Studies on the adsorption of nitrogen dioxide onto manganese dioxide-coated quartz piezoelectric crystals

A technique for obtaining thin; evenly distributed manganese dioxide coatings by melting manganese nitrate is outlined. Responses of an AT-cut quartz piezoelectric crystal coated with manganese dioxide to nitrogen dioxide (12.5-10 000 μl 1^?1) over a range of humidities (400–4,800 μ1 l^?1 water) and temperatures (20–35 °C) are given. The response of the simulated product manganese nitrate, over the same range of humidities, is evaluated in relationship to real product formation. The approach may be applicable to other metal salt/metal oxide systems. The detection limit is 7 μl^?1 nitrogen dioxide.     

1,5-bis(dicarboxymethylaminomethyl)-2,6- dihydroxynaphthalene as a selective spectrofluorimetric reagent for calcium

1,5-Bis(dicarboxymethylaminomethyl)-2,6-dihydroxynaphthalene (BDDN) forms fluorescent complexes with aluminium, barium, beryllium, calcium, magnesium and strontium. All the complexes have 2:1 metal :ligand ratios. Barium, calcium, magnesium and strontium exhibit maximal fluorescence at pH 11.7, with excitation and emission maxima at 385 and 445 nm respectively. Aluminium and beryllium show maximal fluorescence at pH 5.8 and 5.2 respectively, the excitation and emission maxima being at 370 and 405 nm. The formation of the calcium complex provides a highly sensitive and selective determination of calcium in the range 10/2-500 ng. The fluorescence measurement of calcium should be made within 5 min of mixing the solutions because of the instability of the reagent at the given pH. Potassium cyanide may be used as a masking agent and ter- or quadrivalent cations should be removed by preliminary extraction with 8-hydroxyquinoline in chloroform at pH 6.0. In such conditions, of 33 cations studied, only magnesium (>20 ng), strontium (>70 ng) and barium (>150 ng) caused interference in the determination of 300 ng of calcium. Among 16 anions examined, only EDTA interfered seriously.     

Structure of γ-Li3AsO4 by High Temperature Powder Neutron Diffraction

The structure of γ-Li₃AsO₄ has been refined by Rietveld analysis of high resolution powder neutron diffraction data collected at 770 and 850°C. The structure is related to that of γ-Li₃PO₄, being a distorted hexagonal close-packed arrangement of oxide ions with half the tetrahedral sites filled by cations. Arsenic occupies the same sites as phosphorus in γ-Li₃PO₄, Li⁺ ions show positional disorder; Li(1) ions are split into central and off-center positions within their tetrahedral sites; Li(2) ions are distributed over pairs of face sharing tetrahedral sites at 850°C while occupying only one site at 770°C. The powder neutron data show anisotropic broadening of hkl peaks with h = 2n + 1. The broadening has been accounted for using a modified Rietveld code. The broadened peaks correspond to those reflections that are not common to the related low temperature β-phase and are associated with a doubling of the a-axis during the β-γ transition. The origin of the broadening is the small size of the γ-phase domains in the a -direction; adjacent domains are probably connected by antiphase boundaries.     

Unexpected synthesis of a naphthylsilole

The reaction of 1,4-dilithiotetraphenylbutadiene (2) with 1,1′-dichloro-2,3,4,5-tetraphenyl-1-silole (3) leads to 2,3,4,5-tetraphenyl-1-(1,2,3-triphenylnaphthalen-4-yl)-1H-silole (5) instead of the expected octaphenyl-1,1′-spirobisilole (1). The reaction of 2 with SiC1₄ in dioxane produced 1 in low yield, confirming results reported earlier.     

Studies in atomic-fluorescence spectroscopy-VI The fluorescence characteristics and analytical determination of bismuth with an iodine electrodeless discharge tube as source

The atomic-fluorescence characteristics of bismuth atoms in cool nitrogen-hydrogen and argon-hydrogen diffusion flames burning in air are described. Excitation is obtained from the non-resonance iodine line at 2061.63 Å emitted by a microwave-excited electrodeless discharge tube operating at 2450 Mc/s. Fluorescence of the bismuth resonance line at 2061.70 Å is observed and also direct-line fluorescence at 2697 and 3025 A. In addition thirteen other much weaker lines were observed and two unidentified lines at 2880 and 2680 Å. The emissions at 2628 and 2938 Å appear to arise from “thermally assisted direct line fluorescence”. The most intense line at 3025 Å permits linear-dependence analytical atomic-fluorescence measurements to be made in the range 0.1–200 ppm with a detection limit of 0.05 ppm and with no problems of source scatter. No interference was observed from hundred-fold concentrations of fourteen ions. Matrix effects from aluminium and magnesium were overcome by raising the temperature of the cool diffusion flames. A bismuth microwave-excited electrodeless discharge tube was used as a source for atomic-absorption measurement in air-hydrogen and air-propane flames at 2231Å with a detection limit of 1 ppm and a linear-dependence analytical range of 10–100 ppm. With the iodine microwave-excited electrodeless discharge tube the detection limit for atomic absorption was 10 ppm at 2062 Å.     

