Indirect laser photoacoustic detection for trace samples on membranes

An indirect laser photoacoustic technique is described. The basic principle, the experimental set-up and the influencing factors are discussed in detail. This method was used to quantify phenylamine, arginine and methylene blue on membranes. The linear ranges of the calibration curve are up to two orders of magnitude. With 1 microliter of sample solution, the detection limits are 0.25, 1.52 and 0.14 pmol for phenylamine, arginine and methylene blue, respectively.     

A facile entry to l-aryl-4,5-dihydro[1,4]oxazepino-[5,4-a]isoindole-2,7-diones

The titled compounds were prepared by reacting N-(2-bromoethyl)phthalimide with enolates of phenylacetic acid esters. 2,3-Dihydrooxazolo[2,3-a]isoindolones are believed to be intermediates in the process. An X-ray crystallographic analysis was conducted on one of the compounds.     

Reversible temperature-induced transformations of poly(N-ethyl-4-vinylpyridinium) complexes with dodecyl sulfate in aqueous salt solutions

Supramolecular organization of complexes formed by poly(N-ethyl-4-vinylpyridinium bromide) and sodium dodecylsulfate in aqueous salt solutions was studied as a function of temperature and concentration of the complexes. It was shown that a decrease in temperature and/or concentration of complexes led to their reversible disaggregation into a molecularly dispersed (“unipolymer”) state. The ratio between the components in complex particles remained unchanged in this case. It was first found that phase separation in aqueous solutions of the complexes upon temperature elevation is accompanied by the precipitation of a nonstoichiometric complex.     

Influence of the structure of the molecules on the capacity for adsorption of 1,3-dienic hydrocarbons on platinum at high positive potentials

Theoretical and Experimental Chemistry -     

Electrical Resistivity and Magnetic Susceptibility Measurements on Copper Arsenides

Electrical resistivity (4.2–800°K) and magnetic susceptibility (4.2–500°K) measurements are carried out on Cu_3–xAs, Cu_5–xAs₂ and the recently obtained, tetragonal Cu₂As. All three compounds appear to be metallic conductors, but have high residual resistances because of the large defect concentrations (resulting from non-stoichiometry and preparation method). Cu_3–xAs is diamagnetic; Cu_5–xAs₂ is Pauli-paramagnetic; Cu₂As has a very small, constant, positive susceptibility above room temperature and a more pronounced Curie-Weiss behaviour at lower temperatures. The Pauli-paramagnetic contributions have been estimated. A slight anomaly in the electric and magnetic behaviour of Cu_3–xAs is observed at 220°K. To clarify the high-temperature phenomena, a series of D.T.A. and X-ray experiments has also been carried out.     

An ESR study of some organic complexes of tetravalent vanadium

ESR results are reported for solutions and glasses containing vanadyl diethyldithiophosphate, vanadyl and vanadium diethyldithiocarbamates, and vanadium butylxanthogenate. Comparison with compounds of known structure gives the structures of these complexes.