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1992 Volume 8 Issue 6
1992, 8(06): 721-723
doi: 10.3866/PKU.WHXB19920601
Abstract:
Both positive and negative aluminum cluster ions were generated by laser ablation of AIN sample. Their mass distributions were analyzed using a time-of-flight mass spectrometer. The magic numbers are 7, 14 and 23 for cluster cations, and 13, 23, 63 for anions. They all agree very well with spherical jellium model.
Both positive and negative aluminum cluster ions were generated by laser ablation of AIN sample. Their mass distributions were analyzed using a time-of-flight mass spectrometer. The magic numbers are 7, 14 and 23 for cluster cations, and 13, 23, 63 for anions. They all agree very well with spherical jellium model.
1992, 8(06): 724-727
doi: 10.3866/PKU.WHXB19920602
Abstract:
In this paper,thermal isomerization of HCN to isocyanide HNC has been studied. The topological properties of the structures of some points on IRC path in the vicinity of transition state have been analyzed. It is found that the transition state for HCN→HNC isomerization reaction is a bond switching point on IRC path in view of its topological properties. It is a point wherc the "old" chemical bond H—C begins to break and a "new" bond between H atom and the bond critical point of CN begins to form and this state lasts for a period about ΔS=0.3 (from S=0.00 to S=0.30) on the IRC path. The changes of other properties along the IRC reaction path has also been discussed.
Together with the reverse reaction, it is realized that the changing of topological properties of structures in the vicinity of transition state on IRC path is different for exothermal and endothermal reactions.
In this paper,thermal isomerization of HCN to isocyanide HNC has been studied. The topological properties of the structures of some points on IRC path in the vicinity of transition state have been analyzed. It is found that the transition state for HCN→HNC isomerization reaction is a bond switching point on IRC path in view of its topological properties. It is a point wherc the "old" chemical bond H—C begins to break and a "new" bond between H atom and the bond critical point of CN begins to form and this state lasts for a period about ΔS=0.3 (from S=0.00 to S=0.30) on the IRC path. The changes of other properties along the IRC reaction path has also been discussed.
Together with the reverse reaction, it is realized that the changing of topological properties of structures in the vicinity of transition state on IRC path is different for exothermal and endothermal reactions.
1992, 8(06): 728-731
doi: 10.3866/PKU.WHXB19920603
Abstract:
One class of conducting molecular crystals is consisted of the charge transfer molecules crystallizing in segregated stacks of donor and acceptor, such as TTF-TCNQ and its analogues. They behave as quasi-one dimensional conductors. The ex-perimental works gave an approximate law that σ~(-1) increases as T~2 at the temperature range T_p<T<250 K for TTF-TCNQ and TSeF-TCNQ where T_P is phase transition temperature. In this work, we investigated the influence of electron-phonon interaction on the behavior of charge carriers by deformation potential theory. By this theory, only the scattering of electrons by longitudinal acoustic wave is considered. And the interaction matrix element H_(k'k) has been derived to be
|H_(k'k)|~2=E_1~2/2LC ...
One class of conducting molecular crystals is consisted of the charge transfer molecules crystallizing in segregated stacks of donor and acceptor, such as TTF-TCNQ and its analogues. They behave as quasi-one dimensional conductors. The ex-perimental works gave an approximate law that σ~(-1) increases as T~2 at the temperature range T_p<T<250 K for TTF-TCNQ and TSeF-TCNQ where T_P is phase transition temperature. In this work, we investigated the influence of electron-phonon interaction on the behavior of charge carriers by deformation potential theory. By this theory, only the scattering of electrons by longitudinal acoustic wave is considered. And the interaction matrix element H_(k'k) has been derived to be
|H_(k'k)|~2=E_1~2/2LC ...
1992, 8(06): 732-735
doi: 10.3866/PKU.WHXB19920604
Abstract:
Dissociative adsorption of small organic molecules on electrocatalyst is an important molecular process of surface, which includes stages of adsorption, chemical bond broken and new adsorbate formation. The dynamic study on this reaction will contribute to reveal the origin of interaction between electrode surface and reactants, and to develop and enrich theories of electrocatalysis. In the present work, in situ FTIR studies demonstrated that the dissociative products of HCOOH on Pt electrode are CO_(ad) species. The oxidation of CO_(ad) formed from HCOOH dissociative adsorption on Pt(100) electrode was used as probe reactionm, and the dynamic properties of this dissociative adsorption were investigated by a computerized experimental set-up developed recently in our group. From the analysis of current transients the rate of dissociative adsorption of HCOOH on Pt(100) electrode has been evaluated under specified conditions.
Dissociative adsorption of small organic molecules on electrocatalyst is an important molecular process of surface, which includes stages of adsorption, chemical bond broken and new adsorbate formation. The dynamic study on this reaction will contribute to reveal the origin of interaction between electrode surface and reactants, and to develop and enrich theories of electrocatalysis. In the present work, in situ FTIR studies demonstrated that the dissociative products of HCOOH on Pt electrode are CO_(ad) species. The oxidation of CO_(ad) formed from HCOOH dissociative adsorption on Pt(100) electrode was used as probe reactionm, and the dynamic properties of this dissociative adsorption were investigated by a computerized experimental set-up developed recently in our group. From the analysis of current transients the rate of dissociative adsorption of HCOOH on Pt(100) electrode has been evaluated under specified conditions.
1992, 8(06): 736-741
doi: 10.3866/PKU.WHXB19920605
Abstract:
The cmc's of C_8H_(17) (OC_2H_4)_nSO_4Na (C_8E_nS; n=0, 1, 3) under varied conditions have been measured by the drop-volume method. The free energy (ΔG°) and entropy (ΔS°) of the micellization of surfactants, and the counter-ion binding constant (K) of micelle have been calculated. The results show that the cmc of C_8E_nS decreases with increasing n, but the rate of declination gradually slows down; K decreases as n increased; ΔS°increases with n, but the rate of increase slows down untill ΔS°being constant, which is the general trend (for ionic or nonionic surfactants, the conclusion is correct). This may be interpreted as that the oxyethylene group (EO) decrease with the increasing of EO number. The feature of the EO decides its special function in surfactant molecules.
The cmc's of C_8H_(17) (OC_2H_4)_nSO_4Na (C_8E_nS; n=0, 1, 3) under varied conditions have been measured by the drop-volume method. The free energy (ΔG°) and entropy (ΔS°) of the micellization of surfactants, and the counter-ion binding constant (K) of micelle have been calculated. The results show that the cmc of C_8E_nS decreases with increasing n, but the rate of declination gradually slows down; K decreases as n increased; ΔS°increases with n, but the rate of increase slows down untill ΔS°being constant, which is the general trend (for ionic or nonionic surfactants, the conclusion is correct). This may be interpreted as that the oxyethylene group (EO) decrease with the increasing of EO number. The feature of the EO decides its special function in surfactant molecules.
1992, 8(06): 742-748
doi: 10.3866/PKU.WHXB19920606
Abstract:
Viscosities and densities at 293.15 and 298.15 K are reported in this paper for glycine and DL-alanine in methanol-water mixed solvent. The viscosity B coefficients and partial molar volumes at infinite dilution have been calculated. The experimental results show that B coefficients reach a minimum at about 15% for glycine and 25% for DL-alanine respectively. The effect of amino acids on solvent structure has been discussed. Also, the activation parameters for viscous flow for amino acids in methanol-water mixtures have been calculated.
Viscosities and densities at 293.15 and 298.15 K are reported in this paper for glycine and DL-alanine in methanol-water mixed solvent. The viscosity B coefficients and partial molar volumes at infinite dilution have been calculated. The experimental results show that B coefficients reach a minimum at about 15% for glycine and 25% for DL-alanine respectively. The effect of amino acids on solvent structure has been discussed. Also, the activation parameters for viscous flow for amino acids in methanol-water mixtures have been calculated.
1992, 8(06): 749-752
doi: 10.3866/PKU.WHXB19920607
Abstract:
The title compound was obtained by the reaction of Fe_3(CO)_(12) with phosphorotri-thious acid triphenyl ester P(SC_6H_5)_3. Ligand precursor P(SC_6H_5)_3 coordinated to the cluster by its cleaved fragments SC_6H_5 and P(SC_6H_5)_2. The crystal structure of the compound has been determined by a single crystal X-ray diffraction method. The crystal is orthorhombic, space group belongs Pbca, a=1.7422(7), b=1.0634(6), c=2.8987(12) nm; V=5.370 nm, z=8, D_c=1. 579 g·cm~(-3). Coordinates of all nonhydrogen atoms were delermined by idrect method and difference Fourier synthesis, with 3531 observable reflections (I≥3σ(I_0)) refined by a full-matrix least-squares procedure so that the final R=0.054, R_W=0.058. The dihedral angle of the folded Fe_2SP ring along the S…P line or the Fe—Fe bond (76.1° or 82°, respectively) is much smaller than that for other similar compounds with the central Fe_2S_2 or Fe_2P_2 or Fe_2·SP folded rings. Fe—Fe=0.2572(2) nm, Fe—S(1)—Fe=68.6°(1), Fe—P—Fe=70.7°(1).
The title compound was obtained by the reaction of Fe_3(CO)_(12) with phosphorotri-thious acid triphenyl ester P(SC_6H_5)_3. Ligand precursor P(SC_6H_5)_3 coordinated to the cluster by its cleaved fragments SC_6H_5 and P(SC_6H_5)_2. The crystal structure of the compound has been determined by a single crystal X-ray diffraction method. The crystal is orthorhombic, space group belongs Pbca, a=1.7422(7), b=1.0634(6), c=2.8987(12) nm; V=5.370 nm, z=8, D_c=1. 579 g·cm~(-3). Coordinates of all nonhydrogen atoms were delermined by idrect method and difference Fourier synthesis, with 3531 observable reflections (I≥3σ(I_0)) refined by a full-matrix least-squares procedure so that the final R=0.054, R_W=0.058. The dihedral angle of the folded Fe_2SP ring along the S…P line or the Fe—Fe bond (76.1° or 82°, respectively) is much smaller than that for other similar compounds with the central Fe_2S_2 or Fe_2P_2 or Fe_2·SP folded rings. Fe—Fe=0.2572(2) nm, Fe—S(1)—Fe=68.6°(1), Fe—P—Fe=70.7°(1).
1992, 8(06): 753-759
doi: 10.3866/PKU.WHXB19920608
Abstract:
The chemical mechanism that vanadium pentoxide, as an additive, enhances the absorption rate of carbon dioxide in aqueous potassium carbonate solution has been suggested.
Experiments proved that V_2O_5 exists as V_2O_7~(4-) and V_4O_(12)~(4-) in the carbonate solution, as pH value is in the range of 9—12. The catalytic action of V_2O_5 is only related to the concentration of V_2O_7~(4-) and pH value of the solution, the optimum range of pH value is 10.6 to 10.8, and the quantity of V_2O_5 added has to be restricted in order to maintain the optimized pH range.
The chemical mechanism that vanadium pentoxide, as an additive, enhances the absorption rate of carbon dioxide in aqueous potassium carbonate solution has been suggested.
Experiments proved that V_2O_5 exists as V_2O_7~(4-) and V_4O_(12)~(4-) in the carbonate solution, as pH value is in the range of 9—12. The catalytic action of V_2O_5 is only related to the concentration of V_2O_7~(4-) and pH value of the solution, the optimum range of pH value is 10.6 to 10.8, and the quantity of V_2O_5 added has to be restricted in order to maintain the optimized pH range.
1992, 8(06): 760-766
doi: 10.3866/PKU.WHXB19920609
Abstract:
The LLE data of eight ternary systems (n-butanol-water and butanone-water with NaCl, KCl, KBr) were determined experimentally. A saturation-density method was proposed to determine the concentration of mixed solvents containing salt. The Chen model was used to correlate the LLE data satisfactorily.
The LLE data of eight ternary systems (n-butanol-water and butanone-water with NaCl, KCl, KBr) were determined experimentally. A saturation-density method was proposed to determine the concentration of mixed solvents containing salt. The Chen model was used to correlate the LLE data satisfactorily.
1992, 8(06): 767-771
doi: 10.3866/PKU.WHXB19920610
Abstract:
The effect of translational kinetic energy E_k on the activated chemisorption of CH_4 on Ni (polycrystal) surface and La film has been investigated using supersonic molecular beam technique. No dissociative adsorption was observed for CH_4/Ni system when E_k≤58.5 kJ·mol~(-1) and for CH_4/La system when E_k≤52.3 kJ·mol~(-1). Above these threshold values, the initial sticking probability s_0 increases linearly from 0 to 0.54 for CH_4/Ni system as E_k increases from 58.5 to 63.8 kJ·mol~(-1) and from 0 to 0.49 for CH_4/La system as E_k increases from 52.3 to 63.8 kJ·mol~(-1). These results indicate that a rather direct chemisorption process, rather than a classical precursor mechanism proceeds in these systems. Finally the apparent activation energies obtained are 46.8 kJ·mol~(-1) and 38.1 kJ·mol~(-1) for CH_4/Ni and CH_4/La systems respectively.
The effect of translational kinetic energy E_k on the activated chemisorption of CH_4 on Ni (polycrystal) surface and La film has been investigated using supersonic molecular beam technique. No dissociative adsorption was observed for CH_4/Ni system when E_k≤58.5 kJ·mol~(-1) and for CH_4/La system when E_k≤52.3 kJ·mol~(-1). Above these threshold values, the initial sticking probability s_0 increases linearly from 0 to 0.54 for CH_4/Ni system as E_k increases from 58.5 to 63.8 kJ·mol~(-1) and from 0 to 0.49 for CH_4/La system as E_k increases from 52.3 to 63.8 kJ·mol~(-1). These results indicate that a rather direct chemisorption process, rather than a classical precursor mechanism proceeds in these systems. Finally the apparent activation energies obtained are 46.8 kJ·mol~(-1) and 38.1 kJ·mol~(-1) for CH_4/Ni and CH_4/La systems respectively.
1992, 8(06): 772-777
doi: 10.3866/PKU.WHXB19920611
Abstract:
This research has recorded the linewidth of ~(35)Cl of Sr(ClO_4)_2 and Ba(ClO_4)_2 at 0.5 mol·L~(-1) in acetonitrile and ethanol. In terms of nuclear quadrupole moment relaxation mechanism and together with the results for Mg(ClO_4)_2 and Ca(ClO_4)_2 in literature contact type of ion pair for perchlorate salts of alkali earth metals was argued. The linewidth of ~(35)Cl at fixed concentration of Sr (ClO_4)_2 and Ba(ClO_4)_2 in acetonitrile or ethanol as bulk solvent was measured as a function of [B]/[M~(2+)]. where B represents H_2O or DMF. The trend of the plot and the reason for that were explained and the solvation number for Sr~(2+) were estimated. Mole conductivities of salts were also measured and explained for supporting of contact ion pair.
This research has recorded the linewidth of ~(35)Cl of Sr(ClO_4)_2 and Ba(ClO_4)_2 at 0.5 mol·L~(-1) in acetonitrile and ethanol. In terms of nuclear quadrupole moment relaxation mechanism and together with the results for Mg(ClO_4)_2 and Ca(ClO_4)_2 in literature contact type of ion pair for perchlorate salts of alkali earth metals was argued. The linewidth of ~(35)Cl at fixed concentration of Sr (ClO_4)_2 and Ba(ClO_4)_2 in acetonitrile or ethanol as bulk solvent was measured as a function of [B]/[M~(2+)]. where B represents H_2O or DMF. The trend of the plot and the reason for that were explained and the solvation number for Sr~(2+) were estimated. Mole conductivities of salts were also measured and explained for supporting of contact ion pair.
1992, 8(06): 778-782
doi: 10.3866/PKU.WHXB19920612
Abstract:
The title complex has been synthesized by the reaction of CuCl_2 with trimethyl phosphate. Its Infrared spectra from 4000 to 100 cm~(-1) were measured. The assignment of some absorption bands was discussed. It is found that the stretching vibrations of bridge groups O—P—O are divided into two groups according to tbeir bond length. The crystal structure of the complex has been determined from single crystal X-ray diffraction data. The crystals belong to monoclinic system, space group P2_1/c with cell parameters: a=1.0704(4), b=0.5093(2), c=1.9737(6) nm; β=96.23(3)°; V=1.0696(6) nm~3; Z=4, final R=0.044. Copper ion is coordinated to five nonester oxygen atoms to form a distorted square pyramid. The adjacent copper ions are connected by symmetric and non-symmetric bridge groups of O—P—O, forming an infinite one-dimensional chain coordination polymer.
The title complex has been synthesized by the reaction of CuCl_2 with trimethyl phosphate. Its Infrared spectra from 4000 to 100 cm~(-1) were measured. The assignment of some absorption bands was discussed. It is found that the stretching vibrations of bridge groups O—P—O are divided into two groups according to tbeir bond length. The crystal structure of the complex has been determined from single crystal X-ray diffraction data. The crystals belong to monoclinic system, space group P2_1/c with cell parameters: a=1.0704(4), b=0.5093(2), c=1.9737(6) nm; β=96.23(3)°; V=1.0696(6) nm~3; Z=4, final R=0.044. Copper ion is coordinated to five nonester oxygen atoms to form a distorted square pyramid. The adjacent copper ions are connected by symmetric and non-symmetric bridge groups of O—P—O, forming an infinite one-dimensional chain coordination polymer.
1992, 8(06): 783-788
doi: 10.3866/PKU.WHXB19920613
Abstract:
The thermal stability and the solid-solid phase transitions in the [n-C_nH_(2n+1)NH_3]_2CuCl_4 compounds with n=7-12 have been studied by DSC and TG methods. Comparision with C_nZn compounds was made. The nature of three phases of C_9Cu has been discussed in terms of infrared spectroscopy and the assignment of the phase transitions has been given. The thermal stability of C_nCu is lower than that of C_nZn and presents an obvious odd-even effect. All of these compounds exhibit two solid-solid phase transitions in the temperature range of 248-337 K. The peak temperature of phase transitions changes regularly. The peak temperature of the main phase transition increases with the chain length. The total transition enthalpies and entropies increase with increasing chain length. When n≤9, the high temperature phase exists in a partial disorder state. When n≥10, the high temperature phase exists in a conformational disorder state. The main phase transition and the phase transition at 307.7 K of C_9Cu may mainly arise from the change of the packing structure and the change of the partial conformational order-disorder of alkyl chain, respectively.
The thermal stability and the solid-solid phase transitions in the [n-C_nH_(2n+1)NH_3]_2CuCl_4 compounds with n=7-12 have been studied by DSC and TG methods. Comparision with C_nZn compounds was made. The nature of three phases of C_9Cu has been discussed in terms of infrared spectroscopy and the assignment of the phase transitions has been given. The thermal stability of C_nCu is lower than that of C_nZn and presents an obvious odd-even effect. All of these compounds exhibit two solid-solid phase transitions in the temperature range of 248-337 K. The peak temperature of phase transitions changes regularly. The peak temperature of the main phase transition increases with the chain length. The total transition enthalpies and entropies increase with increasing chain length. When n≤9, the high temperature phase exists in a partial disorder state. When n≥10, the high temperature phase exists in a conformational disorder state. The main phase transition and the phase transition at 307.7 K of C_9Cu may mainly arise from the change of the packing structure and the change of the partial conformational order-disorder of alkyl chain, respectively.
1992, 8(06): 789-794
doi: 10.3866/PKU.WHXB19920614
Abstract:
A kinetic model of fat and oil hydrogenation is given in this paper. Hydrogen is adsorbed at the surface of catalyst M forming activated H.It reacts with linolenate, Linoleate and oleat respectively. Adopting Ridel-Langmuir's method, we established the kinetic equation.(4)—(11)
Using refined soybean oil, pure hydrogen, self-made catalyst, we carried out a series of hydrogenation experiments in a high pressure reactor (FDW-01), the fatty acid chromatographer (GC-9A). From the results, straght lines were obtained thus the model has been proved. The pseudofirst order reaction rate constant (k_iN_H) and fatty acid composition of the original oil can be obtained from the figures. All calculated results are coincident with the experimental data.
The allen's empirical formula can be obtained from the present kinetic equations. if k_i was replaced by Arrhenius formula and N_H replaced by eqs.8. If linolenate=0, the present equation will change into the Moharir's formula. If N_H=1, Eqs.(9)—(11) will change into semiempirical formula of Albright.
A kinetic model of fat and oil hydrogenation is given in this paper. Hydrogen is adsorbed at the surface of catalyst M forming activated H.It reacts with linolenate, Linoleate and oleat respectively. Adopting Ridel-Langmuir's method, we established the kinetic equation.(4)—(11)
Using refined soybean oil, pure hydrogen, self-made catalyst, we carried out a series of hydrogenation experiments in a high pressure reactor (FDW-01), the fatty acid chromatographer (GC-9A). From the results, straght lines were obtained thus the model has been proved. The pseudofirst order reaction rate constant (k_iN_H) and fatty acid composition of the original oil can be obtained from the figures. All calculated results are coincident with the experimental data.
The allen's empirical formula can be obtained from the present kinetic equations. if k_i was replaced by Arrhenius formula and N_H replaced by eqs.8. If linolenate=0, the present equation will change into the Moharir's formula. If N_H=1, Eqs.(9)—(11) will change into semiempirical formula of Albright.
1992, 8(06): 795-798
doi: 10.3866/PKU.WHXB19920615
Abstract:
This paper presents the study on thermodynamic characteristics of phase transitions for tanshinone Ⅱ-A, tanshinone Ⅱ-B and saprorthoquinone (hereafter abbreviated to 1,2 and 3 respectively) by Differential Scanning Calorimetry (DSC). The relationships of their molecular structures with thermodynamic parameters were discussed. The experimental results obtained are listed in Table 2.
The differences of nominated compounds for their melting points, melting enthalpies and melting entropies are as follows:
T_m~1>T_m~3, ΔH_m~1>ΔH_m~3, ΔS_m~1=ΔS_m~3;
T_m~1>T_m~2, ΔH_m~1>ΔH_m~2, ΔS_m~1=ΔS_m~2.
This paper presents the study on thermodynamic characteristics of phase transitions for tanshinone Ⅱ-A, tanshinone Ⅱ-B and saprorthoquinone (hereafter abbreviated to 1,2 and 3 respectively) by Differential Scanning Calorimetry (DSC). The relationships of their molecular structures with thermodynamic parameters were discussed. The experimental results obtained are listed in Table 2.
The differences of nominated compounds for their melting points, melting enthalpies and melting entropies are as follows:
T_m~1>T_m~3, ΔH_m~1>ΔH_m~3, ΔS_m~1=ΔS_m~3;
T_m~1>T_m~2, ΔH_m~1>ΔH_m~2, ΔS_m~1=ΔS_m~2.
1992, 8(06): 799-803
doi: 10.3866/PKU.WHXB19920616
Abstract:
Molecular interaction model of olfaction for musk odorants are proposed on the basis of grometric optimization by molecular mechanics. We supose the molecules of musk odorants are composed by three parts: fixing groups (polar groups, oxygen for example, make fixation of odorant molecule); reacting groups (react with the surface of lipid bilayer, give the signal of odor); supporting groups (noble to olfaction, their contribution is putting the reacting groups on the suitable positions). The area of poly n formed by the reacting and fixing groups (accounted with C and O atoms) is about 0.05 nm. Because supporting groups are noble to olfaction, so that it is reasonable, molecules belong to different classes (aliphatic cycles, aromatic cycles, single cycles, poly-cycles) can have the same musk odor.
Molecular interaction model of olfaction for musk odorants are proposed on the basis of grometric optimization by molecular mechanics. We supose the molecules of musk odorants are composed by three parts: fixing groups (polar groups, oxygen for example, make fixation of odorant molecule); reacting groups (react with the surface of lipid bilayer, give the signal of odor); supporting groups (noble to olfaction, their contribution is putting the reacting groups on the suitable positions). The area of poly n formed by the reacting and fixing groups (accounted with C and O atoms) is about 0.05 nm. Because supporting groups are noble to olfaction, so that it is reasonable, molecules belong to different classes (aliphatic cycles, aromatic cycles, single cycles, poly-cycles) can have the same musk odor.
1992, 8(06): 804-808
doi: 10.3866/PKU.WHXB19920617
Abstract:
The molar volumes were determined for the binary mixtures such as benzene-cy-clohexane and benzene-n-hexane at 288.15, 293.15, 298.15, 303.15 and 308.15 K and 250 kPa. For these binary systems, their pressure coefficients have been calcu-lated. The isothermal compressibility of pure liquid coincided well with those from previous measurements.
The molar volumes were determined for the binary mixtures such as benzene-cy-clohexane and benzene-n-hexane at 288.15, 293.15, 298.15, 303.15 and 308.15 K and 250 kPa. For these binary systems, their pressure coefficients have been calcu-lated. The isothermal compressibility of pure liquid coincided well with those from previous measurements.
1992, 8(06): 809-813
doi: 10.3866/PKU.WHXB19920618
Abstract:
Ione pair orbital and their interaction in some nitrogen heterocyclic compound series have been interpreted in terms of through-space and through-bond mechanisms through the study of their gas phase ultraviolet photoelectron spectrocopy. The HAM/3 molecular orbital calculations on each molecule of the studied series were also carried out. The order of experimental vertical ionization potentials of the molecules can be not only predicated, but the spacing of through-space and through-bond interactions splitting of the studied compounds are consistent with the results of HAM/3 calculations.
Ione pair orbital and their interaction in some nitrogen heterocyclic compound series have been interpreted in terms of through-space and through-bond mechanisms through the study of their gas phase ultraviolet photoelectron spectrocopy. The HAM/3 molecular orbital calculations on each molecule of the studied series were also carried out. The order of experimental vertical ionization potentials of the molecules can be not only predicated, but the spacing of through-space and through-bond interactions splitting of the studied compounds are consistent with the results of HAM/3 calculations.
1992, 8(06): 814-818
doi: 10.3866/PKU.WHXB19920619
Abstract:
The formation of uniform spherical hematite particles, obtained by hydrolysis of ferric chloride at elevated temperatures, follows the mechanism of phase transformation from β-FeOOH to α-Fe_2O_3 and recrystallization from tiny α-Fe_2O_3 particles to spherical colliodal α-Fe_2O_3 uniform particles. A new viewpoint on the formation of uniform colloidal particles is suggested, that is, if uniform particles are to be formed by the mechanism of phase transformation-aggregation recrystallizationt, the secondary aggregations of tiny particles must be avoided after the first burst of aggregates. The relationship between initial time of reaching critical supersaturation with the aging temperature, pH and concentration of ferric chloride can be described by a three-parameter logarithmic linear equation.
The formation of uniform spherical hematite particles, obtained by hydrolysis of ferric chloride at elevated temperatures, follows the mechanism of phase transformation from β-FeOOH to α-Fe_2O_3 and recrystallization from tiny α-Fe_2O_3 particles to spherical colliodal α-Fe_2O_3 uniform particles. A new viewpoint on the formation of uniform colloidal particles is suggested, that is, if uniform particles are to be formed by the mechanism of phase transformation-aggregation recrystallizationt, the secondary aggregations of tiny particles must be avoided after the first burst of aggregates. The relationship between initial time of reaching critical supersaturation with the aging temperature, pH and concentration of ferric chloride can be described by a three-parameter logarithmic linear equation.
1992, 8(06): 819-823
doi: 10.3866/PKU.WHXB19920620
Abstract:
The osmotic coefficients and activity coefficients for aqueous solution of naphtha-lene-1,5-disulfonic acid disodium and 2-naphthol-3,6-disulfonic acid sodium salt at 298.15 K have been determined by the isopiestic method. The excess Gibbs free energies were evaluated with the corresponding osmotic coefficients and activity coefficients.
The osmotic coefficients and activity coefficients for aqueous solution of naphtha-lene-1,5-disulfonic acid disodium and 2-naphthol-3,6-disulfonic acid sodium salt at 298.15 K have been determined by the isopiestic method. The excess Gibbs free energies were evaluated with the corresponding osmotic coefficients and activity coefficients.
1992, 8(06): 824-828
doi: 10.3866/PKU.WHXB19920621
Abstract:
The time variation of chemical affinities A_p and entropy production ? of an open Brusselator system has been studied. It was found that the oscillating characteristics of A_p and ? are quite different. While A_p oscillations with a single peak in every period, ? has either a single peak or two-peak oscillations which depend on the kinetic mechanism of oscillation or values of A_p~?. The meaning to study oscillation of thermodynamic quantities was also discussed.
The time variation of chemical affinities A_p and entropy production ? of an open Brusselator system has been studied. It was found that the oscillating characteristics of A_p and ? are quite different. While A_p oscillations with a single peak in every period, ? has either a single peak or two-peak oscillations which depend on the kinetic mechanism of oscillation or values of A_p~?. The meaning to study oscillation of thermodynamic quantities was also discussed.
1992, 8(06): 829-833
doi: 10.3866/PKU.WHXB19920622
Abstract:
The phase equilibrium data of CO(NH_2)_2-H_3BO_3-H_2O system at 25 ℃ and 35 ℃ have been presented and the phase diagrams have been drawn too. According to the diagrams, no complex salts of CO(NH_2)_2 and H_3BO_3 have formed in CO(NH_2)_2-H_3BO_3-H_2O system at 25 ℃ and 35 ℃.
By using the equation of Margules, the phase equilibrium data of CO(NH_2)_2-H_3BO_3-H_2O system at 25 ℃ and 35 ℃ have been calculated. The calculations coincide well with the experimental data.
The phase equilibrium data of CO(NH_2)_2-H_3BO_3-H_2O system at 25 ℃ and 35 ℃ have been presented and the phase diagrams have been drawn too. According to the diagrams, no complex salts of CO(NH_2)_2 and H_3BO_3 have formed in CO(NH_2)_2-H_3BO_3-H_2O system at 25 ℃ and 35 ℃.
By using the equation of Margules, the phase equilibrium data of CO(NH_2)_2-H_3BO_3-H_2O system at 25 ℃ and 35 ℃ have been calculated. The calculations coincide well with the experimental data.
1992, 8(06): 834-841
doi: 10.3866/PKU.WHXB19920623
Abstract:
