Mixed solvent density

The cell is fitted with windows, and the concentration of polymer along its length is determined by optical methods which are based on measurements of refractive index of absorption solvents to be used for ultracentrifugation experiments must be chosen for difference from the polymer in both density and refractive index. An effort be made to avoid mixed solvents. Low solvent viscosity is also desirable. 

In this approach a mixed solvent is chosen so that the relative sedimentation of the two components may give rise to a density gradient. The solute from a band that centres at the point where its effective density is equal to that of the solvent mixture. The band has a Gaussian shape with respect to solute concentration, the half-width is inversely proportional to the molecule weight of solute. A major importance is its sensitivity to small differences in effective density among the solute species. 

Figure 52. Passivation of A1 substrate in LiBOB-based electrolytes Time-decaying current observed on an A1 electrode at various potentials containing 1.0 M LiBOB in EC/EMC. Inset the dependence of steady-state current density at t= 10 s) on applied potential as obtained on an A1 electrode in electrolytes based on various salts in the same mixed solvent. (Reproduced with permission from ref 155 (Eigure 1). Copyright 2002 The Electrochemical Society.)...

A.G. Iroda, BelgP 613336(1962) CA 57, 14045(1962) [Expls prepd by mixing powdered AN, Al, K(or Na) nitrate with a gelatinous mixt of NG, NC and solvent, such as MeOH. After pressing to desired density the solvent is evaporated]... 

The densities p° of the mixed solvents required to calculate the parameters A and B of the Debye-Hiickel equation were measured with a pycnometer of about 25-cm3 capacity. Duplicate determinations were always made, and the values agreed to within 0.005%. 

The densities and volumetric specific heats of some alkali halides and tetraalkylammonium bromides were undertaken in mixed aqueous solutions at 25°C using a flow digital densimeter and a flow microcalorimeter. The organic cosolvents used were urea, p-dioxane, piperadine, morpholine, acetone, dime thy Isulf oxide, tert-butanol, and to a lesser extent acetamide, tetrahydropyran, and piperazine. The electrolyte concentration was kept at 0.1 m in all cases, while the cosolvent concentration was varied when possible up to 40 wt %. From the corresponding data in pure water, the volumes and heat capacities of transfer of the electrolytes from water to the mixed solvents were determined. The converse transfer functions of the nonelectrolyte (cosolvent) at 0.4m from water to the aqueous NaCl solutions were also determined. These transfer functions can be interpreted in terms of pair and higher order interactions between the electrolytes and the cosolvent. 

As the ratio of organic to aqueous in a mixed solvent is increased, the concentration of water molecules around the cation is reduced, decreasing the size of the hydrated cation. One consequence of this is that metal complex anions will be formed at lower anion concentrations than in pure water. Moreover, because the forces that bind the hydration cloud depend on the charge density of the cation, selective destruction of the hydration cloud starts at lower organic aqueous ratios for larger cations.399 As a result, large cations will penetrate a cation exchanger more easily, and differences in the distribution coefficients of elements of different size will be enhanced. 

Another consideration when selecting an extraction solvent is its density [41]. Solvents that are more dense than water will form the lower layer of the pair when mixed together, while solvents that are less dense than water will form the upper layer or float on water. For example, ethyl ether has a density of 0.7133 g/mL at 20°C and would constitute the upper phase when combined with water, which has a density of 0.9982 g/mL at that temperature. On the other hand, the density of chloroform is 1.4892 at 20°C. Therefore, water would form the top layer in a water chloroform solvent pair. 

During a Hittorf transference experiment in a mixed solvent electrolyte solution, the concentration of the electrolyte as well as the composition of the solvent changes in the electrode compartments. The determination of the solvent transport requires detailed analysis of the electrode compartment. This has been done using refractive index or density measurements electrolysis is limited, the... 

The shape of particles is normally that of more or less regular spheres, dense or hollow, with smooth surfaces and sometimes cracks. This is related to the composition and the rate of solvent evaporation, with possible existence of internal pressure inside the drops when a rigid surface layer is being formed (Walton and Mumford 1999). All these characteristics will have some effect on handling properties of powders such as bulk and tapped densities, particle density, (mixing with other powders, storage) wettability and solubility, porosity, specific area (rehydration, instantisation) flowability (size, surface asperities), friability and creation/existence of dust, stability in specific atmosphere and medium (oxidation, humidification, active component release) (Huntington 2004). 

Monte Carlo and molecular dynamics calculations of the density profile of model system of benzene-water [70], 1,2-dichloroethane-water [71], and decane-water [72] interfaces show that the thickness of the transition region at the interface is molecu-larly sharp, typically within 0.5 nm, rather than diffuse (Fig. 4). A similar sharp density profile has been reported also at several liquid-vapor interfaces [73, 74]. The sharpness of interfaces thus seems to be a general characteristic of the boundary between two stable phases and it is likely that the presence of supporting electrolytes would not significantly alter the thickness of the transition region at an ITIES. The interfacial mixed solvent layer [54, 55], if any, would probably have a thickness comparable with this thin inner layer. 

Various Systems. 3.3.1. Water (l)-Malate Dehydrogenase (Hm MalDH) (2)—NaCl (3). For water (1)—Hm MalDH (2)—NaCl (3), experimental data for both F and OSVC are available. 3,44 -pbe partial molar volumes of the components of the protein-free mixed solvent (Vi and V3) were calculated from the densities of the water—NaCl... 

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