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61.
Mukul Biswas Sukhendu K. Das 《Journal of polymer science. Part A, Polymer chemistry》1981,19(8):2017-2026
A low temperature solution condensation method with pyridine as acceptor-catalytic reagent was applied to the synthesis of polyarylates from carbazole and bisphenol A/phenolphthalein. The polyarylates were classified with respect to their structure, thermal stability, and dielectric behavior. 相似文献
62.
Ghosh S Krishnan A Das PK Ramakrishnan S 《Journal of the American Chemical Society》2003,125(6):1602-1606
The critical micelle concentration (CMC) of several surfactants that contain an NLO chromophore, either at the hydrocarbon tail, or at the hydrophilic headgroup, or even as a counterion, was determined by hyper-Rayleigh scattering (HRS). In all cases, the HRS signal exhibited a similar variation with surfactant concentration, wherein the CMC is inferred from a rather unprecedented drop in the signal intensity. This drop is attributed to the formation of small pre-micellar aggregates, whose concentrations become negligible above CMC. In addition, a probe molecule, which upon protonation yielded a species with significantly enhanced HRS intensity, was developed and its utility for the determination of the CMC of simple fatty acids was demonstrated. 相似文献
63.
Upendra Nath Dash Banka Behari Das Uttam Kumar Biswal Tapodhan Panda 《Thermochimica Acta》1984,80(2):331-342
The standard potentials of silver—silver bromide and silver—silver iodide electrodes in glycerol+water mixtures containing 5, 10, 20 and 30 wt% glycerol were determined from electromotive force measurements of the cell Ag(s), AgX(s), KX(c)//KCl(c), AgCl(s), Ag(s), where X is Br or I, at seven different temperatures in the range 5–35°C. The standard potentials in each solvent are represented as a function of temperature. The standard thermodynamic functions for the electrode reactions, the primary medium effects of various solvents upon X−, and the standard thermodynamic quantities for the transfer of 1 g-ion of X− from water to the respective glycerol + water media are evaluated and discussed in the light of ion—solvent interactions as well as the structural changes of the solvents. From the values of the Ag/Ag+ and Ag/AgX, X− electrodes, the thermodynamic solubility product constants of silver chloride, silver bromide and silver iodide have been determined in glycerol + water solvent mixtures at different temperatures. 相似文献
64.
C. K. Das A. K. Ghosh S. Banerjee 《Journal of polymer science. Part A, Polymer chemistry》1977,15(9):2255-2268
The salient features of nonelemental sulfur vulcanization by tetramethylthiuram disulfide (TMTD) and elemental sulfur vulcanization promoted by TMTD both in presence and absence of ZnO and stearic acid have been studied. In stock containing TMTD, a higher rate constant value for dicumyl peroxide (DCP) decomposition was observed. TMTD decreases the crosslinking density due to DCP depending on its concentration. An entirely radical mechanism has been advanced in the absence of ZnO. ZnO or ZnO–stearic acid seems to alter the entire course of reaction. The rate of crosslinking increases in the presence of ZnO or ZnO–stearic acid. Moreover, crosslinks are formed additively (further supported from the activation energy data), and mixed crosslink formation has been confirmed by the methyl iodide test of the vulcanizates. Stearic acid has no effect on crosslink formation. An ionic chain mechanism has been postulated in the presence of ZnO, as suggested by British authors. 相似文献
65.
J. T. Van Elteren H. A. Das C. L. De Ligny J. Agterdenbos D. Bax 《Journal of Radioanalytical and Nuclear Chemistry》1994,179(2):211-219
Differentiation between As(III) and As(V) is accomplished using earlier developed selective preconcentration methods (carbamate and molybdate mediated (co)precipitation of As(III) and As(V) respectively) follewed by AAS detection of the (co)precipitates. Apart from this, separation of methylated arsenic species is performed by an automatable system comprising a continuous flow hydride generation unit in which monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) are converted into their corresponding volatile methylarsines, monomethylarsine (MMA) and dimethylarsine (DMA) respectively. These species are cryogenically trapped in a Teflon-line stainless stell U-tube packed with a gas chromatographic solid-phase and subsequently separated by selective volatilization. A novel gas drying technique by means of a Perma Pure dryer was applied successfully prior to trapping. Detection is by atomic absorption spectrometry (AAS). MMAA and DMAA are determined with absolute limits of detection of 0.2 and 0.5 ng, respectively. Investigation of the behaviour of the methylarsines in the system was conducted with synthesized73As labeled methylated arsenic species. It was found that MMA is taken through the system quantitatively whereas DMA is recovered for about 85%. The opumized system combined with selective As(III)/As(V) preconcentration has been tested out for arsenic speciation of sediment interstitial water from the Chemiehaven at Rotterdam. The obtained concentrations are 28.5, 26.8 and 0.60 ng·ml–1 for As(III), As(V) and MMAA, respectively, whereas the DMAA concentration was below 0.16 ng·ml–1. 相似文献
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69.
Das HA Hegeman WJ Van Der Weijden CH 《Isotopes in environmental and health studies》1996,32(4):341-346
Abstract The mass-transfer coefficient for the volatilization of organic microconstituents from water can be determined by laboratory radiotracer experiments. Formulation and practical aspects are considered and illustrated by the example of a 5.10(-7) M solution of monochlorobenzene. 相似文献
70.