O-carboxyphenyl azo chromotropic acid (sodium salt) as an analytical reagent

Summary O-carboxyphenyl azo chromotropic acid (sodium salt), chromotrope 2C, is introduced as a new metallochromic indicator. Its colour reactions with a few metal ions have been utilised for their quantitative chelatometric determinations with EDTA.     

O-carboxyphenyl azo chromotropic acid (sodium salt) as an analytical reagent

Summary 0-carboxyphenyl azo chromotropic acid (sodium salt), named as chromotrope 2 C, is used as a new colorimetric reagent for the determination of micro amounts of thorium and aluminium. The blue-violet and red-violet complexes show maximum absorption at 590 nm and the colour systems obey Beer's law from 0.1 to 8 ppm for thorium and 0.1 to 1ppm for aluminium. However, their optimum concentration ranges are from 1.6 to 8 ppm for thorium and 0.2 to 0.8 ppm for aluminium, where the percent relative errors per 1% absolute photometric error are, respectively, 3.06 and 2.94. The composition of the complexes, as elucidated by the continuous variation method, suggests a metal to reagent ratio of 23 for thorium and a ratio of 11 for aluminium. The instability constants for the complexes are of the order of 4.044×10^–10 and 1.006 × 10^–6 at 30°C.Part I, see Z. analyt. Chem. 174, 197 (1960)     

Spectrophotometric determination of zirconium with 2-(1-hydroxy-4,6-dinitro-2-phenylazo)-1,8-dihydroxynaphthalene-3,6-disulphonate (picramine ca) as chromogenic reagent

The title compound has been used as a selective reagent for the micro-determination of zirconium in acidic medium (0.5MHCl) and found to be better than Picramine R. Spectrophotometric studies show the formation of a 2:1 (ligand:Zr) water-soluble complex and the reaction is suitable for photometric determination of 0.4-2.8 ppm of zirconium. The colour takes about 90 min to develop fully and is stable for about 20 hr. The molar absorptivity of the complex is 2.4 x 10(4) and the equilibrium constant is of the order of 10(10). The interference due to a number of ions has been studied.     

Ammonium aurin tricarboxylate as a reagent in inorganic analysis

Summary Ammonium aurin tricarboxylate produces characteristic colour with various metallic ions. The colour reactions are quite sensitive especially in the case of uranium and thorium besides aluminium and beryllium. The use of the reagent in analysis is suggested.     

Spectrophotometric determination of microamounts of thorium with disodium salt of 2-(2-hydroxy-3,6-disulfo-1-naphthylazo)-benzenearsonic acid (Thorin) as a chromogenic reagent

A sensitive spectrophotometric method has been developed for the determination of microamounts of thorium using 0.05% thorin in a 3M perchloric acid solution as a chromogenic reagent and measuring the absorbance at 544 nm. The complex of thorium thus formed, is stable for more than two months with a constant absorbance of ±0.55%. Beer's law is obeyed from 0 to 25 g g^–1 of thorium in a solution with a molar absorptivity (544 nm) = 1.69×10⁴ M^–1 cm^–1 at 26±1 °C. Among the anions tested, only phosphate, acetate and cyanide at >200-fold excess of thorium interfere in the determination, whereas cations like Zn(II), Al(III), Na(I), Mg(II), and Ca(II) do not effect the absorbance. Thorium can be determined in the presence of oxalate, nitrate, tartrate, sulfate, thiosulfate, citrate, and ascorbate. The accuracy of the method has been checked by measuring the known concentration of thorium in the range of 100 g-5 mg g^–1 and found to be in the range of 7.7–0.9%. The method has been applied successfully to determine thorium at g g^–1 level in local ore samples with a precision of ±0.3%. The sensitivity of the method on Sandell's scale is 0.082±0.002 g g^–1 cm^–1.     

Base hydrolysis ofcis-dichlorobis(1,2-diaminoethane),cis-α-dichloro(1,8-diamino-3,6-diazaoctane) andcis-α-chlorohydroxo-(1,8-diamino-3,6-diazaoctane) ruthenium(III) complexes

The kinetics of base hydrolysis ofcis-[RuCl₂(en)₂]⁺ (en=1,2-diaminoethane),cis-α-[RuCl₂(trien)]⁺ andcis-α-[RuCl(OH)(trien)]²⁺ (trien=1,8-diamino-3,6-diazaoctane) have been studied. All the reactions are fast and obey the second-order rate law,-d[complex]/dt=k[OH⁻][complex], with complete retention of configuration. A conjugate base mechanism involving a squarepyramidal intermediate is suggested. The Arrhenius parameters and rate constants found are respectively: ΔH^≠ 14.2±0.5, 7.2±0.1, 10.9±0.1 M cal mol⁻¹; ΔS^≠ 1.3, 29, 22 cal deg⁻¹ mol; log A 13.5, 6.9, 8.6 k_OH 533 (27.2°C) 14.5 (24.4° C) 1.65 (25°C) M⁻¹s⁻¹.     

Structure of the product of the reaction of 3,6-dioxa-1,8-(di-2,3-dichloromaleimido)octane with 3,6-dioxaoctane-1,8-diamine

The reaction of 3,6-dioxa-1,8-(di-2,3-dichloromaleimido)octane with 3,6-dioxaoctane-1,8-diamine gave 7,11-diaza-1,4-dioxa-9-en-7,11-oxo-9-chlorobicyclo-[1.2.9]tridecan-8-one. The steric structure of the last was determined by x-ray structural investigation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 394–398, March, 1992.     

7-Amino-1-naphthol-3,6-disulphonic acid (2R-acid) as a chromophoric reagent for trivalent iron

Summary 7-Amino-1-naphthol-3,6-disulphonic acid forms a stable red coloured complex with trivalent iron. Studies on the composition and stability of this complex are described.

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Zusammenfassung 7-Amino-1-naphthol-3,6-disulfonsäure bildet mit Eisen(III) einen beständigen, rotgefärbten Komplex. Über die Untersuchungen zur Zusammensetzung und Stabilität dieses Komplexes wird berichtet.

     

A camphor-derived vinylsulfonium salt as a reagent for a cycloannulation

A chiral, non-racemic vinylsulfonium salt 6 was prepared from camphorquinone in seven steps and reacted with indole-2-carboxaldehyde to give a tricyclic azido alcohol 2 in a 35% yield and 43% e.e. and a 40% recovery of the chiral sulfide.     

Complexes of 1,8-bis(2-pyridyl)-3,6-dithiaoctane with cobalt(II) halides

Summary Several cobalt(II) halide complexes derived from 1,8-bis(2-pyridyl)-3,6-dithiaoctane (bpdto) are described. Chemical analysis suggests their formulae to be: Co(bpdto)X₂ (X=Cl^–, Br^–, or I^–). Electrolytic conductivities in acetonitrile, magnetic moments at different temperatures, solid state i.r. and u.v.-visible spectra support a tetrahedral stereochemistry around the cobalt(II). The ligand is bidentate andN-bonded in all cases.This work was presented in the Fifth Annual Meeting of the Portuguese Chemical Society, Porto (Portugal), March 1982.     

1-(1,2,4-Triazolyl-3-azo)-2-naphthol as a spectrophotometric reagent for inorganic ions

The synthesis, characteristics and analytical reactions of 1-(1,2,4-triazoly 1-3-azo)-2-naphthol are described. Coloured complexes are formed with 21 metal ions. For the cadmiuin(II) complex, the molar absorptivity is 2.8 × 10⁴ 1 mol^-1 cm^-1 at 515 nm for 40% ($\text{v}\text{v}$) ethanolic solutions at pH 8.0. For the mercury(II) complex at pH 10, the molar absorptivity is 2.7 × 10⁴ mol^-1 cm^-1 at 530 nm. Complexes of the ML₂ type are formed.     

Flow injection direct spectrophotometric assay for the speciation of trace chromium(III) and chromium(VI) using chromotropic acid as chromogenic reagent

A new rapid and sensitive FI assay is reported for the simultaneous direct spectrophotometric determination of trace Cr(VI) and Cr(III) in real samples. The method is based upon the reaction of Cr(VI) with chromotropic acid (CA) in highly acidic medium to form a water-soluble complex (λ_max = 370 nm). Cr(III) reacts with CA only after its on-line oxidation to Cr(VI) by alkaline KIO₄. The determination of each chromium species in the sample was achieved by absorbance differences. The calibration curves were linear over the range 3-4000 μg l⁻¹ and 30-1200 μg l⁻¹ for Cr(VI) and Cr(III), respectively, while the precision close to the quantitation limit was satisfactory in both cases (s_r = 3.0% for Cr(VI) and 4.0% for Cr(III) (n = 10) at 10 and 50 μg l⁻¹ level, respectively). The method developed proved to be adequately selective and sensitive (c_L = 1 and 10 μg l⁻¹ for Cr(VI) and Cr(III), respectively). The application of the method to the analysis of water samples (tap and mineral water) gave accurate results based on recovery studies (93-106%). Analytical results of real sample analysis were in good agreement with certified values.     

Glyoxal dithiosemicarbazone as a complexing and chromogenic spray reagent in inorganic TLC

Summary Systematic TLC separations, identification of cations and the determination of the limits of their identification on microcrystalline cellulose layers, incorporating glyoxal dithiosemicarbazone (H₂-GDTS) as a spray reagent have been worked out. Metal-GDTS complexes have also been separated on silica gel G support. Detection called for no spray reagent, owing to the intense and characteristic colours of the complexes.     

Potassium thiocarbonate as a complexing and spray reagent in inorganic thin-layer chromatography

Summary Clean and rapid micro analytical separations of metal ions of qualitative analytical groups 1 to 4 including some platinum metals have been made on silica gel G support by TLC using potassium thiocarbonate (PTC) as a complexing and visualising reagent. A review of the chromatographic behaviour of metal ions using PTC as a complexing and spray reagent in TLC is included.     

Arsenazo, 2-(4-arsonophenyl(azo-7-(4-antipyril)azo-1,8-dihydroxy-3,6-naphtalene disulphonic acid as reagent for calcium ions. New parameters for metallochromic indicator characterization

Ca(II) ions react with arsenazo, 2-(4-arsonophenyl)-azo-7-(4-antipyril)azo-l,8-dihydroxy-3,5-naphtalene disulphonic acid, at pH 10.0 to produce a blue complex, with stoichiometry 11, and stability constant of 6.64×10⁵. Its molar absorptivity is 3.78×10⁴1·mol^–1 cm^–1. This reagent has been used as metallochromic indicator in the complexometric titration of Ca. Its colour transition has been specified by tristimulus colourimetry. New parameters are defined and compared to Ringbom's parameters.