Water-organic mixtures viscosity

Condensation of mixed vapors of immiscible liquids is not well understood. The conservative approach is to assume that two condensate films are present and all the heat must be transferred through both films in series. Another approach is to use a mass fraction average thermal conductivity and calculate the heat-transfer coefficient using the viscosity of the film-forming component (the organic component for water-organic mixtures). 

The viscosity of water/organic mixtures should be considered as an additional parameter in the selection of organic modifier. Acetonitrile/water mixtures show roughly 2.5 times lower viscosity than equivalent methanol/water eluents this means that one can use 2.5 faster flow rates with acetonitrile as organic modifier and develop faster separation methods. 

In the vast majority of cases reported where a streak camera has been used to measure fluorescence lifetimes, the measurements have been made from a single laser shot. Since a high fluorescence efficiency is necessary for single shot experiments, most of these studies have been concerned with measuring the lifetimes and quenching of organic dye molecules in solution. For example, Yu etal. [67] have made a study of the fluorescence lifetime of malachite green as a function of solvent viscosity and the lifetime and relative yield of erythrosin as a function of water concentration in a water—acetone mixture. The fluorescence lifetimes of these dyes are... 

The difference in replacement of the lEP for 19a (pHiEp = 3.6) and 19b (pHiEP = 2.9) is probably connected with the different hydrophobicity of polycarboxybetaine chains, e.g., the cationic group of 19b is more effectively screened by ethyl substituents, as they are bulkier than the methyl groups of 19a. The effect of organic solvent on the solution behavior of 19b was studied [193]. In saline water, the conformation of 19b is compact due to the screening of the electrostatic repulsion by the neutral salt KCl. Addition of ethanol improves the thermodynamic quality of the solvent with respect to the hydrophobic parts of the macromolecules, and the reduced viscosity increases and has the maximal value at 60-80 vol % of ethanol in a water/ethanol mixture. 

At pH 2.5, the EOF is approximately 10 cm /V/s in 50 mM buffer. At pH 7, it is an order of magnitude higher. The EOF is inversely proportional to BGE viscosity and is proportional to temperature, up until the point where heat dissipation is inadequate. Organic modifiers such as methanol decrease the EOF because hydro-organic mixtures have higher viscosity compared to water alone. Acetonitrile does not strongly affect the EOF. Polymer additives such as methylcellu-lose derivatives increase viscosity as well as coat the capillary wall. 

Figure 5.7 shows the temperature dependence of the viscosity of water-methanol and water-acetonitrile mixtures in the entire composition range [132]. The existence of a viscosity maximum for a methanol concentration close to 45% is conspicuous. For water-acetonitrile, there is also a viscosity maximtun, but it is less pronounced and takes place at a lower organic solvent concentration ( 20%). We also show in Figure 5.8 the variation of the viscosity of various aqueous solutions with their composition [135]. 

In all these calculations we need to know the viscosity of the mobile phase. Table 2.2 contains the data for the solvents commonly used in HPLC. Most mobile phases, however, are mixtures of solvents. For nonpolar solvents, one can estimate the viscosity of a mixture by linear interpolation between the viscosities of the component solvents. This is not true for aqueous mixtures due to the strong association of polar solvents. Since aqueous mixtures are the mobile phases for reversed-phase chromatography, it is important to know their viscosity. Figure 2.9 ows the viscosity of the aqueous mixtures of the polar organic solvents commonly used in reversed-phase chromatography. Note that the water-alcohol mixtures exhibit a pronounced viscosity... 

Dioxane is a cyclic diether forming a six-membered ring [20]. Thus it is a nearly nonpolar symmetric molecule. 1,4-Dioxane is an extraordinary solvent, capable of solubilizing most organic compounds, and water in all proportions, and many inorganic compounds. The self-diffusion coefficient of dioxane is 1.1 x 10 cm /s, about half that of a water molecule. The effective diameter of dioxane is 5.5 A - about twice that of a water molecule. One should not forget that a water-dioxane mixture narrowly avoids a lower critical consolute point. However, the effects of criticality are reflected in the values of ffie mutual diffusion coefficient and viscosity. Note that binary mixtures are often chosen so that they are mixable (do not phase separate). Thus, the two components interact attractively and strongly. 

Cordless, rechargeable electro-pneumatic reagent sprayers that can apply solutions that are viscous (e.g., aqueous sulfuric acid) or of normal viscosity (water-organic solvent mixtures) in an even, fine (0.3-10 pm), reproducible aerosol are commercially available (e.g., from Camag and Desaga) to facilitate application of detection reagents (Figure 8.3). 

Tar sand, also variously called oil sand (in Canada) or bituminous sand, is the term commonly used to describe a sandstone reservoir that is impregnated with a heavy, viscous black extra heavy cmde oil, referred to as bitumen (or, incorrectly, as native asphalt). Tar sand is a mixture of sand, water, and bitumen, but many of the tar sand deposits in the United States lack the water layer that is beHeved to cover the Athabasca sand in Alberta, Canada, thereby faciHtating the hot-water recovery process from the latter deposit. The heavy asphaltic organic material has a high viscosity under reservoir conditions and caimot be retrieved through a weU by conventional production techniques. 

Polybutene resins. These liquid resins are obtained by cationic polymerization of petroleum C4 streams in the presence of AICI3 at relatively low temperature. Temperature and AICI3 concentration are important factors as they influence the molecular weight and viscosity of the final resin. After reaction, the mixture is deactivated with water, methanol, ammonia or aqueous sodium hydroxide. The organic layer is separated and distilled to remove solvent and unconverted material. 

If a waste is a mixture of water and organic liquid, you must report it as wastewater unless the organic content exceeds 50 percent. Slurries and sludges containing water must be reported as solid waste if they contain appreciable amounts of dissolved solids, or solids that may settle, such that the viscosity or density of the waste is considerably different from that of process wastewater. 

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