Clear water phase

It is quite clear, first of all, that since emulsions present a large interfacial area, any reduction in interfacial tension must reduce the driving force toward coalescence and should promote stability. We have here, then, a simple thermodynamic basis for the role of emulsifying agents. Harkins [17] mentions, as an example, the case of the system paraffin oil-water. With pure liquids, the inter-facial tension was 41 dyn/cm, and this was reduced to 31 dyn/cm on making the aqueous phase 0.00 IM in oleic acid, under which conditions a reasonably stable emulsion could be formed. On neutralization by 0.001 M sodium hydroxide, the interfacial tension fell to 7.2 dyn/cm, and if also made O.OOIM in sodium chloride, it became less than 0.01 dyn/cm. With olive oil in place of the paraffin oil, the final interfacial tension was 0.002 dyn/cm. These last systems emulsified spontaneously—that is, on combining the oil and water phases, no agitation was needed for emulsification to occur. 

Example 1. Alkaline Hydrolysis of Nylon-6,6 in Isopropanol.9 Isopropanol (209 parts), 267 parts of water, 54 parts of 97% sodium hydroxide, and 100 parts of nylon-6,6 were charged to a 1-gal stainless steel autoclave. Under an atmosphere of nitrogen, the charge, which weighed 1060 g, was heated in the autoclave to 180°C for 1.5 h with constant agitation and then cooled. A clear two-phase liquid was obtained which had an alcoholic upper phase and an... 

In the case of E-IIs, we do not deal with a transport protein as described in Fig. 5. Clearly, the most important difference is that the substrate is chemically modified. Therefore, we do not know whether or not a state Ecyt S is in contact with the internal water phase, if it exists at all. On the other hand, since transport is part of the overall function of E-IIs, translocations as described in Fig. 5 may very well be part of the... 

The partial pressure of H2S on a volumetric basis in the atmosphere in equilibrium with a water phase of sulfide (H2S + HS ) is at a pH of 7, approximately equal to 100 ppm (gS m-3)-1 (Figure 4.2). It is clear that under equilibrium conditions, much lower concentrations than those corresponding to the values shown in Table 4.6 may result in odor and human health problems. This is also seen from the fact that Henry s constant for H2S is rather high, //H2S =563 atm (mole fraction)-1 at 25°C (Table 4.1). However, under real conditions in sewer networks, conditions close to equilibrium rarely exist because of, for example, ventilation and adsorption followed by oxidation on the sewer walls. Typically, the gas concentration found in the sewer atmosphere ranges from 2-20% and is normally found to be less than 10% of the theoretical equilibrium value (Melbourne and Metropolitan Board of Works, 1989). 

Preparation of 4-12-cvclohexenvloxv )-stvrene. A stirred mixture of 34.36g (0.096 mole) methyltriphenylphosphonium bromide and 10.75g (0.096 mole) potassium t-butoxide in 200ml dry THF is treated drop-wise with a solution of 16.16g (0.080 mole) of 4-(2-cyclohexenyl)-benzaldehyde in 30ml THF under inert atmosphere. Once the addition of aldehyde was completed, the mixture was stirred at room temperature for another 2 hours. Ether and water were then added to the reaction mixture until clearly separated phases were obtained with no solid residue. The organic layer was separated and washed three times with water, dried over magnesium sulfate and evaporated. The resulting semi-solid was triturated in 10% ethyl acetate-hexane mixture to remove most of the triphenylphosphine and the evaporated extract was purified by preparative HPLC using hexane as eluent. This afforded 9.35g (58%) of the pure monomer, which was fully characterized by H and C-NMR as well as mass spectrometry. 

In recent monitoring campaigns conducted in Germany, Spain and The Netherlands, where NPEC was also included, the NPEC concentrations detected were almost always higher than NPEO and NP in the water phase. Thus it is clear that it is also necessary to include the NPECs, in particular NPEi 6C, in the group of analytes to be monitored in further sampling campaigns. 

Furthermore from the computed area of the cross-section of the interface occupied by one soap molecule it is clear that the molecules of the soap are relatively close together and orientated in a plane at right angles to the interface. As has already been noted in the case of the air-water interface the fatty acids are orientated with their polar carboxyl groups in the water phase we would consequently anticipate that in the oil-water interface the same orientation would occur, the hydrocarbon chain being immersed in the paraffin phase and the polar —OOONa or —COOK group in the aqueous phase. Such orientation is an important factor in the... 

With this equation the actual membrane concentration of a hydrophobic compound can be estimated if its concentration in the water phase is known. For instance, limonene, a hydrophobic precursor in many biotransformations to produce monoterpenoid flavour compounds (logPoctanoi/water=4.5), would accumulate within membranes in concentrations of up to 530 mM if it is present in the water phase at saturation concentration of only 0.1 mM [19]. This concentration would clearly not allow conventional microorganisms to survive. 

The enzyme may be dissolved in a mixed aqueous-ionic liquid medium, which may be mono- or biphasic or it could be suspended or dissolved in an ionic liquid, with little or no water present. Alternatively, whole cells could be suspended in an ionic liquid, in the presence or absence of a water phase. Mixed aqueous-organic media are often used in biotransformations to increase the solubility of hydrophobic reactants and products. Similarly, mixed aqueous-ionic liquid media have been used for a variety of biotransformations, but in most cases there is no clear advantage over water-miscible organic solvents such as tert-butanol. 

Note that the last paragraph contains two-phase regions (H-V, H-Lhc, and I-H) for hydrate equilibrium with a phase that is not liquid water. There is a common misconception that hydrates cannot form without a liquid water phase, a condition clearly possible in these diagrams. Professor Kobayashi s laboratory measured hydrate conditions without a free water phase from vapor or liquid systems from 1973 to 2000. Such equilibria are of interest for gas and gas condensate pipelines without a free water phase. 

After total addition of 9mL water, resulting in the weight fractions u>il = 0.45, WaicIj = 0.16 and u>h2o = 0.39, the mixture was stirred for 15 min. Subsequently the sample was shaken for an additional 10 min while cooling to ambient conditions. At room temperature the mixture divided into two liquid phases. These phases were separated (Figure 11.19) by centrifugation (20 min at 2460 g). The lower clear and more viscous phase was presumed to be the IL phase and the upper liquid the water phase. At the interface fine particles were collected. 

For the same reason the addition of an oily phase to water-based products can help considerably in promoting perfume stability. Most perfume materials are far more readily soluble in fats and in oils than in water, and to the extent that the product formulation provides an oil or fat phase into which they can escape, they are sheltered from the attack by the hydroxy ions of bases, the hydrogen ions of acids, the oxidizing agents and enzymes—all of which operate only in the water phase. Hence cloudy cold wave lotions, which contain emulsified oil, are easier to perfume than clear ones, cream depilatories cause less severe problems than fat-free formulations, and so on. 

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