Login In
1986 Volume 2 Issue 5
1986, 2(05): 385-391
doi: 10.3866/PKU.WHXB19860501
Abstract:
Using p-phenylene-di-n-alkoxybenzoate homolo us series as stationary liquid, the infinite dilution activity coefficients γ_i~∞, partial molar excess enthalpies H_i~E and entropies S_i~E of xylene isomers, dichlorobenzene isomers, diphenyl and diphenylmethane have been measured in the nematic phase of three liquid crystals. The studied liquid crystal series have the following general formulas,
where n=6(PBH_xB), n=7(PBH_pB) and n=8(PBOB)
The results were explained from theview point of statistical theory of solutions.
Using p-phenylene-di-n-alkoxybenzoate homolo us series as stationary liquid, the infinite dilution activity coefficients γ_i~∞, partial molar excess enthalpies H_i~E and entropies S_i~E of xylene isomers, dichlorobenzene isomers, diphenyl and diphenylmethane have been measured in the nematic phase of three liquid crystals. The studied liquid crystal series have the following general formulas,
where n=6(PBH_xB), n=7(PBH_pB) and n=8(PBOB)
The results were explained from theview point of statistical theory of solutions.
1986, 2(05): 392-399
doi: 10.3866/PKU.WHXB19860502
Abstract:
The thermal decomposition kinetics of α-AIH_3 in helium flow was investigated by differential thermal analysis(DTA).
The thermal decomposition curve for of α-AIH_3 is an endothermal process, it yields sigmoidal fraction of decomposition(x)vs.time, the main part of which can be expressed by Avrami-Erofeev (A-E) equation[-In (1-x)]1/n=r_0e~(R/RT). The correlation formula between DTA curve and kinetic parameters in A-E equation was derived under conditions of linear temperature increase.
As sample quantfties a...
The thermal decomposition kinetics of α-AIH_3 in helium flow was investigated by differential thermal analysis(DTA).
The thermal decomposition curve for of α-AIH_3 is an endothermal process, it yields sigmoidal fraction of decomposition(x)vs.time, the main part of which can be expressed by Avrami-Erofeev (A-E) equation[-In (1-x)]1/n=r_0e~(R/RT). The correlation formula between DTA curve and kinetic parameters in A-E equation was derived under conditions of linear temperature increase.
As sample quantfties a...
1986, 2(05): 400-407
doi: 10.3866/PKU.WHXB19860503
Abstract:
In this reaserch, we have studied the effect of pH value of sodium fluorescein in ethanol solution on its characteristics of laser energy conversion efficiency, absorption spectra and fluorescence spectra. By studying the absorption spectra, we have verified the existence of various tautomers of sodium fluorescein in ethanol solution. Each tautomer with different concentration is in acid-base equilibria in the solution at various pH values. The absorption cross section, σ_p, for λ=337.1 nm and fluorescence quantum yield, φ, of each tautomer are quite different. When pH value increases, the concentration of dianion, which has the largest value of σ_p and φ in all tautomers, gradually increases in the solution. So that, the laser energy conversion efficiency of sodium fluorescein solution will enhance, as its pH value increases due to the dependence of the laser output energy of dye solution on the value of σ_p and φ.
In this reaserch, we have studied the effect of pH value of sodium fluorescein in ethanol solution on its characteristics of laser energy conversion efficiency, absorption spectra and fluorescence spectra. By studying the absorption spectra, we have verified the existence of various tautomers of sodium fluorescein in ethanol solution. Each tautomer with different concentration is in acid-base equilibria in the solution at various pH values. The absorption cross section, σ_p, for λ=337.1 nm and fluorescence quantum yield, φ, of each tautomer are quite different. When pH value increases, the concentration of dianion, which has the largest value of σ_p and φ in all tautomers, gradually increases in the solution. So that, the laser energy conversion efficiency of sodium fluorescein solution will enhance, as its pH value increases due to the dependence of the laser output energy of dye solution on the value of σ_p and φ.
1986, 2(05): 408-416
doi: 10.3866/PKU.WHXB19860504
Abstract:
In this paper we report various factors which affect the voltammetry of PVFc polymer film electrode, and discuss the charge transport process of the polymer film electrode. Size of hydrated anion (counter ion), concentration of the electrolyte, swelling property of the film in the solvent and thickness of the film have significant effects on the voltammetry of the PVFc film electrode. We studied electrocatalysis of Fe(CN)_6~(4-), L-dopa and catechol by PVFc film electrode. We also studied the kinetic processes of these reactants at rotating disk electrode (RDE). The current peaks of the mixture of ascorbic acid and catechol can not be seperated at bare glassy carbon electrode but can be seperated well at PVFc film electrode. This result is meaningful for biochemical analysis.
In this paper we report various factors which affect the voltammetry of PVFc polymer film electrode, and discuss the charge transport process of the polymer film electrode. Size of hydrated anion (counter ion), concentration of the electrolyte, swelling property of the film in the solvent and thickness of the film have significant effects on the voltammetry of the PVFc film electrode. We studied electrocatalysis of Fe(CN)_6~(4-), L-dopa and catechol by PVFc film electrode. We also studied the kinetic processes of these reactants at rotating disk electrode (RDE). The current peaks of the mixture of ascorbic acid and catechol can not be seperated at bare glassy carbon electrode but can be seperated well at PVFc film electrode. This result is meaningful for biochemical analysis.
1986, 2(05): 417-423
doi: 10.3866/PKU.WHXB19860505
Abstract:
The redox reaction of polythiophene displays electrochromic property, which was measured in situ by the electrochemically modulated reflectance spectroscopy. The electrochromic parameter of polythiophene are as follows, transformation time 10—20 ms
life time 10 circles
time of color maintenance several minutes
polythiophene can be used as an ideal eleetrochromic indicator.
The redox reaction of polythiophene displays electrochromic property, which was measured in situ by the electrochemically modulated reflectance spectroscopy. The electrochromic parameter of polythiophene are as follows, transformation time 10—20 ms
life time 10 circles
time of color maintenance several minutes
polythiophene can be used as an ideal eleetrochromic indicator.
1986, 2(05): 424-431
doi: 10.3866/PKU.WHXB19860506
Abstract:
The electronic effect of acidity of supports upon the surface properties and catalytic behaviors of various supported Pt catalysts have been studied by IR spectroscopy, competitive hydrogenation reaction, TPD method and hydrogenation of toluene as test reaction. The supports used are HY zeolite, Al_2O_3-SiO_2, γ-Al_2O_3 etc. Number of acid site and acid strength of supports determined by n-butylamine titration method follow the sequence: for number of acid site: HY>Al_2O_3-SiO_2>γ-Al_2O_3 for acid strength:
for number of acid site: HY>Al_2O_3-SiO_2>γ-Al_2O_3
for acid strength: HY>Al_2O_3-SiO_2>γ-Al_2O_3
...
1986, 2(05): 432-436
doi: 10.3866/PKU.WHXB19860507
Abstract:
Using tetramethyl silicane (TMS) as an external reference, solvent effect on chemical shifts of five extracting solvents, N-methyl-2-pyrrolidone (NMP), sulfolane, N,N-dimethylformamide (DMF), N,N-dimethyl-acetamide (DMA), and γ-butyrolactone (γ-BL), has been investigated in C_6—C_9 aromatics relative to carbon tetrachloride at 60.0 MHz and 36 ℃.
In the aromatic solvents, it has been observed that signals of the extracting molecules shifted significantly to high field and the resonance lines of NMP and γ-BL were splited or overlapped. The upfield shifts of the molecules decrease as the number of methyl group on aromatic ring increases. The extent of upfield shift in styrene is the largest among C_6—C_9 aromatics for NMP, DMF, DMA, and sulfolane. Considering the thermodynamic results obtained previously, it can be deduced that weak chemical interactions between molecules of the extracting solvents and the aromatic hydrocarbons may be existent.
Using tetramethyl silicane (TMS) as an external reference, solvent effect on chemical shifts of five extracting solvents, N-methyl-2-pyrrolidone (NMP), sulfolane, N,N-dimethylformamide (DMF), N,N-dimethyl-acetamide (DMA), and γ-butyrolactone (γ-BL), has been investigated in C_6—C_9 aromatics relative to carbon tetrachloride at 60.0 MHz and 36 ℃.
In the aromatic solvents, it has been observed that signals of the extracting molecules shifted significantly to high field and the resonance lines of NMP and γ-BL were splited or overlapped. The upfield shifts of the molecules decrease as the number of methyl group on aromatic ring increases. The extent of upfield shift in styrene is the largest among C_6—C_9 aromatics for NMP, DMF, DMA, and sulfolane. Considering the thermodynamic results obtained previously, it can be deduced that weak chemical interactions between molecules of the extracting solvents and the aromatic hydrocarbons may be existent.
1986, 2(05): 437-443
doi: 10.3866/PKU.WHXB19860508
Abstract:
Based on the thermodynamic and kinetic analyses of Schlogl model in nonideal condition, the dependent relation between chemical stability and diffusion stability is studied. It is found that, under the conditions that the system is far from chemical equilibrium and is strongly nonideal, both excess entropy δ~2S and its time-derivative for some space-uniform steady state may, independently to a certain extent, be positive or negative. Thus the chemical reactions and diffusion may show same or different stabilities in both cases that diffusion is stable and unstable. The linear stability analysis of kinetic equation for Schlögl model has confirmed this Clansdorff-Pri gine theory of nonequilibrium thermodynamic stability which concerns itself mainly about the chemical stability in diffusionstable systems.
When system is diffusion-unstable but chemically stable, their competition might give rise to the formation of some ordered structures (dissipative structures), as it does when system is diffusion-stable but chemically unstable. The numerical simulations have confirmed this prediction. Since the phenomena of diffusion instability are rather common in practical systems, such consideration of formation of ordered structures through the competition between chemical stability and diffusion instability may expand the applications of the theory of dissipative structures.
Based on the thermodynamic and kinetic analyses of Schlogl model in nonideal condition, the dependent relation between chemical stability and diffusion stability is studied. It is found that, under the conditions that the system is far from chemical equilibrium and is strongly nonideal, both excess entropy δ~2S and its time-derivative for some space-uniform steady state may, independently to a certain extent, be positive or negative. Thus the chemical reactions and diffusion may show same or different stabilities in both cases that diffusion is stable and unstable. The linear stability analysis of kinetic equation for Schlögl model has confirmed this Clansdorff-Pri gine theory of nonequilibrium thermodynamic stability which concerns itself mainly about the chemical stability in diffusionstable systems.
When system is diffusion-unstable but chemically stable, their competition might give rise to the formation of some ordered structures (dissipative structures), as it does when system is diffusion-stable but chemically unstable. The numerical simulations have confirmed this prediction. Since the phenomena of diffusion instability are rather common in practical systems, such consideration of formation of ordered structures through the competition between chemical stability and diffusion instability may expand the applications of the theory of dissipative structures.
1986, 2(05): 444-451
doi: 10.3866/PKU.WHXB19860509
Abstract:
In this the Paper effects of Ru~(3+) and other cations on the PEC properties of n-InP electrode are investigated.
The adsorption of Ru~(3+) doesn't influence the photoanodic polarization curves of n-InP in Fe~(2+)/Fe~(3+) and Fe(CN)_6~(4-)/Fe(CN)_6~(3-) solutions but effects it in S~(2-)/S_x~(2-) solution significantly. A current peak is observed at -0.9 V vs. SCE. and the peak current varies linearly with the square root of the potential sweep rate but the peak potential is unchanged.
The spectral response ...
In this the Paper effects of Ru~(3+) and other cations on the PEC properties of n-InP electrode are investigated.
The adsorption of Ru~(3+) doesn't influence the photoanodic polarization curves of n-InP in Fe~(2+)/Fe~(3+) and Fe(CN)_6~(4-)/Fe(CN)_6~(3-) solutions but effects it in S~(2-)/S_x~(2-) solution significantly. A current peak is observed at -0.9 V vs. SCE. and the peak current varies linearly with the square root of the potential sweep rate but the peak potential is unchanged.
The spectral response ...
1986, 2(05): 452-456
doi: 10.3866/PKU.WHXB19860510
Abstract:
The heats of formation of ternary complex compounds formed of copper(Ⅱ) with 2,2′-bipyridyl or 1,10-phenanthroline and N-(meta-substituted phenyl)glycines have been determinated by calorimatric method at 25 ℃ and Ⅰ=0.1 molL~(-1) (NaClO_4) in 30％(V/V) ethanol solution. By utilizing the data for the protonation of N-(meta-substituted phenyl) glycines determined previously and coupled with the heats of formation of ternary complex compounds, a linear enthalpy relationship: △H_M=Q-β△H_(L1) (r>0.99) with a nogative slope was obtained. In addition linear entropy relationships were also found to exist between the entropy changes on formation of ternary complex compounds and protonation of the second ligands.
The straight lines have approximately the same but negative slopes. The existence of negative slopes for linear enthalpy relationships would imply electrostatic interactions not important in the formation of thernary complex comounds, while back π bonding formation between metal ion and the first ligand and CFSE as well seem to play a significant role. Whereas negative linear entropy relationships might be accounted for by the change of entropy in configuration while the entropy of chelation and of solvation are almost parallel.
The heats of formation of ternary complex compounds formed of copper(Ⅱ) with 2,2′-bipyridyl or 1,10-phenanthroline and N-(meta-substituted phenyl)glycines have been determinated by calorimatric method at 25 ℃ and Ⅰ=0.1 molL~(-1) (NaClO_4) in 30％(V/V) ethanol solution. By utilizing the data for the protonation of N-(meta-substituted phenyl) glycines determined previously and coupled with the heats of formation of ternary complex compounds, a linear enthalpy relationship: △H_M=Q-β△H_(L1) (r>0.99) with a nogative slope was obtained. In addition linear entropy relationships were also found to exist between the entropy changes on formation of ternary complex compounds and protonation of the second ligands.
The straight lines have approximately the same but negative slopes. The existence of negative slopes for linear enthalpy relationships would imply electrostatic interactions not important in the formation of thernary complex comounds, while back π bonding formation between metal ion and the first ligand and CFSE as well seem to play a significant role. Whereas negative linear entropy relationships might be accounted for by the change of entropy in configuration while the entropy of chelation and of solvation are almost parallel.
1986, 2(05): 457-460
doi: 10.3866/PKU.WHXB19860511
Abstract:
Under ordinary conditions, azobenzene exists mainly as transisomer, and its photoisomerism is well known. In this work, We determined the quantum yield of this isomerization reaction by using simulative kinetic model on computer. We suggested a kinetic equation for azobenzene isomerization as
E=E_∞-Aexp(-Bt~σ)
In which, E and E_∞ are the absorbance of the azobenzene solution under radiation and photostatic state respectively, t is the radiation time A, B, C are emperical parameters. The kinetic equation can be solved by computer with a program written by ourselves, the values obtained were fitted to the practical data well.
...
Under ordinary conditions, azobenzene exists mainly as transisomer, and its photoisomerism is well known. In this work, We determined the quantum yield of this isomerization reaction by using simulative kinetic model on computer. We suggested a kinetic equation for azobenzene isomerization as
E=E_∞-Aexp(-Bt~σ)
In which, E and E_∞ are the absorbance of the azobenzene solution under radiation and photostatic state respectively, t is the radiation time A, B, C are emperical parameters. The kinetic equation can be solved by computer with a program written by ourselves, the values obtained were fitted to the practical data well.
...
1986, 2(05): 461-469
doi: 10.3866/PKU.WHXB19860512
Abstract:
In this paper we investigated the influences of a spherical catalyst with δ-function activity profiles on the maerokinetic behaviors of a first-order series reaction. First we solved the dimensionless mass transfer differential equations according to different activity profiles and their boundary conditions. Next we obtained analytical solutions which involve the concentration profiles of each component in the catalyst, the effectiveness factor of the first step reaction, and the selectivity of the intermediate product B. Finally we established some valuable results for analyzing deactivation kinetics and for designing optimum activity profiles of catalysts.
In this paper we investigated the influences of a spherical catalyst with δ-function activity profiles on the maerokinetic behaviors of a first-order series reaction. First we solved the dimensionless mass transfer differential equations according to different activity profiles and their boundary conditions. Next we obtained analytical solutions which involve the concentration profiles of each component in the catalyst, the effectiveness factor of the first step reaction, and the selectivity of the intermediate product B. Finally we established some valuable results for analyzing deactivation kinetics and for designing optimum activity profiles of catalysts.
1986, 2(05): 470-472
doi: 10.3866/PKU.WHXB19860513
Abstract:
The interaction between γ-Al_2O_3 and the oxides of Zinc, Cadium and Mercury have been studied by x-ray diffraetion(XRD). Samples of ZnO/γ-Al_2O_3, CdO/γ-Al_2O_3 and H /γ-Al_2O_3 were prepared by impregnating γ-Al_2O_3 with the corresponding nitrate solutions, then drying and ealeinating. It has been shown that CdO and H can be dispersed on γ-Al_2O_3 surface to form submonolayers. Their dispersion capaeieies derived from Fig.2 and Fig.3 are 0.48g CdO/g γ-Al_2O_3 and 0.16g H /g γ-Al_2O_3, or 0.20g CdO/100m~2 and 0.067g H /100m~2 surface of γ-Al_2O_3 (specific surface of γ-Al_2O_3 is 240m~2/g). On the other hand, ZnO/γ-Al_2O_3 system can not be in a monolayer dispersion state, because ZnO can react with γ-Al_2O_3 to form Zinc spinel at rather low temperature (200 ℃). The difference between these three systems may be attributed to their different ion radius.
The interaction between γ-Al_2O_3 and the oxides of Zinc, Cadium and Mercury have been studied by x-ray diffraetion(XRD). Samples of ZnO/γ-Al_2O_3, CdO/γ-Al_2O_3 and H /γ-Al_2O_3 were prepared by impregnating γ-Al_2O_3 with the corresponding nitrate solutions, then drying and ealeinating. It has been shown that CdO and H can be dispersed on γ-Al_2O_3 surface to form submonolayers. Their dispersion capaeieies derived from Fig.2 and Fig.3 are 0.48g CdO/g γ-Al_2O_3 and 0.16g H /g γ-Al_2O_3, or 0.20g CdO/100m~2 and 0.067g H /100m~2 surface of γ-Al_2O_3 (specific surface of γ-Al_2O_3 is 240m~2/g). On the other hand, ZnO/γ-Al_2O_3 system can not be in a monolayer dispersion state, because ZnO can react with γ-Al_2O_3 to form Zinc spinel at rather low temperature (200 ℃). The difference between these three systems may be attributed to their different ion radius.
1986, 2(05): 473-477
doi: 10.3866/PKU.WHXB19860514
Abstract:
E. L. Heric presented an improved method of compound synthesis that indicated the ternary aqua-sahs phase diagram can be constructed by determining only the aqueous content of the saturated solution in the equilibrium system. Based on Heric's principle an experimental study in constructing aqua-salts phase digrams for four basic types of NaNO_3-Pb(NO_3)_2-H_2O, NH_4Cl-BaCl_2-Ha_2WO_4-Na_2MoO_4-H_2O, Na_2SO_4-MgSO_4-H_2O system was completed, and the results showed fairly consistent with the data in literatures. It proves that Heric's method is feasible. In this paper, the experimental study is described in detail, and the reliability and applicability of Heric's method are discussed.
E. L. Heric presented an improved method of compound synthesis that indicated the ternary aqua-sahs phase diagram can be constructed by determining only the aqueous content of the saturated solution in the equilibrium system. Based on Heric's principle an experimental study in constructing aqua-salts phase digrams for four basic types of NaNO_3-Pb(NO_3)_2-H_2O, NH_4Cl-BaCl_2-Ha_2WO_4-Na_2MoO_4-H_2O, Na_2SO_4-MgSO_4-H_2O system was completed, and the results showed fairly consistent with the data in literatures. It proves that Heric's method is feasible. In this paper, the experimental study is described in detail, and the reliability and applicability of Heric's method are discussed.
1986, 2(05): 478-480
doi: 10.3866/PKU.WHXB19860515
Abstract:
The view point that electrochemical polarization has no effect on the position of Fermi-level within bulk of electrode had been stated in [1—3]. Apparently, there was some confusion between the concepts of kinetic Fermi energy and the position of Fermi-level relative to electron in the vaccum.
The view point that electrochemical polarization has no effect on the position of Fermi-level within bulk of electrode had been stated in [1—3]. Apparently, there was some confusion between the concepts of kinetic Fermi energy and the position of Fermi-level relative to electron in the vaccum.
