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1987 Volume 3 Issue 5
1987, 3(05): 449-452
doi: 10.3866/PKU.WHXB19870501
Abstract:
The principle of structure correlation is applied to 28 crystal structures which contain 44 different five-coordinate molybdenum fragments. The data derived map the reaction pathway for a bimolecular ligand substitution reaction at tetrahedral molybdenum centers. The dihedral-angle method from Muetterties and Guggenberger is employed in order to describe the interconversion between the tri nal bipyramidal (TBP) and the square pyramidal (SQP) conformations via the Berry pseudorotation mechanism in the system of Mo(L)_5 complexes. This structure correlation method provides a convincing mapping of the Berry pathway in this paper.
The principle of structure correlation is applied to 28 crystal structures which contain 44 different five-coordinate molybdenum fragments. The data derived map the reaction pathway for a bimolecular ligand substitution reaction at tetrahedral molybdenum centers. The dihedral-angle method from Muetterties and Guggenberger is employed in order to describe the interconversion between the tri nal bipyramidal (TBP) and the square pyramidal (SQP) conformations via the Berry pseudorotation mechanism in the system of Mo(L)_5 complexes. This structure correlation method provides a convincing mapping of the Berry pathway in this paper.
1987, 3(05): 453-455
doi: 10.3866/PKU.WHXB19870502
Abstract:
Bis(trinitroethyl-N-nitro) ethane (BTNE) is a compound that decomposes thermally in solid state. We have reported the first study of thermal decomposition of crystals of BTNE prepared through various methods of recrystallization. In this work nonisothermal kinetics of the decomposition of BTNE crystals(10 samples)was investigated in more detail.
The unpurified samples of BTNE prepared in laboratory were recrystallized respectively from acetic acid glacial, absolute alcohol, nitromethane, dichloroethane, acetone, butanone or distilled water and ten samples of BTNE were prepared for investigation.
Nonisothermal kinetics study on these crystals was carried on with a Rigaku TG-2000 Thermal Analizer. DSC curves with various heating rates (φ=1.25, 2.50, 5.0, 10.0 ℃·min~(-1))were treated mathematically with equations of Kissinger H.E. and Ozawa T. for the evaluation of the aqqarent energy of activation (E) and then with that of Rogers R.N. and Smith L.C. for the evaluation of the pre-exponen-tial factor (A). In Table 1 the values of E and A for various crystalline samples of BTNE are demonstrated.
On the basis of values of E and A in Table 1 the reaction constants of rate (k) at 120 ℃ are calculated as listed in Table 2. The data in Table 2 show that there exist great differences of k value among samples of BTNE. For example, at 120 ℃ the difference of k between BT-8 and BT-5 amounts to more than two orders of magnitude. Based on these properties, one can evaluate, regulate and control the thermal stability of crystalline BTNE for for its processing and storage. It appears that the phenomenon above mentioned depeds upon the solutility of BTNE in solvent and conditions of recrystallization. The large the value of k, the higher the solubility of BTNE in the pertinent solvent. The four kinds of BTNE having the highest value of k are prepared by method of fast recrystallization. The process of recrystallizaion may change the reactivity of crystalline BTNE.
Generally speaking, process of recrystallization may influence the crystal modification or habit of solids, meanwhile crystals with diversified modification or habit show different reactivity. It is therefore necessary to study the properties of crystals of BTNE prepared by different methods of recrystallization.
Bis(trinitroethyl-N-nitro) ethane (BTNE) is a compound that decomposes thermally in solid state. We have reported the first study of thermal decomposition of crystals of BTNE prepared through various methods of recrystallization. In this work nonisothermal kinetics of the decomposition of BTNE crystals(10 samples)was investigated in more detail.
The unpurified samples of BTNE prepared in laboratory were recrystallized respectively from acetic acid glacial, absolute alcohol, nitromethane, dichloroethane, acetone, butanone or distilled water and ten samples of BTNE were prepared for investigation.
Nonisothermal kinetics study on these crystals was carried on with a Rigaku TG-2000 Thermal Analizer. DSC curves with various heating rates (φ=1.25, 2.50, 5.0, 10.0 ℃·min~(-1))were treated mathematically with equations of Kissinger H.E. and Ozawa T. for the evaluation of the aqqarent energy of activation (E) and then with that of Rogers R.N. and Smith L.C. for the evaluation of the pre-exponen-tial factor (A). In Table 1 the values of E and A for various crystalline samples of BTNE are demonstrated.
On the basis of values of E and A in Table 1 the reaction constants of rate (k) at 120 ℃ are calculated as listed in Table 2. The data in Table 2 show that there exist great differences of k value among samples of BTNE. For example, at 120 ℃ the difference of k between BT-8 and BT-5 amounts to more than two orders of magnitude. Based on these properties, one can evaluate, regulate and control the thermal stability of crystalline BTNE for for its processing and storage. It appears that the phenomenon above mentioned depeds upon the solutility of BTNE in solvent and conditions of recrystallization. The large the value of k, the higher the solubility of BTNE in the pertinent solvent. The four kinds of BTNE having the highest value of k are prepared by method of fast recrystallization. The process of recrystallizaion may change the reactivity of crystalline BTNE.
Generally speaking, process of recrystallization may influence the crystal modification or habit of solids, meanwhile crystals with diversified modification or habit show different reactivity. It is therefore necessary to study the properties of crystals of BTNE prepared by different methods of recrystallization.
1987, 3(05): 456-459
doi: 10.3866/PKU.WHXB19870503
Abstract:
It has been found that the rate constant of thermal decomposition for various crystals of bis(trinitroethyl-N-nitro) ethane (BTNE) is quite different and, in effect, this difference in reactivity depends upon the process of recrystallization of the crystals. In this paper the crystal properties of BTNE have been investigated with such techniques as differential scanning calorimetry (DSC), X-ray powder diffraction and electronic scanning microscope (SEM). Each crystal modification shows a characteristic X-ray diffraction diagram and the transformation of one modification into another causes an endothermic peak on the curve of DSC. However, the DSC curves show that before the appearence of exothermic peak of de-composition the endothermic peak was not found for all samples of BTNE. The results of X-ray diffraction study of BTNE show an identical diffraction diagram. It demonstrates that the crystal modifications of the samples of BTNE are same.
The pictures taken with SEM for crystals of BTNE show fairly different crystal form and surface dislocations. In Fig.2, 3, 4, three typical SEM pictures of BTNE are illustrated. Fig.2 is a picture of BT-5. At a magnification of 6000X the crystal size of BT-5 is quite small, the crystal form is rectangular and rather tidy, and the surface of crystals is rather smooth. Fig.3 is a picture of BT-6. On the surface of crystal BT-6 many streak-form dislocations exist. There are distinct differences when compared with the surface of BT-5. Fig.4 is a picture of BT-3. The crystals of BT-3 look like brokendecaying pieces of wooden logs and on the end of crystal appear a lot of dislocations. Comparing the crystal form and dislocation with the corresponding curves of DSC, it has been seen that the crystals of BTNE having a smooth surface decompose slowly; on the contrry, crystals with rough surfaces dislocation decompose more quickly. In Table 1 the comparison of crystal properties with rate constant of thermal decomposition (at 120 ℃) is demonstrated.
It appears that the factors influencing the reactivity of various crystals of BTNE are the existence and degree of surface dislocation. From a view of solid reaction, the reaction of thermal decomposition for crystalline BTNE begins on the inter- or intrasurfaces. Reaction centres appear more readily at the places of surface dislocations. This means that crystals with more disloctions decompose quite easily and will demonstrate high rate constant of reaction. With a control over the recry-stllizing operation one can prepare BTNE crystals possessing various reactivities. Such peculiarities of crystalline BTNE as here descri bed seem to be worthy of further study.
It has been found that the rate constant of thermal decomposition for various crystals of bis(trinitroethyl-N-nitro) ethane (BTNE) is quite different and, in effect, this difference in reactivity depends upon the process of recrystallization of the crystals. In this paper the crystal properties of BTNE have been investigated with such techniques as differential scanning calorimetry (DSC), X-ray powder diffraction and electronic scanning microscope (SEM). Each crystal modification shows a characteristic X-ray diffraction diagram and the transformation of one modification into another causes an endothermic peak on the curve of DSC. However, the DSC curves show that before the appearence of exothermic peak of de-composition the endothermic peak was not found for all samples of BTNE. The results of X-ray diffraction study of BTNE show an identical diffraction diagram. It demonstrates that the crystal modifications of the samples of BTNE are same.
The pictures taken with SEM for crystals of BTNE show fairly different crystal form and surface dislocations. In Fig.2, 3, 4, three typical SEM pictures of BTNE are illustrated. Fig.2 is a picture of BT-5. At a magnification of 6000X the crystal size of BT-5 is quite small, the crystal form is rectangular and rather tidy, and the surface of crystals is rather smooth. Fig.3 is a picture of BT-6. On the surface of crystal BT-6 many streak-form dislocations exist. There are distinct differences when compared with the surface of BT-5. Fig.4 is a picture of BT-3. The crystals of BT-3 look like brokendecaying pieces of wooden logs and on the end of crystal appear a lot of dislocations. Comparing the crystal form and dislocation with the corresponding curves of DSC, it has been seen that the crystals of BTNE having a smooth surface decompose slowly; on the contrry, crystals with rough surfaces dislocation decompose more quickly. In Table 1 the comparison of crystal properties with rate constant of thermal decomposition (at 120 ℃) is demonstrated.
It appears that the factors influencing the reactivity of various crystals of BTNE are the existence and degree of surface dislocation. From a view of solid reaction, the reaction of thermal decomposition for crystalline BTNE begins on the inter- or intrasurfaces. Reaction centres appear more readily at the places of surface dislocations. This means that crystals with more disloctions decompose quite easily and will demonstrate high rate constant of reaction. With a control over the recry-stllizing operation one can prepare BTNE crystals possessing various reactivities. Such peculiarities of crystalline BTNE as here descri bed seem to be worthy of further study.
1987, 3(05): 460-464
doi: 10.3866/PKU.WHXB19870504
Abstract:
Low energy (1.5 KeV) ISS is a surface sensitive technique for identification of element on the top layer of material. The energy losses of primary particle during the collision in low energy ISS technique are assumed to be completely kinetic, i.e. the electronic interaction energy transfer is generally small and will be neglected. In this paper, however, the electronic effect is measurable for certain supported oxide or halide catalysts by improved experimental technique. The shift of scatter- ing He~+ peak due to electronic effect is remarkable and different for Mo in MoO_3/TiO_2, MoO_3/γ-Al_2O_3, MoO_3/SiO_2 and Cu in CuO/γ-Al-2O_3, CuCl/γ-Al_2O_3. The corresponding “mass increment” was calculated by the binary collision approach. We find out that the “mass increment” may characterize the interaction between active component and carrier in supported catalysts. Thus, low energy ISS is not only a od tool for surface elemental analysis but also an effective probe for chemical information of surface species.
Low energy (1.5 KeV) ISS is a surface sensitive technique for identification of element on the top layer of material. The energy losses of primary particle during the collision in low energy ISS technique are assumed to be completely kinetic, i.e. the electronic interaction energy transfer is generally small and will be neglected. In this paper, however, the electronic effect is measurable for certain supported oxide or halide catalysts by improved experimental technique. The shift of scatter- ing He~+ peak due to electronic effect is remarkable and different for Mo in MoO_3/TiO_2, MoO_3/γ-Al_2O_3, MoO_3/SiO_2 and Cu in CuO/γ-Al-2O_3, CuCl/γ-Al_2O_3. The corresponding “mass increment” was calculated by the binary collision approach. We find out that the “mass increment” may characterize the interaction between active component and carrier in supported catalysts. Thus, low energy ISS is not only a od tool for surface elemental analysis but also an effective probe for chemical information of surface species.
1987, 3(05): 465-467
doi: 10.3866/PKU.WHXB19870505
Abstract:
A new microcalorimetric method has been developed for identifying the en- dgenous cells and resting cells with od accuracy. The method was applied to the identification of E. Coli successfully, The thermogram curves generated during the non-growth metabolism of E. Coli were obtained under the different experimental conditions. These results may be very significant for the studies on microbiology and biochemistry.
A new microcalorimetric method has been developed for identifying the en- dgenous cells and resting cells with od accuracy. The method was applied to the identification of E. Coli successfully, The thermogram curves generated during the non-growth metabolism of E. Coli were obtained under the different experimental conditions. These results may be very significant for the studies on microbiology and biochemistry.
1987, 3(05): 468-473
doi: 10.3866/PKU.WHXB19870506
Abstract:
The 403-700 nm emission spectrum observed in ArF laser photolysis of stibine was recorded for the first time and was assigned to the SbH_2 (Ã~2A_1→X~2B_1) transi- tion. More than fifty emission lines arising from the transitions of Sb (6s→5p) were also observed.
The 403-700 nm emission spectrum observed in ArF laser photolysis of stibine was recorded for the first time and was assigned to the SbH_2 (Ã~2A_1→X~2B_1) transi- tion. More than fifty emission lines arising from the transitions of Sb (6s→5p) were also observed.
1987, 3(05): 474-478
doi: 10.3866/PKU.WHXB19870507
Abstract:
Using LIF technique, the distribution of vibrational temperature of I_2 along a supersonic jet axis has been measured, He, Ar and N_2 are used as carrier gases, The vibrational relaxation cross-section has been estimated, based on the “sudden freeze” model. The classical Landau-Teller theory can not be used to explicate that phenomenon: the vibrational relaxation cross-section become larger in low temperature. The mechanism of vibrational relaxation in jets has been analysed with the “orbiting resonance” model qualitatively.
Using LIF technique, the distribution of vibrational temperature of I_2 along a supersonic jet axis has been measured, He, Ar and N_2 are used as carrier gases, The vibrational relaxation cross-section has been estimated, based on the “sudden freeze” model. The classical Landau-Teller theory can not be used to explicate that phenomenon: the vibrational relaxation cross-section become larger in low temperature. The mechanism of vibrational relaxation in jets has been analysed with the “orbiting resonance” model qualitatively.
1987, 3(05): 479-484
doi: 10.3866/PKU.WHXB19870508
Abstract:
An improved scanning micro reference electrode (SMRE) technique controlled by micro-computer was used to study the pitting initiation in early stage of 18/8 stainless steel in chloride containning solution. It is shown that there exsists a critical potential E_r which characterizes the breakdown of passive film and initia- tion of the micropit corrosion in an early stage of pitting corrosion. The potential value of E_r is usually 100—400 mV less than the pitting potential E_p which corre- sponds to rapid increase of anodiccurrent in the polarization curve. The value of E_r is related closely to the surface states of specimens. On increasing the content of Cl~- and H~+ ions in solution, E_r will become more negative. when the potential is controlled in the vicinity of E_r, the micropit cannot grow to a macropit corrosion generally.
The new concept of “unstable micropitting” was suggested and the physical significance of the characteristic potential of E_r and E_p was expounded according to the experimental facts. Furthermore, the mechanism of local breakdown of passive film and pitting initiation of 18/8 stainless steel in chloride containing solution was also discussed in this paper.
An improved scanning micro reference electrode (SMRE) technique controlled by micro-computer was used to study the pitting initiation in early stage of 18/8 stainless steel in chloride containning solution. It is shown that there exsists a critical potential E_r which characterizes the breakdown of passive film and initia- tion of the micropit corrosion in an early stage of pitting corrosion. The potential value of E_r is usually 100—400 mV less than the pitting potential E_p which corre- sponds to rapid increase of anodiccurrent in the polarization curve. The value of E_r is related closely to the surface states of specimens. On increasing the content of Cl~- and H~+ ions in solution, E_r will become more negative. when the potential is controlled in the vicinity of E_r, the micropit cannot grow to a macropit corrosion generally.
The new concept of “unstable micropitting” was suggested and the physical significance of the characteristic potential of E_r and E_p was expounded according to the experimental facts. Furthermore, the mechanism of local breakdown of passive film and pitting initiation of 18/8 stainless steel in chloride containing solution was also discussed in this paper.
1987, 3(05): 485-490
doi: 10.3866/PKU.WHXB19870509
Abstract:
The crystal structure of the title compound was determined by single crystal X-ray diffraction analysis. The intensity data were collected on an Enraf-Nonius CAD_4 diffractometer with MoK_a radiation, The space group is Cmca with a= 1.3938(1), b=1.6350(2), c=1.61 nm, Z=4, D_c=2.588 g/cm~3, μ=38.115 cm~(-1). The positions of all Mo and As atoms were determined by direct method.The others of the non-H atoms were revealed by difference Fourier synthe- sis. The structure was refined by full-matrix least squares procedure to a final R value of 0.047.
The molecule of the title compound consists of anion, (n-C_3H_7As)_2Mo_6O_(24)~(4-), and four caions CN_3H_6~+. In the anion, six distorted octahedra MoO_6 join together to form a six membered ring, which is capped, top and bottom, by the C_3H_7As groups as a cage. The center of anionis at a special position of symmetry 2/m. The bond angles of O—Mo—O change regularly with different coordinated O atoms. There are many hydrogen bonds betweem the cations and anions throughout the whole crystal. Thus, each anion relates twelve neighbouring ones.
The crystal structure of the title compound was determined by single crystal X-ray diffraction analysis. The intensity data were collected on an Enraf-Nonius CAD_4 diffractometer with MoK_a radiation, The space group is Cmca with a= 1.3938(1), b=1.6350(2), c=1.61 nm, Z=4, D_c=2.588 g/cm~3, μ=38.115 cm~(-1). The positions of all Mo and As atoms were determined by direct method.The others of the non-H atoms were revealed by difference Fourier synthe- sis. The structure was refined by full-matrix least squares procedure to a final R value of 0.047.
The molecule of the title compound consists of anion, (n-C_3H_7As)_2Mo_6O_(24)~(4-), and four caions CN_3H_6~+. In the anion, six distorted octahedra MoO_6 join together to form a six membered ring, which is capped, top and bottom, by the C_3H_7As groups as a cage. The center of anionis at a special position of symmetry 2/m. The bond angles of O—Mo—O change regularly with different coordinated O atoms. There are many hydrogen bonds betweem the cations and anions throughout the whole crystal. Thus, each anion relates twelve neighbouring ones.
1987, 3(05): 491-500
doi: 10.3866/PKU.WHXB19870510
Abstract:
The Synthesis, character and crystal structure of La(NO_3)_3·3Ph_3PO·C_2H_5OH· CHCl_3 has been presented in this paper. Crystal and molecular structure has been determined by single-crystal X-ray diffraction techniques with a four circle diffrac- tometer. The crystal is monoclinic with space group P2_1/n. The unit cell parameters are: a=1.3111(5) nm Z=4 b=2.5075(10) nm F(000)=2687.65 c=1.8725(6) nm μ(MoKa)=9.83 cm~(-1) β=98.53(3)° d_(cal.)=1.45 gcm~(-3) V=6.088 nm d_(lab.)=1.43 gcm~(-3) 8022 independent diffaraction data has been collected, of which 3362 observable independent reflections were used for structure refinement to a final R value of 0.08. The lanthanum atom is coordinated by nine oxygen atoms, of which six from three bidentate nitrate groups and the others from from three Ph_3PO each. The average bond length of La—O is 0.2549 nm.
1987, 3(05): 501-507
doi: 10.3866/PKU.WHXB19870511
Abstract:
The reversible cell without liquid junction consists of the sodium ion glass- electrode and fluoride or chloride selective electrodes respectively, namely
Na~+ glass-electrode | MX(m) |
| w or s | X~- selective electrode
The standard electromotive forces of the cells have been measured in NaF- H_2O-Dioxan and NaCl-H_2O-Dioxan systems, then the standard Gibbs energies of transfer of NaF and NaCI from water to Dioxan-Water mixtures and the activity coefficients have been calculated.
The measured values of △E°_t for NaCl-H_2O-Dioxan systems have been compared with literature results. It indicated that the use of ion selective electrodes to study the thermodynamics of solution is reliable, also, the results of this paper have been compared with those of previous works. This influences of solvents on ΔG_t° have also been discussed.
The reversible cell without liquid junction consists of the sodium ion glass- electrode and fluoride or chloride selective electrodes respectively, namely
Na~+ glass-electrode | MX(m) |
| w or s | X~- selective electrode
The standard electromotive forces of the cells have been measured in NaF- H_2O-Dioxan and NaCl-H_2O-Dioxan systems, then the standard Gibbs energies of transfer of NaF and NaCI from water to Dioxan-Water mixtures and the activity coefficients have been calculated.
The measured values of △E°_t for NaCl-H_2O-Dioxan systems have been compared with literature results. It indicated that the use of ion selective electrodes to study the thermodynamics of solution is reliable, also, the results of this paper have been compared with those of previous works. This influences of solvents on ΔG_t° have also been discussed.
1987, 3(05): 508-513
doi: 10.3866/PKU.WHXB19870512
Abstract:
The ternary system BaO-B_2O_3-GeO_2 (BaO≤50 mol%) has been investigated by means of X-ray diffraction and DTA techniques, The phase diagram of the room temperature section of BaO-B_2O_3-GeO_2 (BaO≤50 mol%) system has been established and a new ternary compound Ba_3B_6Ge_2O_(16)(3BaO·3B_2O_3·2GeO_2) has been found. The phase diagrams of the pseudo-binary system in this ternary system: BaB_2O_4-BaGeO_3; BaB_2O_4-Ba_3B_6Ge_2O_(16); BaGeO_3-Ba_3B_6Ge_2O_(16) have been studied, all of which are eu- tectic system. The eutectic reactions occur at 875±3 ℃; 937±3 ℃; 879±3 ℃ respectively, and the compositions are (BaO)_(0.50)(B_2O_3)_(0.27)(GeO_2)_(0.23); (BaO)_(0.42)(B_2O_3)_(0.42) (GeO_2)_(0.16); (BaO)_(0.42)(B_2O_3)_(0.24)(GeO_2)_(0.34) respectively. The pseudoternary system BaB_2O_4-BeGeO_3-Ba_3B_6Ge_2O_(16) is also a eutectic system. The ternary eutectic temperature is 870±3 ℃ and the composition is (BaO)_(0.46)(B_2O_3)_(0.27)(GeO_2)_(0.27).
The ternary system BaO-B_2O_3-GeO_2 (BaO≤50 mol%) has been investigated by means of X-ray diffraction and DTA techniques, The phase diagram of the room temperature section of BaO-B_2O_3-GeO_2 (BaO≤50 mol%) system has been established and a new ternary compound Ba_3B_6Ge_2O_(16)(3BaO·3B_2O_3·2GeO_2) has been found. The phase diagrams of the pseudo-binary system in this ternary system: BaB_2O_4-BaGeO_3; BaB_2O_4-Ba_3B_6Ge_2O_(16); BaGeO_3-Ba_3B_6Ge_2O_(16) have been studied, all of which are eu- tectic system. The eutectic reactions occur at 875±3 ℃; 937±3 ℃; 879±3 ℃ respectively, and the compositions are (BaO)_(0.50)(B_2O_3)_(0.27)(GeO_2)_(0.23); (BaO)_(0.42)(B_2O_3)_(0.42) (GeO_2)_(0.16); (BaO)_(0.42)(B_2O_3)_(0.24)(GeO_2)_(0.34) respectively. The pseudoternary system BaB_2O_4-BeGeO_3-Ba_3B_6Ge_2O_(16) is also a eutectic system. The ternary eutectic temperature is 870±3 ℃ and the composition is (BaO)_(0.46)(B_2O_3)_(0.27)(GeO_2)_(0.27).
1987, 3(05): 514-519
doi: 10.3866/PKU.WHXB19870513
Abstract:
The adsorption and desoption of oxygen on Ag and Ag-Pd alloy surfaces have been investigated by AES, TDS and by the continuous measurement of work func- tion change. Two kinds of different adsorbed bonding configurations have been revealed: The adsorbed atomic oxygen increases the surface work function, which is due to the transfer of electron from metal to adsorbate, forming the O_(ads)~(-δ) species. For the saturated surface of Ag and Ag-Pd alloy the dipole moment per adsorbed oxygen is 0.24 and 0.34 Debye respectively. The adsorption of molecular oxygen leads to a decrease of work function, which can be explained with the electron feedback from the metal surfaces to molecular oxygen species. Work function change as a function of the exposure of oxygen was also obtained. From these data an approximate experimental sticking coefficient has been derived by using the expression: S=K·P~(-1)·dΔφ/dt. It is shown that the sticking coefficient of oxygen on Ag-Pd alloy surface is slightly less than that on Ag surface, which implies that the alloying of Ag and Pd decreases the surface activity. A continuous change of surface composition for Ag-Pd alloy has been realized by using ar n ion bombardment and subsequently annealing. A conclusion has been reached that both the transformation of the surface structure from disorder to order and the surface enrichment of silver during the annealing of alloy result in the decrease of surface work function.
The adsorption and desoption of oxygen on Ag and Ag-Pd alloy surfaces have been investigated by AES, TDS and by the continuous measurement of work func- tion change. Two kinds of different adsorbed bonding configurations have been revealed: The adsorbed atomic oxygen increases the surface work function, which is due to the transfer of electron from metal to adsorbate, forming the O_(ads)~(-δ) species. For the saturated surface of Ag and Ag-Pd alloy the dipole moment per adsorbed oxygen is 0.24 and 0.34 Debye respectively. The adsorption of molecular oxygen leads to a decrease of work function, which can be explained with the electron feedback from the metal surfaces to molecular oxygen species. Work function change as a function of the exposure of oxygen was also obtained. From these data an approximate experimental sticking coefficient has been derived by using the expression: S=K·P~(-1)·dΔφ/dt. It is shown that the sticking coefficient of oxygen on Ag-Pd alloy surface is slightly less than that on Ag surface, which implies that the alloying of Ag and Pd decreases the surface activity. A continuous change of surface composition for Ag-Pd alloy has been realized by using ar n ion bombardment and subsequently annealing. A conclusion has been reached that both the transformation of the surface structure from disorder to order and the surface enrichment of silver during the annealing of alloy result in the decrease of surface work function.
1987, 3(05): 520-524
doi: 10.3866/PKU.WHXB19870514
Abstract:
Nomatter for its industrial usefulness or theoretical importance as a very con- vient way to study thermodynamic behavior of the salt in a binary solution, the gas-liquid equilibrium data of tenary system with salt as one of components are of values. Actually a lot of isobaric data has been collected, however the isothermal data are very few. In this paper the isothermal data of CH_3OH-H_2O-LiCl, C_2H_5OH- H_2O-LiCl, CH_3COCH_3-H_2O-LiCl and CH_3COCH_8-H_2O-K_2CO_3 systems has been repor- ted and used to discuss the salt solvation. The equipment was designed by ourselves which the acuracy istested by measuring the data of corresponding binary systems without salt, the results proves to be quite satifactory.
We correlated the data using the three parameter Margules formula, where the parameters are determined by Barker′s method. It is desired that one can get the solvated properties from the gas-liquid equilibrium data, Ohe was the first one who proposed a formulism to get the prefer solvated numbers from the gas-liquid data. However for many organic-water-salt system, the solvated numbers from Ohe′s theory is negative in some region. We developed a similar theory for the isothermal data, the calculated solvated numbers are reasonable.
Nomatter for its industrial usefulness or theoretical importance as a very con- vient way to study thermodynamic behavior of the salt in a binary solution, the gas-liquid equilibrium data of tenary system with salt as one of components are of values. Actually a lot of isobaric data has been collected, however the isothermal data are very few. In this paper the isothermal data of CH_3OH-H_2O-LiCl, C_2H_5OH- H_2O-LiCl, CH_3COCH_3-H_2O-LiCl and CH_3COCH_8-H_2O-K_2CO_3 systems has been repor- ted and used to discuss the salt solvation. The equipment was designed by ourselves which the acuracy istested by measuring the data of corresponding binary systems without salt, the results proves to be quite satifactory.
We correlated the data using the three parameter Margules formula, where the parameters are determined by Barker′s method. It is desired that one can get the solvated properties from the gas-liquid equilibrium data, Ohe was the first one who proposed a formulism to get the prefer solvated numbers from the gas-liquid data. However for many organic-water-salt system, the solvated numbers from Ohe′s theory is negative in some region. We developed a similar theory for the isothermal data, the calculated solvated numbers are reasonable.
1987, 3(05): 525-528
doi: 10.3866/PKU.WHXB19870515
Abstract:
Cathodic polarization curves has been measured by means of rotating disc and ring-disc electrodes in cupric pyrophosphate solution. Monovalence pyrophosphoric complex of copper has been detected as intermediate of reduction process. Influence of electrode potential on formation of the intermediate has been observed. By means of rotating disc methode the kinetic current of reduction process has been estamited. It has been found that in more negative potential range contribution of kinetic control yet is appreciable. Based on the polt I_(lim)/ω~(1/2)vs.I_(lim) existence of a preceding chemical process has been evidenced. The following reaction mechanism is proposed
[Cu(P_2O_7)_2]~(6-) <=> [Cu(P_2O_7)]~(2-)+P_2O_7~(4-)
[Cu(P_2O_7)]~(2-)→[Cu(P_2O_7)]~(3-)→Cu+P_2P_7~(4-)
Cathodic polarization curves has been measured by means of rotating disc and ring-disc electrodes in cupric pyrophosphate solution. Monovalence pyrophosphoric complex of copper has been detected as intermediate of reduction process. Influence of electrode potential on formation of the intermediate has been observed. By means of rotating disc methode the kinetic current of reduction process has been estamited. It has been found that in more negative potential range contribution of kinetic control yet is appreciable. Based on the polt I_(lim)/ω~(1/2)vs.I_(lim) existence of a preceding chemical process has been evidenced. The following reaction mechanism is proposed
[Cu(P_2O_7)_2]~(6-) <=> [Cu(P_2O_7)]~(2-)+P_2O_7~(4-)
[Cu(P_2O_7)]~(2-)→[Cu(P_2O_7)]~(3-)→Cu+P_2P_7~(4-)
1987, 3(05): 529-533
doi: 10.3866/PKU.WHXB19870516
Abstract:
The formation constant (K) and thermodynamic parameters (ΔC.ΔH.ΔS) in reactions in which complexes of adenosine triphosphate with magnesium ion and calcium ion are formed have been obtained by a microcalorimetric method.
All experimentes were made at 30 ℃, pH=8.0 and at ionic strength μ=0.2 mol L~(-1). Measured experimental values indicate that complex formation reactions are driven by the entropic factor.
1987, 3(05): 534-538
doi: 10.3866/PKU.WHXB19870517
Abstract:
A new teflon isothermal dilution calorimeter for measuring excess enthalpies of liquid mixtures is described. The calorimeter has been checked by the excess ent- halpies of binary systems of cyclohexane+hexane, benzene+dichloromethane and acetone+water at 298.15 K, The results indicate that this calorimenter is applicable to both endothermic and exothermic excess enthalpy measurements.
A new teflon isothermal dilution calorimeter for measuring excess enthalpies of liquid mixtures is described. The calorimeter has been checked by the excess ent- halpies of binary systems of cyclohexane+hexane, benzene+dichloromethane and acetone+water at 298.15 K, The results indicate that this calorimenter is applicable to both endothermic and exothermic excess enthalpy measurements.
1987, 3(05): 539-543
doi: 10.3866/PKU.WHXB19870518
Abstract:
In this paper, the author deduced the Gradation Rule of the Conjugated Homo- logs E=a+b/N from the Linear Rule of the Homolo us Energy Factor E=a+b((2k-1)/k)sin(kπ/(2N+1)) and acquired a new Homolo us Function E=a+b(2k-1)/(N+1/2), which is better than Gradation Rule of the Conjugated Homologs. Five formulas of Linear Rule resently reported were tested and compared by using 96 series of data of photo-electron spectroscopy and 159 series of data of electren spectroscopy. The author holds that the Linear Rule of the Homol us Energy Factor is better.
In this paper, the author deduced the Gradation Rule of the Conjugated Homo- logs E=a+b/N from the Linear Rule of the Homolo us Energy Factor E=a+b((2k-1)/k)sin(kπ/(2N+1)) and acquired a new Homolo us Function E=a+b(2k-1)/(N+1/2), which is better than Gradation Rule of the Conjugated Homologs. Five formulas of Linear Rule resently reported were tested and compared by using 96 series of data of photo-electron spectroscopy and 159 series of data of electren spectroscopy. The author holds that the Linear Rule of the Homol us Energy Factor is better.
1987, 3(05): 544-546
doi: 10.3866/PKU.WHXB19870519
Abstract:
In this paper the properties of the sigma-phase of Fe-Cr alloy have been stu- died at 109 K and 718 K by calorimetry. At 1093 K the σ→a phase transformn enthalpies are different from reported values~[4] and at 718 K the a→σ phase trans- formation enthalpies reported by no person have been obtained. The X-ray diffrac- tion experiments have been used to determine that no σ phase exists yet at room temperature.
In this paper the properties of the sigma-phase of Fe-Cr alloy have been stu- died at 109 K and 718 K by calorimetry. At 1093 K the σ→a phase transformn enthalpies are different from reported values~[4] and at 718 K the a→σ phase trans- formation enthalpies reported by no person have been obtained. The X-ray diffrac- tion experiments have been used to determine that no σ phase exists yet at room temperature.
1987, 3(05): 547-550
doi: 10.3866/PKU.WHXB19870520
Abstract:
In the present paper, Na_2SO_4-Al_2(SO_4)_3-H_2O system has been studied by ~(23)Na and ~(27)Al NMR quantitative method. It has been shown that the existence of double salt can be easily identified by this method.
In the present paper, Na_2SO_4-Al_2(SO_4)_3-H_2O system has been studied by ~(23)Na and ~(27)Al NMR quantitative method. It has been shown that the existence of double salt can be easily identified by this method.
THE CHARGE-TRANSFER COMPLEXES OF POLY (N-VINYL-CARBAZOLE) AND NITROFLUORENONES IN DIFFERENT SOLVENTS
1987, 3(05): 551-554
doi: 10.3866/PKU.WHXB19870521
Abstract:
The charge-transfer complexes of poly(N-vinylcarbazole) (Mn=7200) and nitro- fluorenones were studied with VPO in different solvents. The relationship between equilibrium constant and solvent dipole moment was examined. The results obtained from polymer and model compound were compared, and the reason of their difference was explained. The relationship between the equilibrium constant and the molecular weight was given:
InK_(CT)=InK_(CT)~∞+2M_0/M(InK°-InK~∞)
The charge-transfer complexes of poly(N-vinylcarbazole) (Mn=7200) and nitro- fluorenones were studied with VPO in different solvents. The relationship between equilibrium constant and solvent dipole moment was examined. The results obtained from polymer and model compound were compared, and the reason of their difference was explained. The relationship between the equilibrium constant and the molecular weight was given:
InK_(CT)=InK_(CT)~∞+2M_0/M(InK°-InK~∞)
1987, 3(05): 555-559
doi: 10.3866/PKU.WHXB19870522
Abstract:
Tri-n-butyl-phosphate (TBP) is one of the important extractants and widely used in solvent extraction of chemical industry. But the thermodynamic properties of molecular interaction between water and TBP is an unsolved question in the extraction process. In this paper, association constant K_c of water and TBP, ΔG° of the association reaction have been studied by means of dielectric polarization measurement. The limiting values of molecular polarizability and dipole moments of TBP and TBP. H_2O in benzene have also been obtained.
Tri-n-butyl-phosphate (TBP) is one of the important extractants and widely used in solvent extraction of chemical industry. But the thermodynamic properties of molecular interaction between water and TBP is an unsolved question in the extraction process. In this paper, association constant K_c of water and TBP, ΔG° of the association reaction have been studied by means of dielectric polarization measurement. The limiting values of molecular polarizability and dipole moments of TBP and TBP. H_2O in benzene have also been obtained.
