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821.
Measurements have been made of the temperatures and enthalpy changes of phase transitions in the systems lead dodecanoate/lead oxide and lead dodecanoate/hendecane. The data have been discussed in terms of the R theory of amphiphylic mesophases. The concepts of the R theory are shown to be useful in the interpretation of phase transitions in molten carboxylate systems. 相似文献
822.
The relaxation time of the Kerr effect of nitrobenzene and m-nitrotoluene in various mixtures with carbon tetrachloride and various alcohols was determined by measuring the kinetics of the Kerr effect using picosecond laser techniques. These measurements yield information on the rotational motion of molecules in liquids. The relaxation time data are interpreted in terms of an effective local viscosity effect, pair correlation, and coupling of rotational motion with shear modes. 相似文献
823.
W. A. Ludwico S. L. Rosen 《Journal of polymer science. Part A, Polymer chemistry》1976,14(9):2121-2134
The effect of dissolved polybutadiene on the initial rate of polymerization of styrene was investigated by using high-precision dilatometric techniques. The dissolved polymer reduced the rate of polymerization by amounts greater than can be accounted for by a reduction in monomer concentration. Rate reductions increased with the amount of dissolved polybutadiene and with its molecular weight and were greater for benzoyl peroxide initiator than for equal concentrations of azobisisobutyronitrile. Surprisingly, analogous rate reductions were observed when polystyrene were substituted for the polybutadienes, except that at high polystyrene concentrations, the expected autoacceleration was observed. These rate reductions showed no correlation with the viscosity of the reaction mass, nor did the dissolved polymer affect initiator efficiency. At a given level of a particular dissolved polybutadiene, rate reductions were diminished by increasing levels of each initiator, and by adding a chain-transfer agent. Good quantitative agreement was obtained with the number-average length of the growing polymer chains, whether varied by using different initiators, changing initiator level, or adding chain-transfer agent. These results are inconsistent with a chemical mechanism, but they are explained by a proposal originated by North and Reed whereby the dissolved polymer makes the reaction mass a “poorer” solvent for the growing polymer chains, reducing their overall coil dimensions and enhancing their rate of diffusion together for termination. 相似文献
824.
The theoretically estimated dipole moments of indolizine, imidazo[1,2-a]pyridine, imidazo-[1,5-a]pyridine and of pyrazolo[ 1,5-a]pyridine obtained by the CNDO/2 approximation have been compared with the experimental values. The bond angles and bond distances for these polyazaindenes have been estimated. 相似文献
825.
A gas chromatographic method for monitoring diacetyl guanfubase A in plasma is described. The procedure involved a single solvent extraction of drug from rabbit plasma into ethyl acetate with guanfubase A as an internal standard. The extract was analyzed subsequently on a gas chromatograph equipped with a hydrogen flame ionization detector. The recovery was 86.43% +/- 6.90% (+/- SD); the RSD of within-day and between-day was 2.81%-5.26% and 5.22%-8.24%, respectively; the regression line was linear over the concentration range of 25-200 micrograms/mL, the limit of detection was 10 micrograms/mL. No endogeneous interference was found in chromatograms of the biological samples. This method was applied to the pharmacokinetic study of diacetyl guanfubase A in rabbits. 相似文献
826.
The analytical methods mass spectrometry, UV/Vis, IR, Raman, Fluorometry, XRD, Mössbauer, and NMR used to elucidate chemical structure are evaluated regarding their capabilities to be used as primary analytical techniques in quantitative measurements, considering the criteria in the CCQM definition of primary methods. This includes a review of the respective measurement equations, the evaluation of the measurement uncertainty, and a discussion of evidence for the “highest metrological level”, as obtained from intercomparisons in contest with other methods. It is shown that only few methods fulfill the CCQM criteria. Quantitative NMR spectroscopy is one of them and may be considered as a potential primary method as recommended by CCQM because of being free of empirical factors in the uncertainty budget. 相似文献
827.
Summary The flow-injection cell based on a light emitting diode and phototransistor as light source and detector respectively has been constructed and tested. As control procedures bismuth determination with Xylenol Orange and phosphate determination with molybdate and ascorbic acid were described. The working curve may be prepared as a function of absorbance or directly of photocurrent intensity.
Photometrische Messungen der Durchfluinjektion in einer Durchfluß-küvette mit Hilfe lichtgebender Dioden
Zusammenfassung Eine Durchfluß-Injektionsküvette in Verbindung mit einer lichtgebenden Diode und einem Phototransistor als Lichtquelle bzw. als Detektor wurden hergestellt und geprüft. Zur Prüfung wurden die Wismuthbestimmung mit Xylenolorange sowie die Phosphatbestimmung mit Molybdat und Askorbinsäure verwendet. Die Standardkurve kann als Funktion der Absorbanz oder als Funktion der Lichtstromstärke konstruiert werden.相似文献
828.
A procedure is described for fitting tabulated theoretical current functions to linear-sweep voltammograms. The method, suitable for a small microcomputer, employs linear extrapolation between current function values, and non-linear regression for minimizing deviations between experimental and theoretical currents. Examples of its use for confirmation of simple electrode reaction mechanisms and estimation of electrochemical parameters are described. 相似文献
829.
Vibrational Spectra of the Cage Compound PAs3S3 The vibrational spectrum of crystalline PAs3S3 and the raman spectrum of the molten title compound have been recorded. The assignment of the frequencies is proposed mainly based on polarization data of a PAs3S3 solution in white phosphorus. In the molten state a partial decomposition takes place according to 2 PAs3S3 ? P2As2S3 + α-As4S3. 相似文献
830.
J.W. Brasch 《Journal of Molecular Structure》1975,29(2):383-384
Force constants and normal coordinates are reported for the spiropentane molecule. These data are based on the recently determined fundamental vibration frequencies of spiropentane-H8.The results have been used to predict the fundamentals of spiropentane-D8, to calculate the centrifugal distortion parameters, in particular the parameter r6, which is non-zero for molecules with a four-fold axis of rotation and to calculate thermodynamic parameters. Good agreement is observed between the calorimetric vapour heat capacity of spiropentane and the value based on our assignments for the fundamental vibrations of spiropentane.The transferability of the cyclopropane force field has been tested and shown to be valid for predicting the deformations of the methylene groups of spiropentane. 相似文献