Login In
1993 Volume 9 Issue 1
1993, 9(01): 1-4
doi: 10.3866/PKU.WHXB19930101
Abstract:
A method for studying the effect of some organic compounds, which are neither soluble in water nor to be made into soluble salts in water, on DNA has been investigated by a series of experiments. The solubility experiments have shown that dimethyl sulphoxide (DMSO) and its aqueous solution are excellent solvents for the hydrophobic multicycles compounds with nitrogen atoms. The data of UV (298 K), CD (298 K), ~(31)P-NMR (323 K) spectra and molar enthalpy changes (298 K) for the effect of DMSO on DNA have not shown that DMSO has an effect on DNA when the pH of solution is equal to 7.0 and its concentration is less than 0.15 mol·L~(-1). This has further proved it is safe when DMSO is used as a carrier of medicinal compounds and enters into human bodies. Under the fixed experimental conditions, no differences were found out from the results of viscous tests (298 K) and UV spectra (298 K) for the effect of harmine hydrochloride on DNA in the presence and absence of DMSO even if the concentration of DMSO reached 0.5 mol·L~(-1). It has indicated that the existence of DMSO in aqueous solutions doesn't disturb the effect of compounds on DNA. The data of UV (298 K), CD(298 K), ~(31)P-NMR (323 K) spectra and molar enthalpy changes (298 K) for the effect of some multicycles compounds with nitrogen atoms on DNA in aqueous solutions of DMSO have also given a clear explanation to the intercalation bindings of these organic compounds to DNA, and a method to study the effect of these compounds on DNA can be developed from these experiments. By analying all the data for the effect of the above compounds on DNA, both the mechanism of interaction between the compounds and DNA and the relationship between the rule of intercalation binding of a series of compounds with same multicycles structures to DNA and their microstructures have been discussed. Since the two multicycles compounds with nitrogen atoms including harmine have high bioactivity, the further experiments inside animal bodies and clinical trial on patients as anticancer drugs should be carried out.
1993, 9(01): 5-7
doi: 10.3866/PKU.WHXB19930102
Abstract:
This note reports a successful preparation of a new catalyst particles through the reaction between Ni~(2+) and H_2PO_2~- in aqueoud solution at room temperature. X-ray diffraction pattern indicates that the particles are in amorphous and alloying state. Transmission electron micrograph shows that the particles are spherical and the size distribution is very narrow. The average diameter of the particles is determined to be about 100 nm which is in“ultrafine”scale.
This note reports a successful preparation of a new catalyst particles through the reaction between Ni~(2+) and H_2PO_2~- in aqueoud solution at room temperature. X-ray diffraction pattern indicates that the particles are in amorphous and alloying state. Transmission electron micrograph shows that the particles are spherical and the size distribution is very narrow. The average diameter of the particles is determined to be about 100 nm which is in“ultrafine”scale.
1993, 9(01): 8-12
doi: 10.3866/PKU.WHXB19930103
Abstract:
In this paper, a new way to increase the specific surface areas of supported catalysts has been suggested. The results for MoO_3/ZrO_2, WO_3/ZrO_2, CuO/ZrO_2, SO_4~(2-)/ZrO_2, NiO/ZrO_2, Fe_2O_3/ZrO_2, Fe_2(SO_4)_3/ZrO_2, MoO_3/TiO_2, WO_3/TiO_2, SO_4~(2-)/TiO_2, NiSO_4/TiO_2, NiO/TiO_2, V_2O_5/TiO_2 etc. systems show that the specific surface areas of the samples, prepared by impregnating some hydroxides then calcinating at high temperature, are much larger than those of the samples prepared with a traditional method——impregnating their oxides calcinated at the same temperature. Using this way, the specific surface areas of some supported catalysts can increase by several times. The surface areas of some supports such as zirconia and titania are not large enough, and they are easy to sinter at high temperature. In these cases, the advantage of of this preparation method is fully displayed, and the specific surface areas of the resulting zirconia-or titania-supported catalysts can compare favourably with those of the catalysts prepared from some classical supports (such ar γ-Al_2O_3, SiO_2).
In addition, it has been proved by means of XPS, XRD, LRS, and DTA that as an active component disperse on a support as a monolayer and its content comes up to its monolayer dispersion capacity, the specific surface area of the obtained catalyst would be the largest. We suggest a mechanism that an active component covered on a support can not only segregate its particles, but also hinder the surface diffusion of support, and as a result, its crystalline growth, an accompanying phase transformation and inter-crystalline sintering are all retarded.
