Microgram determination of vanadium from natural resources

Vanadium has been extracted and determined from a number of natural resources by liquid-liquid extraction technique using N-m-tolyl-o-methoxybenzohydroxamic acid.     

Head-to-head polymers—I. The preparation and some properties of head-to-head polypropylene

Samples of head-to-head polypropylene have been prepared by the hydrogenation of two polydienes; 1,4-poly(2,4-hexadiene) and 1,4-poly(2,3-dimethyl-1,3-butadiene). Glass transition temperatures were found to be marginally lower than for conventional polypropylene suggesting that the head-to-head placements in the chain increased the polymer flexibility.     

Room-temperature fluorescence spectrometry of some pharmaceutical compounds

Room-temperature fluorescence of 66 pharmaceutical drugs are presented using a mixture of ethanol/water as solvent. The analytical figures of merit for the fluorescent species are reported with limits of detection ranging between 1 and 30 ng/ml for most of them and with average blank standard deviation of 7.6%. The spectral band half-widths are also reported.     

Diels-Alder reaction of furan with some dienophiles

The reaction of furan and maleic acid was carried out in several solvents. The endo-adduct was isolated and the structure established by its spectral properties and conversion into known compounds. The adducts of furan with fumaric acid, diethyl fumarate and diethyl maleate are reported.     

The thermal stability of some pulping materials

The thermal stabilities of three annual plants (reed, kenaf and Glycyrrihiza glablra L.) are studied. Various types of pulps were prepared from reed stalks by employing the soda, kraft and soda-anthraquinone processes. Their thermal stabilities are reported.It is shown that the thermal stability measured thermogravimetrically depends, to some extent, on the amount of lignin remaining in the raw materials, i.e. the kappa number.The activation energy of the decomposition process and the decomposition temperatures of the pulps are also reported.     

The electrical conductance of some molten car☐ylate mixtures

Data are presented for the electrical conductivities in the melt for lead(II) octadecanoate/lead(II) decanoate, lead(II) hexadecanoate/lead(II) decanoate, lead(II) hexadecanoate/zinc hexadecanoate and lead(II) hexadecanoate/cadmium hexadecanoate mixtures over their complete composition ranges. The electrical conductivities are measured as a function of temperature from just above the melting point to just below the decomposition point of the mixtures. The Arrhenius plots for the mixtures are linear in all cases and the activation energies are determined. While the activation energies for lead(II) octadecanoate/lead(II) decanoate and lead(II) hexadecanoate/lead(II) decanoate mixtures are mole fraction independent over the concentration range studied, rendering support to previous models advanced by other workers that the major charge carrier is the free metal cation, the other systems show no such simple behaviour. In these systems there are indications of deviations from ideal behaviour, suggesting that entropy and enthalpy of mixing might be important.     

Thermodynamics of weak interactions: Excess enthalpies of some binary bromoform mixtures

Excess enthalpies of bromoform + toluene, +o-xylene +m-xylene and +p-xylene have been determined at 308.15 K. These compounds have been examined for Barker's theory in order to understand the magnitude and nature of various interactions between the components of these mixtures. It has been concluded that the H-atom and one bromine atom of bromoform interact with the π cloud of the aromatic ring. These conclusions have been supplemented by n.m.r. studies. An approximate distance of the bromoform proton from the plane of the aromatic ring has also been calculated and examined in the light of the proposed geometry of the molecular complexes. Equilibrium constants for the complexations reaction have also been determined.     

Infrared spectroscopic properties of water molecules dissolved in some oxygen bases

The infrared spectra in the OH-stretching and HOH-bending regions of H₂O, and in the OH-stretching region of HDO dissolved in a number of ketones and ethers have been recorded. The number of component bands and their wavenumbers, halfwidths and intensities, as well as the total OH-stretching intensity in each solvent, have been interpreted in terms of a model for the types of hydrogen bonded solvent:water complexes formed in these systems.The effect of temperature on the spectra of H₂O in some of the ketones has been rationalized on the basis of the equilibrium existing between the different hydrogen bonded species present in solution.     

Ferromagnetic resonance studies in some polycrystalline magnesium nickel ferrites

Ferromagnetic resonance measurements were carried out on various compositions of magnesium nickel ferrites prepared by various heat treatments. Corrections were applied for polycrystalline and size effects for calculating the g factor and linewidth. The variation of these parameters has been explained on the basis of the cation distribution in these compounds as obtained from magnetization data assuming a collinear model of spin distribution.     

Heats of mixing of 2,2-dimethoxypropane and diethoxymethane with some 1-alkenes

The excess enthalpies of 2,2-dimethoxypropane + 1-hexene, + 1-heptene and + 1-octene, and of diethoxymethane + 1-hexene + 1-octene have been measured at 298.15 K. The values of H^E for all the systems are positive and increase with increasing chain length of the alkene. The results are analysed in term of the quasi-lattice theory of mixtures using the zeroth approximation.     

Relative olefin—metal bond strengths in some platinum (O) compounds

Measurements are reported for the enthalphy of the reaction L₂Pt(c)+nCS₂(l) → L₂PtCS₂(soln)+olefin(soln)+(n-1)CS₂(1) where L is triphenylphosphine, and the olefins used were ethylene, phenylethylene, and cis- and trans-1,2-diphenylethylene. These enthalphies, when combined with othe data, lead to the conclusion that the relative strengths of the platinum—olefin bonds decrease in the order: trans-1,2-diphenylethylene >cis-1,2-bisphenylethylene > phenyl-ethylene > ethylene.The difference between the cis and trans compounds is relatively small. The above order is in agreement with qualitative observations on the relative stabilities of these compounds.     

Thermal decomposition kinetics of p-toluenesulphonamide and some of its n-halogeno and n-metal derivatives

The TG, DTG and DTA traces of p-toluene sulphonamide, chloramine-T, dichloramine-T, dibromamine-T and the Ag and Hg derivatives of p-toluene sulphonamide are given and interpreted. The kinetic parameters (energies and entropies of activation and pre-exponential factors) for the main decomposition stages have been calculated.     

Solvent extraction and spectrophotometric determination of palladium(II) with some nitrogen-containing heterocyclic hydrazones in the presence of chloride ions

Three terdentate hydrazones, all containing the 1-phthalazino grouping in the hydrazine moiety but differing in the heterocyclic substituent in the aldehyde moiety, have been used as analytical reagents for palladium(II), the optimal conditions for the extractive spectrophotometric determination of palladium(II) in the presence of chloride ions being deduced. These compounds are highly selective and sensitive reagents for palladium(II), since they are not extracted into chloroform from sulfuric acid solutions and do not react with other platinum group metals. The desirable spectral properties of the palladium(II) complex of benzothiazole-2-aldehyde-1-phthalazinohydrazone (BAPhH) have also been discussed with respect to preference of the C  N structural form in the heterocyclic ring on the aldehyde moiety of the ligand.