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1991 Volume 7 Issue 5
1991, 7(05): 513-517
doi: 10.3866/PKU.WHXB19910501
Abstract:
Thermally induced phase separation in the mixture of poly (methyl methacrylate) (PMMA) with poly (styrene-co-acrylonitrile) (SAN) has been studied with pulsed nuclear magnetic resonance(NMR). It is shown that the single spin-lattice relaxation time T_1 of the compatible mixture splitted into two T_1 corresponding to those of PMMA-rich and SAN-rich domains. Meanwhile, both T_1 gradually changing with annealing time provides the direct evidence that the phase separation takes place with a spinodal decomposition mechanism. Diffusion coefficient was estimated to be negative, indicating an uphill diffusion characteristics. The basic parameters verning its kinetics were estimated using NMR data which were in od agreement with those evaluated from time-resolved light scattering experiments for a 60/40(PMMA/SAN) mixture annealed at 180.0 ℃.
Thermally induced phase separation in the mixture of poly (methyl methacrylate) (PMMA) with poly (styrene-co-acrylonitrile) (SAN) has been studied with pulsed nuclear magnetic resonance(NMR). It is shown that the single spin-lattice relaxation time T_1 of the compatible mixture splitted into two T_1 corresponding to those of PMMA-rich and SAN-rich domains. Meanwhile, both T_1 gradually changing with annealing time provides the direct evidence that the phase separation takes place with a spinodal decomposition mechanism. Diffusion coefficient was estimated to be negative, indicating an uphill diffusion characteristics. The basic parameters verning its kinetics were estimated using NMR data which were in od agreement with those evaluated from time-resolved light scattering experiments for a 60/40(PMMA/SAN) mixture annealed at 180.0 ℃.
1991, 7(05): 518-523
doi: 10.3866/PKU.WHXB19910502
Abstract:
This paper described a detailed theoretical analysis of ESR spectrum line width of the cobalt complex (RC_2R/)Co(CO)(PR"_3)_2 in solution. Triple-jump kinetic model was first used in the Trans-Cis isomerism of the complex.A formula concerning ESR line width as a function of the basic line width T_(20)~(-1), hyperfine splitting constants of all isomers in solution, and lifetime of the exchange of ligand PR"_3 were suggested on the relationship between the correlation function and the hyperfine splitting constant. The calculated, exchange lifetime of the ligand P(OEt)_3 in the title complex (Ph_2C_2)Co(CO)[P(OEt)_3]_2 at 290 K is 5.6×10~(-11) s.
This paper described a detailed theoretical analysis of ESR spectrum line width of the cobalt complex (RC_2R/)Co(CO)(PR"_3)_2 in solution. Triple-jump kinetic model was first used in the Trans-Cis isomerism of the complex.A formula concerning ESR line width as a function of the basic line width T_(20)~(-1), hyperfine splitting constants of all isomers in solution, and lifetime of the exchange of ligand PR"_3 were suggested on the relationship between the correlation function and the hyperfine splitting constant. The calculated, exchange lifetime of the ligand P(OEt)_3 in the title complex (Ph_2C_2)Co(CO)[P(OEt)_3]_2 at 290 K is 5.6×10~(-11) s.
1991, 7(05): 524-530
doi: 10.3866/PKU.WHXB19910503
Abstract:
A kinematic viscosity equation is suggested for capillary viscometers. The equation shows od accuracy in a wide range of viscosity as well as the Reynolds number:
v=η/ρ=At-Bt~(-1)+C
where v is the kinematic viscosity, t is the efflux time, and A,B,C are instrumental constants. The terms of -Bt~(-1) and C are corres ρ onding to the kinetic energy correction and the drainage correction respectively.
In order to simplify the calculation, a linear [η]～[η]~* correlation has been found, where [η] and [η]~* denote the accurate and the approximate (based on ...
A kinematic viscosity equation is suggested for capillary viscometers. The equation shows od accuracy in a wide range of viscosity as well as the Reynolds number:
v=η/ρ=At-Bt~(-1)+C
where v is the kinematic viscosity, t is the efflux time, and A,B,C are instrumental constants. The terms of -Bt~(-1) and C are corres ρ onding to the kinetic energy correction and the drainage correction respectively.
In order to simplify the calculation, a linear [η]～[η]~* correlation has been found, where [η] and [η]~* denote the accurate and the approximate (based on ...
1991, 7(05): 531-535
doi: 10.3866/PKU.WHXB19910504
Abstract:
The rate constants of catalytic reaction of ferrocyanide-ascorbic acid and ferrocyanide-histidine system were determined by transmitted spectroelectrochemistry using a group of cyclindrical microelectrodes. It is the first time to find that the reaction can still be considered as the pseudo-first-order reaction when the concentration of ascorbic acid or histidine is close to and even slightly lower than the concentration of ferrocyanide. The determined rate constants are in agreement with the reported values. A reasonable explaination was given.
The rate constants of catalytic reaction of ferrocyanide-ascorbic acid and ferrocyanide-histidine system were determined by transmitted spectroelectrochemistry using a group of cyclindrical microelectrodes. It is the first time to find that the reaction can still be considered as the pseudo-first-order reaction when the concentration of ascorbic acid or histidine is close to and even slightly lower than the concentration of ferrocyanide. The determined rate constants are in agreement with the reported values. A reasonable explaination was given.
Collision-Induced Rotational Energy Transfer in Small Molecules by Double Resonance MPI Spectroscopy
1991, 7(05): 536-542
doi: 10.3866/PKU.WHXB19910505
Abstract:
Collision-induced rotational energy transfer in the A~2Σ~+(v=0) state of NO has been measured by two-color double resonance-multiphoton ionization spectroscopy. Rotationally resolved relaxation spectra have been obtained for initial rotational levels N_i=1,7,13. The state-to-state rotational energy transfer rate constants have been determined from the experimental spectra by means of the rate equations under single collision approximation. The rate constant decreases with increasing rotational-quantum-number change ΔN. Exponential- and power-gap scaling laws have been used to analyze the experimental results and it has been found that the power-law fitting is better than the exponential-law fitting, especially for N_i=1. It has to be pointed out that the relaxation spectra from different initial ortational levels cannot be fitted well with a single set of parameters for either energy-based law. This results indicates that in addition to the energy gap some factors related to molecular rotation, e.g. the rotation period to the collision time ratio, must be taken into consideration in the collision model in order to describe the rotational energy transfer in detail. Similar rotational relaxation spectrum has been observed in NO-Xe (1:4) collision system. R-T energy transfer is considered to be the dominant pathway in collision-induced energy transfer between NO* and NO molecules or between NO* molecule and Xe atom. In addition, the rotation relaxation in the B∏(O_u~+) state of I_2 has been studied by OODR-MPI and the observed spectral line broadening discussed.
Collision-induced rotational energy transfer in the A~2Σ~+(v=0) state of NO has been measured by two-color double resonance-multiphoton ionization spectroscopy. Rotationally resolved relaxation spectra have been obtained for initial rotational levels N_i=1,7,13. The state-to-state rotational energy transfer rate constants have been determined from the experimental spectra by means of the rate equations under single collision approximation. The rate constant decreases with increasing rotational-quantum-number change ΔN. Exponential- and power-gap scaling laws have been used to analyze the experimental results and it has been found that the power-law fitting is better than the exponential-law fitting, especially for N_i=1. It has to be pointed out that the relaxation spectra from different initial ortational levels cannot be fitted well with a single set of parameters for either energy-based law. This results indicates that in addition to the energy gap some factors related to molecular rotation, e.g. the rotation period to the collision time ratio, must be taken into consideration in the collision model in order to describe the rotational energy transfer in detail. Similar rotational relaxation spectrum has been observed in NO-Xe (1:4) collision system. R-T energy transfer is considered to be the dominant pathway in collision-induced energy transfer between NO* and NO molecules or between NO* molecule and Xe atom. In addition, the rotation relaxation in the B∏(O_u~+) state of I_2 has been studied by OODR-MPI and the observed spectral line broadening discussed.
1991, 7(05): 543-548
doi: 10.3866/PKU.WHXB19910506
Abstract:
A new method, Solvated Metal Atom Impregnation (SMAI) technique, was em- ployed to prepare Fe/γ-Al_2O_3, Fe/SiO_2, Co/γ-Al_2O_3, Co/SiO_2, Ni/γ-Al_2O_3 and Ni/SiO_2 catalysts. The results of TEN, XRD and H_2 chemisorption measurements showed that the average particle dimensions of Fe, Co, Ni in these catalysts were <3.0 nm and the dispersions of the metals were >500%. The catalytic behavior of Fe/γ-Al_2O_3, Co/γ-Al_2O_3 and Ni/γ-Al_2O_3 for CO+H_2 reaction was studied. Hydrocarbon product distributions and specifie activities were determined. It showed that, as the H_2/CO ratio and reaction temperature increased, the percentage yield of higher molecular weight molecules decreased and methane formation was favored. The specific activites of these catalysts was in the order as Fe>Ni>Co.
A new method, Solvated Metal Atom Impregnation (SMAI) technique, was em- ployed to prepare Fe/γ-Al_2O_3, Fe/SiO_2, Co/γ-Al_2O_3, Co/SiO_2, Ni/γ-Al_2O_3 and Ni/SiO_2 catalysts. The results of TEN, XRD and H_2 chemisorption measurements showed that the average particle dimensions of Fe, Co, Ni in these catalysts were <3.0 nm and the dispersions of the metals were >500%. The catalytic behavior of Fe/γ-Al_2O_3, Co/γ-Al_2O_3 and Ni/γ-Al_2O_3 for CO+H_2 reaction was studied. Hydrocarbon product distributions and specifie activities were determined. It showed that, as the H_2/CO ratio and reaction temperature increased, the percentage yield of higher molecular weight molecules decreased and methane formation was favored. The specific activites of these catalysts was in the order as Fe>Ni>Co.
1991, 7(05): 549-552
doi: 10.3866/PKU.WHXB19910507
Abstract:
Based on the model of dipole orientation distribution presented in previous paper, the monolayer adsorption isotherm for solvent molecules at the interface of solid me- tal electrode wsa derived. The dependence of inner-layer differential capacity(C_1) on the surface charge density(σ) was estimated by curve-fitting for Ag(111), Ag(100) and Ag(110)/aqueous solution interface. The calculated results are shown. In analyzing the fitting parameters obtained from this treatment, it was found that the water molecules would preferentially be strongly adsorped on the top sites of (111)-plane, but would be on the hollow site at (110)-or(100)-plane. The high values of the inner-layer differential capacity for silver single crystal electrodes were interpreted in terms of those effects, i.e., the thickness of adsorption monolayer was diminished due to water molecules stably adsorbed on the hollow site of crystal face, and the influence of the interaction between metal and water molecules or between dipole-dipole of adsorbed molecules on the variation of potential drop acrossed the inner-layer with the surface charge at electrode.
Based on the model of dipole orientation distribution presented in previous paper, the monolayer adsorption isotherm for solvent molecules at the interface of solid me- tal electrode wsa derived. The dependence of inner-layer differential capacity(C_1) on the surface charge density(σ) was estimated by curve-fitting for Ag(111), Ag(100) and Ag(110)/aqueous solution interface. The calculated results are shown. In analyzing the fitting parameters obtained from this treatment, it was found that the water molecules would preferentially be strongly adsorped on the top sites of (111)-plane, but would be on the hollow site at (110)-or(100)-plane. The high values of the inner-layer differential capacity for silver single crystal electrodes were interpreted in terms of those effects, i.e., the thickness of adsorption monolayer was diminished due to water molecules stably adsorbed on the hollow site of crystal face, and the influence of the interaction between metal and water molecules or between dipole-dipole of adsorbed molecules on the variation of potential drop acrossed the inner-layer with the surface charge at electrode.
1991, 7(05): 553-557
doi: 10.3866/PKU.WHXB19910508
Abstract:
In this paper we report the method of calculating the positions and the size of the microscopic holes exist in condensed matter on the basis of the phase orbit obtained from the computer simulation. We have calculated lots of microscopic holes in LiCl system at different temperatures and have defined the radial distribution function of the microscopic holes to describe the statistical distribution of them better. We also have obtained the distribution character of the microscopic holes with different radii. In the paper we discuss the relationship among the volume of the microscopic holes, self-diffusion coefficient and shear viscosity as well.
In this paper we report the method of calculating the positions and the size of the microscopic holes exist in condensed matter on the basis of the phase orbit obtained from the computer simulation. We have calculated lots of microscopic holes in LiCl system at different temperatures and have defined the radial distribution function of the microscopic holes to describe the statistical distribution of them better. We also have obtained the distribution character of the microscopic holes with different radii. In the paper we discuss the relationship among the volume of the microscopic holes, self-diffusion coefficient and shear viscosity as well.
1991, 7(05): 558-565
doi: 10.3866/PKU.WHXB19910509
Abstract:
This paper proposes a new equation for the determination of the limiting slope of activity coefficient vs mole fraction (dlnγ_1/dx_1)_((x_1)→0) from gas chromatography measurements, the equation has been ri rously derived and is convenient to be applied. A method to predict the vapor liquid equilibrium of dilute solutions from the infinite dilute activity coefficient γ_1~∞ and (dlnγ_1/dx_1)_((x_1)→0) has also been presented by virtue of the activity coefficient models for dilute solutions proposed recently. The results of predictions for 7 systems are satisfactory in comparison with those from direct measurements by the GC method. Finally, our model for (dlnγ_1/dx_1)_((x_1)→0) is compared with that proposed by Valentin and Guiochon, and the results show that our model is a od improvement.
This paper proposes a new equation for the determination of the limiting slope of activity coefficient vs mole fraction (dlnγ_1/dx_1)_((x_1)→0) from gas chromatography measurements, the equation has been ri rously derived and is convenient to be applied. A method to predict the vapor liquid equilibrium of dilute solutions from the infinite dilute activity coefficient γ_1~∞ and (dlnγ_1/dx_1)_((x_1)→0) has also been presented by virtue of the activity coefficient models for dilute solutions proposed recently. The results of predictions for 7 systems are satisfactory in comparison with those from direct measurements by the GC method. Finally, our model for (dlnγ_1/dx_1)_((x_1)→0) is compared with that proposed by Valentin and Guiochon, and the results show that our model is a od improvement.
1991, 7(05): 566-570
doi: 10.3866/PKU.WHXB19910510
Abstract:
A method for the measurement of excess thermodynamic functions of ternary—— pseudobinary liquid mixtures
(1-x)[(1-y)A+yC]+x[(1-y)B+yC]
has been proposed. The excess volumes of two systems A=cyclohexane, B=benzene, C=toluene or methylcyclohexane have been measured at 298.15 K. Using vdW one-fluid approximation and the classical van der Waals equation, the vdW parameters of pure fluids have been evaluated by the least squares method from the V~E data of binary system. Moreover, the excess volumes of pseudobinary system can be calculated with appropriate vdW parameters of pure fluids. It has been found that the calculated values are in fairly od agreement with the experimental results.
A method for the measurement of excess thermodynamic functions of ternary—— pseudobinary liquid mixtures
(1-x)[(1-y)A+yC]+x[(1-y)B+yC]
has been proposed. The excess volumes of two systems A=cyclohexane, B=benzene, C=toluene or methylcyclohexane have been measured at 298.15 K. Using vdW one-fluid approximation and the classical van der Waals equation, the vdW parameters of pure fluids have been evaluated by the least squares method from the V~E data of binary system. Moreover, the excess volumes of pseudobinary system can be calculated with appropriate vdW parameters of pure fluids. It has been found that the calculated values are in fairly od agreement with the experimental results.
1991, 7(05): 571-576
doi: 10.3866/PKU.WHXB19910511
Abstract:
A method of constructing and computing the Voronoi polyhedron of every ion in the simulation unit cell extended with periodic boundary condition directly by definition without resorting to any similarity, so called successive cutting method is described. According to the phase orbit t by the simulation of LiCl system with molecular dynamics method and considering the periodic boundary condition, more than 20,000 Voronoi polyhedrons have been constucted and computed, At each of the following temperatures, 900 K, 698 K, 498 K and 298 K, we have calculated about 5,000 Voronoi polyhedrons. The results of statistical analysis of all information about these Voronoi polyhedrons including the number of side faces, volume, vertex, edge, and poly n of side face are reported. The statistical analysis shows clearly that different phase of the LiCl system possesses different character of the local structure. It merits our attention that at 298 K the distribution of the numbers of side faces of Voronoi polyhedrons is very concentrative. Therefore we define the coordinaton number of Li~+ ion and Cl~- ion by the volume and its component of the Voronoi polyhedron. The coordination number and its composition had baen evalua ted too.
A method of constructing and computing the Voronoi polyhedron of every ion in the simulation unit cell extended with periodic boundary condition directly by definition without resorting to any similarity, so called successive cutting method is described. According to the phase orbit t by the simulation of LiCl system with molecular dynamics method and considering the periodic boundary condition, more than 20,000 Voronoi polyhedrons have been constucted and computed, At each of the following temperatures, 900 K, 698 K, 498 K and 298 K, we have calculated about 5,000 Voronoi polyhedrons. The results of statistical analysis of all information about these Voronoi polyhedrons including the number of side faces, volume, vertex, edge, and poly n of side face are reported. The statistical analysis shows clearly that different phase of the LiCl system possesses different character of the local structure. It merits our attention that at 298 K the distribution of the numbers of side faces of Voronoi polyhedrons is very concentrative. Therefore we define the coordinaton number of Li~+ ion and Cl~- ion by the volume and its component of the Voronoi polyhedron. The coordination number and its composition had baen evalua ted too.
1991, 7(05): 577-581
doi: 10.3866/PKU.WHXB19910512
Abstract:
The UV/VIS spectra for pyridine solution of complexes [Fe_2MO(CH_3COO)_6Py_2]·Py and THF solution of complexes Fe_2MO(CCl_3COO)_6(THF)_3 were studied. The d-d transitions were assigned and the ligand field parameters(B,D_q,β) were calculated for the related metal ions according to ligand field theory (Tanabe-Sugano diagram) in terms of O_h symmetry and reasonably od fits were obtained for the calculated and observed frequencies. The calculated results show that (1) the larger the ionic potential for M~(2+) ion, the larger the values of B, D_q for Fe~(3+) ion (2) the ligand field parameters of metal ions vary in parallel with the electronagativity of R in RCOO~-.
1991, 7(05): 582-585
doi: 10.3866/PKU.WHXB19910513
Abstract:
The absorption spectra of 4-hydroxybenzylidene malononitrile in different solvent systems have been studied in this work. It was found that this compound has a proton equilibrium under the different pH condition that results in a variation of absorption spectra observed. Thereby, the title compound is expected to be used as a new acidic indicator in nonaqueous media.
The absorption spectra of 4-hydroxybenzylidene malononitrile in different solvent systems have been studied in this work. It was found that this compound has a proton equilibrium under the different pH condition that results in a variation of absorption spectra observed. Thereby, the title compound is expected to be used as a new acidic indicator in nonaqueous media.
1991, 7(05): 586-588
doi: 10.3866/PKU.WHXB19910514
Abstract:
An isoperibel calorimeter for measnring heat of solid-liquid, liquid-liquid reactions was developed. Rection vessel made by resisting hard glass, its volume is about 100 cm~3, The precisions of cotrolling and measuring the tempreture were±0.001 K and ±0.0001 K respectively. The measnring error was 0.5%. The measured enthalpy of solution KCl in water at 298.2 K was 17597±17 J·mol~(-1), enthalpy of reaction of THAM (from NBC-724a in USA) in 0.1000 mol·L~(-1) HCl at 298.2 K was -29779±16J·mol~(-1). The values are in well agreement with the published results. The relability of this calorimeter has been confirmed.
An isoperibel calorimeter for measnring heat of solid-liquid, liquid-liquid reactions was developed. Rection vessel made by resisting hard glass, its volume is about 100 cm~3, The precisions of cotrolling and measuring the tempreture were±0.001 K and ±0.0001 K respectively. The measnring error was 0.5%. The measured enthalpy of solution KCl in water at 298.2 K was 17597±17 J·mol~(-1), enthalpy of reaction of THAM (from NBC-724a in USA) in 0.1000 mol·L~(-1) HCl at 298.2 K was -29779±16J·mol~(-1). The values are in well agreement with the published results. The relability of this calorimeter has been confirmed.
1991, 7(05): 589-592
doi: 10.3866/PKU.WHXB19910515
Abstract:
The pyrrole can be seletively photoelectro-polymerized on substrates, such as Pt, Au, Ag, Cu(1), in neutral aqueous solutions. A clear light point polypyrrole film can be formed bellow the threshold set up for the electropolymerization of pyrrole under normal conditions. This kind of photocatalytic effect is of great interests in preparing the conductive polypyrrole pattern of metal parts, especially in the case of Cu(1) substrate.
The pyrrole can be seletively photoelectro-polymerized on substrates, such as Pt, Au, Ag, Cu(1), in neutral aqueous solutions. A clear light point polypyrrole film can be formed bellow the threshold set up for the electropolymerization of pyrrole under normal conditions. This kind of photocatalytic effect is of great interests in preparing the conductive polypyrrole pattern of metal parts, especially in the case of Cu(1) substrate.
1991, 7(05): 593-600
doi: 10.3866/PKU.WHXB19910516
Abstract:
1991, 7(05): 601-604
doi: 10.3866/PKU.WHXB19910517
Abstract:
In the previous articles~[1,2], a data processing method for studies on thermokinetics of a first order reaction in liquid phase had been developed. It was called the dimensionless parameter method, in which the dimensionless parameter and the rate constant of a reaction system were calculated from the thermogram's peak-area. In this paper in the light of a theoretical thermogram's equation of a first order reaction, a novel data processing method is proposed, in which the dimensionless parameter and the rate constant are calculated from the thermogram's peak-heights with-out using any peak-area. Thereby the problems arisen from the peak-area-computation can be avoided.
In order to test the validity of this novel method, ...
1991, 7(05): 605-608
doi: 10.3866/PKU.WHXB19910518
Abstract:
In this work mica powder was treated with n-butyl aldehyde plasma of radio frequency. Then the apparent contact angle of different liquids on the powder was determined by measuring the penetration rate of the liquid through the packed powder. The surface tension of mica powder and interface tension between the powder and typical linear macromolecules were calculated from the data of contact angle obtained under Fowkes' assumption. Rationalized conclusions were as follows: (i) For polar liquids, wetting of treated mica is more difficult than the untreated one and for nonpolar liquids, no difference has been observed. (ii) The surface tension of mica powder drops from 41.34 (N·m~(-1)·10~(-3)) to 31.51 after 5 min plasma treatment and to 25.59 (N·m~(-1)·10~(-3)) after 30 min plasma treatment. (iii) The polar component of interface tension between the mica powder and any linear macromolecule monotonically decreases with the time of plasma treating. However, the whole interface tension changes after plasma treatment, depending on the polymer used.
In this work mica powder was treated with n-butyl aldehyde plasma of radio frequency. Then the apparent contact angle of different liquids on the powder was determined by measuring the penetration rate of the liquid through the packed powder. The surface tension of mica powder and interface tension between the powder and typical linear macromolecules were calculated from the data of contact angle obtained under Fowkes' assumption. Rationalized conclusions were as follows: (i) For polar liquids, wetting of treated mica is more difficult than the untreated one and for nonpolar liquids, no difference has been observed. (ii) The surface tension of mica powder drops from 41.34 (N·m~(-1)·10~(-3)) to 31.51 after 5 min plasma treatment and to 25.59 (N·m~(-1)·10~(-3)) after 30 min plasma treatment. (iii) The polar component of interface tension between the mica powder and any linear macromolecule monotonically decreases with the time of plasma treating. However, the whole interface tension changes after plasma treatment, depending on the polymer used.
1991, 7(05): 609-612
doi: 10.3866/PKU.WHXB19910519
Abstract:
The electrodeposition of magnesium in dimethylformamide has been studied by means of galvanostatic method The overpotential has been recorded during constant current pulses with a duration time that permits only a few monolayers deposition per pulse The experiments were carried out under conditions aimed at reducing contamination of the electrode surface. The kinetics coefficients of electrodeposition of Mg have been measured. The electron transfer step in the electrodeposition of Mg is the ratedetermining step has been confirmed in this book.
The electrodeposition of magnesium in dimethylformamide has been studied by means of galvanostatic method The overpotential has been recorded during constant current pulses with a duration time that permits only a few monolayers deposition per pulse The experiments were carried out under conditions aimed at reducing contamination of the electrode surface. The kinetics coefficients of electrodeposition of Mg have been measured. The electron transfer step in the electrodeposition of Mg is the ratedetermining step has been confirmed in this book.
1991, 7(05): 613-617
doi: 10.3866/PKU.WHXB19910520
Abstract:
LKB8700 precision titration calorimeter has been improved and equipped with a microcomputer in our laboratory, which can be operated conveniently and automatically. Error analysis of titration calorimetry suggests that experiments can be performed accurately.
The improved and on-line calorimeter is especially suitable for investigation of oil-water-surfactant systems which are directly related to the enhanced oil recovery. The calorimetric system has been checked by means of measuring heat of dilution and heat of reaction of Tris (Trihydroxymethylaminomethane) with HCl. The result (-47.46 J·mol~(-1)) obtained agrees well with the literature's value.
LKB8700 precision titration calorimeter has been improved and equipped with a microcomputer in our laboratory, which can be operated conveniently and automatically. Error analysis of titration calorimetry suggests that experiments can be performed accurately.
The improved and on-line calorimeter is especially suitable for investigation of oil-water-surfactant systems which are directly related to the enhanced oil recovery. The calorimetric system has been checked by means of measuring heat of dilution and heat of reaction of Tris (Trihydroxymethylaminomethane) with HCl. The result (-47.46 J·mol~(-1)) obtained agrees well with the literature's value.
1991, 7(05): 618-622
doi: 10.3866/PKU.WHXB19910521
Abstract:
The heteronuclear cross-relaxation rates in polymers were determined by selective and conventional ~(13)C spin-lattice relaxation experiments, the proton-carbon distances were calculated by the theoretical formula, and two-dimensional NOE spectra of the polymers were also measured. The results showed that (1) the measured proton-carbon distances coincide with the distances from molecular models, (2) there is the observable dipolar cross-relaxation effect between the quaternary carbons and their neighboring protons, and (3) the optimum mixing times depend on the relaxation properties of the proton and carbon.
The heteronuclear cross-relaxation rates in polymers were determined by selective and conventional ~(13)C spin-lattice relaxation experiments, the proton-carbon distances were calculated by the theoretical formula, and two-dimensional NOE spectra of the polymers were also measured. The results showed that (1) the measured proton-carbon distances coincide with the distances from molecular models, (2) there is the observable dipolar cross-relaxation effect between the quaternary carbons and their neighboring protons, and (3) the optimum mixing times depend on the relaxation properties of the proton and carbon.
1991, 7(05): 623-626
doi: 10.3866/PKU.WHXB19910522
Abstract:
This paper presents a new analytical result between peak current (I_(max)) and sweep rate (v) by a mathematieal model of porous growing layer on the surface of the electrodes of carbon steel. The linear relation between (I_(max)) and (v/I_(max)) is confirmed by linear potential sweep voltammetry.
This paper presents a new analytical result between peak current (I_(max)) and sweep rate (v) by a mathematieal model of porous growing layer on the surface of the electrodes of carbon steel. The linear relation between (I_(max)) and (v/I_(max)) is confirmed by linear potential sweep voltammetry.
Study on Thermodynamics of the Dissociation of o-Phthalic Acid in Isopropanol-Water Solvent Mixtures
1991, 7(05): 627-631
doi: 10.3866/PKU.WHXB19910523
Abstract:
The first thermodynamic dissociation constants of o-phthalic acid were determined at five temperatures from 278.15 to 318.15 K in 10, 14.93 and 20 wt% isopropanol-water solvent mixtures, by precise e. m. f. measurements of hydrogen-silver chlorld electrodes in cells without liquid junction. On the basis of Pitzer's theory, the method of polynomial approximation was used to determine the dissociation constants of H_2P and the results obtained were compared with traditional extrapolation according to the extended Debye-Huckel equation Results obtained from both methods agree within experimental error. The dependence of the first thermodynamic dissociation constant on temperature was given as a function of the thermodynamic temperature T by the empirical equation: pK_1=A_0+A_1/T+A_2/T. The thermodynamic quantities of dissociation in the mixed solvents have been calculated, and the results have been discussed.
The first thermodynamic dissociation constants of o-phthalic acid were determined at five temperatures from 278.15 to 318.15 K in 10, 14.93 and 20 wt% isopropanol-water solvent mixtures, by precise e. m. f. measurements of hydrogen-silver chlorld electrodes in cells without liquid junction. On the basis of Pitzer's theory, the method of polynomial approximation was used to determine the dissociation constants of H_2P and the results obtained were compared with traditional extrapolation according to the extended Debye-Huckel equation Results obtained from both methods agree within experimental error. The dependence of the first thermodynamic dissociation constant on temperature was given as a function of the thermodynamic temperature T by the empirical equation: pK_1=A_0+A_1/T+A_2/T. The thermodynamic quantities of dissociation in the mixed solvents have been calculated, and the results have been discussed.
1991, 7(05): 632-640
doi: 10.3866/PKU.WHXB19910524
Abstract:
