共查询到20条相似文献,搜索用时 31 毫秒
1.
The solubility studies on silver salicylate at different temperatures were made to derive (a) the standard electrode potential of the silver—silver salicylate electrode, (b) the mean activity coefficient of silver salicylate, (c) the dissociation constant of salicylic acid, and (d) the standard thermodynamic quantities, Δ G0t, Δ H0t, Δ S0t, and δ C0pt, for the transfer of silver salicylate from the standard state in water to the standard state in water + 10, + 20, and + 40 mass percent of dioxane. The results are discussed in terms of the preferential solvation of the ions. 相似文献
2.
The surface tension isotherms for pure oligooxypropylenated piperidine and morpholine at the aqueous solution—air interface were determined and interpreted. The surface excess concentration, Γ, the surface area per molecule, A, and the standard free energy of adsorption, Δ G°, were calculated according to a new empirical adsorption equation. The standard free energy contribution for the oxypropylene group (PO) in morpholine derivatives,Δ G° (PO) = −3.34 kJ mol −1, is substantially lower than that for the PO group located in the piperidine derivatives, i.e. Δ G° (PO)= −3.12 kJ mol −1. 相似文献
3.
The thermodynamic data (Δ G0, Δ H0 and TΔ S0) of the solvation of tetraphenylarsonium-tetraphenylborate (Ph 4AsPh 4B) and its neutral parts, tetraphenylgermanium (Ph 4Ge) and tetraphenylmethane (Ph 4C) in methanol— N,N-dimethylformamide mixed solvents are discussed. The values of the free energy of transfer, ΔsMG0, are calculated from measurements of the solubilities of Ph4AsPh4B, Ph4Ge and Ph4C in the successive fractions of MeOH in DMF at three different temperatures (15, 25, 35°C). The values of ΔsMH0 and TΔsMS0 for the derivatives are calculated from ΔsMG0 values. The values of ΔsMG0, ΔsMH0 and TΔsMS0 of tetraphenylarsonium and tetraphenylborate ions have also been carefully calculated. The ratios of ΔsMG0 values (ΔsMG0 = ΔG0(+)/ΔG0(−)) were found to be greater than unity. Similarly, the ratios of ΔsMH0 and TΔsMS0 for the positive and negative ions were found to be greater than unity. 相似文献
4.
The standard thermodynamic quantities, Δ G0, Δ H0, and Δ S0, associated with the ionization process of benzoic acid in formamide have been evaluated. The standard potentials of the Ag(s)/AgCNS(s)/CNS − and the Ag(s)/Ag 3Ci(s)/Ci 3− electrode, and the standard thermodynamic quantities for the electrode processes have been calculated in formamide, at different temperatures. 相似文献
5.
Manganese hydrogen phosphate monohydrate, MnHPO 4·H 2O, a new phase, is synthesized. Its solubility is investigated in the temperature range 35–50°C and pH range 3.4–7.5. Ksp, Δ H0, ΔS 0 and Δ G0 for the dissolution are reported. The decrease in solubility with increase in pH is explained as due to a surface coating of insoluble basic phosphate. 相似文献
6.
Three nonionic surfactants; p-isooctylphenol ethoxylates p-[i-OPE10], p-[i-OPE15], and p-[i-OPE20], were phosphorylated to produce three anionic phosphate ester surfactants. In addition, N-diethoxylated perfluorooctanamide ( N-DEFOA) was also prepared. The surface and thermodynamic properties of the three types of surfactants and mixtures of the fluorocarbon surfactant (FC) with the hydrocarbon surfactants (HC) have been investigated. Surface tension as a function of concentration of the surfactant in aqueous solution was measured at 30, 40, 50 and 60°C, using the spinning drop technique. From these measurements the critical micelle concentration (CMC), the surface tension at the CMC ( γCMC), the maximum surface excess concentration ( Γmax), the minimum area per molecule at the aqueous solution/air interface ( Amin), and the effectiveness of surface tension reduction ( πCMC), were calculated. The thermodynamic parameters of micellization (Δ Gmic, Δ Hmic, Δ Smic) and of adsorption (Δ Gad, Δ Had, Δ Sad) for these surfactants and their mixtures were also calculated. Structural effects on micellization, adsorption and effectiveness of surface tension reduction are discussed in terms of these parameters. The results show that the FC surfactant and its mixtures with HC surfactants enhance the efficiency in surface tension reduction and adsorption in the mixed monolayer at the aqueous solution/air interface, and also, reduce γCMC and the tendency towards micellization. 相似文献
7.
Δ G0, Δ H0 and Δ S0 protonation values of some pairs of diastereoisomeric dipeptides have been determined by potentiometry and calorimetry in aqueous solution at 25°C and I = 0.1 mol dm −3 (KNO 3). On the basis of the results obtained it has been possible to assess the role played by two different non-covalent interactions, namely the electrostatic interaction and the solvophobic interaction, on the thermodynamic stereoselectivity in the proton complex formation, shown by the systems investigated. 相似文献
8.
Liposomes can be effectively deposited on the inner surface of a capillary wall by flushing the electrophoretic system with a liposome suspension followed by air-drying of the capillary and removal of the excess of loosely bound liposomes by a 0.1 M NaOH wash. It was demonstrated that capillaries prepared in this way could be used for studies of analyte (drug)–liposome binding. The results were expressed as free binding energy changes [Δ(Δ G0)] relatively to an arbitrarily selected standard (acetylsalicylic acid). The results were compared to [Δ(Δ G0)] changes obtained from binding studies effected by capillary electrophoresis using a stable liposome plug in a capillary with minimized endoosmotic flow. Good agreement of data reported in the literature (without correction for the residual endoosmotic flow), our previous data obtained in a similar way (however, after the correction for the residual endoosmotic flow) and data obtained by the immobilized liposome affinity electrochromatography reported in this communication was achieved. 相似文献
9.
The e.m.f. of the galvanic cells Pt,C,Te(l),NiTeO 3,NiO/15 YSZ/O 2 ( Po2 = 0.21 atm),Pt and Pt,C,NiTeO 3,Ni 3TeO 6,NiO/15 YSZ/O 2 ( Po2 = 0.21 atm),Pt (where 15 YSZ=15 mass% yttria-stabilized zirconia) was measured over the ranges 833–1104 K and 624–964 K respectively, and could be represented by the least-squares expressions E(1)±1.48 (mV) = 888.72 − 0.504277 (K) and E(II) ±4.21 (mV) = 895.26 − 0.81543 T (K). After correcting for the standard state of oxygen in the air reference electrode, and by combining with the standard Gibbs energies of formation of NiO and TeO2 from the literature, the following expressions could be derived for the ΔG°f of NiTeO3 and Ni3TeO6: ΔGf°(NiTeO3) ± 2.03 (kJ mol−1) = −577.30 + 0.26692T (K) and ΔG°f(Ni3TeO6)±2.54 (kJ mol−1) = −1218.66 + 0.58837T (K). 相似文献
10.
The heat capacities of NaNO 3 and KNO 3 were determined from 350 to 800 K by differential scanning calorimetry. Solid-solid transitions and melting were observed at 550 and 583 K for NaNO 3 and 406 and 612 K for KNO 3, respectively. The entropies associated with the solid-solid transitions were measured to be (8.43± 0.25) J K −1 mole −1 for NaNO 3 and (13.8±0.4) J K −1 mole −1 for KNO 3. At 298.15 K the values of C0P S0P, { H0( T)- H0(0)}/ T and -{ G0( T)- H0(0)}/ T, respectively, are 91.94, 116.3, 57.73, and 58.55 J K −1 mole −1 for NaNO 3 and 95.39, 133.0, 62.93, and 70.02 J K −1 mole −1 for KNO 3. Values for S0T, { H0( T)- H0(0)}/ T, and -{ G0( T)- H0(0)}/ T were calculated and tabulated from 15 to 800 K for NaNO 3 and KNO 3. 相似文献
12.
The binding of a homologous series of n-alkyltrimethyl ammonium bromides with Jack bean urease (JBU) have been studied previously. It has been suggested that both electrostatic and hydrophobic interactions are involved in the formation of surfactant-protein complexes, but there is not any quantities analyzing method for resolution of their contributions in the process. In the present study, at first, the intrinsic Gibbs free energy of binding, Δ Gb,ν, has been calculated for these systems and the trend of variation for both binding sets have been interpreted on basis of cooperativity and hydrophobicity of surfactants. Subsequently, a novel approach has been introduced for estimation of electrostatic and hydrophobic interactions in Δ Gb,ν, by considering of this fact that Δ Gb,ν is the summation of electrostatic, Δ Gb,ν(ele), and hydrophobic, Δ Gb,ν(hyd), parts and considering this fact that just Δ Gb,ν(hyd) is a function of hydrocarbon tail length of surfactant ( Cn). The results represents the higher positive rule of electrostatic interactions in binding affinity of first set and inhibiting rule of this interaction in the second binding set. The predominate driving force in the second binding set is entropy statistical effect, which arises from numerous number of binding sites in this set. A binding mechanism on basis of structural changes in JBU due to its interaction with cationic surfactants has also been proposed. 相似文献
13.
Electrochemical measurements were performed to investigate the effectiveness of cationic surfactants of the N-alkyl quaternary ammonium salt type, i.e. myristyltrimethylammonium chloride (MTACl), cetyldimethylbenzylammonium chloride (CDBACl), and trioctylmethylammonium chloride (TOMACl), as corrosion inhibitors for type X4Cr13 ferritic stainless steel in 2 M H 2SO 4 solution. Potentiodynamic polarization measurements showed that these surfactants hinder both anodic and cathodic processes, i.e. act as mixed-type inhibitors. It was found that the adsorption of the N-alkyl ammonium ion in 2 M H 2SO 4 solution follows the Langmuir adsorption isotherm. Plots of log [ θ/(1 − θ)] versus log cinh yielded straight lines with a slope, which changed drastically at the critical micelle concentration (CMC) of the surfactants studied. Accordingly, the CMC could be accurately determined from these measurements. The calculated values of the free energy of adsorption Δ Gads are, in cases when the charge on the metal surface is negative with respect to the PZC, relatively high what is characteristically for the chemisorption. On the other hand, for positive metal surfaces it is assumed that SO 42− anions are adsorbed first, so the cationic species would be limited by the surface concentration of anions. Accordingly Δ Gads values were lower in this case and the adsorption is due to merely electrostatic attraction, which is characteristically of physisorption. 相似文献
14.
Thermodynamic characterisation of the adsorption process (at a low temperature) of dihydrogen on the zeolite Li-ZSM-5 was carried out by means of variable-temperature infrared spectroscopy, with the simultaneous measurement of temperature and equilibrium pressure. Adsorption renders the H–H stretching mode infrared active, at 4092 cm −1. The standard adsorption enthalpy and entropy resulted to be Δ H0=−6.5(±0.5) kJmol −1 and Δ S0=−90(±5) Jmol −1 K −1, respectively. The adsorption enthalpy is significantly larger than the liquefaction heat, and this fact renders Li-ZSM-5 a potential cryoadsorbent for hydrogen storage. 相似文献
15.
High-pressure magnetic susceptibility measurements have been carried out on Fe(dipy) 2(NCS) 2 and Fe(phen) 2(NCS) 2 in the pressure range 1–10 kbar and tempeature range 80–300 K in order to investigate the factors responsible for the spin-state transitions. The transitions change from first order to second or higher order upon application of pressure. The temperature variation of the susceptibility at different pressures has been analysed quantitatively within the framework of available models. It is shown that the relative magnitudes of the Δ G0 of high-spin and low-spin conversion and the ferromagnetic interaction between high-spin complexes determines the nature of the transition. 相似文献
16.
The effect of Cal-Red on the structure of human serum albumin (HSA) was studied using Resonance light scattering (RLS), Fourier transformed Infrared (FT-IR) and Circular dichroism (CD) spectroscopic methods. The RLS spectroscopic results show that the RLS intensity of HSA was significantly increased in the presence of Cal-Red. The binding parameters of HSA with Cal-Red were studied at different temperatures of 289, 299, 309 and 319 K at pH 4.1. It is indicated by the Scatchard plots that the binding constant K decreased from 4.03 × 10 8 to 7.59 × 10 7 l/mol and the maximum binding number N decreased from 215 to 152 with increasing the temperature, respectively. The binding process was exothermic and spontaneous, as indicated by the thermodynamic analyses, and the major part of the binding energy is hydrophobic interaction. The enthalpy change Δ H0, the free energy change Δ G0 and the entropy change Δ S0 of 289 K were calculated to be −42.75 kJ/mol, −47.56 kJ/mol and 16.66 J/mol K, respectively. The alterations of protein secondary structure in the presence of Cal-Red in aqueous solution were quantitatively calculated from FT-IR and CD spectroscopy with reductions of -helices content about 5%, β-turn from 10% to 2% and with increases of β-sheet from 38% to 51%. 相似文献
17.
The interactions between oleanolic acid and bovine serum albumin (BSA) have been studied by fluorescence, circular dichroism (CD), UV–vis absorption and Fourier transform infrared spectroscopy (FTIR) under physiological conditions. Spectroscopic analysis of the emission quenching at different temperatures has revealed that the quenching mechanism of bovine serum albumin by oleanolic acid is static quenching mechanism. The binding sites number n and binding constants K are obtained at various temperatures. The distance r between oleanolic acid and the protein is evaluated according to the theory of Forster energy transfer. The results by FTIR, CD and UV–vis absorption spectra experiment indicate that the secondary structures of protein have been perturbed in the presence of oleanolic acid. The thermodynamic parameters Δ H0, Δ G0, and Δ S0 are calculated according to van’t Hoff equation, which indicates that the hydrogen bonds and van der-waals are the intermolecular forces stabilizing the complex. Molecular modeling studies the interaction BSA with oleanolic acid. 相似文献
18.
The gaseous equilibria involving the molecules AuSi, AuSi 2 and Au 2Si have been studied by means of the Knudsen effusion technique combined with mass spectrometric analysis of the vapor. The experimentally determined reaction enthalpies were combined with appropriate literature data to obtain the following atomization energies (in kJ mole −1): D00[AuSi(g)] = 301.0 ± 6.0, D00[Au 2Si(g)] = 582.7 ± 15 and D00[AuSi 2(g)] = 602.1 ± 15. The corresponding D0298 values are: 305.2 ± 6.0, 589.1 ± 15 and 610.5 ± 15, and the standard heats of formation, Δ H0f,298, 518.6, 602.9 and 668.9, respectively. Comparison of the atomization energies of these silicon—gold molecules with the literature values for the corresponding germanium—gold and tin—gold molecules indicates similarity in the nature of bonding. 相似文献
19.
Measurements were made of the dissolution heats of NaBPh 4 and Ph 4PCl in water- n-propanol mixtures over the whole range of compositions. Assuming the equality of Δ Htr+ (Ph 4P +) and Δ Htr+ (BPh −4), the transfer enthalpies of several ions from water to water- n-propanol mixtures at 298.15 K were calculated. 相似文献
20.
Activities of solutes and compositions of solutions may be expressed corretly in terms of molarity ( c), molality ( m) or mole fraction ( x), leading to corresponding equilibrium constants Kc, Km, or Kx. Equations for differences between Δ G° c, Δ G° m, and Δ G° x values are derived. Common errors in calculations involving (dln Kc/d T) and (dln Kc/d P) are identified and remedies for these errors are presented. 相似文献
|