O)_m^{3 + } + 3 HL_{(0)} \mathop \rightleftharpoons \limits^{K_{ex} } LnL_{3(0)} + 3 H^ + + mH_2 O$$ The extraction constants (K _ex ) and two-phase stability constants (β ₃ ^x ) forLnL ₃ complexes have been evaluated.     

Spectrophotometric determination of uranium with 1-(2-pyridylazo)-2-naphthol

1-(2-Pyridylazo)-2-naphthol (PAN) rcacts with uranium to form a deep red precipitate in ammoniacal solutions, this can be extracted with chloroform if sodium chloride or sulfate is added and it has a maximum absorption at 560 mμ The color is stable and follows Beer's law. Trace amounts of uranium may be determined in the presence of many metals without prior separation if strong complexing agents, such) as EDTA or cyanide, are added     

Solvent extraction of certain rare earth metal ions with 1-(2-pyridylazo)-2-naphthol (PAN)

The solvent extraction of Yb(III) by 1-(2-pyridylazo)-2-naphthol (PAN or HL) in carbon tetrachloride from aqueous—ethanol phase has been investigated as a function of thepH ^X of the polar phase and the concentrations ofPAN or ethanol (EtOH) in the organic phase. It was confirmed that the addition of ethanol to the aqueous phase causes an increase of the Yb(III) distribution coefficient. The equation for the extraction reaction has been suggested as: $$Yb(H_2 O)_{m(^p )}^{3 + } + 3H L_{(o)} + t Et OH_{(o)} \rightleftharpoons Yb L_3 \left( {EtOH} \right)_{t(o)} + 3H_{(^p )}^ + + mH_2 O$$ wheret changes from 0 to 3. The extraction equilibrium constant (K _ex ) and two-phase stability constants (β ₃ ^× ) for the YbL ₃ (EtOH)₃ complex have been evaluated. The formation of solvates YbL ₃ (EtOH) _t is probably the main reason of the synergistic effect which was observed.     

Spectrophotometric extractive titrations-VI Titrations with 1-(2-pyridylazo)-2-naphthol

The possibility of using PAN as a titrant in spectrophotometric extractive titrations has been investigated. Conditions suitable for the titration of zinc and of cadmium were found, with the aid of equations derived earlier and after investigation of the absorption spectra and pH- and reagent-dependence of the extraction of the chelates involved. For the purpose of spectrophotometric extractive titration of copper with PAN the formation and extraction of ion-association pairs CuPAN(+).Br(-) and CuPAN(+).CNS(-) were studied in detail. This titration was found to be highly selective. Dilute solutions of PAN in ethanol are much more stable than solutions of dithizone.     

Colorimetric determination of zirconium with 1-(2-pyridylazo)-2-naphthol

A method is described for the determination of as little as 50 ppm of zirconium in uranium-fission element alloys and zinc magnesium-uranium-fission element alloys. Zirconium is extracted from a nitric acid-aluminium nitrate medium with dibutyl phosphate in toluene. The uranium co-extracted with the zirconium is removed by scrubbing with hydrochloric acid-ammonium thiocyanate solution. A portion of the organic phase is mixed with pyridine-toluene solution of 1-(2-pyridylazo)-2-naphthol to develop the colour.     

Spectrophotometric determination of hafnium(IV) with 1-(2-pyridylazo)-2-naphthol

Summary The red complex formed between hafnium(IV) and 1-(2-pyridylazo)-2-naphthol (1 2) at pH 4.0 is used for Spectrophotometric determination of hafnium., the absorbance being measured at 545 nm. Beer's law is obeyed for hafnium concentration of 0.2 to 3.6g per ml. Molar absorptivity is 3.86×10⁴ and Sandell sensitivity is 0.0046g per cm². Hafnium has been determined in the presence of 6-fold amounts of zirconium. The relative standard deviation is ± 1.0%.

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Zusammenfassung Der rote, bei pH 4,0 sich bildende Komplex mit 1-(2-Pyridylazo)-2-naphthol (1 2) dient zur Bestimmung von Hafnium (IV). Seine Extinktion wird bei 545 nm gemessen. Zwischen 0,2 und 3,6g Hf/ml ist das Beersche Gesetz gültig. Hafnium läßt sich in Gegenwart der sechsfachen Menge Zirkonium bestimmen. Die relative Standardabweichung beträgt ± 1,0%.

