The equation is shown to be applicable in fitting the analytically useful concentration range of atomic absorption calibration curves. In this equation C is the concentration, A the observed absorbance, and the K's are coefficients which must be determined during calibration. Typical calibration data for four diverse elements (Ag, Bi, Co and Cu) determined in an air-acetylene flame are shown and rules for choosing the standards to be used are discussed. 相似文献
The current status of research on the Karplus equation for the vicinal spin—spin coupling constants (SSCC)3JHH, of fundamental significance in applications of NMR spectroscopy for establishing the configuration and conformational features of organic compounds in solutions, is discussed in the review. The data on the analysis of the fundamental molecular factors that affect the3JHH SSCC were generalized: the dihedral angle between interacting protons, the electronegativities of - and -substituents, the H-C-C valence angles, the C-C bond length, and effects of "proximity of substituents." The stereochemical applications of different modifications of the Karplus equation proposed in recent years were examined and comparatively analyzed. Possible ways of improving the accuracy of predicting the3JHH SSCC by using modern modifications of the Karplus equation and the method of molecular mechanics were discussed.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1483–1506, July, 1992. 相似文献
The densities and speeds of sound of (cyclohexane + nonane) were measured at four temperatures from 298.15 K to 328.15 K, and the respective values of excess volumes and adiabatic compressibility were calculated. Thereafter, the densities for the last system were measured at elevated pressures (0.1 to 40) MPa at four temperatures over the range 298.15 K to 328.15 K with a high-pressure apparatus. The high-pressure density data were fitted to the Tait equation and the isothermal compressibilities were calculated with a novel procedure with the aid of this equation. The low- and high-pressure values of calculated from the density data show that the deviations from ideal behaviour in the system decrease slightly as the temperature and pressure are raised. The data were fitted to the fourth-order Redlich-Kister equation, with the maximum likelihood principle being applied for the determination of the adjustable parameters. 相似文献
The density and refractive index were determined for four binary mixtures of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl) cyclotrisiloxane with octamethyl-cyclotetrasiloxane, hexamethyldisiloxane, 2,4,6,8-tetramethyl-cyclotetrasiloxane and 2,4,6,8-tetramethyl-2,4,6,8-tetraethenylcyclotetrasiloxane at different temperatures T = (308.15, 313.15, 318.15, 323.15 and 328.15) K and atmospheric pressure using a DMA4500/RXA170 combined system. The excess molar volume, partial excess volume at infinite dilution, isobaric coefficient of thermal expansion, excess refraction indices, Lorentz–Lorenz molar refraction and the deviation in molar refraction have been calculated using this data. The results have been incorporated into the Redlich–Kister equation and used to estimate the binary interaction parameters and standard deviation. The values of partial excess volume at infinite dilution and excess refraction indices for the four binary systems at different temperatures were calculated using the adjustable parameters of the Redlich–Kister smoothing equation. The factors that affect these excess quantities are discussed. 相似文献
Adsorption of gold on TBP extracting resin from HCl solution was researched.All the effects of factors,such as solution acidity,TBP content,temperature,etc.,on adsorption equilibrium were discussed and the equilibrium equation was formulated.The breakthough time of adsorption process with fixed bed was studied through experiment. 相似文献
Summary A general orientation equation for rigid particles embedded in a continuum has been derived. The equation includes hydrodynamic, thermodynamic, diffusional and kinetic terms, corresponding to physically different orientation mechanisms. Some special solutions of the general equation are presented, and discussed conditions under which the general equation reduces to more simple cases. Numerical examples of orientation in polyethylene subjected to uniaxial forces are discussed.With 6 figuresSome results contained in this paper have been presented before the V-th Europhysics Conference on Macromolecular Physics Orientation Effects in Solid Polymers, Budapest, April 1976. 相似文献
In this article, the fixed gel/nongel point and critical gel point experiments are designed for formulating the regulation of esterification reaction between epoxy resin and carboxyl acrylic polymer in the presence of tertiary amine in organic solvent. Ternary diagrams are employed to illustrate experimental results. It is disclosed that some factors, such as mole ratio of the ternary reactants, molecular weight of epoxy resin, even the hydrophilic solvent content of system, play important roles in the gelling effect of esterification reaction. In order to explain these experimental results, a suggested reaction process is put forward and, subsequently, a critical gel equation is derived from Carothers gelation theory. The equation provides an explicit connection between the critical gel composition and the relevant parameters of the reaction system such as average carboxyl functionality of acrylic resin, average molecular weight of epoxy resin, the base intensity of tertiary amine, and the solid content of system. The regressive critical gel curve based on the equation is well consistent with the experiment data. It expresses that the suggested reaction process is reasonable. Finally, based on the critical gel equation, the important factors that influence the esterification result are discussed qualitatively. All the achievements are beneficial to understanding the reaction process and avoiding useless gelation in preparing the water-reducible compositions. 相似文献
Paliperidone is an antipsychotic drug, which is used for the acute and maintenance treatment of schizophrenia. In this study, a new method was developed for the determination of Paliperidone in its extended-release tablets. Face-centered central composite design was applied for optimization of the method. Factors were decided as acetonitrile content, pH of the mobile phase and buffer concentration through preliminary studies. Optimal flow rate (1?mL/min), column temperature (35°C) and internal standard (Bupropion) were also determined during preliminary studies. Retention factors and tailing factors of Paliperidone and Bupropion were selected as responses. Derringer’s desirability function was applied for simultaneously optimization of these four responses. Optimal conditions were predicted as phosphate buffer (pH:3, 23?mM): acetonitrile (76:24, v:v). Developed method was validated in terms of linearity, detection and quantification limits, accuracy, precision, specificity and robustness. Method was found linear in the concentration range of 0.125-100?µg/mL. Mean equation of the calibration curve was y?=?0.0807 x - 0.0102 (R2?=?0.9999). Accuracy and precision of the method was evaluated with recovery values (98-102%) and relative standard deviation values (<2%), respectively. All other parameters were found acceptable. The method was successfully applied for the determination of Paliperidone in its extended-release tablets. 相似文献