Mössbauer conversion electron studies of tantalum metal surface layers

Conversion electrons following the Mössbauer absorption of the 6.2 keV -rays of¹⁸¹Ta were observed in backscattering geometry. Mössbauer spectra for tantalum single crystal and foil surfaces (mean-depth 330 Å) are compared with normal transmission spectra for tantalum foils (bulk). While no broadening of lines is observed for carefully polished single crystal furfaces, foil surfaces show considerably broader lines than bulk spectra. The linewidth and isomer shift indicate an increase of the concentration of absorbed residual gases at the foil surfaces. The observed dispersion term arising from the interference between photo- and conversion electrons for this E1-transition, depends only on the absorber thickness.     

Emission spectral analysis with the glow discharge source and a resonance detector

A Grimm-type glow discharge lamp was found to have emission lines which are narrow enough to allow the advantageous use of resonance detection. Design of a cathodic sputtering cell which has an exchangeable cathode is described. The fluorescence signal from this lamp was detected electronically by either a synchronous (lock-in) detection system or a dual-gated integration (boxcar) system. It was found that the dual-gated system improved detection limits by a factor of 50 over the synchronous detection system. Calibration curves for copper in aluminium and silver in gold were found to be linear from the detection limit (about 1 ppm for both elements) up to approximately 20% in the case of copper in aluminium, and 5% silver in gold. Reproducibility of signal measurements was 1%.     

Nickel(II) complexes of a thiosemicarbazone prepared from 2-Acetylpyridine

Summary The ligand 3-azabicyclo[3.2.2]nonane-3-thiocarboxylic acid 2-[1-(2-pyridinyl)ethylidene]hydrazide (HL), which is observed in an unusual tautomeric form in the solid state, and its selenium analogue (HLSe) have been used to prepare a series of nickel(II) complexes. Compounds of the general formula [NiLX] (X=Cl, Br, NCS, N₃, NO₂ or NCSe) as well as [Ni(LSe)Cl] have been found to be diamagnetic, planar complexes. A single crystal study of [NiL(NCS)] shows the deprotonated ligand bound in a tridentate mannervia its pyridyl nitrogen, imine nitrogen and the thione sulphur atom with the nitrogen atom of the thiocyanato-ligand occupying the fourth coordination position. The solids prepared from the nickel(II) salts having tetrafluoroborate, nitrate and iodide ions approximate to octahedral symmetry and have neutral HL ligands coordinated in a bidentate fashionvia the pyridine and imine nitrogens with the remaining coordination sites being occupied by the anions or water molecules. The [NiL₂] solid is also octahedral with the two deprotonated ligands bonding as tridentate groupsvia the same atoms as in the [NiLX] complexes.     

Determination of trace amounts of antimony by spectrofluorimetry in hydrobromic acid medium at liquid nitrogen temperature

Trace amounts of antimony(III) may be determined in 6M hydrobromic acid by measurement of the red fluorescence of its bromide complex at -196 degrees , the optimum wavelengths of excitation and emission (360 and 586 nm respectively) being used. Calibration graphs are linear between 0.01 and 0.25 ppm. The effect of the presence of 50-fold molar amounts of 55 foreign ions has been studied. Of the ions studied, only iron(III) and tellurium(IV) interfere, and these may be tolerated at the 50- and 20-fold levels respectively. A 1000-fold molar amount of arsenic(III) causes no interference.     

Ion trapping and its effect on the conductivity of LISICON and other solid electrolytes

Conductivity data for the lithium ion conducting solid electrolyte, LISICON, Li_2+2xZn_1?xGeO₄ over a particularly wide composition range, 0.15 < x < 0.85, and over the temperature range ～25 to 150°C show that both the activation energy and preexponential factor pass through maxima around x ～ 0.4 to 0.5, at which the preexponential factor exhibits anomalously high values, ～10¹³ ohm^?1 cm^?1 K. An explanation is offered which involves the trapping of mobile Li⁺ ions by the immobile sublattice at lower temperatures. This model also accounts for ageing effects observed at lower temperatures in which the conductivity decreases slowly with time. In the isostructural Li⁺ electrolytes, Li_3+xSi_xY_1?xO₄ (Y = P, As, V), the compositional dependence of both the preexponential factor and activation energy is less marked and no evidence for ion trapping effects is observed.