Aqueous solutions of lithium hydroxide at various temperatures: Conductivity and activity coefficients

The conductivity of LiOH aqueous solutions has been determined at 15, 25, and 45°C. The data analysis showed that LiOH is a slightly associated electrolyte, its association increasing with temperature. The association constant and distance parameter obtained from the conductivity data were successfully employed to calculate the activity coefficients of the solutions. The same procedure applied to very precise conductivity data for NaOH aqueous solutions enabled us to assess the reliability of this method of calculation of activity coefficients up to 0.1m. The alkali metal hydroxides show a reverse trend in the way their properties change with cationic radius, as is the case for the fluorides with which they are compared.     

The group of isometries ofH p

Summary The Lie group structure of the group U^p of isometries of H^p,1⩽p<∞, p≠2, is studied. In particular, it is shown that U^p is an extension of the circle group by the group of all M?bius transformations of the disc. The cocycle of the extension is calculated. It is further shown that only the trivial subspaces of H^p are invariant under U^p. Entrata in Redazione il 19 ottobre 1977. The work of this author was supported by a National Science Foundation grant. The research of this author was done while he was a Visiting Professor at the University of Florence through a grant from the Consiglio Nazionale delle Ricerche (Italy).     

Diolefin rhodium(I) complexes with tropolone and related ligands

Summary Rhodium(I) tropolonate and salicylaldehydate complexes of the general formula Rh(A)(diolefin) (A = tropolonate, -iso-propyltropolonate, -methyltropolonate and salicylaldehydate; diolefin = 1,5-cyclooctadiene, 2,5-norbornadiene and tetrafluorobenzobarrelene) have been prepared by several routes. The ability of Rh(trop)(COD) to function as an intermediate for the synthesis of other neutral and cationic rhodium(I) complexes has been studied and its hydroformylation activity has been explored briefly.     

Absorptiometric determination of bismuth with thorin

A simple, precise absorptiomotric method for bismuth based upon its reaction with Thorin is described. The effect of foreign elements was established.     

Resonant quenching of gas-phase Cs atoms induced by surface polaritons

Near-field coupling between an excited atom and a surface-polariton mode can dramatically modify atomic branching ratios, because of surface-induced enhancement of a resonant decay channel. We show here that Cs(6D(3/2)) transfer towards Cs(7P(1/2)) (at lambda = 12.15 microm), negligible in free space, becomes efficient in the vicinity (< or =100 nm) of a sapphire window, due to a 12 microm resonance in the surface-polariton modes. The experiment relies on a selective reflection probing on the 7P(1/2)-10D(3/2) transition.     

One pot synthesis of 2-phenylbenzoxazoles by potassium cyanide assisted reaction of o-aminophenols and benzaldehydes

The 2-phenylbenzoxazoles were obtained in moderate to good yields by reaction of the substituted o-aminophenols with benzaldehydes in the presence of one equivalent of potassium cyanide as an equimolecular catalyst in N,N-dimethylformamide at room temperature.     

Handling time misalignment and rank deficiency in liquid chromatography by multivariate curve resolution: Quantitation of five biogenic amines in fish

Biogenic amines (BAs) are used for identifying spoilage in food. The most common are tryptamine (TRY), 2-phenylethylamine (PHE), putrescine (PUT), cadaverine (CAD) and histamine (HIS). Due to lack of chromophores, chemical derivatization with dansyl was employed to analyze these BAs using high performance liquid chromatography with a diode array detector (HPLC-DAD). However, the derivatization reaction occurs with any primary or secondary amine, leading to co-elution of analytes and interferents with identical spectral profiles, and thus causing rank deficiency. When the spectral profile is the same and peak misalignment is present on the chromatographic runs, it is not possible to handle the data only with Multivariate Curve Resolution and Alternative Least Square (MCR-ALS), by augmenting the time, or the spectral mode. A way to circumvent this drawback is to receive information from another detector that leads to a selective profile for the analyte. To overcome both problems, (tri-linearity break in time, and spectral mode), this paper proposes a new analytical methodology for fast quantitation of these BAs in fish with HPLC-DAD by using the icoshift algorithm for temporal misalignment correction before MCR-ALS spectral mode augmented treatment. Limits of detection, relative errors of prediction (REP) and average recoveries, ranging from 0.14 to 0.50 µg mL⁻¹, 3.5–8.8% and 88.08%–99.68%, respectively. These are outstanding results obtained, reaching quantification limits for the five BAs much lower than those established by the Food and Agriculture Organization of the United Nations and World Health Organization (FAO/WHO), and the European Food Safety Authority (EFSA), all without any pre-concentration steps. The concentrations of BAs in fish samples ranged from 7.82 to 29.41 µg g⁻¹, 8.68–25.95 µg g⁻¹, 4.76–28.54 µg g⁻¹, 5.18–39.95 µg g⁻¹ and 1.45–52.62 µg g⁻¹ for TRY, PHE, PUT, CAD, and HIS, respectively. In addition, the proposed method spends less than 4 min in an isocratic run, consuming less solvent in accordance with the principles of green analytical chemistry.