Vapor pressure measurements on non-aqueous electrolyte solutions. Part 2. Tetraalkylammonium salts in methanol. Activity coefficients of various 1-1 electrolytes at high concentrations

Precise vapor pressure data for solutions of Et₄NBr, Bu₄NBr, Bu₄Nl, Bu₄NClO₄, and Am₄NBr in methanol at 25°C in the concentration range 0.04–1]<1.6 are communicated and discussed. Polynomials in molalities are given which may be used for calculating precise vapor pressure depressions of these solutions. Osmotic coefficients are calculated by taking into account the second virial coefficient of methanol vapor. Discussion of the data at low concentrations is based on the chemical model of electrolyte solutions taking into account non-coulombic interactions; ion-pair association constants are compared to those of conductance measurements. Pitzer equations are used to reproduce osmotic and activity coefficients at high concentrations; the set of Pitzer parameters b=3.2, ₁ = 2.0, and ₂ = 20.0 is proposed for methanol solutions.     

Vapor pressure measurements on non-aqueous electrolyte solutions. Part 3: Solutions of sodium lodide in ethanol, 2-propanol,and acetonitrile

Precise vapor pressure data for solutions of Nal in ethanol from 0.04 to 1.9m, and 2-propanol and acetonitrile from approximately 0.06 to 1.5m are communicated and discussed. Polynomials in molalities are given for calculating precise reference values. Osmotic coefficients were calculated by taking into account the second virial coefficients of solvent vapors. Discussion of the data at low concentrations is based on the chemical model of electrolyte solutions and ion-pair association constants are compared to those obtained from other properties of sodium iodide solutions. Pitzer equations are used to reproduce osmotic and activity coefficients at high concentrations; the set of Pitzer parameters for methanol solutions b=3.2, ₁ = 2.0, and ₂ = 20.0 may be used for ethanol, 2-propanol, and acetonitrile solutions.     

The formation of percolative composites with a high dielectric constant and high conductivity

The dielectric constant and electrical conductivity of a composite of two insulators, poly(1,1-difluoroethylene) (yellow) and K(2) CO(3) (white), increased dramatically near the percolation threshold?f(c) (f=concentration of K(2) CO(3) ). This intriguing phenomenon can be interpreted in terms of interface percolation caused by the formation of chemically activated interfaces.     

Vapor pressure data for non-aqueous electrolyte solutions. Part 5. Tetraalkylammonium salts in acetonitrile

Precise vapor pressure data for solutions of Et₄NBr (concentration range of 0.04–1]<0.4), Pr₄NBr (0.044NBr (0.024NCl (0.044NI (0.054NBr (0.06相似文献   

Vapor pressures of non-aqueous electrolyte solutions. Part 1. Alkali metal salts in methanol

Precise vapor pressure data for solutions of NaCl, NaBr, NaI, NaClO₄, KBr, KI, RbI, and CsI in methanol at 25°C in the concentration range 0.02m (mol-kg^–1)0.7 are communicated and discussed. Measurements were carried out by procedures and equipment known to produce data of high precision. Polynomials of fourth degree in molalities are given for the vapor pressure of methanol solutions which can be used for calculating precise reference values as needed in indirect methods. Osmotic coefficients were calculated by taking into account the second virial coefficient of methanol vapor. Discussion of the data is based on the chemical model of electrolyte solutions taking into account short range interactions. Ion-pair association constants are compared to those of conductance measurements.     

Theory of swelling of a crosslinked substance in equilibrium with a pure solvent in various phases. Part II: The variation of the pressure

A theory of swelling is presented which describes the equilibrium swelling of a body in a solvent in its various states. The pressure dependence of the pressure-concentration swelling curves is treated for the swelling agent occurring in the liquid, crystalline or vapor phase. The slopes of the pressureconcentration swelling curves are dependent on the differential volume of dilution of the solvent and, additionally, on the volume changes of vaporization, crystallization, and sublimation of the solvent corresponding to the state of the swelling agent. At the melting and boiling pressure of the swelling agent the swelling curves change their slopes with a discontinuity, which is most distinct at the evaporation transition. By measurements of the slopes of the swelling curves at the transition pressure the derivative ₁/w₁ at constant temperature and pressure, which is the change of the chemical potential of the solvent with its weight fraction, is obtained. Thus, a further equation is given to test statistical theories at the transition pressures. Simultaneous variations of the swelling with changes of temperature are also treated.     

Phase equilibria in polymer/solvent systems. Part V: Thermodynamic theory of the swelling pressure equilibrium of a crosslinked substance with a solvent in various phases

A thermodynamic theory has been developed to define the swelling pressure equilibrium between a homogeneous gel and a pure solvent, where phase transitions of the solvent, such as evaporation and crystallization can occur. It is shown that the equilibrium curve, which describes the temperature dependence of the composition in the gel phase under the condition of a constant swelling pressure, has distinct bends at the transition temperatures. These bends are related to the enthalpies of transition of the pure solvent at the transition temperatures. As a consequence of the phase transition of the solvent the swelling pressure-temperature curve at constant composition of the gel shows a discontinuous behavior at the transition point. Numerical calculations with a modified Flory-Huggins expression, based on results of swelling and deswelling measurements of the system crosslinked PEG/water, are presented.The discussion includes natural systems, which are in the gel state, where water may crystallize in the extracellular space.     

The theoretical basis of column chromatography in multicomponent separations. Part 1: Analytical requirements and peak resolution. Development of a high performance column system

The point of our published papers since 1957 is reviewed. The relations between the required value of peak resolution, K₁ (or R), and peak separation, K₃ (eqn 9); K₁ and relative accuracy of a peak height quantitative method, P_h (eqn. 10); K₁ and relative accuracy of a peak area method, P_a, (eqn. 12) at different concentration ratios, ?, are derived. The final result in Table 2 shows a large influence of ? on the required value of K₁. The approximately linear relation between peak width and retention value (eqn. 18) exists not only in GC. but also in HPLC. Plate height values H¹ and H^∞ for a solute with capacity ratio, k′, equal to unity or approaching infinity, respectively, are used to evaluate the column efficiency (eqn. 20). The measuring methods (eqn. 21,22,23) and parameters effecting on H¹ and H^∞ are given for GC packed column (eqn. 24), GC open tubular column (eqn. 25) and HPLC (eqn. 26). In the light of this, columns of high efficiency were developed. Some typical chromatograms for high speed analysis and separation of complex mixtures are given.     

On the statistical independence of various column contributions to band broadening. Part 2: The non-equilibrium contribution predicted by a slow,statistically independent relaxation of concentrations

The mass balance changes of Said's so-called “stage” model, based on the movement of the mobile phase with mean velocity ū (=L/t _m), are synchronized by introduction of the relaxation time of Giddings, t_r=1/(k_m+k_s) where k_m and k_s are the general overall mass rate constants for sample transfer to and from the stationary phase, respectively. This makes the “stage” length equal to the true theoretical plate height, ΔL, related to the classical HETP contribution due to non-equilibrium, H_(α), according to the “discontinuous-ΔL” relation Here k = (t _ms ? t _m)/t _m is the central moment-based capacity ratio, L the column length, and σ²_(α) the second moment contribution from the non-equilibrium only. Correct application of the relaxation-time model to chromatography requires that the real sample concentration in the stationary phase at a given position and time, C_s,l,t, is in a continuous equilibrium with the real sample concentration in the mobile phase, C_m,l+ΔL/2,t at that time displaced down the column by a distance This leads to the classical HETP contribution obtained from various other continuous models, which implies that ΔL is a good estimation of the true theoretical plate height.