In this paper, a new way to increase the specific surface areas of supported catalysts has been suggested. The results for MoO_3/ZrO_2, WO_3/ZrO_2, CuO/ZrO_2, SO_4~(2-)/ZrO_2, NiO/ZrO_2, Fe_2O_3/ZrO_2, Fe_2(SO_4)_3/ZrO_2, MoO_3/TiO_2, WO_3/TiO_2, SO_4~(2-)/TiO_2, NiSO_4/TiO_2, NiO/TiO_2, V_2O_5/TiO_2 etc. systems show that the specific surface areas of the samples, prepared by impregnating some hydroxides then calcinating at high temperature, are much larger than those of the samples prepared with a traditional method——impregnating their oxides calcinated at the same temperature. Using this way, the specific surface areas of some supported catalysts can increase by several times. The surface areas of some supports such as zirconia and titania are not large enough, and they are easy to sinter at high temperature. In these cases, the advantage of of this preparation method is fully displayed, and the specific surface areas of the resulting zirconia-or titania-supported catalysts can compare favourably with those of the catalysts prepared from some classical supports (such ar γ-Al_2O_3, SiO_2).
In addition, it has been proved by means of XPS, XRD, LRS, and DTA that as an active component disperse on a support as a monolayer and its content comes up to its monolayer dispersion capacity, the specific surface area of the obtained catalyst would be the largest. We suggest a mechanism that an active component covered on a support can not only segregate its particles, but also hinder the surface diffusion of support, and as a result, its crystalline growth, an accompanying phase transformation and inter-crystalline sintering are all retarded.
1993, 9(01): 13-20
doi: 10.3866/PKU.WHXB19930104
Abstract:
A series of WO_3/titania-alumina samples was prepared by impregnation method. The results of XRD and XPS show that WO_3 is dispersed as a monolayer on the surface of titania-alumina. The dispersion threshold is 0.22 gWO_3/(100 m~2). It approximately agrees with the value, 0.198 gWO_3/(100 m~2), calculated from the model on assuming that the WO_3 is dispersed as a elose-packed monolayer on titania-alumina surface. With LRS measurement, it can be found that as the loading of WO_3 is lower than 0.082 gWO_3/(100 m~2 titania-alumina), only distorted tetrahedral coordinated tungsten will be located on the surface, however as the loading of WO_3 is higher than 0.082 gWO_3/(100 m~2 titania-alumina), octahedral coordinated tungsten dominates. LRS measurements also show no Al_2(WO_4)_3 is formed as the WO_3/titania-alumina samples were calcined at 550 ℃. The formation of Al_2(WO_4)_3 at higher temperature also has been studied.
A series of WO_3/titania-alumina samples was prepared by impregnation method. The results of XRD and XPS show that WO_3 is dispersed as a monolayer on the surface of titania-alumina. The dispersion threshold is 0.22 gWO_3/(100 m~2). It approximately agrees with the value, 0.198 gWO_3/(100 m~2), calculated from the model on assuming that the WO_3 is dispersed as a elose-packed monolayer on titania-alumina surface. With LRS measurement, it can be found that as the loading of WO_3 is lower than 0.082 gWO_3/(100 m~2 titania-alumina), only distorted tetrahedral coordinated tungsten will be located on the surface, however as the loading of WO_3 is higher than 0.082 gWO_3/(100 m~2 titania-alumina), octahedral coordinated tungsten dominates. LRS measurements also show no Al_2(WO_4)_3 is formed as the WO_3/titania-alumina samples were calcined at 550 ℃. The formation of Al_2(WO_4)_3 at higher temperature also has been studied.
1993, 9(01): 21-26
doi: 10.3866/PKU.WHXB19930105
Abstract:
The binding of cationic polyelectrolytes PAm·MG and P(St-Am·MG) with methyl orange(MO) and the binding of P(St-Am·MG) with MO homologue ethyl orange(EO) and orange-Ⅳ(O-Ⅳ) have been studied thermodynamically by the method of equi-librium dialysis at 25, 35, 45 and 55 ℃. The equilibrium constant K_1 and △H, △S, △G have been obtained. It has been found that the binding ability of P(St-Am·MG) is stronger than that of PAm·MG since the former contains hydrophobic group. The binding ability of dyes with P(St-Am·MG) is in the order: O-IV>EO>MO, i.e., the larger the hydrophobic group in the dyes, the stronger is the binding ability. When urea or methanol is added, the hydrophobic interaction of the polyelectrolyte and the dyes is destroyed resulting in weakening the polymer-dye binding.
The binding of cationic polyelectrolytes PAm·MG and P(St-Am·MG) with methyl orange(MO) and the binding of P(St-Am·MG) with MO homologue ethyl orange(EO) and orange-Ⅳ(O-Ⅳ) have been studied thermodynamically by the method of equi-librium dialysis at 25, 35, 45 and 55 ℃. The equilibrium constant K_1 and △H, △S, △G have been obtained. It has been found that the binding ability of P(St-Am·MG) is stronger than that of PAm·MG since the former contains hydrophobic group. The binding ability of dyes with P(St-Am·MG) is in the order: O-IV>EO>MO, i.e., the larger the hydrophobic group in the dyes, the stronger is the binding ability. When urea or methanol is added, the hydrophobic interaction of the polyelectrolyte and the dyes is destroyed resulting in weakening the polymer-dye binding.
1993, 9(01): 27-34
doi: 10.3866/PKU.WHXB19930106
Abstract:
In this work, reversible microdisk electrode reactions with coupled first-order homogeneous chemical reactions are discussed by means of the equivalence between the recombinated steady state diffusion equations and the Laplace transformed tran-sient diffusion equation of electrode reactions. First, general solution for transient diffusion equation of reversible microdisk electrode reactions is derived with “uni-form concentration” approach which is acceptable if D_O is close to D_R. And then, expressions for steady state current of CE, EC, EC' and ECE reactions at microdisk electrode are derived with the help of that general solution.
In this work, reversible microdisk electrode reactions with coupled first-order homogeneous chemical reactions are discussed by means of the equivalence between the recombinated steady state diffusion equations and the Laplace transformed tran-sient diffusion equation of electrode reactions. First, general solution for transient diffusion equation of reversible microdisk electrode reactions is derived with “uni-form concentration” approach which is acceptable if D_O is close to D_R. And then, expressions for steady state current of CE, EC, EC' and ECE reactions at microdisk electrode are derived with the help of that general solution.
1993, 9(01): 35-40
doi: 10.3866/PKU.WHXB19930107
Abstract:
In this paper, a mathematical expression of the response of mediator-type enzyme electrode is presented by considering the influence of effective factors such as the electrode potential,concentration polarization, etc. Primary test of the modified electrode with glucose oxidase and mathematical simulation have been performed, the experimental result is in agreement with the theoretical conclusion.
In this paper, a mathematical expression of the response of mediator-type enzyme electrode is presented by considering the influence of effective factors such as the electrode potential,concentration polarization, etc. Primary test of the modified electrode with glucose oxidase and mathematical simulation have been performed, the experimental result is in agreement with the theoretical conclusion.
Structural Frame Model with Numerical Representation of 2D Molecular Information and its Application
1993, 9(01): 41-49
doi: 10.3866/PKU.WHXB19930108
Abstract:
In the researches of the Quantitative Structure-Activity Relationship, one of the difficult problems is the representation and the extraction of molecule structural informations.In order to solve this problem generally, authors propose a numerical representation method of molecule structural factors——Structural Frame Model method(SFM).
First, a model for describing molecule structural factors is defined on a set of compounds being studied. In the set of compounds, there must be a common mole-cular backbone. From the model definitions, the factors reflecting the differences of molecular structures can be completely extracted.
Then the whole topological strcuture information can be transfered to a numerical matrix.
...
In the researches of the Quantitative Structure-Activity Relationship, one of the difficult problems is the representation and the extraction of molecule structural informations.In order to solve this problem generally, authors propose a numerical representation method of molecule structural factors——Structural Frame Model method(SFM).
First, a model for describing molecule structural factors is defined on a set of compounds being studied. In the set of compounds, there must be a common mole-cular backbone. From the model definitions, the factors reflecting the differences of molecular structures can be completely extracted.
Then the whole topological strcuture information can be transfered to a numerical matrix.
...
1993, 9(01): 50-55
doi: 10.3866/PKU.WHXB19930109
Abstract:
NH_4Y, USY, PrHY, USPrHY and FSPrHY were prepared. Their compositions and physical properties were determined. The difference among their hydroxyl group has been compared on the IR system. The acid strength of every sample was deter-mined by IR-Pyridine method. The order of Bronsted acid strength are FSPrHY>FSY>USPrHY>USY>PrHY>NH_4Y. ~(29)Si MAS NMR spectra,showed that Si(0Al) content in USPrHY and FSPrHY is more than in PrHY and NH_4Y. These results show that the 0-NNN and 1-NNN strong acidity site is more than 2-NNN and 3-NNN weak acidity site on USPrHY and FSPrHY Zeolites. All the results of IR ~(39)Si MAS NMR and activity test are consistent with a model of strong acidity in which both the presence of 0-NNN strong acidity site and polyvalent cations in the β-cages are important. Praseodymium ions in the form of (?) and Pr(OH)~(2+) species are believed to be responsible for the withdrawal of electrons from the framework hydroxyl groups, thus making the protons more acidic, the cracking disproportionation and dealkylation activity were heightened.
