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1992 Volume 8 Issue 1
1992, 8(01): 1-3
doi: 10.3866/PKU.WHXB19920101
Abstract:
This paper describes in situ X-ray diffraction and cyclic voltammetric studies of silver electrode in alkaline solution (NaOH or KOH). The results have shown that the oxides are Ag_2O and A , other than A H and Ag_2O, at potential E=0.20, 0,42 V(SCE), respectively.
This paper describes in situ X-ray diffraction and cyclic voltammetric studies of silver electrode in alkaline solution (NaOH or KOH). The results have shown that the oxides are Ag_2O and A , other than A H and Ag_2O, at potential E=0.20, 0,42 V(SCE), respectively.
1992, 8(01): 4-7
doi: 10.3866/PKU.WHXB19920102
Abstract:
A new electrochemically modulated time resolved uv/vis spectroscopic(EMTRUV/VS) technique based on optical multienannel analyzer (OMA) has been presented. EM-TRUV/VS measurement apparatus consists of five units: an optical signal detection unit which includes a detector, a polychromator, a detector module; an optics unit; a spe-ctroelectrochemical cell unit, which includes optical transparent electrode (OTE); an electrochemical control unit. The limit of time resolution can reach the order of ms by continuously scanning mode and the order of μs by gate mode which is suitable to reversible system with respect to a potential change, respectively. A high S/N ratio can be obtained by subtractive spectrum method. The electrochromism of a poly-o-phenylenediamine (POPD)-coated Au OTE in aqueous 1 mol·L~(-1) H_2SO_4 solution was studied by EMTRUV/VS technique. The optical absorption (λ_(max)=550 nm) of oxidized POPE is ascribed to n→π* transition. The time resolved spectra acquired suggest that the oxidation reaction of PDPD occurs during the first 500 μs and that the electrochromism is controled by H~+ transport.
A new electrochemically modulated time resolved uv/vis spectroscopic(EMTRUV/VS) technique based on optical multienannel analyzer (OMA) has been presented. EM-TRUV/VS measurement apparatus consists of five units: an optical signal detection unit which includes a detector, a polychromator, a detector module; an optics unit; a spe-ctroelectrochemical cell unit, which includes optical transparent electrode (OTE); an electrochemical control unit. The limit of time resolution can reach the order of ms by continuously scanning mode and the order of μs by gate mode which is suitable to reversible system with respect to a potential change, respectively. A high S/N ratio can be obtained by subtractive spectrum method. The electrochromism of a poly-o-phenylenediamine (POPD)-coated Au OTE in aqueous 1 mol·L~(-1) H_2SO_4 solution was studied by EMTRUV/VS technique. The optical absorption (λ_(max)=550 nm) of oxidized POPE is ascribed to n→π* transition. The time resolved spectra acquired suggest that the oxidation reaction of PDPD occurs during the first 500 μs and that the electrochromism is controled by H~+ transport.
1992, 8(01): 8-9
doi: 10.3866/PKU.WHXB19920103
Abstract:
Cluster ions of niobium and sulfur were generated in laser plasma reactions on a self-built apparatus. Among all Nb_nS_m~+, the cluster cations with the compositions of n<4, m=n+1; n>3, m=n+2 have special high ion intensities in mass spectrum. The cluster anions of high intensities have four more sulfur atoms compared with the relative cations. By analo using to [Mo_3S_4]~(4+) clusters, it is proposed that these cluster ions contain non-planar puckered rings with quasi-aromaticity.
Cluster ions of niobium and sulfur were generated in laser plasma reactions on a self-built apparatus. Among all Nb_nS_m~+, the cluster cations with the compositions of n<4, m=n+1; n>3, m=n+2 have special high ion intensities in mass spectrum. The cluster anions of high intensities have four more sulfur atoms compared with the relative cations. By analo using to [Mo_3S_4]~(4+) clusters, it is proposed that these cluster ions contain non-planar puckered rings with quasi-aromaticity.
1992, 8(01): 10-17
doi: 10.3866/PKU.WHXB19920104
Abstract:
The electronic structure and chemical bonding of [Nd(SSCNH_2)_4]~-, a simplified model of complex anion {Nd[SSCN(C_2H_5)_2]_4}~-, have been studied in detail. In view of the contribution to the binding energy, it may be inferred that the binding between Nd and S atoms is mainly ionic in character, but the covalent binding must be con-sidered contributing to the bond formation to a certain extent, taking account of the charge redistribution. For the Nd-S and Nd-S′ bonds, the sigma-bonding plays the main role, the bond order of the pi bonds is only 1/5 to 1/6 of that of the sigma bonds. The reason why only a very few of organosulfur-coordinated lanthanide compounds have been synthesized while there exist a great number of stable inorganic composite sulfides of lanthanides has been analyzed based on the calculation results. Several possible approaches have been suggested to synthesize stable organosulfur-coordinated lanthanide compounds.
The electronic structure and chemical bonding of [Nd(SSCNH_2)_4]~-, a simplified model of complex anion {Nd[SSCN(C_2H_5)_2]_4}~-, have been studied in detail. In view of the contribution to the binding energy, it may be inferred that the binding between Nd and S atoms is mainly ionic in character, but the covalent binding must be con-sidered contributing to the bond formation to a certain extent, taking account of the charge redistribution. For the Nd-S and Nd-S′ bonds, the sigma-bonding plays the main role, the bond order of the pi bonds is only 1/5 to 1/6 of that of the sigma bonds. The reason why only a very few of organosulfur-coordinated lanthanide compounds have been synthesized while there exist a great number of stable inorganic composite sulfides of lanthanides has been analyzed based on the calculation results. Several possible approaches have been suggested to synthesize stable organosulfur-coordinated lanthanide compounds.
1992, 8(01): 18-21
doi: 10.3866/PKU.WHXB19920105
Abstract:
The low-frequency Raman spectrum of n-decylammonium chloride was measured as a function of temperature in the temperature range from 290 to 340 K, and the longitudinal acoustical mode vibration band was assigned. The results showed that there are two phase transitions at 313 K and 321 K, respectively. The phase transition at 313 K is mainly induced by change of hydrocarbon chain conformations, while that at 321 K is mainly induced by change of order degree of molecular packing. The results suggest low-frequency Raman spectroscopy is a useful probe of structural phase transition for long-chain compounds.
The low-frequency Raman spectrum of n-decylammonium chloride was measured as a function of temperature in the temperature range from 290 to 340 K, and the longitudinal acoustical mode vibration band was assigned. The results showed that there are two phase transitions at 313 K and 321 K, respectively. The phase transition at 313 K is mainly induced by change of hydrocarbon chain conformations, while that at 321 K is mainly induced by change of order degree of molecular packing. The results suggest low-frequency Raman spectroscopy is a useful probe of structural phase transition for long-chain compounds.
1992, 8(01): 22-26
doi: 10.3866/PKU.WHXB19920106
Abstract:
Effect of the amount of solubilized toluene on the hydrodynamic radius R_h of micelle of polyoxythylene(PEO)-polyoxypropylene(PPO) block copolymer was inves-tigated by dynamic lightscattering at different temperatures.
The result showed that the values of R_h were rather high due to strong hydration of PEO chains at 25 ℃, the amount of toluene in micelle had little effect on the values of R_h. As the temperature increased, hydration of micelle decreased and R_h decreased also. Near the temperature of the cloud point, the dehydration of micelle might be very strong, PPO core was swollen by toluent and aggregation number increased at higher temperatures, this made R_h increasing linearly with the amount of solubliized toluene.
Effect of the amount of solubilized toluene on the hydrodynamic radius R_h of micelle of polyoxythylene(PEO)-polyoxypropylene(PPO) block copolymer was inves-tigated by dynamic lightscattering at different temperatures.
The result showed that the values of R_h were rather high due to strong hydration of PEO chains at 25 ℃, the amount of toluene in micelle had little effect on the values of R_h. As the temperature increased, hydration of micelle decreased and R_h decreased also. Near the temperature of the cloud point, the dehydration of micelle might be very strong, PPO core was swollen by toluent and aggregation number increased at higher temperatures, this made R_h increasing linearly with the amount of solubliized toluene.
1992, 8(01): 27-32
doi: 10.3866/PKU.WHXB19920107
Abstract:
Based on the structural information on 449 molybdenum cluster compounds in CSD (Cambridge Stuctural Database), the sum of valence electrons of molybdenum clusers, the average bond valences of Mo-Mo and the average bond lengths of Mo-Mo have been calculated. The current method uses the functions of retrieval, molecular plots and statistics in CSD. It is suggested that the valence electron counting rule ofmolybdenum cluster compouds is:
The sum of valence electrons of molybdenum cluster(k)+the sum of bond
valences for Mo-Mo×2=18×n-2×ΣΔ_i
and the sum of bond valence for Mo-Mo can be counted by using the formula:
v=(18×n-k)/2-ΣΔ_i
the geometry...
Based on the structural information on 449 molybdenum cluster compounds in CSD (Cambridge Stuctural Database), the sum of valence electrons of molybdenum clusers, the average bond valences of Mo-Mo and the average bond lengths of Mo-Mo have been calculated. The current method uses the functions of retrieval, molecular plots and statistics in CSD. It is suggested that the valence electron counting rule ofmolybdenum cluster compouds is:
The sum of valence electrons of molybdenum cluster(k)+the sum of bond
valences for Mo-Mo×2=18×n-2×ΣΔ_i
and the sum of bond valence for Mo-Mo can be counted by using the formula:
v=(18×n-k)/2-ΣΔ_i
the geometry...
1992, 8(01): 33-38
doi: 10.3866/PKU.WHXB19920108
Abstract:
An ab initio PD/LSF and (exp-6-1) model has been used to deal with intramolecular non-bonded interaction of 1,1-difluoro-ethane and 1.2-difluoroethane. It is concluded that the energy difference of isomers comes from intramolecular non-bonded inter-acion between the atoms. This model provides a useful, simple and easily understood approximation to intramolecular non-bon-ded interaction.
An ab initio PD/LSF and (exp-6-1) model has been used to deal with intramolecular non-bonded interaction of 1,1-difluoro-ethane and 1.2-difluoroethane. It is concluded that the energy difference of isomers comes from intramolecular non-bonded inter-acion between the atoms. This model provides a useful, simple and easily understood approximation to intramolecular non-bon-ded interaction.
1992, 8(01): 39-44
doi: 10.3866/PKU.WHXB19920109
Abstract:
In this paper, the full relaxation matrix analysis method was applied for processing the peak intensity matrix of the phase sensitive NOESY spectrum for which a relati-vely long mixing time was used for the small molecules in the "extreme narrowing" condition. According to this method, the cross relaxation rates between nuclei were obtained by dia nalizing the 2D peak intensity matrix, then the inter-nuclear distances were calculated according to R_(ij) ∝τ_0·r_(ij)~(-6). This method was employed to investigate the structure of TRANILAST in acetone solution, and the results agree with the data from molecular mechanics calculation. Thus the molecular structure was determined and it was found that there is an internal hydrogen bond in the molecule.
In this paper, the full relaxation matrix analysis method was applied for processing the peak intensity matrix of the phase sensitive NOESY spectrum for which a relati-vely long mixing time was used for the small molecules in the "extreme narrowing" condition. According to this method, the cross relaxation rates between nuclei were obtained by dia nalizing the 2D peak intensity matrix, then the inter-nuclear distances were calculated according to R_(ij) ∝τ_0·r_(ij)~(-6). This method was employed to investigate the structure of TRANILAST in acetone solution, and the results agree with the data from molecular mechanics calculation. Thus the molecular structure was determined and it was found that there is an internal hydrogen bond in the molecule.
1992, 8(01): 45-51
doi: 10.3866/PKU.WHXB19920110
Abstract:
By means of the basic vectors matched for group chain ((O?D_3?C_3)×SU(2))~N, the Slater functions of the direct product for single electron can be used as the basis vectors of the irreducible representations of d~N ions or the direct summa-tion representations of two one-dimensional representation. The matrix element ex-pressions related and the calculation of EPR parameters are systematically derived and the corresponding computer programs for all d~N ion in tri nal field have been compiled.
By means of the basic vectors matched for group chain ((O?D_3?C_3)×SU(2))~N, the Slater functions of the direct product for single electron can be used as the basis vectors of the irreducible representations of d~N ions or the direct summa-tion representations of two one-dimensional representation. The matrix element ex-pressions related and the calculation of EPR parameters are systematically derived and the corresponding computer programs for all d~N ion in tri nal field have been compiled.
1992, 8(01): 52-58
doi: 10.3866/PKU.WHXB19920111
Abstract:
The kinetics and mechanism of the reaction between Eu~(2+) and Xylenol orange (XO) in aqueous solution has been studied by means of stop-flow spectrophotometric method. The kinetic parameters of the rate-controlling step, i,e, reaction order (n=2), rate constant at various temperatures (k_(278 K)=5.7×10~8 L·mol~(-1)·s~(-1), k_(338 K)=1.01×10~9 L·mol~(-1)·s~(-1)…), activation energy (E=7.6×10~3 J·mol~(-1)) and preexponential factor (A=1.5×10~(10) L·mol~(-1)·s~(-1)) have been determined. It has been established that the electron transfer reaction between Eu~(2+) and XO is a diffusion controlled reaction.
The possible mechanisms of the reaction between Eu~(2+) and XO both in the presence of excess XO and Eu~(2+) also have been suggested. The relation between the rate constants of each step were estimated.
The kinetics and mechanism of the reaction between Eu~(2+) and Xylenol orange (XO) in aqueous solution has been studied by means of stop-flow spectrophotometric method. The kinetic parameters of the rate-controlling step, i,e, reaction order (n=2), rate constant at various temperatures (k_(278 K)=5.7×10~8 L·mol~(-1)·s~(-1), k_(338 K)=1.01×10~9 L·mol~(-1)·s~(-1)…), activation energy (E=7.6×10~3 J·mol~(-1)) and preexponential factor (A=1.5×10~(10) L·mol~(-1)·s~(-1)) have been determined. It has been established that the electron transfer reaction between Eu~(2+) and XO is a diffusion controlled reaction.
The possible mechanisms of the reaction between Eu~(2+) and XO both in the presence of excess XO and Eu~(2+) also have been suggested. The relation between the rate constants of each step were estimated.
1992, 8(01): 59-63
doi: 10.3866/PKU.WHXB19920112
Abstract:
Adsorption and oxidation of 1,2-propanediol at a platinum electrode in acid solutions were investigated by cyclic voltammetry and in-situ FTIR spectroscopy. The results demonstrated that 1,2-propanediol oxidized on Pt electrode via a dual path reaction mechanism. 1,2-propanediol may be oxidized into CO_2 through its disso-ciative products on Pt surface. But at lower potentials these dissociative products, which were mainly CO_(ad) and[﹥C=CH_2]_(ad) as detected by in situ-FTIR spectroscopy, may adsorb strongly and accumulate on electrode, empoisoning Pt electrode and suppressing consequently other reactions. However all dissociative products may be oxidized and desorbed from Pt surface when E>0.3 V, which reactivates Pt electrode and enables that 1,2-propanediol oxidizes via reactive intermediates into CO_2. The reactive intermediates were detected by in-situ FTIR spectroscopy under present conditions as OHC—CHOHCH_3 (or CH_2OH—COCH_3) and HOOC—COCH_3 (or HOOC—COCH_3) species.
Adsorption and oxidation of 1,2-propanediol at a platinum electrode in acid solutions were investigated by cyclic voltammetry and in-situ FTIR spectroscopy. The results demonstrated that 1,2-propanediol oxidized on Pt electrode via a dual path reaction mechanism. 1,2-propanediol may be oxidized into CO_2 through its disso-ciative products on Pt surface. But at lower potentials these dissociative products, which were mainly CO_(ad) and[﹥C=CH_2]_(ad) as detected by in situ-FTIR spectroscopy, may adsorb strongly and accumulate on electrode, empoisoning Pt electrode and suppressing consequently other reactions. However all dissociative products may be oxidized and desorbed from Pt surface when E>0.3 V, which reactivates Pt electrode and enables that 1,2-propanediol oxidizes via reactive intermediates into CO_2. The reactive intermediates were detected by in-situ FTIR spectroscopy under present conditions as OHC—CHOHCH_3 (or CH_2OH—COCH_3) and HOOC—COCH_3 (or HOOC—COCH_3) species.
1992, 8(01): 64-69
doi: 10.3866/PKU.WHXB19920113
Abstract:
Fourier-transform infrared(FT-IR) emission spectroscopic technique has been establi-shed to study metal oxide catalysts. An in situ infrared emission cell was specially de-signed to treat sample in vacuo or in various gases at a wide temperature range (r.t. -700 ℃). Infrared emission spectrum of MoO_3 was presented and the results demons-trated that FT-IR emission spectroscopy is a sensitive method to detect vibrational information of metal oxide catalysts.The experimental conditions including sample preparation, effects of temperature and sample thickness on the infrared emission spectrum were detailed. It was found that the spectrum was severely disordered when the sample thickness of MoO_3 was beyond 1.00 mg·cm~2 and the more intensive emission bands were detected at higher temperatures. Infrared emission spectra recorded in the course of H~2 reduction of MoO_3 showed that surface linkage Mo—O—Mo species giving the band at 880 cm~(-1) is more easily reduced comparing to the terminal Mo=O species giving the band at 990 cm~(-1), vice versa, the Mo=O species are preferentially formed than the Mo—O—Mo species during the reoxidation of the partially reduced MoO_3.
Fourier-transform infrared(FT-IR) emission spectroscopic technique has been establi-shed to study metal oxide catalysts. An in situ infrared emission cell was specially de-signed to treat sample in vacuo or in various gases at a wide temperature range (r.t. -700 ℃). Infrared emission spectrum of MoO_3 was presented and the results demons-trated that FT-IR emission spectroscopy is a sensitive method to detect vibrational information of metal oxide catalysts.The experimental conditions including sample preparation, effects of temperature and sample thickness on the infrared emission spectrum were detailed. It was found that the spectrum was severely disordered when the sample thickness of MoO_3 was beyond 1.00 mg·cm~2 and the more intensive emission bands were detected at higher temperatures. Infrared emission spectra recorded in the course of H~2 reduction of MoO_3 showed that surface linkage Mo—O—Mo species giving the band at 880 cm~(-1) is more easily reduced comparing to the terminal Mo=O species giving the band at 990 cm~(-1), vice versa, the Mo=O species are preferentially formed than the Mo—O—Mo species during the reoxidation of the partially reduced MoO_3.
1992, 8(01): 70-81
doi: 10.3866/PKU.WHXB19920114
Abstract:
We developed a method for analyzing time-of-flight spectra of Secondary products from sequential dissociation reactions fol-lowing photon absorption by the parent molecule. This work complements the original discussion by Kroger and Riley, and shows that substantial information can be extracted even from highly aveyaged data. This information includes the average translational energy release and anisotropy of the secondary pro-duct recoil, as well as the relative yields of the secondary frag-ments for competing pathways. Model results are examined in order to illustrate the basic features of secondary dissociation.
We developed a method for analyzing time-of-flight spectra of Secondary products from sequential dissociation reactions fol-lowing photon absorption by the parent molecule. This work complements the original discussion by Kroger and Riley, and shows that substantial information can be extracted even from highly aveyaged data. This information includes the average translational energy release and anisotropy of the secondary pro-duct recoil, as well as the relative yields of the secondary frag-ments for competing pathways. Model results are examined in order to illustrate the basic features of secondary dissociation.
1992, 8(01): 82-86
doi: 10.3866/PKU.WHXB19920115
Abstract:
A conducting polyaniline (PAn) film modified glassy carbon (GC) electrode was prepared by electrochemical polymerization. The electrochemical behavior of ascorbic acid (AH_2) in aqueous solution at this PAn modified electrode was studied in detail. The experimental results show that PAn film modified electrode has od electrocatalytic activity on the oxidation of ascorbic acid in aqueous solution over a wide range of pH value, among which pH 4 is the optimum condition. The oxidation process of ascorbic acid at PAn film electrode can be regarded as an EC catalytic mechanism. The kinetic process of the catalytic reaction was investigated by rotating disk electrode (RDE) coated with PAn films. The rate constant of the catalytic reaction was evaluated. The catalytic peak currents are proportional to the concentrations of ascorbic acid in the range of 5×10~(-2)—1×10~(-6) mol·L~(-1). The PAn film electrodes give very stable responce for the oxidation of ascorbic acid. The present investigation shows the posibility of using PAn film modified electrode for the determination of ascorbic acid.
A conducting polyaniline (PAn) film modified glassy carbon (GC) electrode was prepared by electrochemical polymerization. The electrochemical behavior of ascorbic acid (AH_2) in aqueous solution at this PAn modified electrode was studied in detail. The experimental results show that PAn film modified electrode has od electrocatalytic activity on the oxidation of ascorbic acid in aqueous solution over a wide range of pH value, among which pH 4 is the optimum condition. The oxidation process of ascorbic acid at PAn film electrode can be regarded as an EC catalytic mechanism. The kinetic process of the catalytic reaction was investigated by rotating disk electrode (RDE) coated with PAn films. The rate constant of the catalytic reaction was evaluated. The catalytic peak currents are proportional to the concentrations of ascorbic acid in the range of 5×10~(-2)—1×10~(-6) mol·L~(-1). The PAn film electrodes give very stable responce for the oxidation of ascorbic acid. The present investigation shows the posibility of using PAn film modified electrode for the determination of ascorbic acid.
1992, 8(01): 87-93
doi: 10.3866/PKU.WHXB19920116
Abstract:
The inhibition mechanism of 2-aminopyrimidine (2-AP) for copper corrosion in chloride solutions with various pH values has been investigated using XPS, X-AES, SERS and electrochemical techniques. The results showed that the 2-AP is a better inhibitor for the copper corrosion in acidic solutions, less effective in neutral solutions and completely ineffective in basic solutions. In acidic solutions a protective polymeric complex film consisting of 2-AP, Cl~- and surface copper atoms(or cations) on the copper surface, which is stable in a wide potential range, is responsible for the corrosion inhibition of copper.
The inhibition mechanism of 2-aminopyrimidine (2-AP) for copper corrosion in chloride solutions with various pH values has been investigated using XPS, X-AES, SERS and electrochemical techniques. The results showed that the 2-AP is a better inhibitor for the copper corrosion in acidic solutions, less effective in neutral solutions and completely ineffective in basic solutions. In acidic solutions a protective polymeric complex film consisting of 2-AP, Cl~- and surface copper atoms(or cations) on the copper surface, which is stable in a wide potential range, is responsible for the corrosion inhibition of copper.
1992, 8(01): 94-99
doi: 10.3866/PKU.WHXB19920117
Abstract:
The activity coefficients of KCl and LiCl in KCl-LiCl aqueous mixtures have been measured at 25 ℃ in ionic strength range of 0.1～4.0 mol·kg~(-1). The measurement were made using K-ISE and Li-ISE vs. Cl-ISE in a wide range of compositions from pure KCl to pure LiCl. The data were fitted to Pitzer's equation using regressin method, Pitzer parameters were obtained.
The activity coefficients of KCl and LiCl in KCl-LiCl aqueous mixtures have been measured at 25 ℃ in ionic strength range of 0.1～4.0 mol·kg~(-1). The measurement were made using K-ISE and Li-ISE vs. Cl-ISE in a wide range of compositions from pure KCl to pure LiCl. The data were fitted to Pitzer's equation using regressin method, Pitzer parameters were obtained.
1992, 8(01): 100-108
doi: 10.3866/PKU.WHXB19920118
Abstract:
The crystal structure of four 1-oxo-4-(substituent)-1-phospha-2,6,7-trioxacyclo(2,2,2) octane have been determinded by dimention single-crystal X-ray analysis.
All intensity data were collected with an Enraf-Nonius CAD4 diffractometer, using graphite monochromated Cu-K_α radiation and ω/2θ scan, and corrected for LP and emperical absorption factors. All crystal structures were solved by MULTAN and refined by full matrix least-squares with lsotropic thermal vibration factors for H and anisotropic for the others.
Crystal data, (I) X=NH, R=H, ...
The crystal structure of four 1-oxo-4-(substituent)-1-phospha-2,6,7-trioxacyclo(2,2,2) octane have been determinded by dimention single-crystal X-ray analysis.
All intensity data were collected with an Enraf-Nonius CAD4 diffractometer, using graphite monochromated Cu-K_α radiation and ω/2θ scan, and corrected for LP and emperical absorption factors. All crystal structures were solved by MULTAN and refined by full matrix least-squares with lsotropic thermal vibration factors for H and anisotropic for the others.
Crystal data, (I) X=NH, R=H, ...
1992, 8(01): 109-112
doi: 10.3866/PKU.WHXB19920119
Abstract:
Structuring of water on glass surface has been widely reported. There exists a debate on the thickness of the structured water layer on these surfaces, sometimes long-range, sometimes short-range structuring of the surface water was inferred. We used a porosimeter to measure the pore volume of controlled pore glass with pore radius 12.1 nm, which had pre-adsorbed various amount of water, and to study the behaviour of water on controlled pore glass surfaces. It has been found that the first 2-3 layers of the adsorbed water were modified from the bulk water. The thickness of this modified water layer on the controlled pore glass was calculated to be about 0.5 nm and the density of this water was much higher than that of the bulk water. The rest of the adsorbed water was similar to bulk water.
No abnormal phenomena was found for n-Decan in the controlled pore glass. For any amount of adsorbed n-Decan, they had similar property as that of the bulk n-Decan.
Structuring of water on glass surface has been widely reported. There exists a debate on the thickness of the structured water layer on these surfaces, sometimes long-range, sometimes short-range structuring of the surface water was inferred. We used a porosimeter to measure the pore volume of controlled pore glass with pore radius 12.1 nm, which had pre-adsorbed various amount of water, and to study the behaviour of water on controlled pore glass surfaces. It has been found that the first 2-3 layers of the adsorbed water were modified from the bulk water. The thickness of this modified water layer on the controlled pore glass was calculated to be about 0.5 nm and the density of this water was much higher than that of the bulk water. The rest of the adsorbed water was similar to bulk water.
No abnormal phenomena was found for n-Decan in the controlled pore glass. For any amount of adsorbed n-Decan, they had similar property as that of the bulk n-Decan.
1992, 8(01): 113-116
doi: 10.3866/PKU.WHXB19920120
Abstract:
In this paper a study of the spin lattice relaxation times of dioxane(DO) adsorbed on various charcoals is presented. Results show that the magnetziation of DO decays biexponentially (Table 1) as observed in the case of adsorbed hydrocarbons~[6]. The fast relaxing molecules are considered to be those adsorbed in micropores with radii less than 1.0 nm whose motion is restricted and slowed down, thus they form a solid like phase. However, the slow relaxing ones are those condensed in the micropores, they are free to move and form the liquid like phase. Molecules condensed in the interior of the micropores exchange rapidly with those situated in the vicinity of the pore wall according to Eq.(2).
Comparison of data in Table 1 may lead to a conclusion that charcoal with greater density of surface acidic groups and greater percentage of pore capacity with radius<1.0 nm (V_(10)/V_(30)) has a greater percentage of solid like phase (P_f). Although V_(10)/V_(30) of density of surface acidic groups. It is apparent that surface acidic groups in micropores play an important role in the formation of solid like phase of DO on charcoals. It seems that DO form hydrogen bond with the surface acidic groups. It is this hydrogen bond and the hinderance effect of pores restrict the DO from moving freely, which results in the formation of the so called solid like phase. It can be found from small (0.10 ml/gC). This implies that DO vapour may first condense in the micropores having more acidic groups and higher activation energy, and then fill in other pores step by step as the adsorption process proceeds.
In this paper a study of the spin lattice relaxation times of dioxane(DO) adsorbed on various charcoals is presented. Results show that the magnetziation of DO decays biexponentially (Table 1) as observed in the case of adsorbed hydrocarbons~[6]. The fast relaxing molecules are considered to be those adsorbed in micropores with radii less than 1.0 nm whose motion is restricted and slowed down, thus they form a solid like phase. However, the slow relaxing ones are those condensed in the micropores, they are free to move and form the liquid like phase. Molecules condensed in the interior of the micropores exchange rapidly with those situated in the vicinity of the pore wall according to Eq.(2).
Comparison of data in Table 1 may lead to a conclusion that charcoal with greater density of surface acidic groups and greater percentage of pore capacity with radius<1.0 nm (V_(10)/V_(30)) has a greater percentage of solid like phase (P_f). Although V_(10)/V_(30) of density of surface acidic groups. It is apparent that surface acidic groups in micropores play an important role in the formation of solid like phase of DO on charcoals. It seems that DO form hydrogen bond with the surface acidic groups. It is this hydrogen bond and the hinderance effect of pores restrict the DO from moving freely, which results in the formation of the so called solid like phase. It can be found from small (0.10 ml/gC). This implies that DO vapour may first condense in the micropores having more acidic groups and higher activation energy, and then fill in other pores step by step as the adsorption process proceeds.
1992, 8(01): 117-122
doi: 10.3866/PKU.WHXB19920121
Abstract:
The unimolecular charge separation reactions of the doubly charged ions FeC_(10)H_(10)~(2+)、FeC_(10)H_9~(2+)、FeC_(10)H_8~(2+) produced in the ion source by electron impact from ferrocene have been studied using Mass analyzed Ion Kinetic Energy Spectrometry (MIKES) technique. From the values of the kinetic energy releases (T), the intercharge distances (R) of the exploding doubly charged ions in their transition structures have been estimated and some structural informations about the transition states can be obtained. The collision induced reactions of the FeC_(10)H_(10)~(2+) ion with Ar have been studied using MIKES, we postulate a new type of continuing reaction which may be "collisional charge separation induced dissociation".
The unimolecular charge separation reactions of the doubly charged ions FeC_(10)H_(10)~(2+)、FeC_(10)H_9~(2+)、FeC_(10)H_8~(2+) produced in the ion source by electron impact from ferrocene have been studied using Mass analyzed Ion Kinetic Energy Spectrometry (MIKES) technique. From the values of the kinetic energy releases (T), the intercharge distances (R) of the exploding doubly charged ions in their transition structures have been estimated and some structural informations about the transition states can be obtained. The collision induced reactions of the FeC_(10)H_(10)~(2+) ion with Ar have been studied using MIKES, we postulate a new type of continuing reaction which may be "collisional charge separation induced dissociation".
1992, 8(01): 123-127
doi: 10.3866/PKU.WHXB19920122
Abstract:
The thermal decomposition of NH_4HSO_4 was studied by means of thermogravi-metry both at cosntant temperature and linearly increasing of temperature. Three-stage identification of the function depending on a mechanism was suggested. The experi-mental results and theoretical analysis showed that the thermal decomposition of NH_4HSO_4 is an one dimensional phase boundary reaction.
Kinetic paramters:
E=141.25 kJ·mol~(-1), A=1.563×10~(10) min~(-1) (isothermal run)
E=131.83 kJ·mol~(-1), A=3.3113×10~9 min~(-1)(dynamic run)
Kinetic compensition effect:
lgA=0.0899E-2.5143
The thermal decomposition of NH_4HSO_4 was studied by means of thermogravi-metry both at cosntant temperature and linearly increasing of temperature. Three-stage identification of the function depending on a mechanism was suggested. The experi-mental results and theoretical analysis showed that the thermal decomposition of NH_4HSO_4 is an one dimensional phase boundary reaction.
Kinetic paramters:
E=141.25 kJ·mol~(-1), A=1.563×10~(10) min~(-1) (isothermal run)
E=131.83 kJ·mol~(-1), A=3.3113×10~9 min~(-1)(dynamic run)
Kinetic compensition effect:
lgA=0.0899E-2.5143
1992, 8(01): 128-131
doi: 10.3866/PKU.WHXB19920123
Abstract:
The phase transitions of a new group of mesogens, 2-(4-alkoxyphenyl)-6-substituted benzothiazoles were thermodynamically studied by DSC, and their transition temperatures and enthalpy changes were measured, from which the transition entropy changes were calculated. The results obtained were discussed. In addition, the phe-nomenon of super-cooling of the compounds were quantitatively observed.
The phase transitions of a new group of mesogens, 2-(4-alkoxyphenyl)-6-substituted benzothiazoles were thermodynamically studied by DSC, and their transition temperatures and enthalpy changes were measured, from which the transition entropy changes were calculated. The results obtained were discussed. In addition, the phe-nomenon of super-cooling of the compounds were quantitatively observed.
1992, 8(01): 132-135
doi: 10.3866/PKU.WHXB19920124
Abstract:
Standard potentials (E°_m) of the Ag-AgCl electrode in Glycine+H_2O mixture at 25 ℃, 30 ℃, 35 ℃, 40 ℃, and 45 ℃ have been determined from the EMF measurements of cells of the type:
Pt, H (g, 101.325 kPa)|HCl(m)+Glycine+H_2O|AgCl-Ag
These values have been utilized to evaluate the transfer energetics (ΔG°_t, ΔH°_t, ΔS°_t) accompanying the transfer of 1 mol HCl from the standard state in water to the standard state in Glycine+H_2O mixtures. Attempts have been made to explain the transfer energetics varying with different compositions of Glycine+H_2O mixtures in the light of ion-solvent interactions and the structureal effects of the solvents.
Standard potentials (E°_m) of the Ag-AgCl electrode in Glycine+H_2O mixture at 25 ℃, 30 ℃, 35 ℃, 40 ℃, and 45 ℃ have been determined from the EMF measurements of cells of the type:
Pt, H (g, 101.325 kPa)|HCl(m)+Glycine+H_2O|AgCl-Ag
These values have been utilized to evaluate the transfer energetics (ΔG°_t, ΔH°_t, ΔS°_t) accompanying the transfer of 1 mol HCl from the standard state in water to the standard state in Glycine+H_2O mixtures. Attempts have been made to explain the transfer energetics varying with different compositions of Glycine+H_2O mixtures in the light of ion-solvent interactions and the structureal effects of the solvents.
1992, 8(01): 136-144
doi: 10.3866/PKU.WHXB19920125
Abstract:
