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Solvents, mixed aqueous openness

In recent years Ciobanu et al. [55] paid attention to the Ag Ag2S electrode embedded into an acrylic copolymer matrix. Their studies have shown that such electrode exhibits stable potential in different media including aqueous solutions of different species and in mixed (aqueous/nonaqueous) and nonaqueous solvents. As the authors suggest [55] such electrodes may be successfully applied in electrochemical microanalysis when the volume of the analyzed sample is on the pm level. The open circuit potential was stable in the limits 2 mV in different solvents. [Pg.102]

Recall that the mass balance equations of Eqs. (1.1a) and (1.1b) incorporate not only terms for internal chemical reactions but also terms for physical mass transport across the boundaries of the control volume. Often, useful control volume boundaries coincide with boundaries between phases, such as between air and water or between water and solid bottom sediment, as discussed for the lake control volume in Section 1.3.1. Note, however, that the terms "environmental media" and "phases" are not interchangeable. For example, chemicals in the gas phase can refer to chemicals present in gaseous form in the atmosphere or in air bubbles in surface waters or in air-filled spaces in the subsurface environment. Chemicals in the aqueous phase are chemicals dissolved in water. Chemicals in the solid phase include chemicals sorbed to solid particles suspended in air or water, chemicals sorbed to soil grains, and solid chemicals themselves. In addition, an immiscible liquid (i.e., a liquid such as oil or gasoline that does not mix freely with water) can occur as its own nonaqueous phase liquid (NAPL, pronounced "napple"). Some examples of mass transport between phases are the dissolution of oxygen from the air into a river (gas phase to aqueous phase), evaporation of solvent from an open can of paint (nonaqueous liquid phase to gas phase), and the release of gases from new synthetic carpet (solid phase to gas phase). Mass transport between phases is affected both by physics and by the properties of the chemical involved. Thus, it is important to imderstand both the types of chemical reactions that are common in the environment, and the relative affinities that various chemicals have for gas, liquid, and solid phases. [Pg.21]

Figure 27 shows the temperature dependence of the transmittance of the solution of complexes composed of PVPo-PMAA and PVPo-PAA in water and DMF. The transmittance is measured immediately after mixing the solution of PMAA and PVPo at constant temperature, because when the complex molecules are once formed they tend to aggregate with each other in the process of time. Such aggregation phenomenon of intercomplexes is discussed in detail in Sect. 4.3. At elevated temperatures, it is expected that the kinetic energy of a polymer chain and hydrophobic interactions increase (up to 60 °C in aqueous medium) and the dielectric constant of the solvent decreases. In aqueous medium (indicated by open circles in Fig. 27), the transmittance... [Pg.52]

Alkyl halide (10 — 25 mg) is mixed with 0.5 ml of a 2% acetonic thiourea solution and heated in a sealed glass ampoule in a water bath for various time intervals iodides, 1 hr bromides, 2 hr chlorides (if the mixture was additioned with 10 mg of sodium iodide as catalyst) 3 hr. After cooling, the ampoule is opened and the contents transferred into a small test tube, and the solvent is evaporated on a water bath. The residue is dissolved in two drops of water and mixed by dropwise addition and shaking with 1 ml 2% aqueous sodium 3,5-dinitrobenzoate solution. The separatedamo rphous product is dissolved by immersing the test tube into a hot water bath, and is then allowed to crystallize by slow cooling. The product is recrystallized from 0.5 — 1 ml of hot water. [Pg.141]

Aqueous solutions of amine are considered as promising solvent but the selection of the best adapted molecule is still open. Then important experimental work will be necessary to characterize and test the dissolution of carbon dioxide. In this domain, determination of calorimetric properties such as enthalpy of solution of carbon dioxide in absorbent solutions will be essential. The enthalpies of solution are particularly important for the estimation of the energy required for the solvent regeneration step of an industrial process. For theoretical point of view, this thermodynamic property participates to the development of thermodynamic models representative of gas-absorbent systems. This chapter has focused on mixing calorimetric techniques used to investigate gas dissolution in liquid absorbents. The presented techniques can be adapted, in studies of CO2 dissolution in aqueous solution of amines, to investigate for example each chemical reaction involved such as amine protonation or carbamate formation. [Pg.500]


See other pages where Solvents, mixed aqueous openness is mentioned: [Pg.1483]    [Pg.141]    [Pg.227]    [Pg.1306]    [Pg.584]    [Pg.1487]    [Pg.7]    [Pg.264]    [Pg.210]    [Pg.299]    [Pg.131]    [Pg.139]    [Pg.1823]    [Pg.163]    [Pg.184]    [Pg.645]    [Pg.1823]    [Pg.286]    [Pg.140]    [Pg.126]    [Pg.1823]    [Pg.274]    [Pg.115]    [Pg.74]    [Pg.382]    [Pg.263]    [Pg.359]    [Pg.57]    [Pg.72]    [Pg.26]    [Pg.327]    [Pg.325]    [Pg.633]    [Pg.549]    [Pg.206]    [Pg.445]    [Pg.443]    [Pg.654]   
See also in sourсe #XX -- [ Pg.78 ]




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