NH_4Y, USY, PrHY, USPrHY and FSPrHY were prepared. Their compositions and physical properties were determined. The difference among their hydroxyl group has been compared on the IR system. The acid strength of every sample was deter-mined by IR-Pyridine method. The order of Bronsted acid strength are FSPrHY>FSY>USPrHY>USY>PrHY>NH_4Y. ~(29)Si MAS NMR spectra,showed that Si(0Al) content in USPrHY and FSPrHY is more than in PrHY and NH_4Y. These results show that the 0-NNN and 1-NNN strong acidity site is more than 2-NNN and 3-NNN weak acidity site on USPrHY and FSPrHY Zeolites. All the results of IR ~(39)Si MAS NMR and activity test are consistent with a model of strong acidity in which both the presence of 0-NNN strong acidity site and polyvalent cations in the β-cages are important. Praseodymium ions in the form of (?) and Pr(OH)~(2+) species are believed to be responsible for the withdrawal of electrons from the framework hydroxyl groups, thus making the protons more acidic, the cracking disproportionation and dealkylation activity were heightened.
1993, 9(01): 56-62
doi: 10.3866/PKU.WHXB19930110
Abstract:
The reaction and adsorption of syngas and paraformaldehyde on Ru-Co/SiO_2 ca-talysts prepared from Ru-Co bimetallic carbonyl clusters have been investigated by infrared, mass spectroscopies. The spectra of reaction of CO+H_2 with Ru-Co/SiO_2 catalysts showed a band appearing at 1584 cm~(-1), which has a od relationship to the activity and selectivity for oxygenates in CO hydrogenation. Thus it was proposed that 1584 cm~(-1) is a possible intermediate to produce oxygenated products. Isotopic tracer studies of D_2 and ~(13)CO suggest that 1584 cm~(-1) can possibly be assigned to the formyl group, which is in od agreement with the adsorption of paraformaldehyde. The chemical trapping of 1584 cm~(-1) adspecies provided an evidence to demonstrate that 1584 cm~(-1) is attributed to formyl. The reaction of 1584 cm~(-1) species with H_2 produced CH_4 and CH_3OH, and the introduction of D_2 into 1584 cm~(-1) species resulted in the formation of CHD_3 and CHD_2OD.
The reaction and adsorption of syngas and paraformaldehyde on Ru-Co/SiO_2 ca-talysts prepared from Ru-Co bimetallic carbonyl clusters have been investigated by infrared, mass spectroscopies. The spectra of reaction of CO+H_2 with Ru-Co/SiO_2 catalysts showed a band appearing at 1584 cm~(-1), which has a od relationship to the activity and selectivity for oxygenates in CO hydrogenation. Thus it was proposed that 1584 cm~(-1) is a possible intermediate to produce oxygenated products. Isotopic tracer studies of D_2 and ~(13)CO suggest that 1584 cm~(-1) can possibly be assigned to the formyl group, which is in od agreement with the adsorption of paraformaldehyde. The chemical trapping of 1584 cm~(-1) adspecies provided an evidence to demonstrate that 1584 cm~(-1) is attributed to formyl. The reaction of 1584 cm~(-1) species with H_2 produced CH_4 and CH_3OH, and the introduction of D_2 into 1584 cm~(-1) species resulted in the formation of CHD_3 and CHD_2OD.
1993, 9(01): 63-69
doi: 10.3866/PKU.WHXB19930111
Abstract:
Temperature programmed reduction and volumetric chemisorption of O_2, H_2 and CO have been used to provide insight into the functions of cobalt and ruthenium in a series of sulfided Co-Mo/Al_2O_3, Ru-Mo/Al_2O_3, Ru-Co-Mo/Al_2O_3 catalysts. Cobalt interacted with molybdenum to form a stable species, i.e. CoMoS phase, which decreased the amount of oxygen chemisorption and increased uptake of CO on the Co-Mo/Al_2O_3 catalyst. Ru promotion is found to cause reduction temperature of Mo sites shifting to lower temperature and increase obviousely the amounts of O_2 and H_2 adsorbed on Mo sites. The function of ruthenium is explained by a concept of hydrogen spillover from Ru centers to Mo sites.
Temperature programmed reduction and volumetric chemisorption of O_2, H_2 and CO have been used to provide insight into the functions of cobalt and ruthenium in a series of sulfided Co-Mo/Al_2O_3, Ru-Mo/Al_2O_3, Ru-Co-Mo/Al_2O_3 catalysts. Cobalt interacted with molybdenum to form a stable species, i.e. CoMoS phase, which decreased the amount of oxygen chemisorption and increased uptake of CO on the Co-Mo/Al_2O_3 catalyst. Ru promotion is found to cause reduction temperature of Mo sites shifting to lower temperature and increase obviousely the amounts of O_2 and H_2 adsorbed on Mo sites. The function of ruthenium is explained by a concept of hydrogen spillover from Ru centers to Mo sites.
1993, 9(01): 70-76
doi: 10.3866/PKU.WHXB19930112
Abstract:
The kinetics and mechanism of oxidation of ethanolamide by potassium ferrate(Ⅵ) in the pH range of 9.89 to 10.70 has been investigated spectrophotometrically by the stoppedflow method. The order both with respect to potassium ferrate and ethanolamide was found to be unity and that with respect to OH a negative fraction. There was no effect on the variation of ionic strength. A mechanism which includes a twoelectron transfer throngh hydrogen bridge between the ion and the molecule was suggested. The rate equation derived from this mechanism can explain all the observed experimental facts satisfactorily and some rate constants were obtained.
The kinetics and mechanism of oxidation of ethanolamide by potassium ferrate(Ⅵ) in the pH range of 9.89 to 10.70 has been investigated spectrophotometrically by the stoppedflow method. The order both with respect to potassium ferrate and ethanolamide was found to be unity and that with respect to OH a negative fraction. There was no effect on the variation of ionic strength. A mechanism which includes a twoelectron transfer throngh hydrogen bridge between the ion and the molecule was suggested. The rate equation derived from this mechanism can explain all the observed experimental facts satisfactorily and some rate constants were obtained.
1993, 9(01): 77-84
doi: 10.3866/PKU.WHXB19930113
Abstract:
Deacetylchitins of similar molar mass (6.1, 6.9, 7.2×10~5 g·mol~(-1)) but different aminecontent(93%, 78%, 62%) were tested as flocculants for bentonite suspensions. Flocculant performance was assessed by determining the turbidity change of the suspensions with time, the extent of the deacetylchitin adsorption and the electrokinetic potential of the treated particles. The suspension concentration was kept constant at 2 g (bentonite).dm~(-3) in 10~(-3) mol·dm~(-3) NaCl solution; pH was varied from 3 to 6. It was found that bridging was the predominant mechanism of the flocculation, but neutralization of the particle charge by the adsorption of macroelectrolytes did play a contributory role in the destabilization of the suspensions.
Similar experiments were carried out using a nonionic acrylamide of high molar mass (1～3×10~6 g·mol~(-1). The efficacy of flocculation by polymer bridging did not counteract the increasing self-repulsion of the bentonite particles with increasing pH which produced poor floc formation.
Deacetylchitins of similar molar mass (6.1, 6.9, 7.2×10~5 g·mol~(-1)) but different aminecontent(93%, 78%, 62%) were tested as flocculants for bentonite suspensions. Flocculant performance was assessed by determining the turbidity change of the suspensions with time, the extent of the deacetylchitin adsorption and the electrokinetic potential of the treated particles. The suspension concentration was kept constant at 2 g (bentonite).dm~(-3) in 10~(-3) mol·dm~(-3) NaCl solution; pH was varied from 3 to 6. It was found that bridging was the predominant mechanism of the flocculation, but neutralization of the particle charge by the adsorption of macroelectrolytes did play a contributory role in the destabilization of the suspensions.
Similar experiments were carried out using a nonionic acrylamide of high molar mass (1～3×10~6 g·mol~(-1). The efficacy of flocculation by polymer bridging did not counteract the increasing self-repulsion of the bentonite particles with increasing pH which produced poor floc formation.
1993, 9(01): 85-88
doi: 10.3866/PKU.WHXB19930114
Abstract:
We have prepared polyamine capsules with ethylenediamine and diethylenetri-amine or their mixtures as aqueous phase monomer, and sebacoyl chloride as oil phase monomer. By using cell-tensiometer, their critical tensile pressures were measured, which could contrast the tensile strength of all kinds of capsules quantitatively. We have also compare the porous properties of the capsules qualitatively by the permeable efficiencies of KCI through the capsule wall. The results showed that the tensile strength and porous properties could be related to the proportion of ethylenediamine to diethylenetriamine monomeres.
We have prepared polyamine capsules with ethylenediamine and diethylenetri-amine or their mixtures as aqueous phase monomer, and sebacoyl chloride as oil phase monomer. By using cell-tensiometer, their critical tensile pressures were measured, which could contrast the tensile strength of all kinds of capsules quantitatively. We have also compare the porous properties of the capsules qualitatively by the permeable efficiencies of KCI through the capsule wall. The results showed that the tensile strength and porous properties could be related to the proportion of ethylenediamine to diethylenetriamine monomeres.
1993, 9(01): 89-93
doi: 10.3866/PKU.WHXB19930115
Abstract:
The electrochemical roduction of methylene blue has been studied by long path-length thin-layer spectroelectrochemical method. It was found that the reduction of methylene blue at SnO_2 electrode is a two electron transfer reversible process. The standard potential E(?) determined was 0.286 V(vs. SCE). The acid dissociation constants for the leuco methylene blue were obtained as pK_(α1)=5.18, pK_(α1)=6.03. The mechanism of electrode reaction has been proposed.
The electrochemical roduction of methylene blue has been studied by long path-length thin-layer spectroelectrochemical method. It was found that the reduction of methylene blue at SnO_2 electrode is a two electron transfer reversible process. The standard potential E(?) determined was 0.286 V(vs. SCE). The acid dissociation constants for the leuco methylene blue were obtained as pK_(α1)=5.18, pK_(α1)=6.03. The mechanism of electrode reaction has been proposed.
1993, 9(01): 94-98
doi: 10.3866/PKU.WHXB19930116
Abstract:
Procedures have been developed which may yield spherical type bismuth oxych-loride particles with narrow size distribution by forced hydrolysis of bismuth nitrate solutions at elevated temperature. The particle size and shape characteristics in each precipitation region were investigated by electron microscopy. The presence of sur-factants during the precipitation and aging processes has a marked effect on the properties of the sols resulted.
Procedures have been developed which may yield spherical type bismuth oxych-loride particles with narrow size distribution by forced hydrolysis of bismuth nitrate solutions at elevated temperature. The particle size and shape characteristics in each precipitation region were investigated by electron microscopy. The presence of sur-factants during the precipitation and aging processes has a marked effect on the properties of the sols resulted.
1993, 9(01): 99-102
doi: 10.3866/PKU.WHXB19930117
Abstract:
The photocurrent-potential relationship for copper and brass electrodes under periodic illumination was obtained during slow (6 mV·s~(-1)) cyclic potential scans with lock-in amplifier in 0.1 molo·L~(-1) Na_2B_4O_7 contianing variable concentration of NaCl. Only cathodic photocurrent was exhibited on photocurrent vs. potential curves in absence of or in the presence of low concentrations of chloride ion in the solution. The minimum concentration of NaCl at which an anodic photocurrent peak appeared is 7.5×10~(-4) g·g~(-1) for copper and 3.8×10~(-3) g·g~(-1) for brass. With the continuous increase of NaCl concentraton the peak area of anodic photocurrent increases and that of cathodic decreases. The appearance of anodic photocurrent peak and its magnitude on photocurrent vs. potential curve may be served as a criterion for the characterization of the corrosion extent of copper material by Cl~-.
The photocurrent-potential relationship for copper and brass electrodes under periodic illumination was obtained during slow (6 mV·s~(-1)) cyclic potential scans with lock-in amplifier in 0.1 molo·L~(-1) Na_2B_4O_7 contianing variable concentration of NaCl. Only cathodic photocurrent was exhibited on photocurrent vs. potential curves in absence of or in the presence of low concentrations of chloride ion in the solution. The minimum concentration of NaCl at which an anodic photocurrent peak appeared is 7.5×10~(-4) g·g~(-1) for copper and 3.8×10~(-3) g·g~(-1) for brass. With the continuous increase of NaCl concentraton the peak area of anodic photocurrent increases and that of cathodic decreases. The appearance of anodic photocurrent peak and its magnitude on photocurrent vs. potential curve may be served as a criterion for the characterization of the corrosion extent of copper material by Cl~-.
1993, 9(01): 103-106
doi: 10.3866/PKU.WHXB19930118
Abstract:
Five kinds of thioether p-CH_3C_6H_4SR (R=n-C_4H_9, C_6H_(13), C_8H_(17), C_(10)H_(21), and C_(12)H_(25)) and their palladium complexes Pd(p-CH_3C_6H_4SR)_2Cl_2 were synthesized. The thermal decomposition of these complexes have been studied by using TG and DTG methods. It was found that the former two of the complexes firstly decompos into organic ligands and PdCl_2, then PdCl_2 to chlorine atoms and palladium; The latter three of complexes decompose into organic ligands chorine atoms and palladium almost simultaneously. Kinetic parameters such as activation energy E, frequency factor A and reaction order n were obtained using the Coats-Redfern and Freeman-Carroll methods. In addition, entropy of activation ΔS has also been calculated.