     

Spectrophotometric determination of cobalt with 1-(2-pyridylazo)-2-naphthol and surfactants

A simple and highly selective spectrophotometric method for the determination of cobalt based upon the rapid reaction with PAN in the presence of surfactants and minute amounts of ammonium persulphate at pH 5.0 is described. The cobalt(III) chelate is made water-soluble by a neutral surfactant. Triton X-100, combined with sodium dodecylbenzene sulphonate (DBS). Iron(III), bismuth, tin(IV) and aluminium are masked with oxalate or citrate. Iron(II) must be absent. The other metal-PAN chelates, except that of nickel, are readily decomposed by EDTA. Up to 150 microg of nickel does not interfere. When larger amounts up to 625 microg are present, the absorbance can be corrected by measurements at two wavelengths. In a strongly acid medium (below pH 0.5) the nickel and other metal chelates are completely and instantaneously decomposed, while the cobalt(III) chelate remains unchanged. When, in place of EDTA, several ml of 6M hydrochloric acid are added after the colour development, nickel in quantities up to 1250 microg can be tolerated. A several hundredfold excess of zinc and manganese does not interfere. At 620 nm Beer's law is obeyed over the cobalt concentration range 0.4-3.2 microg/ml. The precision (95% confidence) is +/- 1.0 microg for 100 microg of cobalt. The molar absorptivity is 1.90 x 10(4) l. mole(-1) .cm(-1).     

Complexes of organolead and organotin ions with 1-(2-pyridylazo)-2-naphthol

The stability constants of the complexes of 1-(2-pyridylazo)-2-naphthol with several organotin and lead ions were determined spectrophotometrically in aqueous 20% (v/v) dioxane and were shown to have very high values. The extraction of the complex of (C₂H₅)₂Pb²⁺ from water into chloroform was studied, and the formation of an extractable (C₂H₅)₂Pb(PAN)(OH) complex is postulated.     

Mass spectrometric investigation of copper chelates with 1-(2-pyridylazo)-2-naphthol

The mass spectra of copper chelates of 1-(2-pyridylazo)-2-naphthol, HX, prepared by different methods, are discussed. Peaks due to Cu(2)X(2)(+), CuX(2)(+) and CuXCl(+) have been positively identified and all copper-containing species have the expected isotopic ratios. The significance of probe temperature and impurities are discussed and it is concluded that the spectra are more in accordance with the known chemical facts than those reported earlier by Betteridge and John.     

Spectrophotometric determination of rare earth metals with 1-(2-pyridylazo)-2-naphthol

1-(2-Pyridylazo)-2-naphthol (PAN) reacts very sensitively with rare earth metals to form a deep red precipitate in alkaline solution; this can be extracted with ether, except in the case of lanthanum, cerium and scandium. Absorption maxima occur at 530 and 560 mμ. Traces of rare earth metals may be determined in the presence of many foreign metals.     

Vibrational spectra and normal coordinate analysis of Ni and Zn complexes with 1-(2-pyridylazo)-2-naphthol

Infrared and resonance Raman spectra of Ni(PAN)₂ and Zn(PAN)₂ (where PAN denotes 1-(2-pyridylazo)-2-naphthol) have been measured in the solid state. In addition, the nickel complex dissolved in CS₂ has also been investigated by Raman spectroscopy at room temperature and 16 K. A normal coordinate analysis was performed to characterize the observed vibrational transitions in terms of potential energy distribution.     

Sensitive spectrophotometric determination of La(III) with 1-(2-pyridylazo)-2-naphthol

A simple and sensitive method for spectrophotometric determination of lanthanum has been developed. At pH 9.6, in presence of 50% ethanol, lanthanum reacts with 1-(-2-pyridylazo)-2-naphthol (PAN) to form a red complex which has two absorption maxima, at 545 and 510 nm. The molar absorptivity at 545 nm is 0.55 × 10⁴ liters · mol^?1 cm^?1. On the other hand, lanthanum reacts with PAN in pure ethanol to form a red complex at 530 nm, with high molar absorptivity (8 × 10⁴ liters · mol^?1 cm^?1).     

1-(2-pyridylazo)-2-naphthol (PAN) as extractant in solid-liquid extraction of some trivalent rare earth elements

In the present paper, solid-liquid extraction behaviour of RE(III) (RE La, Ce, Pr, Nd, Sm, Gd, Dy and Yb) by the use of 1-(2-pyridylazo)-2-naphthol (PAN, HL) as an extractant in paraffin (m.p. 48 approximately 50 degrees) has been investigated at 80 +/- 0.07 degrees. The effect of equilibrium time, pH of aqueous phase, concentration of extractant in paraffin and solid diluent as well as buffer solution used on the extraction efficiency of RE(III) have been discussed. The extraction reaction is RE(3+) + 2HL(o) + Cl(-) <==> REL(2)Cl(o) + 2H(+).