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1991 Volume 7 Issue 1
1991, 7(01): 1-9
doi: 10.3866/PKU.WHXB19910101
Abstract:
High silica mordenites with Si/Al ratios in the range of 6-15 were prepared by acid leaching, steaming plus acid leaching and isomorphous substitution with (NH_4)_2SiF_6 methods. The relative crystallinity, hydroxyl nest mole fraction, unit cell parameters, infrared asymmetric stretch frequency, thermal and hydrothermal stability, surface acidity and catalytic activities of the mordenites were investigated with various techniques. It has been found that the properties of the mordenites depend strongly on the preparation methods. Samples prepared with various dealumination procedures show significant difference in many aspects. These differences were described in detail and explained in relation to structural changes of the zeolites.
High silica mordenites with Si/Al ratios in the range of 6-15 were prepared by acid leaching, steaming plus acid leaching and isomorphous substitution with (NH_4)_2SiF_6 methods. The relative crystallinity, hydroxyl nest mole fraction, unit cell parameters, infrared asymmetric stretch frequency, thermal and hydrothermal stability, surface acidity and catalytic activities of the mordenites were investigated with various techniques. It has been found that the properties of the mordenites depend strongly on the preparation methods. Samples prepared with various dealumination procedures show significant difference in many aspects. These differences were described in detail and explained in relation to structural changes of the zeolites.
1991, 7(01): 10-15
doi: 10.3866/PKU.WHXB19910102
Abstract:
A series of La_(2-x)Sr_xNiO_4(0.0≤x≤1.0) oxides with the tetra nal K_2NiF_4 structure were prepared. The cell parameters were measured by powder X-ray diffraction (XRD) technique; the reducibility was determined by temperature programmed reduction(TPR). Results show that the changing orders of the highest reducing peak temperature with composition(x) contrast to that of cell parameter a, but agree with that of c. The reducing mechanism for La_(1.7)Sr_(0.3)NiO_4 was investigated by TPR and XRD technique. We found that the first two reducing peaks in TPR profile correspond mainly to the reducing process from Ni~(3+) ion to Ni~(2+). This point was also identified by the calculation of axial ratio indirectly; therefore the highest reducing peak is the structural destroying peak.
A series of La_(2-x)Sr_xNiO_4(0.0≤x≤1.0) oxides with the tetra nal K_2NiF_4 structure were prepared. The cell parameters were measured by powder X-ray diffraction (XRD) technique; the reducibility was determined by temperature programmed reduction(TPR). Results show that the changing orders of the highest reducing peak temperature with composition(x) contrast to that of cell parameter a, but agree with that of c. The reducing mechanism for La_(1.7)Sr_(0.3)NiO_4 was investigated by TPR and XRD technique. We found that the first two reducing peaks in TPR profile correspond mainly to the reducing process from Ni~(3+) ion to Ni~(2+). This point was also identified by the calculation of axial ratio indirectly; therefore the highest reducing peak is the structural destroying peak.
1991, 7(01): 16-21
doi: 10.3866/PKU.WHXB19910103
Abstract:
The α-Fe_2O_3/NaY zeolite samples were prepared by impregnating NaY zeolite with ammonium ferrioxalate solution and calcining at high temperature. The maximum dispersion amount of α-Fe_2O_3 on NaY zeolite measured with XRD quantitative phase analysis is 0.060 gα-Fe_2O_3/gNaY, which is only 5.5% of the monolayer capacity of α-Fe_2O_3 on NaY according to a close-packed monolayer model. For the first time positron lifetime spectroscopy has been used to detect the dispersion amount of oxide on zeolite. The maximum dispersion amount of α-Fe_2O_3 obtained is fully consistent with that obtained from XRD phase analysis. TPR spectra of the samples show that the reduction of α-Fe_2O_3 on the zeolite consists of two steps, α-Fe_2O_3 is first reduced to Fe_2O_3 at low temperature and then to the metal at higher temperature. Both reduction reactions are ingibited by the strong interaction of the dispersed α-Fe_2O_3 phase with the zeolite.
The α-Fe_2O_3/NaY zeolite samples were prepared by impregnating NaY zeolite with ammonium ferrioxalate solution and calcining at high temperature. The maximum dispersion amount of α-Fe_2O_3 on NaY zeolite measured with XRD quantitative phase analysis is 0.060 gα-Fe_2O_3/gNaY, which is only 5.5% of the monolayer capacity of α-Fe_2O_3 on NaY according to a close-packed monolayer model. For the first time positron lifetime spectroscopy has been used to detect the dispersion amount of oxide on zeolite. The maximum dispersion amount of α-Fe_2O_3 obtained is fully consistent with that obtained from XRD phase analysis. TPR spectra of the samples show that the reduction of α-Fe_2O_3 on the zeolite consists of two steps, α-Fe_2O_3 is first reduced to Fe_2O_3 at low temperature and then to the metal at higher temperature. Both reduction reactions are ingibited by the strong interaction of the dispersed α-Fe_2O_3 phase with the zeolite.
1991, 7(01): 22-29
doi: 10.3866/PKU.WHXB19910104
Abstract:
本文研究了氧、温度和4-甲基-4-苯基-2-戊酮(Mpp)对乙醇辐解的影响。Mpp在实验使用的浓度范围内对乙醛的G值没有影响, G(2,3-丁二醇)值随Mpp浓度增加而下降, 最后达0.9恒值。使用Mpp求得原初过程形成的G_(H_2)=1.9, 动力学处理求得G_H=2.4, k_(12)/k_(11)=(11.9±1.8)×10~3。
实验证明Mpp清除了体系中的H原子, 抑制了CH_3CHOH自由基的形成, 从而抑制了2,3-丁二醇的生成, 但不影响乙醛的产额。这一研究否定了传统文献所述的在γ辐解乙醇时相当量的羟乙基自由基歧化反应生成乙醛。
本文还对乙醇γ辐解机理进行了讨论, 并求得了乙醇辐解的物料平衡。
本文研究了氧、温度和4-甲基-4-苯基-2-戊酮(Mpp)对乙醇辐解的影响。Mpp在实验使用的浓度范围内对乙醛的G值没有影响, G(2,3-丁二醇)值随Mpp浓度增加而下降, 最后达0.9恒值。使用Mpp求得原初过程形成的G_(H_2)=1.9, 动力学处理求得G_H=2.4, k_(12)/k_(11)=(11.9±1.8)×10~3。
实验证明Mpp清除了体系中的H原子, 抑制了CH_3CHOH自由基的形成, 从而抑制了2,3-丁二醇的生成, 但不影响乙醛的产额。这一研究否定了传统文献所述的在γ辐解乙醇时相当量的羟乙基自由基歧化反应生成乙醛。
本文还对乙醇γ辐解机理进行了讨论, 并求得了乙醇辐解的物料平衡。
1991, 7(01): 30-35
doi: 10.3866/PKU.WHXB19910105
Abstract:
MINDO/3 MO method has been used to study the mechanism of thermolysis of nitroguanidine. The geometric structures of the transition states are optimized by Powell's method, and confirmed by vibrational frequency analysis. The reaction pathways of the thermolysis have been traced by intrinsic reaction coordinate (IRC) proposed by Fukui. Our results show that there are two pathways for this thermal decomposition reaction (pathway Ⅰ giving rise to products. N_2O, H_2O and H_2NCN; pathway Ⅱ giving rise to products: N_2O, NH_3 and HNCO). They coexist and compete each other.
MINDO/3 MO method has been used to study the mechanism of thermolysis of nitroguanidine. The geometric structures of the transition states are optimized by Powell's method, and confirmed by vibrational frequency analysis. The reaction pathways of the thermolysis have been traced by intrinsic reaction coordinate (IRC) proposed by Fukui. Our results show that there are two pathways for this thermal decomposition reaction (pathway Ⅰ giving rise to products. N_2O, H_2O and H_2NCN; pathway Ⅱ giving rise to products: N_2O, NH_3 and HNCO). They coexist and compete each other.
1991, 7(01): 36-42
doi: 10.3866/PKU.WHXB19910106
Abstract:
The self-association of isomeric butanols in carbon tetrachloride, n-heptane, benzene and 1,2-dichloroethane has been studied by infrared sprectrometry in the range of 3800-3000 cm~(-1). It has been found that the area ratios of polymer band to monomer band are related to the characteristics of the solutes and solvents, and the plots of the ratios against mass percent of the alcohol show od linear relation in the measured concentration range. The IR data have also been treated by use of 1-n (cyclic) association models. According to the results obtained, branched chain causes a decrease in some extent of the self-association. In addition, the specific interaction between isomeric butanols and benzene or 1,2-dichloroethane leads to much less self-association of butanols. In diluted solutions, butanol molecules mainly exist in the form of monomer-dimer in benzene and 1,2-dichloroethane, and of monomer-trimer in carbon tetrachloride. In heptane, however, the monomer-tetramer for n-butanol and the monomer-trimer for the other butanols may be the best models accounting for the IR data.
The self-association of isomeric butanols in carbon tetrachloride, n-heptane, benzene and 1,2-dichloroethane has been studied by infrared sprectrometry in the range of 3800-3000 cm~(-1). It has been found that the area ratios of polymer band to monomer band are related to the characteristics of the solutes and solvents, and the plots of the ratios against mass percent of the alcohol show od linear relation in the measured concentration range. The IR data have also been treated by use of 1-n (cyclic) association models. According to the results obtained, branched chain causes a decrease in some extent of the self-association. In addition, the specific interaction between isomeric butanols and benzene or 1,2-dichloroethane leads to much less self-association of butanols. In diluted solutions, butanol molecules mainly exist in the form of monomer-dimer in benzene and 1,2-dichloroethane, and of monomer-trimer in carbon tetrachloride. In heptane, however, the monomer-tetramer for n-butanol and the monomer-trimer for the other butanols may be the best models accounting for the IR data.
1991, 7(01): 43-48
doi: 10.3866/PKU.WHXB19910107
Abstract:
Differential scanning calorimetry was used to investigate the thermal denaturation of the proteinase K (EC 3.4.21.14) in the temperature range from 310 to 450 K. The influence of hydration and pH upon the thermal denaturation was studied in the range of total water content from 0.048 to 4.39 g H_2O/g dry enzyme and in the pH range from 3.29 to 8.49, respectively. The dependence of the denaturational temperature T_d, the specific enthalpy of denaturation ΔH_d and the maximum of excess apparent specific heat C_ex~(max) upon the degree of hydration h and the pH of the buffer is presented respectively. The relationship between the denaturational temperature T_d and the water content is of the Flory-Garrett's type. Besides this, the thermodynamic characteristics of the thermal denaturation of proteinase K are different from those reported of globular proteins, double-stranded coiled-coils and triple-stranded coiled-coils. The influence of primary hydration water upon the thermodynamic parameters of the thermal denaturation is the greatest. The external variable, the pH of the buffer used to dissolve the enzyme influences its thermostability to some extent.
Differential scanning calorimetry was used to investigate the thermal denaturation of the proteinase K (EC 3.4.21.14) in the temperature range from 310 to 450 K. The influence of hydration and pH upon the thermal denaturation was studied in the range of total water content from 0.048 to 4.39 g H_2O/g dry enzyme and in the pH range from 3.29 to 8.49, respectively. The dependence of the denaturational temperature T_d, the specific enthalpy of denaturation ΔH_d and the maximum of excess apparent specific heat C_ex~(max) upon the degree of hydration h and the pH of the buffer is presented respectively. The relationship between the denaturational temperature T_d and the water content is of the Flory-Garrett's type. Besides this, the thermodynamic characteristics of the thermal denaturation of proteinase K are different from those reported of globular proteins, double-stranded coiled-coils and triple-stranded coiled-coils. The influence of primary hydration water upon the thermodynamic parameters of the thermal denaturation is the greatest. The external variable, the pH of the buffer used to dissolve the enzyme influences its thermostability to some extent.
1991, 7(01): 49-56
doi: 10.3866/PKU.WHXB19910108
Abstract:
Excess volumes have been measured by means of a continuous dilution dilatometer or a vibrational tube densimeter for both tetrachloromethane and trichloromethane+N,N-dimethylformamide (DMF), +N,N-dimethylacetamide (DMA), +N-methylpyrrolidone(NMP), +γ-butyroIactone(γ-BL) , +dimethysulfoxide(DMSO), at 298.15 K V~E values are negative over the entire range of composition for all systems except (trichloromethane + dimethylsulfoxide) which exhibits a sigmoid curve with negative values in the trichloromethane rich region. |V_(min)~E| values of the two series decrease in the order NMP>γ-BL>DMF≈DMA?DMSO. The results are interpreted in terms of forming charge-transfer complexes between tetrachloromethane and Lewis bases, and forming hydrogen-bonding associations between trichloromethane and Lewis bases respectively.
Excess volumes have been measured by means of a continuous dilution dilatometer or a vibrational tube densimeter for both tetrachloromethane and trichloromethane+N,N-dimethylformamide (DMF), +N,N-dimethylacetamide (DMA), +N-methylpyrrolidone(NMP), +γ-butyroIactone(γ-BL) , +dimethysulfoxide(DMSO), at 298.15 K V~E values are negative over the entire range of composition for all systems except (trichloromethane + dimethylsulfoxide) which exhibits a sigmoid curve with negative values in the trichloromethane rich region. |V_(min)~E| values of the two series decrease in the order NMP>γ-BL>DMF≈DMA?DMSO. The results are interpreted in terms of forming charge-transfer complexes between tetrachloromethane and Lewis bases, and forming hydrogen-bonding associations between trichloromethane and Lewis bases respectively.
1991, 7(01): 57-63
doi: 10.3866/PKU.WHXB19910109
Abstract:
In previous reports the ternary system Na_2SO_4-CuSO_4-H_2O was investigated by osmotic coefficient and solubility work. This paper reports the determenations of the mean activity coefficients of Na_2SO_4 in the ternary system at 25 ℃ and ionic strength 1.0 and 2.0 by emf method using a Na sensitive glass electrode vs. Hg-Hg_2SO_4 electrodes.
The Hg-Hg_2SO_4 electrodes were prepared in our laboratory and performance tests for the electrode pair were carried out. Linear near-Nernst response and od reproducibility and stability were observed.
Pitzer's recent equations were used to derived...
In previous reports the ternary system Na_2SO_4-CuSO_4-H_2O was investigated by osmotic coefficient and solubility work. This paper reports the determenations of the mean activity coefficients of Na_2SO_4 in the ternary system at 25 ℃ and ionic strength 1.0 and 2.0 by emf method using a Na sensitive glass electrode vs. Hg-Hg_2SO_4 electrodes.
The Hg-Hg_2SO_4 electrodes were prepared in our laboratory and performance tests for the electrode pair were carried out. Linear near-Nernst response and od reproducibility and stability were observed.
Pitzer's recent equations were used to derived...
1991, 7(01): 64-71
doi: 10.3866/PKU.WHXB19910110
Abstract:
The electronic structure and chemical bonding of the five coordinate iron clusters [Fe(XCHCHS)_2]_2~n-[X=O, (Ⅰ); X=S, (Ⅱ); n=2, 3, 4] and their monomers have been studied. The calculated data of the quadrupole splitting and chemical isomer shift are in od agreement with those of experiments.The multiplet of the iron in the oxidized ground state of cluster(Ⅰ) is 6, while that of (Ⅱ) is 4, in accordance with the experimental results. The calculation result shows that the oxidation-reduction process in fact takes place on iron, but the electrons gained or lost transfer to the ligand atoms through charge relaxation. The formation of these clusters can be considered as dimerization of two fragments through interaction of their orbitals in the frontier region. An explanation about the configuration difference between (I) and (II) is proposed.
The electronic structure and chemical bonding of the five coordinate iron clusters [Fe(XCHCHS)_2]_2~n-[X=O, (Ⅰ); X=S, (Ⅱ); n=2, 3, 4] and their monomers have been studied. The calculated data of the quadrupole splitting and chemical isomer shift are in od agreement with those of experiments.The multiplet of the iron in the oxidized ground state of cluster(Ⅰ) is 6, while that of (Ⅱ) is 4, in accordance with the experimental results. The calculation result shows that the oxidation-reduction process in fact takes place on iron, but the electrons gained or lost transfer to the ligand atoms through charge relaxation. The formation of these clusters can be considered as dimerization of two fragments through interaction of their orbitals in the frontier region. An explanation about the configuration difference between (I) and (II) is proposed.
1991, 7(01): 72-76
doi: 10.3866/PKU.WHXB19910111
Abstract:
FT-IR transmission spectra of the 3—11 monolayer Langmu ir-Blodgett(LB) films of stearic acid, have been observed compared with FT-IR ATR spectra. As an easily feasible technique, transmission method can offer supplementery information to the ATR one. The intensity ratios between the vibrational bands obtained by the two methods give the orientation aspect of molecular fregments of complecated LB films.
FT-IR transmission spectra of the 3—11 monolayer Langmu ir-Blodgett(LB) films of stearic acid, have been observed compared with FT-IR ATR spectra. As an easily feasible technique, transmission method can offer supplementery information to the ATR one. The intensity ratios between the vibrational bands obtained by the two methods give the orientation aspect of molecular fregments of complecated LB films.
1991, 7(01): 77-81
doi: 10.3866/PKU.WHXB19910112
Abstract:
On the basis of the data of single crystal structure analysis, the thermal motion analysis for the crystal molecules of N-phenylphthalimide (Ⅰ) and 2-phenylquinoxaline (Ⅱ) was carried out. It is shown that in solid state the molecule of compound I behaves dynamicaly as a rigid molecule and an intramolecular vibration of the substitued pheny group with <ω~2>=53(25) deg·~2 around C(8)—C(9) should be included in the molecular thermal motion of compound Ⅱ .
On the basis of the data of single crystal structure analysis, the thermal motion analysis for the crystal molecules of N-phenylphthalimide (Ⅰ) and 2-phenylquinoxaline (Ⅱ) was carried out. It is shown that in solid state the molecule of compound I behaves dynamicaly as a rigid molecule and an intramolecular vibration of the substitued pheny group with <ω~2>=53(25) deg·~2 around C(8)—C(9) should be included in the molecular thermal motion of compound Ⅱ .
1991, 7(01): 82-86
doi: 10.3866/PKU.WHXB19910113
Abstract:
The stability constants of binary complex compounds of nickel (Ⅱ) with Lproline, L-valine, α-aminoisobutyric acid and oxalate were determined at 25.0±0.1 ℃, Ⅰ=0.1 mol·dm~(-3) (KNO_3) by pH method. The heats of formation of these binary systems and the heat of protonation of oxalate were determined by calorimetry under the same conditions. The fact that the heat effect of protonation of oxalate was found to be endothermic can be interpreted on account of the existence of seven membered ring of oxalate formed in aqueous solution through hydrogen bonds with water molecule.
The stability constants of binary complex compounds of nickel (Ⅱ) with Lproline, L-valine, α-aminoisobutyric acid and oxalate were determined at 25.0±0.1 ℃, Ⅰ=0.1 mol·dm~(-3) (KNO_3) by pH method. The heats of formation of these binary systems and the heat of protonation of oxalate were determined by calorimetry under the same conditions. The fact that the heat effect of protonation of oxalate was found to be endothermic can be interpreted on account of the existence of seven membered ring of oxalate formed in aqueous solution through hydrogen bonds with water molecule.
1991, 7(01): 87-91
doi: 10.3866/PKU.WHXB19910114
Abstract:
The resonance Raman spectra of phenothiazine radical cation, phenothiazine dication and phenoxazine dication have been recorded, which have been formed by chemical oxidation of their parent compounds with Br_2 or Pb(Ac)_4. The bands of CNC and CSC skeletal deformations show the most enhancement and large positive shifts from the corresponding parent after one or two electrons are subtracted from phenothiazine. The number of bands in ring C=C stretching frequency range are increased obviously in the spectrum of phenothiazine dication. The spectral data reveal that the degree of fold along the S—N axis vanishes and a greater aromatic resonance structure comes into being with the loss of two electrons in phenothiazine. The spectrum of phenoxazine dication is more similar to that of its parent, which shows that the loss of electrons in phenoxazine leads to less structureal change compared with phenothiazine.
The resonance Raman spectra of phenothiazine radical cation, phenothiazine dication and phenoxazine dication have been recorded, which have been formed by chemical oxidation of their parent compounds with Br_2 or Pb(Ac)_4. The bands of CNC and CSC skeletal deformations show the most enhancement and large positive shifts from the corresponding parent after one or two electrons are subtracted from phenothiazine. The number of bands in ring C=C stretching frequency range are increased obviously in the spectrum of phenothiazine dication. The spectral data reveal that the degree of fold along the S—N axis vanishes and a greater aromatic resonance structure comes into being with the loss of two electrons in phenothiazine. The spectrum of phenoxazine dication is more similar to that of its parent, which shows that the loss of electrons in phenoxazine leads to less structureal change compared with phenothiazine.
1991, 7(01): 92-96
doi: 10.3866/PKU.WHXB19910115
Abstract:
In order to investigate the influences of specific salt effect of added electrolyte on the classic buffer experiments for distinguishing general and specific acid or base catalysis, the rate constants of the hydrolysis of benzaldehyde di-ter-butyl acetal, triethyl orthobenzoate and N-p-methoxybenzyli-denepyrrolidinium ion in acetate buffers were measured under various conditions. It is found that, for a given reaction, the presence or absence of specific effect of an added salt depends mainly on the ionic stregth and solvent of the buffer solution. In buffers of low ionic strength, e.g. 0.1 mol·L~(-1), using water or mixed solvents containing a small fraction of organic constituent, specific salt effect can be eliminated or considerably reduced and the classic diagnostic buffer experiments can be satisfactory.
In order to investigate the influences of specific salt effect of added electrolyte on the classic buffer experiments for distinguishing general and specific acid or base catalysis, the rate constants of the hydrolysis of benzaldehyde di-ter-butyl acetal, triethyl orthobenzoate and N-p-methoxybenzyli-denepyrrolidinium ion in acetate buffers were measured under various conditions. It is found that, for a given reaction, the presence or absence of specific effect of an added salt depends mainly on the ionic stregth and solvent of the buffer solution. In buffers of low ionic strength, e.g. 0.1 mol·L~(-1), using water or mixed solvents containing a small fraction of organic constituent, specific salt effect can be eliminated or considerably reduced and the classic diagnostic buffer experiments can be satisfactory.
1991, 7(01): 97-101
doi: 10.3866/PKU.WHXB19910116
Abstract:
A twin, differential, high-temperature calorimeter for the measuremens of enthalpies of formation and transformation in solid alloys has been developed. This apparatus works at temperature up to 1500 K. Its sensitivity and reliability are proved by measuring the heats of transformation of α-to γ-phase in iron. The experimental results are in considerable agreement with those in the published literature.
The calorimeter was used to determine the heats of formation of eight alloy compositions, comprising of σ-and γ-phase, of Fe-Ni-V system. These data have not been measured before. The results show that the enthalpies of Fe-Ni-V solid alloys are negative and tend to decrease generally while the composition of alloy varies from Fe-V side to Ni-V side.
A twin, differential, high-temperature calorimeter for the measuremens of enthalpies of formation and transformation in solid alloys has been developed. This apparatus works at temperature up to 1500 K. Its sensitivity and reliability are proved by measuring the heats of transformation of α-to γ-phase in iron. The experimental results are in considerable agreement with those in the published literature.
The calorimeter was used to determine the heats of formation of eight alloy compositions, comprising of σ-and γ-phase, of Fe-Ni-V system. These data have not been measured before. The results show that the enthalpies of Fe-Ni-V solid alloys are negative and tend to decrease generally while the composition of alloy varies from Fe-V side to Ni-V side.
1991, 7(01): 102-105
doi: 10.3866/PKU.WHXB19910117
Abstract:
The DNMR Spectra of the intramolecular processes occurring in Mg-, Ca-, Sr-and Ba-1,2-propylenediamine-tetraacetic acids(1,2-PDTA) are reported in this paper. The relative activation parameters have been obtained by performing computer line shape analysis. The experimental results show that the rates of the lone pair inversion of the two nitrogen atoms in these complexes are different, but their activation energies are similar. The nitrogen inversion process of these complexes belongs to twist mechanism through a tri nal prismatic intermediate.
The DNMR Spectra of the intramolecular processes occurring in Mg-, Ca-, Sr-and Ba-1,2-propylenediamine-tetraacetic acids(1,2-PDTA) are reported in this paper. The relative activation parameters have been obtained by performing computer line shape analysis. The experimental results show that the rates of the lone pair inversion of the two nitrogen atoms in these complexes are different, but their activation energies are similar. The nitrogen inversion process of these complexes belongs to twist mechanism through a tri nal prismatic intermediate.
1991, 7(01): 106-109
doi: 10.3866/PKU.WHXB19910118
Abstract:
This paper describes the DSC study of 4-trifluorocoumarin derivatives, C_(481), C_(485), C_(500) and C_(480), providing their DSC thermograms and thermodynamic parameters during the phase transitions of these compounds. Singlemelting peaks were observed on DSC thermogram respectively.Experimental results show the existence of certain correlations between the melting point, heat of fusion and molecular structure for this series of compounds.
1991, 7(01): 110-112
doi: 10.3866/PKU.WHXB19910119
Abstract:
The surface area and crystal hibit of an AgBr dispersion were determined by a in situ method. In this method, the difference of the absorption spectra of an cationic cyanine dye Ⅰ in adsorption and solution state was used for the measurement of AgBr surface area. It was 17.1 m~2/g AgBr. And the crystal habit was determined hased upon the absorption spectra of an other two cyanine dyes (Ⅱ and Ⅲ) in adsorption state. It showed a cubic crystal.
The surface area and crystal hibit of an AgBr dispersion were determined by a in situ method. In this method, the difference of the absorption spectra of an cationic cyanine dye Ⅰ in adsorption and solution state was used for the measurement of AgBr surface area. It was 17.1 m~2/g AgBr. And the crystal habit was determined hased upon the absorption spectra of an other two cyanine dyes (Ⅱ and Ⅲ) in adsorption state. It showed a cubic crystal.
1991, 7(01): 113-116
doi: 10.3866/PKU.WHXB19910120
Abstract:
It was found by means of the small angle X-ray scattering (SAXS),that layer distance of the liquid-crystal system consisting of egg yolk phospholipid (PC) and 5% water changes with the addition of benzene,methylbenzene or chlorobenzene. From this experiment it can be seen that layer distance in 5% H_2O-PC system changes alternatively as the benzene content is increased. It is considered that Water-PC and Benzene-PC bimolecular double layers are formed. As chlorobenzene content is increased, the system is disordered easily. This phenomenon can be explained by the ability of the polar groups and hydro-carbon chain tail of the egg yolk phospholipid being attracted by molecules of chlorobenzene.
It was found by means of the small angle X-ray scattering (SAXS),that layer distance of the liquid-crystal system consisting of egg yolk phospholipid (PC) and 5% water changes with the addition of benzene,methylbenzene or chlorobenzene. From this experiment it can be seen that layer distance in 5% H_2O-PC system changes alternatively as the benzene content is increased. It is considered that Water-PC and Benzene-PC bimolecular double layers are formed. As chlorobenzene content is increased, the system is disordered easily. This phenomenon can be explained by the ability of the polar groups and hydro-carbon chain tail of the egg yolk phospholipid being attracted by molecules of chlorobenzene.
1991, 7(01): 117-120
doi: 10.3866/PKU.WHXB19910121
Abstract:
This paper describs the structural character of liquid-crystal of 5%H_2O-egg yolk phospholipid (PC) containing in avarious salt's solution, the layer distance was determined by means of SAXS method. Experimental results show that the layer distance of liquid crystal phase is increased in the 5%H_2O-PC system as the amount of solution of NaCl or KCl is increased. But on the addition of Na_2CO_3 or K_2CO_3 solution into the 5%H_2O-PC system the layer distance of liquid-crystal phase is held constant. It is considered that Na_2CO_3 or K_2CO_3, might be hydrolyzed producing OH~- ions, so that the latter could stablize the interfacial potential between water and egg yolk phospholipid. Absence of this behavior for solution of NaCl or KCl might be due to NaCl and KCl are salts which formed by strong acids and strong bases.
This paper describs the structural character of liquid-crystal of 5%H_2O-egg yolk phospholipid (PC) containing in avarious salt's solution, the layer distance was determined by means of SAXS method. Experimental results show that the layer distance of liquid crystal phase is increased in the 5%H_2O-PC system as the amount of solution of NaCl or KCl is increased. But on the addition of Na_2CO_3 or K_2CO_3 solution into the 5%H_2O-PC system the layer distance of liquid-crystal phase is held constant. It is considered that Na_2CO_3 or K_2CO_3, might be hydrolyzed producing OH~- ions, so that the latter could stablize the interfacial potential between water and egg yolk phospholipid. Absence of this behavior for solution of NaCl or KCl might be due to NaCl and KCl are salts which formed by strong acids and strong bases.
1991, 7(01): 121-124
doi: 10.3866/PKU.WHXB19910122
Abstract:
Solubilities of nitrogen in binary mixtures of n-octane and n-heptane have been measured at temperatures from 20 to 70 ℃ and pressures up to 130 atm using a precision gas-liquid solubility apparatus. Experimental results can be expressed by the following equation
Inx_(N_2)=A+BP_(N_2)+CP_(N_2)~2+DInP
From the results obtained, the partial molar volume of dissolved nitrogen and the Henry's Law constants have also been calculated.
Solubilities of nitrogen in binary mixtures of n-octane and n-heptane have been measured at temperatures from 20 to 70 ℃ and pressures up to 130 atm using a precision gas-liquid solubility apparatus. Experimental results can be expressed by the following equation
Inx_(N_2)=A+BP_(N_2)+CP_(N_2)~2+DInP
From the results obtained, the partial molar volume of dissolved nitrogen and the Henry's Law constants have also been calculated.
1991, 7(01): 125-128
doi: 10.3866/PKU.WHXB19910123
Abstract:
Pulse-reacting experiments of gaseous CO with catalyst surface oxygen and gaseous O_2 with reduced catalyst surface were designed in order to measure the activation energy of oxygen offering and the activation energy of oxygen reproducing on the catalyst surface. By the separate measurement of these two kinds of activation energy, the difference in behavior of Pt/HM and Pd/HM catalysts was explained.
The activation energy of oxygen offering on Pt/HM is lower than that on Pd/HM, but the oxygen reproducing activation energy on Pt/HM is higher than that on Pd/HM.
Pulse-reacting experiments of gaseous CO with catalyst surface oxygen and gaseous O_2 with reduced catalyst surface were designed in order to measure the activation energy of oxygen offering and the activation energy of oxygen reproducing on the catalyst surface. By the separate measurement of these two kinds of activation energy, the difference in behavior of Pt/HM and Pd/HM catalysts was explained.
The activation energy of oxygen offering on Pt/HM is lower than that on Pd/HM, but the oxygen reproducing activation energy on Pt/HM is higher than that on Pd/HM.