Five kinds of thioether p-CH_3C_6H_4SR (R=n-C_4H_9, C_6H_(13), C_8H_(17), C_(10)H_(21), and C_(12)H_(25)) and their palladium complexes Pd(p-CH_3C_6H_4SR)_2Cl_2 were synthesized. The thermal decomposition of these complexes have been studied by using TG and DTG methods. It was found that the former two of the complexes firstly decompos into organic ligands and PdCl_2, then PdCl_2 to chlorine atoms and palladium; The latter three of complexes decompose into organic ligands chorine atoms and palladium almost simultaneously. Kinetic parameters such as activation energy E, frequency factor A and reaction order n were obtained using the Coats-Redfern and Freeman-Carroll methods. In addition, entropy of activation ΔS has also been calculated.
1993, 9(01): 107-110
doi: 10.3866/PKU.WHXB19930119
Abstract:
The monodisperse sol of Cu_2O was prepared by reduction of sulfate copper or acetate copper with glucose, hydroxychloride amine and hydrazine hydrate. The dis-tribution of particle radius is very narrow. Different types of Cu_2O sol can be obtained under different conditions.
The monodisperse sol of Cu_2O was prepared by reduction of sulfate copper or acetate copper with glucose, hydroxychloride amine and hydrazine hydrate. The dis-tribution of particle radius is very narrow. Different types of Cu_2O sol can be obtained under different conditions.
1993, 9(01): 111-116
doi: 10.3866/PKU.WHXB19930120
Abstract:
The experimental retention time obtained for a series of the different injection concentration are compared to formula related the retention time to injection con-centration, which is derived from the nonlinear chromatography equation. The results show that the theoretical formula is a appropriate approximation to the practical nonliear chromatography.
The experimental retention time obtained for a series of the different injection concentration are compared to formula related the retention time to injection con-centration, which is derived from the nonlinear chromatography equation. The results show that the theoretical formula is a appropriate approximation to the practical nonliear chromatography.
1993, 9(01): 117-120
doi: 10.3866/PKU.WHXB19930121
Abstract:
The isomer conversion of formanilide was investigated by ~(13)C 2D-EXSY NMR, and the conversion rate was obtained by approximation method proposed by ourselves~[5]. Cis-and Trans-isomer coexist at ambient temperature. It was due to amide bond restricted rotation and intermolecular association.
The isomer conversion of formanilide was investigated by ~(13)C 2D-EXSY NMR, and the conversion rate was obtained by approximation method proposed by ourselves~[5]. Cis-and Trans-isomer coexist at ambient temperature. It was due to amide bond restricted rotation and intermolecular association.
1993, 9(01): 121-124
doi: 10.3866/PKU.WHXB19930122
Abstract:
The aggregation structure of monolayer was discussed by the observations of electron diffraction patterns and bright field images. When 2C_(14)SNa was spread on pure water surface, a homogeneous monolayer was formed before compressing as the result of electrostatic repulsion among hydrophilic anionic groups, the crystallization was occurred in the process of compressing, i.e., it was a compressing crystallized monolayer. When 2C_(14)SNa was spread on PEI solution surface, a crystalline monolayer with an un-oriented domain structure was formed before compressing as the results of anchoring effect of ion complex and the weakened electrostatic repulsion, the orientation was occurred in the process of compressing, i.e., it was a compressing oriented crystalline monolayer. The formation of polyion complex at the air/water interface greatly affected the aggregation state of monolayer.
The aggregation structure of monolayer was discussed by the observations of electron diffraction patterns and bright field images. When 2C_(14)SNa was spread on pure water surface, a homogeneous monolayer was formed before compressing as the result of electrostatic repulsion among hydrophilic anionic groups, the crystallization was occurred in the process of compressing, i.e., it was a compressing crystallized monolayer. When 2C_(14)SNa was spread on PEI solution surface, a crystalline monolayer with an un-oriented domain structure was formed before compressing as the results of anchoring effect of ion complex and the weakened electrostatic repulsion, the orientation was occurred in the process of compressing, i.e., it was a compressing oriented crystalline monolayer. The formation of polyion complex at the air/water interface greatly affected the aggregation state of monolayer.
1993, 9(01): 125-128
doi: 10.3866/PKU.WHXB19930123
Abstract:
~1H NMR spectra of acetoxime have been measured as a function of the mole fraction of certain aromatic hydrocarbons in mixed solvent of CCl_4 and benzene or toluene. It has been found that the chemical shifts of the two methyl groups in acetoxime and of benzene or toluene move upfield gradually in the mixed solvent as the mole fraction of aromatic component increases. The moving rate of the resonance absorption line of the two methyl groups in acetoxime are different. The △δ of β-CH_3 is larger than that of α-CH_3. The absorption line of the two methyl groups is a singlet in CCl_4 and splits to a doublet when the concentration of benzene or toluene in the solvent is higher than 30% (mole/mole). The experimental results also show that the extent of upfield shifts of either the methyl groups in acetoxime or the aromatic hydrogens are reduced when a hydrogen of benzene is substituted by methyl group. All of the chemical shifts can be correlated with a linear equation as δ=A+Bx, Where, x is the mole fraction of benzene or toluene in the mixed solvent. The correlation coefficients R are approximately equal to -1.
~1H NMR spectra of acetoxime have been measured as a function of the mole fraction of certain aromatic hydrocarbons in mixed solvent of CCl_4 and benzene or toluene. It has been found that the chemical shifts of the two methyl groups in acetoxime and of benzene or toluene move upfield gradually in the mixed solvent as the mole fraction of aromatic component increases. The moving rate of the resonance absorption line of the two methyl groups in acetoxime are different. The △δ of β-CH_3 is larger than that of α-CH_3. The absorption line of the two methyl groups is a singlet in CCl_4 and splits to a doublet when the concentration of benzene or toluene in the solvent is higher than 30% (mole/mole). The experimental results also show that the extent of upfield shifts of either the methyl groups in acetoxime or the aromatic hydrogens are reduced when a hydrogen of benzene is substituted by methyl group. All of the chemical shifts can be correlated with a linear equation as δ=A+Bx, Where, x is the mole fraction of benzene or toluene in the mixed solvent. The correlation coefficients R are approximately equal to -1.
1993, 9(01): 129-133
doi: 10.3866/PKU.WHXB19930124
Abstract:
The cathodic reduction of Co~(2+) ions in solutions of pH 4—6 has been inves-tigated by using polarization measurements and ac impedance technique. The reduction behaviour depends to a great extent on the acidity of solution. Based on the mechanism proposed, which is characterized by a stepwise reduction and the inter-mediate formation of an adsorbed monovalent cobalt, (CoOH)_(ads), and with the reaction sequence as a model, an impedance analysis is made of the electrode process. The consistency of the conclution derived from the analysis with experimental electrochemical impedance spectroscopy (EIS) further confirms the reasonableness of the proposed mechanism. The present impedance study also gives evidence that there exists no one-to-one correspondence between a given reaction path (mechanism) and a certain mode of EIS, as ascertained by Cao~[12], and the method of equivalent circuit is limited in studying reaction mechanism.
The cathodic reduction of Co~(2+) ions in solutions of pH 4—6 has been inves-tigated by using polarization measurements and ac impedance technique. The reduction behaviour depends to a great extent on the acidity of solution. Based on the mechanism proposed, which is characterized by a stepwise reduction and the inter-mediate formation of an adsorbed monovalent cobalt, (CoOH)_(ads), and with the reaction sequence as a model, an impedance analysis is made of the electrode process. The consistency of the conclution derived from the analysis with experimental electrochemical impedance spectroscopy (EIS) further confirms the reasonableness of the proposed mechanism. The present impedance study also gives evidence that there exists no one-to-one correspondence between a given reaction path (mechanism) and a certain mode of EIS, as ascertained by Cao~[12], and the method of equivalent circuit is limited in studying reaction mechanism.
1993, 9(01): 134-136
doi: 10.3866/PKU.WHXB19930125
Abstract:
Conformational studies of antitumor drug phenyl-tri-azenes were carried out using MINDO/3 MO method. The conformational energy has been calculated as a function of torsion angles θ_1 and θ_2. The rotation barrier of θ_2 is about ten times as high as θ_1. The original conformation may be play an important role in the antitumor procedure.
Conformational studies of antitumor drug phenyl-tri-azenes were carried out using MINDO/3 MO method. The conformational energy has been calculated as a function of torsion angles θ_1 and θ_2. The rotation barrier of θ_2 is about ten times as high as θ_1. The original conformation may be play an important role in the antitumor procedure.
1993, 9(01): 137-144
doi: 10.3866/PKU.WHXB19930126
Abstract:
