Influence of Masking Agents on the Color Reactions of Dithizone with Pd(II), Hg(II), and Ag(I) Ions after the Sorption of Their Chloride Complexes on the Fibrous Filled Anion Exchanger AV-17

The influence of masking agents (acetate, thiosulfate, tartrate, and iodide ions; thiourea; and ethylenediaminetetraacetic acid (EDTA)) in a dithizone solution on the complexation of Hg(II), Pd(II), and Ag(I) ions on the solid phase of the fibrous anion exchanger filled with AV-17 was studied. Mercury, palladium, and silver were adsorbed as chloride complexes. The possibility of the simultaneous group determination of the three elements and the selective determination of palladium in the presence of mercury and silver by measuring the diffuse reflection coefficient at two wavelengths (580 and 680 nm, respectively) was demonstrated. A mixture of dithizone with EDTA, acetate, iodide, or thiosulfate can be used for masking concomitant elements. The reaction of palladium with dithizone on the solid phase can be used for the test determination of palladium with the detection limit 0.01 mg/L.     

A Test Method for the Determination of Mercury(I, II) on a Polymer Surface

It was found that mercury(I, II) reacts with 5-chloro-2-hydroxy-3-[(tetrahydro-2,4-dithioxo-1,3-thiazin-5-yl)azo]benzenesulphonic acid (tyrodine) in weakly acid solutions in the presence of acetates, formates, and some organic solvents (ethanol and acetone) to give an intensely colored insoluble compound (_max = 600 nm, > 3 × 10⁴). The composition of the solution affected the sensitivity of the color reaction between mercury and tyrodine. A test procedure was developed for the determination of mercury(I, II) on the surface of a polycaproamide membrane with a detection limit of <50 ng in the adsorbent zone. The procedure involves the quantitative and selective adsorption of the mercury complex of tyrodine on the support surface from 0.5 M acetate solutions of pH 3–4 in the dynamic mode; the sample volume was 5–25 mL. Mercury was then determined by the change in the support color using a color scale or by the change in diffuse reflectance at 600 nm. The adsorption of the mercury complex was accompanied by an abrupt change in the color of the support surface from pale crimson (reagent) to stable blue-violet. The test procedure was used in the analysis of an industrial sample of complex composition with a mercury concentration of lower than 0.05%. The determination error (relative standard deviation) was 20%.     

Determination of Arsenic(V) as a Heteropoly Acid after Its Adsorption on a Fibrous Anion Exchanger

The conditions were found for determining arsenic(V) as a heteropoly acid after its adsorption on a fibrous anion exchanger. A blue form of a molybdoarsenic heteropoly acid formed on the adsorbent at any order of the adsorption of the reactants; however, the sensitivity of determination was higher if arsenic was adsorbed first. A detection limit of 4 ng/mL was attained using adsorption from a 100-mL portion of a test solution. The sensitivity and selectivity of the proposed method are significantly higher than those of known methods because of the preconcentration of arsenate ions on an anion exchanger as a heteropoly acid followed by the direct determination of the heteropoly acid in the solid phase.     

Test method for the separate determination of mercury(II), cadmium, and lead in one sample on the fibrous sorbent PANV-AV-17

The sorption of Hg(II), Cd(II), and Pb(II) as anionic complexes on the solid phase of polyacrylonitrile fiber filled with the AV-17 anion exchanger from NaCl and KI solutions and their complexation with 4-(2-pyridylazo)resorcinol (PAR) and dithizone were studied. A test method was developed for the individual determination of Hg(II), Cd(II), and Pb(II) from one sample on three support disks. From the same solution, by the successive sorption on two disks from a 0.2 M NaCl solution, mercury was determined with dithizone and cadmium was determined with PAR. After the addition of a KI solution and sorption on the third disk, lead was determined with PAR. Using the added-found method, the procedure was approved in the analysis of natural sodium chloride water. The detection limit was 0.01 mg/L for Hg(II) and 0.02 mg/L for Cd(II) and Pb(II) for a volume of the analyzed sample of 25 mL. The time of the analysis of five or six samples (determination of three elements) is no longer than 50 min.     

Sequential determination of nickel(II) and zirconium(IV) with dimethylglyoxime and arsenazo III after adsoprtion on one substrate disc

The possibility of the sequential determination of nickel with dimethylglyoxime and zirconium with arsenazo III from a single aliquot portion using polyacrylonitrile fiber as a solid phase impregnated with a KU-2 cation exchanger is studied. Conditions for the simultaneous adsorption of nickel and zirconium in the dynamic mode from 0.01 M HNO₃ are found as along with the ones for their sequential determination on one disc. The calibration functions are linear in the range 5–50 ng/mL, the detection limits for both elements are 2 ng/mL. In their simultaneous presence, the determination of nickel and zirconium is not affected by 10-fold weight amounts of Fe(III), Cu(II), Co(II), Al, Mn(II), Pb, Zn, Cd, Cr(VI), Mo(VI), and V(V). A method is proposed for determining nickel and zirconium from a single aliquot portion on a single substrate disc at their ratios from 1: 1 to a 5-fold excess of each element.     

Electrical properties of heterovalently doped apatite-like oxosilicates

Oxygen-ion-conductive apatite-like oxosilicate and silicophosphate ceramics has been prepared by sintering sol-gel synthesis products at temperatures 200°C below those of solid-phase synthesis. The electrical properties of the ceramics obtained have been studied by impedance spectroscopy in the range 400–1000°C. A positive effect of heterovalent substitutions in the silicon sublattice on the bulk and intergrain conductivities is established. The increase in the oxygen-ion conductivity in La_9.6Si_5.7Mg_0.3O_26.1 in comparison with the other studied oxosilicates by more than two orders of magnitude is related to the formation of additional interstitial positions for oxygen ions as a result of partial substitution of the silicon ion, tetrahedrally coordinated by oxygen, with the Mg ion having a characteristic octahedral coordinatio     

Overtone spectroscopy of some benzaldehyde derivatives

Overtone spectrum of o, m and p-nitrobenzaldehydes and p-chlorobenzaldehyde has been studied in 2000–12000 cm⁻¹ region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined. We have also determined the internuclear distances for the aryl CH bond in the different molecules. The small variation observed in these distances is an indication of the substitution effect. It is observed that in the case of p-disubstituted benzens, the shift in aryl CH bond is proportional to sum of the Hammet σ of the substituents. However in the case of o-disubstituted benzenes it is only 80% of the para-substituted shift.