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81.
The partial molar volumes at infinite dilution of cryptand-222 (C-222) in water, methanol, acetonitrile, ethanol, dimethylsulfoxide, propanol, 2-propanol, chloroform, benzene, 1-butanol, cyclohexane, butyl-methylketone, hexane, tetrahydronaphthalene, heptane, octane, cyclohexylbenzene and decane were measured at concentrations ranging from 0.01 to 0.1 mol-L–1 at 25°C. The partial molar volumes at infinite dilution showed remarkable dependency on the molar volume of the solvent. The partial molar volumes at infinite dilution for C-222 increase as the solvent molar volume increases. 相似文献
82.
Eugenio?Garcia-Pa?eda Pilar?Guardado Alfredo?MaestreEmail author 《Journal of solution chemistry》2004,33(10):1277-1293
Partial molar volumes at infinite dilution, V02, of alkali–metal halides (LiCl, NaCl KCl RbCl CsCl, NaBr, KBr, KI), tetra-n-alkylammonium bromides, R4NBr (R=Me, Et, n-Pr, n-Bu, n-Pen), NaBPh4, and Ph4PCl have been determined in binary solvent mixtures of water with 2-methyl-2-butanol covering the water-rich region and the alcohol-rich region at 298.15 K. V02 for alkali–metal halides show relatively little dependence on the solvent composition. However, in the case of hydrophobic electrolytes the observed effects are more pronounced. A good linear dependence between V02(R4NBr) and the molecular weight of the tetra-n-alkylammonium cation is found. Limiting single-ion volumes have been obtained using the assumption that V0(Ph4P+)–V0(BPh–4)=2.0 cm3-mol–1. The trends in the single-ion volumes are discussed in both solvent regions. 相似文献
83.
I. Gascón S. Martín P. Cea M. C. López F. M. Royo 《Journal of solution chemistry》2002,31(11):905-915
Densities and speeds of sound of the binary mixtures 1,3-dioxolane + 1-butanol, 1,3-dioxolane + 2-butanol, 1,4-dioxane + 1-butanol, and 1,4-dioxane + 2-butanol have been measured at 25 and 40°C. The excess molar volumes and excess isentropic compressibility coefficients were calculated from experimental data and fitted to a Redlich–Kister polynomial function. Results were analyzed in terms of molecular interactions and compared with literature data. 相似文献
84.
María?Belén?Sierra Marcela?A.?Morini Pablo?C.?SchulzEmail author María?Luján?Ferreira 《Colloid and polymer science》2005,283(9):1016-1024
Following the studies on the effect of double bonds in the surfactant hydrophobic tail on the formation of mixed surfactant aggregates, we studied the viscosity and density of the system Sodium 10-undecenoate (SUD)–decyltrimethylammonium bromide (DTAB)–water. We found that the partial molar volume (pmv) and intrinsic viscosity of both, micellised and unmicellised mixtures, are non-ideal, dependent on the mixture composition and related to structural changes in micelles. These phenomena are caused by the presence of the double bond at the distal extreme of the SUD molecule, which has some affinity with water by formation of hydrogen bonds. In particular, as far as we know, this is the first report on non-ideal behavior of the pmv in mixed micelles. 相似文献
85.
Synthesis, structure and magnetic properties of the S=1/2, one-dimensional antiferromagnet, Y5Re2O12
Lisheng Chi 《Journal of solid state chemistry》2003,172(2):451-457
Single crystals of Y5Re2O12 have been grown, and the crystal structure has been determined by X-ray diffraction. This compound crystallizes in space group C2/m with cell dimensions of a=12.4081(10) Å b=5.6604(5)Å, c=7.4951(6) Å, β=107.837(3)°, Z=2. The final refinement led to R1=0.0238, WR2=0.0459 for 1053 observed reflections with F>4σ(F0). Edge-sharing ReO6 octahedra form infinite linear [ReO2O4/2]n chains along the b direction with alternating short and long Re-Re distances. Three crystallographically independent yttrium atoms surround O2 to form OY4 tetrahedra, which share edges and corners in the ab plane to form a two-dimensional Y5O4 network which separates the [ReO2O4/2]n magnetic chains. This compound is therefore isostructural with the series Ln5Re2O12Ln=Gd-Lu, which have been known since 1969. The average Re oxidation state is +4.5 in the chains and a reasonable, if qualitative MO scheme results in one unpaired electron per Re dimer. Consistent with this, magnetic susceptibility data can be fitted to the one-dimensional antiferromagnetic Heisenberg model with S=1/2 and parameters Jintra/k=−89(1)K, g=2.15(4) and χ(TIP)=5(1)×10−4 emu/mol. There is no sign of long-range magnetic order down to 2 K. These results are contrasted with those for the isostructural Y5Mo2O12. 相似文献
86.
Density of supercritical CO_2-tetrahydrofuran binary mixture and the partial molar volume of the cosolvent 总被引:1,自引:0,他引:1
The densities of supercritical CO2-tetrahydrofuran (cosolvent) binary mixture weremeasured at temperatures in range of 308.15 to 323.15 K and at pressure up to 16.5 MPa.The concentrations of tetrahydrofuran were from 0 to 0.57 mol/L.The partial molar volume of tetrahydrofuran was calculated based on the relationship between the density of the mixture and the concentration of the cosolvent.It is observed that the partial molar volume of the cosolvent is negative and the absolute value decreases with increasing pressure and the concentration of the cosolvent. 相似文献
87.
Measurements of acoustic absorption and velocity as a function of frequency and concentration in KH2PO4–K2HPO4 buffers at 4°C and pH 5-7 are reported. The dependence of the observed acoustic relaxation parameters on concentration is consistent with that to be expected from perturbation of a monomer-dimer equilibrium with an equilibrium constant [for 2H2PO
4
–
(H2PO4)2
2–] of 0.21 M–1, a bimolecular rate constant of 5×108 M–1-sec–1 and a standard volume change of –5 cm3 mole. The equilibrium constant for H2PO
4
–
+ HPO4
2–H3(PO4)2
3– is estimated to be 0.7 M–1. 相似文献
88.
89.
90.
The concentration dependence of the apparent molar volumes of lithium halides (and electrolytes in general) in alcohols (and
solvents permitting association in general) is, in the first instance, due to changes in the degree of association and to
the inherent difference between the apparent molar volumes of the ions and of the ion pairs. Previous publications on the
molar volumes of electrolytes in organic solvents, disregarding altogether ion pairing, appear to be incorrect. Data from
the literature for lithium chloride and lithium bromide in normal primary alcohols and several branched alcohols from C1 to C8 and data from our laboratory for lithium halides in 1-hexanol and 2-ethyl-1-hexanol served for the determination of φ
V
and φ
E
. Electrical and structural contributions to the values of these functions for the ions and for the ion pairs are discussed. 相似文献