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11.
12.
Yan Yao Ruiling Wang Xucun Ma Pengsheng Song 《Journal of Thermal Analysis and Calorimetry》1995,45(1-2):117-130
Emf measurements were made on the cell without liquid junction: Li?ISE LiCl(m1), Li2SO4(m2) Ag/AgCl. The performances of the electrode pairs constructed in our laboratory were tested and exhibited near-Nernstian behavior. The mean activity coefficients of LiCl for the system Li+?Cl??SO 4 2? ?H2O have been investigated by the emf values at temperatures of 0, 15, 35°C and constant total ionic strengths of 0.05, 0.1, 0.5, 1.0, 2.0, 3.0 and 5.0 mol·kg?1. The activity coefficients decrease with increasing temperature and the ionic strength fraction of Li2SO4 in the mixtures. The thermodynamic properties are interpreted by use of Harned's empirical equations and Pitzer's ion interaction approach including the contribution of higher order electrostatic terms. The experimental results obey Harned's rule and are described by using Pitzer equations satisfactorily. The activity coefficients of Li2SO4, the osmotic coefficients and the excess free energies of mixing for the system in the experimental temperature range were reported. 相似文献
13.
微粉化技术提高水不溶性药物溶解度 总被引:4,自引:0,他引:4
药物的微粉化可以改善颗粒的润湿性,进而提高水不溶性药物的溶解度和溶解速率。目前普遍采用的药物微粒化技术主要包括机械研磨、超临界流体过程、低温喷淋和溶剂蒸发沉积过程。本文介绍了这些微粉化制备技术的基本原理以及该类技术的应用进展。 相似文献
14.
已有熔铁氨合成催化剂中添加稀土的报道.我们通过添加稀土得到了几种活性较高的催化剂,经进一步改进制备工艺(水浸处理后),活性又有所提高.本文利用XRD和AES等,对经水浸前后的含稀土催化剂的结构进行了测试,探讨了水浸后活性提高的原因. 相似文献
15.
Enthalpies of solution have been measured from 5 to 85°C for aqueous tetraethyl- and tetrapropylammonium bromides, and the integral heat method is employed to evaluate
for these electrolytes over a wide temperature range. Data taken from the literature have been used to evaluate
for aqueous Bu4NBr over a similar temperature range. These data, along with similar data for Me4NBr, previously reported, have been used to evaluate absolute ionic heat capacities. While the absolute values agree only qualitatively with two other methods of division, the temperature dependences of the three methods essentially agree up to 65°C. Heat capacities due to structural effects on the solvent, obtained by subtracting the inherent heat capacities of the ions, are extraordinarily positive for all four tetraalkylammonium ions and have negative temperature coefficients, indicating that all four ions, including the tetramethylammonium ion, are structure-making ions. 相似文献
16.
17.
Laurence E. Strong Christopher L. Brummel Robert Ryther John R. Radford Alan D. Pethybridge 《Journal of solution chemistry》1988,17(12):1145-1167
Precision molar conductances of benzoic, o-toluic, 2,6-dimethylbenzoic, 2,3,6-trimethylbenzoic, and, o-fluorobenzoic acids have been determined in aqueous solution as a function of temperature and of concentration up to near saturation (<0.035 M). At the higher concentrations molar conductances are found to be less than anticipated for the simple dissociation of a 1-1 electrolyte. Although the deviations are only 1% or less they have been interpreted to show that these acids are dimerized in solution. The interpretation includes an assumption that the dimer ionizes to produce a triple ion. Increasing numbers of methyl groups lead to increasing dimerization. For those acids with two ortho groups the dimerization increases with increasing temperature while the other three show decreasing dimerization with increasing temperature. Temperature functions have been determined for the dimerization constants and from these functions standard changes in enthalpy, entropy, and heat capacity have been determined. Comparisons are made with dimerization studies in non-aqueous solvents. From these as well as the behavior of benzene in water it is concluded that a major factor driving the dimerization is hydrophobic interaction. To provide a limiting conductance of the triple ion needed in the dimerization calculations a conductance study was also made for o-Phenylbenzoic acid on the assumption that its anion provides an approximate model of the triple ion. 相似文献
18.
Using flow microcalorimetry, the ion association reaction M2+(aq)+Fe(CN)
6
4–
(aq)=MFe(CN)
6
2–
(aq) (M=Ca, Mg) has been studied at 25°C over the ionic strength range 0.02 to 0.08 mol-dm–3. Analyses of the data to obtain Ho, the enthalpy change at infinite dilution, are described. The value obtained for Ho is sensitive to the kind of functions used to correct for non-ideal behavior. 相似文献
19.
Ziya Kantarci Celal Batyak Ergün Kasap 《Journal of inclusion phenomena and macrocyclic chemistry》2001,39(1-2):103-108
Infrared spectra of Mn(NH3)2Zn(CN)4.2C6H6 andMn(ethylenediamine)Zn(CN)4.2C6H6 are reported. The spectral data suggest that these compounds are similar in structure toHofmann-Td-type and the en-Td-type clathrates,respectively. There is good evidence for H-bonding from ammoniaN–H to benzene as a to H-bond. 相似文献
20.
Geneviève Roux David Roberts Gérald Perron Jacques E. Desnoyers 《Journal of solution chemistry》1980,9(9):629-647
The heat capacities per unit volume and the densities of aqueous solutions of 2-propanol, neopentanol, tert-amylalcohol, 2-amino-2-methylpropanol, triethylamine and diethylmethylamine were measured, in many cases as a function of temperature, over the whole mole fraction or solubility range. Apparent and partial molal heat capacities, volumes and expansibilities were derived. The concentration dependence of these functions suggest the existence of transitions in some of these systems, in the water-rich region, qualitatively similar to micellization. The large relaxation contribution observed with some of the thermodynamic functions of hydrophobic alcohols and amines suggests a reinforcement of hydrophobic hydration due to strong hydrogen-bonding interactions of the polar groups with water. 相似文献