摘要:

AbstractA high‐performance liquid chromatography (HPLC) method has been developed for the analysis of dialkyltin compounds in polyvinyl chloride (PVC) materials. The PVC sample was first dissolved in tetrahydrofuran. Concentrated hydrochloric acid was then added to convert the dissolved dialkyltin stabilizers into the chloride forms, followed by extraction with hexane. The extracted dialkyltin chlorides were preconcentrated and were finally separated by HPLC. Separation was performed using a C18column and an eluent of aqueous methanol containing 8‐hydroxyquinoline (oxine) as the completing agent. Photometric detection of the dialkyltin‐oxine complexes was carried out at 380 mm. Under optimum experimental conditions, the detection limits for dimethyltin, dibutyltin and dioctyltin are 1.7 ng, 2.1 ng and 2.9 ng (all as tin), respectively. Residual dialkyltin stabilizers in several commercially available PVC products were successfully analyzed via this m

ISSN:0009-4536    

DOI:10.1002/jccs.199000028

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe electron impact mass spectra of eleven N‐arylglycines and seven substituted aniline‐N,N‐diacetic acids were obtained under 70 eV and 14 eV ionization energies. The fragmentation patterns are similar to those of α‐amino acids except for the degree of cleavage. The dehydration process of the diacetic acids may be considered as the characterestic process for this group of c

ISSN:0009-4536    

DOI:10.1002/jccs.199000029

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractDinitrophenol was removed from aqueous solution by various adsorptive bubble separation techniques. Foam fractionation of dinitrophenol with hexadecyltrimethylammonium bromide(HTA) was most effective with over 99% removal in 15 min. The addition of a surfactant in greater than stoichiometric amounts was required for effective separation. Solvent sublation of the dinitrophenol‐HTA complex was also effective. The separation efficiency of solvent sublation of dinitrophenol‐HTA was similar to that of foam fractionation. The separation by solvent sublation of dinitrophenol without adding any surfactant was very poor. Adsorbing colloid flotation with Fe(OH)3was not effective in removing dinitrophenol from aqueous solut

ISSN:0009-4536    

DOI:10.1002/jccs.199000030

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe microemulsion of the H2O/Tween 80/benzene derivative (C6H6, CH3C6H5, NO2C6H5and NH2C6H5) was investigated by the technique of Photon correlation spectroscopy. Autocorrelation data were measured at 90 scattering angle and were analyzed by using a quadratic fit and linear fit. The quadratic fit was found to describe all Properties better than the linear fit, and thus the linear fit was limited to the region of very short sampling time. When the amount of benzene derivative added to the sample solution was lower thanVmax, the Z‐average mean radius,z, and the polydispersit Y, μ2/Γ2, increased as the amount of benzene derivative was increased. When the amount of benzene derivative was larger than Vmax, the aqueous and organic phases separated and thez, and μ2/Γ2of all phases remained constant. Emulsification did not occur in the organic phase of the H2O/Tween 80/aniline system. When we adjusted the Tween 80 concentration, it was found thatz and μ2/Γ2decreased as the Tween 80 concentration in

ISSN:0009-4536    

DOI:10.1002/jccs.199000031

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractA method for preparing a new polar substituted triazine stationary phase is described. The structure of the triazine phase on silica was characterized by elemental analysis, and by FTIR, solid state FT‐13C NMR, and29Si NMR spectral analysis. The chromatographic properties of this packing material have been evaluated by using a number of different solutes, and the properties compared with those of a commercial stationary phase RP‐18. It is found that this triazine phase has weak π‐donor ligands on the silica s

ISSN:0009-4536    

DOI:10.1002/jccs.199000032

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe acid dissociation constants of 1,2‐bis(cis‐aminophenoxy)ethane‐N,N,N′,N′;‐tetraacetic acid (H4BAPAT or H4Z), and the stability constants of its chelates with tripositive rare‐earth metal ions have been determined by the potentiometric titration and mercury indicator electrode methods at 15°, 25′ and 35°C and an ionic strength of 0.1 (KNO3). The existence of a monohydrogen chelate species, LnHZ, and the normal chelate, LnZ−, is illustrated. Enthalpy and entropy changes characterizing the formation of the normal chelates and the dissociation of the last two protons of chelating acid have been calculated at 25°C. These functions have been compared with corresponding values for rela

ISSN:0009-4536    

DOI:10.1002/jccs.199000033

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractAb initio and MNDO calculations of VSEPR model were carried out on CH2, CH2+, CH2−, SiH2, SiH2+and SiH2−. Comparisons between the second row carbon and its third row silicon analogue as unshared electron pair contributors are considered. The repulsion effects as well as the volume requirement of the unshared electron pair on several structural and energetic properties arc investiga

ISSN:0009-4536    

DOI:10.1002/jccs.199000034

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractMetal silicates of ZSM‐5 type structure were prepared by doping silicate gels with chromium, manganese, cobalt, nickel, and copper ions, respectively, followed by reacting hydrothermally. The resultant materials were characterized by the metal content, x‐ray powder diffraction, ion exchange capacity, surface area, thermal stability, and temperature programmed desorption of ammonia for acidity measurement. In addition, the catalytic properties of these metal silicates were examined using ethanol conversion as a probe reaction. The effect of transition metal content on the catalysis for dehydration, dehydrogenation, oligomerization, cracking, and cyclization to the aromatics was established and compared with that of HZSM‐5 cat

ISSN:0009-4536    

DOI:10.1002/jccs.199000035

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe mass‐transter characteristics of a two‐phase system formed by mixing a fixed quantity (20 v/v%) of organic solvent with an aqueous ferricyanide electrolyte solution in an RDE system were studied. The Levich eqution, I1= 0.62 nFACbD2/3v−1/6ω1/2, was found to be applicable to the two‐phase system with only a minor modification in the angular velocity (ω) at Reynolds numbers between 3–5 × 104. The experimental results indicate that the interfacial tension is the most important variable for the two‐phase system. One group of organic solvents with smaller interfacial tension, such as benzene or toluene, needs a modification of the Levich equation by replacing the observed angular velocity (ωo) with the true angular velocity (ωt) which was observed to be 1.1 times the observed angular velocity. For the other group with larger interfacial tension, such as n‐hexane or cyclohexane, there is no need to modify the observed angular velocity. In other words, the Levich equation may be expressed as I1= 0.65 nFACbD2/3v−1/6ω1/2for two‐phase solution if the interfacial tension is sm

ISSN:0009-4536    

DOI:10.1002/jccs.199000036

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe quantitative relationships between29Si chemical shifts and (a) the SiOT (T = Al or Si) angles and (b) the nature of the cations of the alkali forms of zeolites can be account for by the changes of charge density and p electron population of the Si atoms as calculated by the extended Hückel method on cluster models

ISSN:0009-4536    

DOI:10.1002/jccs.199000037

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY