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1988 Volume 4 Issue 1
1988, 4(01): 1-3
doi: 10.3866/PKU.WHXB19880101
Abstract:
An idea and theory of finding the general solution of three dimensional diffusion equation by using the the experimental electrode response to single-shot transient perturbation are presented. The following formulas were derived for the electrode reaction O+ne<=>R at an electrode of any shape or array of electrodes:
∫∫cds=Ac~*_O/P+A_0(P,D_0,Ω)exp{-PL[I(t,D_0,Ω)]z/FAD_0c′_0}
0≤z<δ
∫∫c_Rds=Ac~*_R/P+A_R(P,D_R,Ω)exp{-PL[I(t,D_R,Ω)/FD_Rc′_0}
When I(t,D'_O,Ω) is the expression for experimental current response of a standard system of n=1 to large amplitude potential step, then I(t,D_O,Ω)and I(t,D_R,Ω) could be obtained by substitution of D_0 and D_R of system studied for D′_0 in I(t,D′_0,Ω) respectively. A=∫∫ds is the total surface area of electrode or array of electrodes. While Ω is the domain of all points on surface of electrodes. δ is a very small value. c′_0 is the bulk concentration of electroactive specie in the standard samples, c~*_0 and c~*_R are bulk concentrations of elecroactive specie in any sample to be studied. L is the operator of the Laplace trasformation, P is the variable of the Laplace transfrmation. c_0 and c_R are the Laplace trasformation of c_0 and c_r respectively. A_0(P,D_0,Ω) and A_R(P,D_R,Ω) depend on experimental method employed in investigating studied system.
【DOI】 cnki:ISSN:1000-6818.0.1988-
An idea and theory of finding the general solution of three dimensional diffusion equation by using the the experimental electrode response to single-shot transient perturbation are presented. The following formulas were derived for the electrode reaction O+ne<=>R at an electrode of any shape or array of electrodes:
∫∫cds=Ac~*_O/P+A_0(P,D_0,Ω)exp{-PL[I(t,D_0,Ω)]z/FAD_0c′_0}
0≤z<δ
∫∫c_Rds=Ac~*_R/P+A_R(P,D_R,Ω)exp{-PL[I(t,D_R,Ω)/FD_Rc′_0}
When I(t,D'_O,Ω) is the expression for experimental current response of a standard system of n=1 to large amplitude potential step, then I(t,D_O,Ω)and I(t,D_R,Ω) could be obtained by substitution of D_0 and D_R of system studied for D′_0 in I(t,D′_0,Ω) respectively. A=∫∫ds is the total surface area of electrode or array of electrodes. While Ω is the domain of all points on surface of electrodes. δ is a very small value. c′_0 is the bulk concentration of electroactive specie in the standard samples, c~*_0 and c~*_R are bulk concentrations of elecroactive specie in any sample to be studied. L is the operator of the Laplace trasformation, P is the variable of the Laplace transfrmation. c_0 and c_R are the Laplace trasformation of c_0 and c_r respectively. A_0(P,D_0,Ω) and A_R(P,D_R,Ω) depend on experimental method employed in investigating studied system.
【DOI】 cnki:ISSN:1000-6818.0.1988-
1988, 4(01): 4-7
doi: 10.3866/PKU.WHXB19880102
Abstract:
We have carried out investigations of the surfaces of the Y-Ba-Cu-O superconductor with XPS.Our experiments deal with the surface species and the peak splitings. The results show that the atmosphere plays an important role.
We have carried out investigations of the surfaces of the Y-Ba-Cu-O superconductor with XPS.Our experiments deal with the surface species and the peak splitings. The results show that the atmosphere plays an important role.
1988, 4(01): 8-13
doi: 10.3866/PKU.WHXB19880103
Abstract:
The reduction and oxidation character of Pd-CuO/TiO_2 catalyst has been investigated, exploring, the effect of semiconductor support TiO_2 and metal Pd, using Pd-CuO/Al_2O_3 as a comparing system.
By means of TPR, it was shown that Cue supported on TiO_2 was much more readily reduced than that on Al_2O_3 and without support. The temperatures of the respective reduction peak for Cue were ca.200, 265 and 285 ℃. If as low as 0.3 wt.% of Pd was present, then the reduction peak of Cue on TiO_2 was further shifted to below 100 ℃ while that on Al_2O_3 was hardly changed.
The TPO spectra of catalyst sample pre-reduced by H_2 at 250 ℃ demonstrated the different behavior of supports TiO_2 and Al_2O_3 as well in correlation with XRD pattern, it revealed CuO on TiO_2 may be oxidized stepwise much more readily, i.e. Cu~0→Cu~+→Cu~(++), in contrast with the resistance to oxidation of CuO on Al_2O_3.
These results could be explained by that TiO_2 as n-type semiconductor oxide can easily provide n-type defect, Ti~(3+) or oxygen vacancy, which might play the role of relay for charge transfer. Particularly in presence of noble metal, H_2 being strongly activated, the action of n-type defect was effectively enhaned so that the charge trasition between components was promoted. Thus the reduction and oxidation of CuO_x could proceed smoothly on TiO_2 but not so as it was supported on Al_2O_3.
The reduction and oxidation character of Pd-CuO/TiO_2 catalyst has been investigated, exploring, the effect of semiconductor support TiO_2 and metal Pd, using Pd-CuO/Al_2O_3 as a comparing system.
By means of TPR, it was shown that Cue supported on TiO_2 was much more readily reduced than that on Al_2O_3 and without support. The temperatures of the respective reduction peak for Cue were ca.200, 265 and 285 ℃. If as low as 0.3 wt.% of Pd was present, then the reduction peak of Cue on TiO_2 was further shifted to below 100 ℃ while that on Al_2O_3 was hardly changed.
The TPO spectra of catalyst sample pre-reduced by H_2 at 250 ℃ demonstrated the different behavior of supports TiO_2 and Al_2O_3 as well in correlation with XRD pattern, it revealed CuO on TiO_2 may be oxidized stepwise much more readily, i.e. Cu~0→Cu~+→Cu~(++), in contrast with the resistance to oxidation of CuO on Al_2O_3.
These results could be explained by that TiO_2 as n-type semiconductor oxide can easily provide n-type defect, Ti~(3+) or oxygen vacancy, which might play the role of relay for charge transfer. Particularly in presence of noble metal, H_2 being strongly activated, the action of n-type defect was effectively enhaned so that the charge trasition between components was promoted. Thus the reduction and oxidation of CuO_x could proceed smoothly on TiO_2 but not so as it was supported on Al_2O_3.
1988, 4(01): 14-19
doi: 10.3866/PKU.WHXB19880104
Abstract:
The changes in the conductivity and electron spin resonance intensity of polyaniline before and after reduction with temperature have been reported. The energy band gap E_g of polyaniline after reduction is 0.252 eV which was obtained from the plot of logσ vs.1/T, its unpaired electron density is approximately 1.84×10~(23)m~(-3) or 1.06×10~(20)kg~(-1), its conductivity-temperature relation is given by σ_t= σ_(20)-9.17×10~(-4) (20-t) S.m~(-1). The conductivity of polyaniline before reduction decreases with rising temperature above 20 ℃ and increases with rising temperature below 20 ℃. Its unpaired electron density is approximately 2.55×10~(27)m~(-3) or 1.47×10~(24)kg~(-1). The density and peak-peak linewidth ΔH_(p-p) of the electron spin resonance of both forms of polyaniline change with temperature. Each of susceptibility of polyaniline before reduction is zero at the different temperatures.
The changes in the conductivity and electron spin resonance intensity of polyaniline before and after reduction with temperature have been reported. The energy band gap E_g of polyaniline after reduction is 0.252 eV which was obtained from the plot of logσ vs.1/T, its unpaired electron density is approximately 1.84×10~(23)m~(-3) or 1.06×10~(20)kg~(-1), its conductivity-temperature relation is given by σ_t= σ_(20)-9.17×10~(-4) (20-t) S.m~(-1). The conductivity of polyaniline before reduction decreases with rising temperature above 20 ℃ and increases with rising temperature below 20 ℃. Its unpaired electron density is approximately 2.55×10~(27)m~(-3) or 1.47×10~(24)kg~(-1). The density and peak-peak linewidth ΔH_(p-p) of the electron spin resonance of both forms of polyaniline change with temperature. Each of susceptibility of polyaniline before reduction is zero at the different temperatures.
1988, 4(01): 20-26
doi: 10.3866/PKU.WHXB19880105
Abstract:
The crystal and molecular structures of 2,3-dihydro-5,6-dipenylpyrazine (C_(16)H_(14)N_2) and its complex with silver nitrate AgNO_3(C_(16)H_(14)N_2)_2 were determined by CAD4 single crystal diffractometer, using graphite monochromated Mo-Kα radiation. The crystallographic data are: (1) C_(16)H_(14)N_2, monoclinic, P2_1/n, α=0.5685(3), b=0.7928(1), c=2.7261(8) nm, β=95.02(6)°, V=1.2287 nm, z=4. (2) AgNO_3 (C_(16)H_(14)N_2)_2, monoclinic, A_2, α=0.5655(3), b=0.7791(2), c=3.0502(5) nm, β=94.90(2)°, V=1.3355 nm, z=2.
The structure of (1) was solved by direct method and (2) by heavy atom method. The full matrix least squares refinement for (1) with isotripic thermal parameters for H atoms and anisotropic for the others was converged at R=0.031, and R_W=0.033, the refinement for (2), excluding H atoms, at R=0.033 and R_W=0.028. In the structure of C_(16)H_(14)N_2, bond lengths and angles are not unexpected, and dihedral angles between pyrazine ring plane and each plane of the two phenyls are 151.9° and 136.7° respectively. In the structure of AgNO_3 (C_(16)H_(14)N_2)_2, the Ag atom is positioned on a 2-fold axis, and coordinated by two N and four O atons to form a severely distorted octahedron, the distance Ag(1)—O(1) is 2.828, Ag(1)—O(2) 2.520, and Ag(1)—N(31) 0.2399 nm. The conformation of the C_(16)H_(14)N_2 molecule in the complex was compared with that of the free ligand.
The crystal and molecular structures of 2,3-dihydro-5,6-dipenylpyrazine (C_(16)H_(14)N_2) and its complex with silver nitrate AgNO_3(C_(16)H_(14)N_2)_2 were determined by CAD4 single crystal diffractometer, using graphite monochromated Mo-Kα radiation. The crystallographic data are: (1) C_(16)H_(14)N_2, monoclinic, P2_1/n, α=0.5685(3), b=0.7928(1), c=2.7261(8) nm, β=95.02(6)°, V=1.2287 nm, z=4. (2) AgNO_3 (C_(16)H_(14)N_2)_2, monoclinic, A_2, α=0.5655(3), b=0.7791(2), c=3.0502(5) nm, β=94.90(2)°, V=1.3355 nm, z=2.
The structure of (1) was solved by direct method and (2) by heavy atom method. The full matrix least squares refinement for (1) with isotripic thermal parameters for H atoms and anisotropic for the others was converged at R=0.031, and R_W=0.033, the refinement for (2), excluding H atoms, at R=0.033 and R_W=0.028. In the structure of C_(16)H_(14)N_2, bond lengths and angles are not unexpected, and dihedral angles between pyrazine ring plane and each plane of the two phenyls are 151.9° and 136.7° respectively. In the structure of AgNO_3 (C_(16)H_(14)N_2)_2, the Ag atom is positioned on a 2-fold axis, and coordinated by two N and four O atons to form a severely distorted octahedron, the distance Ag(1)—O(1) is 2.828, Ag(1)—O(2) 2.520, and Ag(1)—N(31) 0.2399 nm. The conformation of the C_(16)H_(14)N_2 molecule in the complex was compared with that of the free ligand.
1988, 4(01): 27-31
doi: 10.3866/PKU.WHXB19880106
Abstract:
(1) The effect of pH on the cyclic voltammogram of platinum in HClO_4 containing HCOOH and HCOONa mixture was observed. The results show that the shape of the cyclic voltammogram of platinum is similar in all cases, but the peak potentials decrease with the increase of pH (see Fig.2). In addition, the oxidation peak for cathodic sweep consists of two sub-oxidation peaks which overlap each other and their current curves are coadjacent(see Fig.4).
(2) The experiment suggested by Razaq and Pletcher for the comparison between the rates of the electrooxidation of HCOOH and DCOOH on platinum was repeated. The results are coincident essentially, that is, there is a noticeable isotopic effect (see Fig.5).
(3) The experiment of pre-adsorption of formic acid in situ shown in the PTS in Fig.6 was programmed. It appears that the peak current for the first oxidation peak in i-E profile in creases after pre-adsorption, but decreases with the increase of pre-adsorbed time.
(4) According to the facts mentioned above, we suggest that a dissociative adsorption of formic acid on platinum surface takes place by cleaving a O—H bond, and an adsorbed intermediate HCOO_(ad) which behaves as the multiple adsorbed states is formed. The ordinary oxidation of formic acid (i.e. making on mention of formation and oxidation for the strongly adsorbed intermedites) on platinum anode proceeds via the reaction sequence(3).
(1) The effect of pH on the cyclic voltammogram of platinum in HClO_4 containing HCOOH and HCOONa mixture was observed. The results show that the shape of the cyclic voltammogram of platinum is similar in all cases, but the peak potentials decrease with the increase of pH (see Fig.2). In addition, the oxidation peak for cathodic sweep consists of two sub-oxidation peaks which overlap each other and their current curves are coadjacent(see Fig.4).
(2) The experiment suggested by Razaq and Pletcher for the comparison between the rates of the electrooxidation of HCOOH and DCOOH on platinum was repeated. The results are coincident essentially, that is, there is a noticeable isotopic effect (see Fig.5).
(3) The experiment of pre-adsorption of formic acid in situ shown in the PTS in Fig.6 was programmed. It appears that the peak current for the first oxidation peak in i-E profile in creases after pre-adsorption, but decreases with the increase of pre-adsorbed time.
(4) According to the facts mentioned above, we suggest that a dissociative adsorption of formic acid on platinum surface takes place by cleaving a O—H bond, and an adsorbed intermediate HCOO_(ad) which behaves as the multiple adsorbed states is formed. The ordinary oxidation of formic acid (i.e. making on mention of formation and oxidation for the strongly adsorbed intermedites) on platinum anode proceeds via the reaction sequence(3).
1988, 4(01): 32-36
doi: 10.3866/PKU.WHXB19880107
Abstract:
The ~(13)C and ~1H NMR spectra of antitumor alkaloid platinum complexes such as caffeine, theophylline and theobromine platinum (Ⅱ)complexes were recorded. The ~1H, ~(13)C chemical shifts and carbon-hydrogen coupling constants were obtained for these alkaloids and their platinum complexes. Comparing the variations of δ_H and δ_C in the ligands before and after coordination and combining with the determination of carbon-platinum and hydrogen-platinum coupling constants, we find that the alkaloids coordinate to platinum unidentately, the coordination site is the double bond nitrogen atom on the five membered imidazole ring. The platinum (II) is coordinated with three chloride anions and one alkaloid ligand to form a mononuclear complex anion (PtLCl_3)~-. By heteronuclear proton selected decoupling technique, all the ~1H and ~(13)C NMR spectral lines were assigned.
The ~(13)C and ~1H NMR spectra of antitumor alkaloid platinum complexes such as caffeine, theophylline and theobromine platinum (Ⅱ)complexes were recorded. The ~1H, ~(13)C chemical shifts and carbon-hydrogen coupling constants were obtained for these alkaloids and their platinum complexes. Comparing the variations of δ_H and δ_C in the ligands before and after coordination and combining with the determination of carbon-platinum and hydrogen-platinum coupling constants, we find that the alkaloids coordinate to platinum unidentately, the coordination site is the double bond nitrogen atom on the five membered imidazole ring. The platinum (II) is coordinated with three chloride anions and one alkaloid ligand to form a mononuclear complex anion (PtLCl_3)~-. By heteronuclear proton selected decoupling technique, all the ~1H and ~(13)C NMR spectral lines were assigned.
1988, 4(01): 37-43
doi: 10.3866/PKU.WHXB19880108
Abstract:
The reducibility of hydrocarbon-steam reforming catalysts has been studies by temperature programmed reduction (TPR) method. We found that the reduction mechanism of these catalysts is in accordance with nucleation model. The interaction between nickel and other components present in catalysts affects their reduction property. Addition of M and cement into those catalysts lead to an increase in their reduction temperature. A decrease in reduction temperature, however, has been observed by adding rare earth oxides.
The reduction kinetic parameters of Ni catalysts with or without CeO_2 have been obtained from the peak analysis of their TPR curves. It has been found that CeO_2 promotes the reduction process by decreasing its activation energy. There is a od correlation between the reduction activation energy and the degree of dispersion of Ni, the higher the dispersion, the lower the activation energy. A mechanism of the promoting effect on reduction by CeO_2 has been suggested.
The reducibility of hydrocarbon-steam reforming catalysts has been studies by temperature programmed reduction (TPR) method. We found that the reduction mechanism of these catalysts is in accordance with nucleation model. The interaction between nickel and other components present in catalysts affects their reduction property. Addition of M and cement into those catalysts lead to an increase in their reduction temperature. A decrease in reduction temperature, however, has been observed by adding rare earth oxides.
The reduction kinetic parameters of Ni catalysts with or without CeO_2 have been obtained from the peak analysis of their TPR curves. It has been found that CeO_2 promotes the reduction process by decreasing its activation energy. There is a od correlation between the reduction activation energy and the degree of dispersion of Ni, the higher the dispersion, the lower the activation energy. A mechanism of the promoting effect on reduction by CeO_2 has been suggested.
1988, 4(01): 44-49
doi: 10.3866/PKU.WHXB19880109
Abstract:
The oxidation of hydroxylamine by 12-tungstocobalt (Ⅲ) ate (Co(Ⅲ)W) in the acetate buffer solution has been investigated. It was found that the reaction proceeds in the presence of some metal ions, especially Fe (Ⅲ). The stoichiometry of the reaction catalyzed by Fe(Ⅲ) has been estimated bromatometrically and a kinetic study has been performed spectrophotometrically in the pH range 3.9-5.0. The empirical rate equation of the reaction is
-(d[Co(III)W])/dt=k(∑[Fe(III)]+c)∑[NH_2OH])[H~+]~(-1)
when concn. of Fe(Ⅲ) is less than 3×10~(-6)mol L~(-1). The value of k is 4.2×10~(-3)s~(-1) at 293 K and C=1.3×10~(-7)mol L~(-1). Over the temperature range 293—323 K, the values of the activation parameters of the reaction have evaluated. A mechanism of the catalyzed reaction in accordance with the rate law has been suggested.
The oxidation of hydroxylamine by 12-tungstocobalt (Ⅲ) ate (Co(Ⅲ)W) in the acetate buffer solution has been investigated. It was found that the reaction proceeds in the presence of some metal ions, especially Fe (Ⅲ). The stoichiometry of the reaction catalyzed by Fe(Ⅲ) has been estimated bromatometrically and a kinetic study has been performed spectrophotometrically in the pH range 3.9-5.0. The empirical rate equation of the reaction is
-(d[Co(III)W])/dt=k(∑[Fe(III)]+c)∑[NH_2OH])[H~+]~(-1)
when concn. of Fe(Ⅲ) is less than 3×10~(-6)mol L~(-1). The value of k is 4.2×10~(-3)s~(-1) at 293 K and C=1.3×10~(-7)mol L~(-1). Over the temperature range 293—323 K, the values of the activation parameters of the reaction have evaluated. A mechanism of the catalyzed reaction in accordance with the rate law has been suggested.
1988, 4(01): 50-56
doi: 10.3866/PKU.WHXB19880110
Abstract:
Ti/RuO_2+TiO_2 and Ti/SnO_2+CuCo_2O_4 anodes were used to study oxygen evolution in alkaline solutions and to compare the kinetics on both electrodes.On both electrodes the existence of two Tafel regions are confirmed. At low cd's ψ/lgi=2.303RT/(1+β)F and at high cd's it is 2.303RT/βF.On Ti/SnO_2+CuCo_2O_4 electrodes the reaction order with respect to α_(OH)- is 1 in the/low cd region. For the high cd region the reaction orders are 0.33 and 1 in concentrated alkaline and dilute alkaline solutions respectively.
On Ti/RuO_2+TiO_2 electrodes, the reaction order with respect to a_W a_(OH~-) is 1 in the low cd region. For the high cd region, the reaction order with respect to a_W is 1 in concentrated alkaline solutions, and the reaction order with respect to a_(OH~-) is 0.1~0.5 in dilute alkaline solutions.
The kinetic data obtained show that the rate determing stept of anodic evolution of oxygen are
RuO_2·OH_(ads)+H_2O→RuO(OH)~+_3+e
and (SOH)~(n+)_(ads)→(SOH)~((n+1)+)_(ads)+e
on Ti/RuO_2+TiO_2 electrode and Ti/SnO_2+CuCo_2O_4 electrode, respectively.
Ti/RuO_2+TiO_2 and Ti/SnO_2+CuCo_2O_4 anodes were used to study oxygen evolution in alkaline solutions and to compare the kinetics on both electrodes.On both electrodes the existence of two Tafel regions are confirmed. At low cd's ψ/lgi=2.303RT/(1+β)F and at high cd's it is 2.303RT/βF.On Ti/SnO_2+CuCo_2O_4 electrodes the reaction order with respect to α_(OH)- is 1 in the/low cd region. For the high cd region the reaction orders are 0.33 and 1 in concentrated alkaline and dilute alkaline solutions respectively.
On Ti/RuO_2+TiO_2 electrodes, the reaction order with respect to a_W a_(OH~-) is 1 in the low cd region. For the high cd region, the reaction order with respect to a_W is 1 in concentrated alkaline solutions, and the reaction order with respect to a_(OH~-) is 0.1~0.5 in dilute alkaline solutions.
The kinetic data obtained show that the rate determing stept of anodic evolution of oxygen are
RuO_2·OH_(ads)+H_2O→RuO(OH)~+_3+e
and (SOH)~(n+)_(ads)→(SOH)~((n+1)+)_(ads)+e
on Ti/RuO_2+TiO_2 electrode and Ti/SnO_2+CuCo_2O_4 electrode, respectively.
1988, 4(01): 57-63
doi: 10.3866/PKU.WHXB19880111
Abstract:
The reaction mechanism of the homogeneous prolysis of β-propiolactone (3-oxetanone) was studied by means of ab initio SCF MO method with 3-2lG basis set. There are two possible reaction channels:
C_2H_4+CO_2(1)←CH_2—C—O—CH_2→(2)CH_2=C=O+H_2CO
The geometries of the reactant, transition states and products of (1) and (2) have been optiminzed by energy gradient technique. Second order Mφller-Plesset perturbation (MP2) calculations were carried out at the HF optimized geometries to obtain better energetics. The activation barriers are 116.0 and 302.0 kJ mol~(-1) for (1) and (2) respectively. From the results of calculations it can be seen that pyrolysis must chiefly proceed via the reaction path (1). This conclusion is in accordance with experimental observations.
The reaction mechanism of the homogeneous prolysis of β-propiolactone (3-oxetanone) was studied by means of ab initio SCF MO method with 3-2lG basis set. There are two possible reaction channels:
C_2H_4+CO_2(1)←CH_2—C—O—CH_2→(2)CH_2=C=O+H_2CO
The geometries of the reactant, transition states and products of (1) and (2) have been optiminzed by energy gradient technique. Second order Mφller-Plesset perturbation (MP2) calculations were carried out at the HF optimized geometries to obtain better energetics. The activation barriers are 116.0 and 302.0 kJ mol~(-1) for (1) and (2) respectively. From the results of calculations it can be seen that pyrolysis must chiefly proceed via the reaction path (1). This conclusion is in accordance with experimental observations.
1988, 4(01): 64-70
doi: 10.3866/PKU.WHXB19880112
Abstract:
Any axilally symmetric ESR powder pattern can be divided into several component curves.Each of them has only one step and one divergence peak. According to this idea, approximate expressions for the powder pattern based on a delta line shape of an individual crystallite are presented and ones based on a Lorentzian line shape are also derived.The calculated spectra for powder K_3CrO_3 and CuTAPP are in od agreemant with experimental ones.
Any axilally symmetric ESR powder pattern can be divided into several component curves.Each of them has only one step and one divergence peak. According to this idea, approximate expressions for the powder pattern based on a delta line shape of an individual crystallite are presented and ones based on a Lorentzian line shape are also derived.The calculated spectra for powder K_3CrO_3 and CuTAPP are in od agreemant with experimental ones.
1988, 4(01): 71-73
doi: 10.3866/PKU.WHXB19880113
Abstract:
XPS studies show that ceric sulfate seems to be a mixed valent compound. The ground state is considered as a mixture of two configurations, i.e. 4f~0 and 4f~1. The products of thermal decomposition of ceric sulfate and hence the valence of cerium are related to temperature. For example, after heating Ce(SO_4)_2·4H_2O at temperature between 250 ℃ and 700 ℃ for 2 hours, cerous sulfate (or probably also cerous oxysulfates) were formed. After heating at 800 ℃ for 2 hours, Ce(SO_4)_2·4H_2O was ultimately decomposed into CeO_2.
XPS studies show that ceric sulfate seems to be a mixed valent compound. The ground state is considered as a mixture of two configurations, i.e. 4f~0 and 4f~1. The products of thermal decomposition of ceric sulfate and hence the valence of cerium are related to temperature. For example, after heating Ce(SO_4)_2·4H_2O at temperature between 250 ℃ and 700 ℃ for 2 hours, cerous sulfate (or probably also cerous oxysulfates) were formed. After heating at 800 ℃ for 2 hours, Ce(SO_4)_2·4H_2O was ultimately decomposed into CeO_2.
1988, 4(01): 74-76
doi: 10.3866/PKU.WHXB19880114
Abstract:
The emission spectra of BiO has been first obtained by studying the reaction: Bi+O_2(~1△_g)in the atomic-beam apparatus. 22 new bands has been obtained from the emission spectra of BiO (A ~2Π_g) which are attributed to the collisional energy transfer process of BiO(X,v)+O_2(b ~1Σ_g~+). The O_2(b ~1Σ_g~+) is produced by the following process: O_2(~1△_g)+O_2(~1△_g)→O_2(b ~1Σ_g~+)+O_2(X ~3Σ_g~-).
The emission spectra of BiO has been first obtained by studying the reaction: Bi+O_2(~1△_g)in the atomic-beam apparatus. 22 new bands has been obtained from the emission spectra of BiO (A ~2Π_g) which are attributed to the collisional energy transfer process of BiO(X,v)+O_2(b ~1Σ_g~+). The O_2(b ~1Σ_g~+) is produced by the following process: O_2(~1△_g)+O_2(~1△_g)→O_2(b ~1Σ_g~+)+O_2(X ~3Σ_g~-).
1988, 4(01): 77-79
doi: 10.3866/PKU.WHXB19880115
Abstract:
The emission spectra of BiO(A ~2Π_(1/2)) have been first obtained by studying the reaction Bi+N_2O in the heat pipe oven. 18 new bands are obtained from the emission spectra of BiO(A ~2Π_(1/2)) which are attributed to the reaction of atomic Bi~*(~2D_(3/2)) with N_2O(~1Σ_g~+). The metastable Bi~*(~2D_(3/2)) is produced by the following processes: Bi(~4S_(3/2))+N_2O(~1Σ_g~+)→BiO(X_2~2Π_(3/2)), and then,BiO(X_2~2Π_(3/2))+Bi(~4S_(3/2))→Bi~*(~2D_(3/2))+BiO(X_1~2Π_(1/2)).
The emission spectra of BiO(A ~2Π_(1/2)) have been first obtained by studying the reaction Bi+N_2O in the heat pipe oven. 18 new bands are obtained from the emission spectra of BiO(A ~2Π_(1/2)) which are attributed to the reaction of atomic Bi~*(~2D_(3/2)) with N_2O(~1Σ_g~+). The metastable Bi~*(~2D_(3/2)) is produced by the following processes: Bi(~4S_(3/2))+N_2O(~1Σ_g~+)→BiO(X_2~2Π_(3/2)), and then,BiO(X_2~2Π_(3/2))+Bi(~4S_(3/2))→Bi~*(~2D_(3/2))+BiO(X_1~2Π_(1/2)).
1988, 4(01): 80-83
doi: 10.3866/PKU.WHXB19880116
Abstract:
The crystal and molecular structure of the title compound has been determined by CAD4 single crystal diffractometer, using graphite monochromated Mo-K_α radiation. The crystal belongs to monoclinic system with space group P2_1α and crystallography data: α=0.7667(2), b=1.4802(8), c=0.8676(1) nm, β=101.46(2)°, V=0.965 nm, z=2. The molecular formula of the compocnd is Co(SCN)_2.C_(14)H_(26)O_4N_2, and M=525.58.
The crystal structure was solved by heavy atom method and refined by full matrix least squares with isotropic thermal parameters for H atoms and anisotropic for the others, using 1847 unique reflections having I>3σ. The final discrepancy factors R=0.041, R_w=0.037.
The crystal consists of discrete isolated molecules. The molecule is crystallographically centrosymmetric as shown in Fig.1. The Co atom is coordinated by two O and four N atoms octahedrally. The bond lengths Co-N(2) is 2.165, Co-N(1) 2.039 and Co-O(1) 0.2295 nm. The conformation of the ligand molecules in the complex was found to be significantly diffrent with those for the free ligand.
The crystal and molecular structure of the title compound has been determined by CAD4 single crystal diffractometer, using graphite monochromated Mo-K_α radiation. The crystal belongs to monoclinic system with space group P2_1α and crystallography data: α=0.7667(2), b=1.4802(8), c=0.8676(1) nm, β=101.46(2)°, V=0.965 nm, z=2. The molecular formula of the compocnd is Co(SCN)_2.C_(14)H_(26)O_4N_2, and M=525.58.
The crystal structure was solved by heavy atom method and refined by full matrix least squares with isotropic thermal parameters for H atoms and anisotropic for the others, using 1847 unique reflections having I>3σ. The final discrepancy factors R=0.041, R_w=0.037.
The crystal consists of discrete isolated molecules. The molecule is crystallographically centrosymmetric as shown in Fig.1. The Co atom is coordinated by two O and four N atoms octahedrally. The bond lengths Co-N(2) is 2.165, Co-N(1) 2.039 and Co-O(1) 0.2295 nm. The conformation of the ligand molecules in the complex was found to be significantly diffrent with those for the free ligand.
1988, 4(01): 84-87
doi: 10.3866/PKU.WHXB19880117
Abstract:
Method of cyclic voltammetry for static systems has been modified through its recording system in order to apply it to follow the oscillating change of concentrations of some species in a chemical oscillation reaction. In this paper, oscillation of the concentration of bromide-ion in Melonic-acid-KBrO_2-H_2SO_4-MnSO_4 systems was followed by this modified method. It was found that, for systems investigated in this paper, the bromide-ion concentrations oscillate in the range of IO~(-4) mol dm~(-3) which is 1-2 orders of magnitude higher than that observed by the bromide-ion selective electrode. A frozen-titration method for bromide-ion was also used to check the result which was found to be in agreement with that of the modified method.
Method of cyclic voltammetry for static systems has been modified through its recording system in order to apply it to follow the oscillating change of concentrations of some species in a chemical oscillation reaction. In this paper, oscillation of the concentration of bromide-ion in Melonic-acid-KBrO_2-H_2SO_4-MnSO_4 systems was followed by this modified method. It was found that, for systems investigated in this paper, the bromide-ion concentrations oscillate in the range of IO~(-4) mol dm~(-3) which is 1-2 orders of magnitude higher than that observed by the bromide-ion selective electrode. A frozen-titration method for bromide-ion was also used to check the result which was found to be in agreement with that of the modified method.
1988, 4(01): 88-91
doi: 10.3866/PKU.WHXB19880118
Abstract:
The equilibium constants of acid-base interaction between Mi(Octyl_dtp)_2 and alkylamine were determined by GLC method at several temperatures. Thermodynamic parameters △H and △S were evaluted as follows:
ethylamine: △H=-11.5kJ mol~(-1) △S=-22.7J K~(-1) mol~(-1)
diethylamine: △H=-18.1kJ mol~(-1) △S=-42.1J K~(-1) mol~(-1)
The variations of logK versus temperature fit following equations:
ethylamine: lgK=-1.19+598.9/T
diethylamine: lgK=-2.20+945.6/T
The equilibium constants of acid-base interaction between Mi(Octyl_dtp)_2 and alkylamine were determined by GLC method at several temperatures. Thermodynamic parameters △H and △S were evaluted as follows:
ethylamine: △H=-11.5kJ mol~(-1) △S=-22.7J K~(-1) mol~(-1)
diethylamine: △H=-18.1kJ mol~(-1) △S=-42.1J K~(-1) mol~(-1)
The variations of logK versus temperature fit following equations:
ethylamine: lgK=-1.19+598.9/T
diethylamine: lgK=-2.20+945.6/T
1988, 4(01): 92-97
doi: 10.3866/PKU.WHXB19880119
Abstract:
We present the optothermal and optoacoustic spectra of CF_3Br in TEA CO_2 laser 00°1—02°0 R branch. Three absorption peaks has been observed at R(14) line (1074.6 cm~(-1)), R(18) line (1077.3cm~(-1)), and R(22) line (1079.9cm~(-1)) respectively. The peak at R(22) coincides with the position of P branch of CF_3Br linear IR spectrum, but two peaks at R(14) and R(18) can be interpreted as the hot bands.
We also studied the multiphoton dissociation of CF_3Br and carbon isotope seperation.
We present the optothermal and optoacoustic spectra of CF_3Br in TEA CO_2 laser 00°1—02°0 R branch. Three absorption peaks has been observed at R(14) line (1074.6 cm~(-1)), R(18) line (1077.3cm~(-1)), and R(22) line (1079.9cm~(-1)) respectively. The peak at R(22) coincides with the position of P branch of CF_3Br linear IR spectrum, but two peaks at R(14) and R(18) can be interpreted as the hot bands.
We also studied the multiphoton dissociation of CF_3Br and carbon isotope seperation.
1988, 4(01): 98-107
Abstract:
