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1989 Volume 5 Issue 5
A preliminary study of oxide on the surface of glassy carbon electrode by the use of in-situ infrared reflection spectroelectrochemical method has been done. In the electrochemical polarization of carbon electrode by high anodic potential(>1.6 V vs. SCE), the formation of adsorbed carbon monooxide, microcrystal graphite, as well as other oxide species on the surface of carbon electrode can be detected. Ester and acid anhydride are proposed to be two main oxide species being produced on the surface of glassy carbon electrode.
The superconducting phase(Bi_(1.7)Pb_(0.2)In_(0.1))Sr_2Ca_2Cu_3O_(10) with on-set T_c near 112K and zero resistivity at 95K has been prepared. The Unit cell is. body-centered tetra nal, space group I4/mmm, a=0.3.817(1) nm, c=3.704(1) nm. Chemical substitution of Pb and In in Bi—Sr—Ca—Cu—O series results in the growth of 2223 phase. The superconductivity and the formation mechanism are associated with the structural features.
Both wire and porous A electrodes were studied using photoelectrochemical method during their cathodic polarization. Much information has been available through their photoresponse measurements. The maximum open-circuit photopotential ΔV_(Ph, oc) occurred at the moment when the surface of electrode was fully covered with Ag_2O and dendritic Ag was just about to appear. The ratio of ΔV_(Ph, oc) for these two electrodes may be related to the pore configaration of the porous electrode. The photoresponse waveforms of n-p-n transition were first seen by means of signal averaging technique.
A new kind of nitrone, 2, 4,-dinitrophenyl-t-butyl nitrone (DNPBN), has been used for investigating the photolytic mechanism of chlorohydroearbon and trapping active chlorine atom and other C-centre radicals produced therein. The results show that under the irradiation of high-pressure mercury lamp, for polychlorohydrocarbon, the more the substitute chlorine atom, the easier the homolysis of C—Cl bond of its and seldem chlorine can be trapped from mono- or dichlorohydrocarbons. On the other hand, both chlorine, a more persistent adduct (Cl—DNPBN)~· than other famillar adducts, such as (Cl—PBN)~·, can be obtained.
The heats of protonation of N, N′-bis (p-substituted phenyl) ethylenediamine (R=CH_3O; CH_3; H; CI) and the heats of formation of their binary and ternary complex compounds with Ni(Ⅱ)-and Ni(Ⅱ)-bipy-respectively, were determined by MS-80 Calvet microcalorimeter at 25 ℃ and I=0.1 mol·dm~(-3) (NaClO_4) in 50% (V/V) dioxane solution. The linear enthalpy relationships between the former and the latter was found again. In addition, the linear entropy relationships between also the entropies of protonation and of formation of binary (or ternary) system were also found to exist.
The direct methods procedure MAGEX80 has been incorporated in MULTAN87 and proved to be useful programme for solving crystal structures. Here will be described some improvement and a new version of the procedure. An al rithm is used to select starting set reflexions which differs from the convergence method. By comparision with MULTAN82, the MAGEX87 takes less computing time and seems more efficient than the random starting-phase method.
A concise method——isodesorption rate method(IDRM) is presented for the determination of E_d and k_0 from a temperature programmed desorption (decomposition)(TPD) spectrum with no re-adsorption. Based on the Arrhenius equation and the constant heating rate, we have Eqs.(1) and (2)(see the text), where T, b, t, θ, k_0, E_d, and R are temperature, heating rate, time, Surface coverage, pre-exponential factor, activation energy of desorption (decomposition), and standard gas constant, respectively. For the desorption (decomposition) rate of h_i at T_i is equal to that of h_j at T_j (see Fig.1), Eqs.(3)—(5) (1st order) and Eqs.(11)—(13) (2nd order) are deduced. The values of h_i, h_j, θ_i and θ_j may be evaluated by Eqs.(6) and (7), where W_(T_ih_ih_jT_j) is the weight of the paper corresponding to the rectangle T_ih_ih_jT_j, W_0 is that under the spectrum T_Lh_ih_mh_jT_H, and W_i, W_j are that of the peak areas of T≥T_i, T_j respectively. By substituting Eqs.(6) and (7) to Eqs.(3)—(5) and (11)—(13), the resultant Eqs.(8)—(10) (1st order) and (14)—(16) (2nd order) are obtained for determining E_d and k_0. Table 1 shows that the results determinedby different methods coincide with each other quite well. It also proves that the selected kinetic orders of desorption (decomposition) are correct because the relative errors between the E_d′s by IDRM and CTM~[5] are <3% otherwise that will be about 30% when the desorption (decomposition) order is erroneously selected. So the combination of IDRM andCTM is benificial for determining the kinetic order of desorption (decomposition).
The role of cetyl pyridine bromide in the corrosion inhibition of aluminium in hydrochloric acid has been investigated by weight loss method. The experimental data have been treated with adsorption theory and Sekine method. The adsorption heat has been calculated. It is found that adsorption of cetyl pyridine bromide from hydrochloric acid solution on aluminium surface obeys basically Langmuir′s isotherm, so the adsorption on aluminium surface was believed to be an important reason of corrosion inhibition. The corrosion inhibition efficiency increases with raising temperature. Relationship between adsorption and corrosion inhibition has been discussed according to the experimental results.
The effective core poteutials (ECP′s) are used for studying the electronic structures of mercury halides (HgX_2,X=Cl, Br, I). For Hg and I, potentials including relativistic effects are employed. It is found that the interaetion of 5d_z2-6s hybrid orbital of mercury with p_z of halogen dominates the mereury-halogen bonding. On the bases of one-electron operator approximation, spin-orbit coupling is introduced and the results are compared with the corresponding experimental photoelectron spectra.
Positron annihilation lifetime measurements were carried out under different evacuation temperatures for zeolite NaY, HY and NH_4Y. Four lifetime components have been observed in these systems. The two shorter ones, τ_1 and τ_2, were assigned to positron annihilation in the bulk, self-annihilation of ρ-Ps, pick-off annihilation of ο-Ps in the bulk and annihilation of positron trapped in the cages. The two longer ones, τ_3 and τ_4, were assigned to annihilation of ο-Ps on the surface and in the cages of the zeolites respectively. The Brönsted acid in the zeolites oxidized o-Ps readily, so that the o-Ps lifetime τ_3 and τ_4 were reduced significantly in zeolite HY. The deammoniation of NH_4Y at higher evacuation temperatures can be monitored through measurements of o-Ps lifetimes. Brönsted acid in the zeolites does not inhibit the formation of o-Ps. However, o-Ps annihilates more readily on the surface as the concentration of Brönsted acid is increased, and hence the value of I_3 much largerthan I_4 in HY. The o-Ps annililation rates on the surface and in the cages, λ_3 and λ_4, are linearly proportional to the concentration of of Brönsted acid in the zeolites. First-order kinetics has been applied to the oxidation reactions of o-Ps and apparent rate constants k_3 and k_4, are 9.67×10~7 (mmol/g)s~(-1) and 2.36×10~7 (mmol/g)~(-1) s~(-1) respectively. The experimental results obtained demonstrate that positron annihilation spectroscopy is a sensitive technique to probe thesurface properties and pore structure of porous materials
By using an LKB 8721-3 vaporization calorimeter, the standard enthalpiea of vaporization of some multichloro-alkanes have been determined as the following: 1, 2-dichloroethane, 35.12±0.05; 1,1-dichloroethane, 30.57±0.05; 1,2-dichloropropane, 36.14±0.05; 1,3-dichloropropane, 40.61±0.10; 1,2,3-trichloropropane, 47.75±0.10; 1,4-dichlorobutane, 46.36±0.03; 1,2-dichlorobutane, 40.16±0.12 kJ mol~(-1) respectively. A linear equation, ΔH_ν~0=21.33+0.1589 t_b, can be used to fit the experimental data of dichloroalkanes, where t_b is the normal boiling point of compounds. A comparison of the ΔH_v~0 of dichloroalkanes and their molecular structures shows that (1) when a Cl atom on the primary carbon isomerizes onto the secondary carbon, the ΔH_v~0 of the isomer will decrease; (2) when the number of carbon atoms linked between the two chlorine atoms increases, the ΔH_v~0 of the isomer will increase in the order: 2,2-<1,1-<1,2-<1,3-<1,4-≈1,5-dichloroalkanes. This can be considered as a result of the Cl…Cl interaction in the molecules which makes a decrease in the depole moment of C—Cl bonds or in the formal charge on the Cl atoms, and so in the intermolecular electroatatic interaction energy. The decreae in the latter is estimated from the difference between calculated value from the equation, ΔH_v~0 (a,b-Cl_2C_nH_(2n))=ΔH_v~0 (a-ClC_nH_(2n+1))+ΔH_v~0 (b-ClC_nH_(2n+1))-ΔH_v~0 (C_nH_(2n+2)), and experimental result as the following: for 1,1-≈2,2-dichloroalkanes, ~7; 1,2-dichloroalkanes, ~4; 1,3-dichloroalkanes, ~1.5; 1,4-≈1,5-dichloroalkanes, ~0 kJ mol~(-1), respectively.
Li/LiClO_4-Propylene Carbonate is one of lithium electrode systems studied often. In this article we present some new findings obtained with a. c. impedance and SEM methods. The variation of R_p×C_p with logarithm of time shows three distinct periods, corresponding to three different stages of growth of the film on lithium surface. In the initial period of film growth R_p×C_p is constant, corresponding to growth of primary compact layer consisting of Li_2CO_3, an ionic conductor. Resistivity of film was callculated to be 1.4×10~8 Ω·cm, and the thickness of film is several hundred angstrons. In the second period of film growth the product of another compact layer, which consists of Li_2CO_3 and organic compounds including organic polymers. Because of inclusion of organic components, the conductivity of the film decreases and it is diffcult to calculate the thickness of film. The third period is charactered by chaotic vibration, which is probably caused by periodic breaking and resealing of the compact layer and the growth of a porous layer. Upon polarization the primary compact layer probably unden es no significant change and has no effect on the reversibility of the electrode system, while the outer compact layer and porous layer definitely have unfavourable influence on the revesibility of charging and discharging processess.
In recent years the Monte Carlo sampling technique has proved its value for calculating the thermodynamic properties of model fluids and solids. In this paper, the osmotic pressures are calculated by Metropolis Monte Carlo techniques. The activity coefficients of solvents in various TBP-diluent systems are obtained.The results are in agreement with experimental data and other theoretical values.A special tech nique is developed which improves the convergence of the calculation considerably.
The thermodynamic functions of protonation reactions of phenylalanine, leucine, tryptophan and methionine have been determined by titration calorimetry combined with computer fit program for thermodynamic function and it has been reported that there are differences between ΔH, logβ, ΔG and ΔS of protonation reactions of amino acids. From the experimental results, the differences are related to the nature of the side chain substituent group R of asymmetric carbon atom of α-amino acid and the sequence of the differences has also been reported.
The molecular configuration of diphenyl ether has been studied by MNDO method, The most stable configuration of diphenyl ether was obtained by means of optimization of molecular geometric configuration. The rotational potential surface describing internal rotation about the two C—O bond of diphenyl ether was drawn. The calculated results show that the minimum of the rotation potential surface is at θ=φ=65°, ∠COC=120.46° and the two benzene rings are easy to rotate about the two C—O bond within certain range. The three configurations which had been considered as the most stable configuration are discussed in this paper.
The emfs of Cu|CuSO_4|Hg_2SO_4-Hg were determined at 5 temperature points from 278.15 K to 313.15 K. Based on the Pitzer' s Equation a polynomial approximation for the determination of standard emf, E_m, was proposed. The values of E_m obtained by author's method agree with values of E_m obtained by the extended Debye-Huckel equation within experimental errors. Compared with the extrapolation result of extended Debye-Huckel equation, the uncertainty by the selecting of parameter of ion size was avoided. By the use of polynomial approximation method the standard emf's for different type cells in the literature were also determinded. The results were more satisfactary.
The heat capacity of 2,2-bishydroxymethyl-1,3-propanediol was measured over the temperature range 275 to 510 K by means of an automated adiabatic calorimeter. A solid-solid phase transition was found at 416.60 K. The enthalpy and entropy of the transition were determined to be 41.37 kJ tool~(-1) and 89.62 J K~(-1) mol~(-1) respectively. Using the enthalpy of the transition, the destroyed average hydrogen bond energy of the compound was deduced to be 9.69 kJ mol~(-1).
The complex oscillation in the system of GA-BrO_3~--Mn~(2+)-H_2SO_4 was studied in a closed system. The oscillating wave can be divided into five different parts. It is found that the complex phenomena in the title system are due to the oscillations in the following systems, (ⅰ) GA-BrO_3~--H_2SO_4 system, the uncatalyzed oscillation; (ⅱ) GA-BrO_3~--H_2SO_4-Mn~(2+) system, the catalyzed oscillation; (ⅲ) BrGA-BrO_3~--H_2SO_4-Mn~(2+) system, the little catalyzed oscillation.
The uptake of Cu(Ⅱ) on chitosan is corresponding to the monolayer adsorption model at 30.0℃ and the equilibrium concentration of Cu(Ⅱ) is less than 61.1 mg dm~(-3). When the pH values are 6.00 and 4.88 respectively, the saturated specific adsorption amounts are kept constant, 26.5 mg·g~(-1), but the adsorption constants are dropped down from 0.202 to 0.0491 dm~3·mg~(-1). It means that an acidized solution may cause the desorption of Cu(Ⅱ) from chitosan uptaken the ions before. Chitosan is very stable at pH～2 by using a 2.5 mol·dm~(-3) acidized NaCl solution because the ionic strength of solution is high enough to prevent the swelling of chitosan. The effect of pH of 0.2 mol·dm~(-3) acidized NaCl solutions on the desorption percentage of Cu(II) from samples used is determined, and the desorption percentage is found to be 81.5% when pH is 3.87.
A LKB 2107-030 sorption microcalorimeter has been installed and equipped with a microcomputer. The apparatus was tested with a standard reaction of TRIS and HCl. It was shown that this microcalorimeter is suitable for our proiect.
A silica gel was chosen as a model surface for studying adsorption of surfactants used in enhanced oil recovery. A TG analysis of it was done and was used to select its activation temperature. The immersion heats of the silica into water, toluene and heptane were measured using this microcalorimeter. Before every experiment, silica sample placed in batch cell was activated at 170 ℃ and 10~(-2) mmHg. The results are generally in agreement with those recently obtained by Leo A. Noll and Thomas E. Burchfield.
In this paper, we have determined the multiplication rate constant and activation energy of E, coli. at differential culture mediums using microcalorimeter. According to the transition state theory of reaction dynamics, the activation entropy (△S) activation Gibbs free energy (△G) and equilibrium constant (K) have been calculated. From these results some thermodynamies analysis about the bacterial growth metabolism have been made.
The solid state complexes of trivalent lanthanid, yttrium and scandium with cyclohexane carboxylic acid have been isolated and characterized by IR and Raman spectroscopy. It was found that there are only chelated carboxylate groups in the scandium complex and that there are the chelated, bridged and chelate-bridged carboxylate groups in other rare earth complexes. The former is a mononuclear complex and the latter is a polynuclear polymer. The RE—O coordinate bonds possess the characters of convalent ionic bond.
The compounds with molecular formula Mn(NCS)_2·4H_2O·18C6 and (Mn_2Cl_2·8H_2O)·18C6·2Cl were synthesized and their FT-IR, Raman spectra were measured over region of 4000-100 cm~(-1). The vibrational spectra show that in both compounds the Mn~(2+) ion are not coordinated to 18C6 but combined with 18C6 by hydrogen bonds originated from the hydrous water of manganese.
In addition, by means of the changes of vibration for crowa ether ring in IR together with that the appearance of a band near 867 cm~(-1), which belongs to the breath vibration of ring, or not, one can predicate that the transition element crown compound with a single nucleus or a long chain structure.
In this article, equilibrium and kinetics of the ligand exchange reaction between a series of N,N-disubstituted dithiocarhamate chelates of Nickel (Ⅱ)
have been studied by means of high-performance liquid chromatography in various solvents such as chloroform, dichloromethane, methylbenzene, ethyl acetate and DMF (dimethyl formamide) etc. at 30 ℃. The activation parameters of two selected reactions with different disubstituted alkyl groups have been determined in toluene. The experimental results indicate that steric effect of the alkyl groups may influence to some extent the rate of ligand exchange. The reactions of ligand exchange conform to an S_N2 mechanism. Statistical factor seems to enter the evaluation of the equilibrium constants. Solvation effect may contribute to the influence of solvents on reaction rate.
