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141.
Summary An analytical procedure has been developed for simultaneous determination of solvent mixture vapors to enable evaluation of
occupational exposure. To determine the desorption efficiency the volatile components of the solvent mixtures were generated
from a glass tube filled with glass wool. This device is easy to prepare and use. These vapors were then collected in activated
charcoal tubes and analyzed by capillary gas chromatography. The method was tested with a mixture of 22 solvents, including
aliphatic and aromatic hydrocarbons, alcohols, ethers, esters, and ketones, all at low concentrations. All the components
were detected. When a 99∶1 mixture of carbon disulfide-dimethylformamide was used for desorption the efficiency was>75% for
most of the solvents. 相似文献
142.
The reversed-phase high-performance liquid Chromatographic (RP-HPLC) behaviour of the binary chelates of V(V) and V(IV) with 4-(2-pyridylazo) resorcinol (PAR) and ternary chelates of vanadium with PAR and auxiliary ligands: hydrogen peroxide, hydroxylamine, tartrate and citrate were studied using a C18 column. The complex double-peak chromatograms of V(IV)/V(V)-PAR systems were studied and the origin of each peak was proved. Vanadium in ternary systems with PAR and hydrogen peroxide was found exclusively in V(V)-H2O2-PAR complex (single peak on the chromatogram) despite its initial oxidation state. The double role of hydroxylamine (complex agent and reductor) in vanadium systems with PAR was confirmed: in the V(V) system three species were identified (V(V)-PAR, V(V)-NH2OH-PAR and V(IV)-PAR), but in the V(IV) system only two: V(IV)-PAR and V(V)-NH2OH-PAR. Citrate and tartrate giving single peak were found as auxiliary ligands in ternary V(V) systems of analytical importance. Due to its masking potential towards iron (III) ions, citrate was chosen as the most suitable third component of a ternary vanadium system with PAR, to form the basis of an RP-HPLC method for direct determination of V in steel. 相似文献
143.
Mutual diffusion coefficients and densities were measured for aqueous ZnCl2–KCl mixtures at 25° by using free-diffusion Rayleigh interferometry and pycnometry, respectively. The ZnCl2 concentrations were fixed at 1.5 mol-dm–3, whereas those of KCl were 0.5, 1.25, 2.0, or 4.0 mol-dm–3. This corresponds to a half charged zinc-chlorine storage battery at various suporting electrolyte concentrations. The main-term coefficient of ZnCl2 only varies by 10% with KCl concentration, whereas that of KCl varies by about 22%. The ZnCl2 cross-term coefficient remains small and positive; in contrast the KCl cross-term coefficient goes through a maximum and is negative at high and low KCl concentrations. At KCl concentrations of 0.5 and 4.0 mol-dm–3, solutions with the KCl c0 are statically and dynamically (diffusively) unstable at the top and bottom of the boundary. Evaluation of the parameters of the non-linear least-squares solution to the diffusion equation is difficult for the 1.25 mol-dm–3 KCl case, since this system has nearly equal eigenvalues in its diffusion coefficient matrix. 相似文献
144.
Summary Three aspects with respect to the selection of solvents for static coating of capillary columns, i.e. coating speed, occurrence of bumping and solubility of stationary phases are discussed. Hypotheses are proposed in an attempt to explain the observed facts that mixed solvents result in much higher coating speeds than those obtained from pure solvents, that a proper choice of solvents together with a good and uniform deactivitation of the column inner wall is needed to prevent bumping. Stationary phase solubility vs. solvent composition is also briefly discussed. 相似文献
145.
146.
GHOLAM HOSSEIN ROUNAGHI RAZYEH SANAVI KHOSHNOOD 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):309-314
A series of competitive metal ion transport experiments have been performed. Each involved transport from an aqueous source phase across an organic membrane phase into an aqueous receiving phase. The source phase contained equimolar concentrations of cobalt(II), nickel(II), cupper(II), zinc(II), cadmium(II), silver(I) and lead(II) metal cations. The membrane phase incorporated ionophore, decyl-18-crown-6. The membrane solvents include: chloroform, dichloromethane, 1,2-dichloroethane, nitrobenzene and chloroform–nitrobenzene binary solvents. A good transport efficiency and selectivity of Pb2+ transport from aqueous solutions are observed in this investigation. The selectivity order for competitive bulk liquid membrane transport of the studied transition and post transition metal cations through chloroform is: Pb2+>Co2+>Ni2+>Ag+>Cd2+, but in the case of dichloromethane, 1,2-dichloroethane and nitrobenzene as liquid membranes, the selectivity sequences were found to be: Pb2+>Co2+>Cd2+>Cu2+>Ag+>Ni2+>Zn2+, Pb2+>Co2+>Ag+>Ni2+>Zn2+ and Pb2+>Co2+>Ni2+>Zn2+>Cd2+>Ag+, respectively. The transport rate of the metal cations in chloroform–nitrobenzene binary solvents is sensitive to the solvent composition. The transport processes were studied in absence and presence of the stearic acid and the results show that the sequence of selectivities and ion transport rates change in the presence of stearic acid. 相似文献
147.
The effective ionization coefficients and electron drift velocities in gas mixtures of CF3I with N2 and CO2 obtained from Boltzmann equation analysis
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The electron swarm parameters including the density-normalized effective ionization coefficients(α-η)/N and the electron drift velocities V e are calculated for a gas mixture of CF3I with N2 and CO2 by solving the Boltzmann equation in the condition of a steady-state Townsend(SST) experiment.The overall density-reduced electric field strength is from 100 Td to 1000 Td(1 Td = 10-17V·cm2),while the CF3I content k in the gas mixture can be varied over the range from 0% to 100%.From the variation of(αη)/N with the CF3I mixture ratio k,the limiting field strength(E/N) lim for each CF3I concentration is derived.It is found that for the mixtures with 70% CF3I,the values of(E/N) lim are essentially the same as that for pure SF 6.Additionally,the global warming potential(GWP) and the liquefaction temperature of the gas mixtures are also taken into account to evaluate the possibility of application in the gas insulation of power equipment. 相似文献
148.
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149.
The effect of the quenching rate on the phase separation of partially miscible liquid mixtures is studied, showing that it may influence the growth rate of single-phase domains. In particular, the phase separation of metastable binary mixtures in the presence of strong emulsifiers appears to be heavily retarded. These effects constitute an important limitation to the phase transition extraction process introduced by the authors in previous works, which is based on the fact that phase separation of unstable mixtures is rapid, even in the presence of surface active compounds. 相似文献
150.
Reaction of Ni2+ and SnS as a Way to Form Ni@SnS and Sn2Ni3S2 Nanocrystals: Control of Product Formation and Shape
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Stefan Michael Rommel Dr. Richard Weihrich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9863-9867
Reductive diffusion of Ni2+ into SnS particles was shown to selectively form Sn2Ni3S2, hybrid, or even core‐shell Ni@SnS, Ni1.523Sn, and Ni3S2, by tuning the reaction conditions at low temperatures. The mechanism of Ni2+ reduction and diffusion into SnS was observed in ethylene glycol, which served both as solvent and reducing agent. Tuning of reaction temperature and duration, morphology of the template SnS, and the application of ethylenediamine as supporting chelating agent, influence the formation of the final products. Their formation was controlled by carefully adjusting redox and equilibrium reactions. The products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X‐ray spectroscopy analysis (EDX). 相似文献