Spectrophotometric determination of nitrite with p-nitroaniline and 2-methyl-8-quinolinol in hexadecyl-trimethylammonium bromide solution

Nitrite ion at low concentrations is determined spectrophotometrically by diazotization of p-nitroaniline and coupling of the diazonium salt with 2-methyl-8-quinolinol. The resulting dye is solubilized in hexadecyltrimethylammonium bromide micelles. The molar absorptivity is 4.72 × 10⁴ l mol^-1 cm^-1, and the Sandell sensitivity is 9.7 × 10^-4 μg cm^-2. Some interferences are reported, and preconcentration by evaporation is evaluated. The solubility of hexadecyltrimethylammonium bromide in water was determined as a function of temperature; the Krafft point is 19.6°C. Salting-in of the surfactant by potassium nitrate is described.     

Synthesis of the enantiomers of 4-substituted γ-lactones with known absolute configuration

The highly pure enantiomers of several 4-alkyl (or alkenyl)-γ-lactones of known absolute configuration were synthesized from glutamic acid enantiomers. The key step is selective tosylate displacement rather than ring opening of the lactone tosylate (7→1) by lithium dialkylcuprate or dialkenylcuprate. The enantiomeric purity of synthesized γ-caprolactone was confirmed within the limitations of Pirkle's chiral solvating agent. The enantiomers of synthesized (Z)-6-dodecen-4-olide were used for reference to determine the enantiomeric composition of the pheromone isolated from the black-tailed deer.     

Effects of γ-radiation on spectrophotometric determination of uranium as thiocyanate

The effects of γ-radiation on the spectrophotometric determination of uranium as the thiocyanate complex in water and acetone-water solutions have been studied. When tin(II) chloride is present, the absorbance of uranium thiocyanate in aqueous solution decreases with increasing radiation dose until the appcarance of radiolytic elemental sulfur causes an apparent increase. In the absence of tin(II) chloride, the turbidity caused by radiolytic sulfur causes an increase in absorbance over the whole dose range studied. In acetone-water solution, similar but much more severe effects occur. Observations of radiation effects of some of the individual reagents used in the spectrophotometric determinations are included, as well as indications of the errors caused by specific radiation doses.     

火焰原子吸收光谱法测定粮食中的铁

用火焰原子吸收光谱法测定粮食中的铁.方法简便、快速,精密度和准确度较好.回收率:97.4%-102.3%.     

Model calculations of atom-surface scattering

The elastic scattering of light mass, thermal-energy atoms from simple surfaces is investigated. The surface is represented by the model of a single planar square array of hard spheres. The effect of the surface potential well is treated semiclassically by simply shifting the energy of the incident atom ; furthermore a constant imaginary term is added to the energy to account for inelastic scattering and adsorption. As in the multiple scattering formalism of LEED the total scattering matrix of the lattice is expanded in terms of the individual gas atom-surface atom t-matrices. Propagation of the incident atom on the surface is described in terms of a one particle Green's function propagator with complex energy. The terms in the multiple scattering series are summed to all orders, by using standard matrix inversion techniques. The size of the matrix to be inverted limits to ten the total number of phase shifts that are included in the calculation. Thermal effects are included through angle dependent Debye-Waller factors.Model calculations have been performed to study the intensity of the specular and the diffracted beams as a function of the angles of incidence. The importance of surface temperature (introduced by the Debye-Waller factors), the incident energy and the depth of the potential well of the gas-surface interaction are discussed. The main feature of the results is the decrease of the intensity of the specular beam in going from glancing incidence to normal incidence and the presence of structure due to the appearance and disappearance of diffracted beams across the surface. The azimuthal behavior of the specular beam is in agreement with experimental observations.