Organic film fractionation

In Equation (16), P is the partial pressure in equilibrium with a solute having mole fraction Xom and activity coefficient yom in the organic film (yom —> 1 as Xom — 1). Pankow s expression for Kp based on absorption considerations is ... 

The Pankow absorption model supposes that gaseous POPs partition into a liquid-like organic film on the aerosol. It uses P,s, the fraction of organic matter in the particle (fom), and the activity coefficient of the solute in the liquid film (yorJ. The latter is apt to vary substantially among different chemical classes of POPs. 

In this section, we are concerned with a mirror-like electrode surface covered with a redox-active thin organic film. Assume that the redox interconversion of the species in the film causes detectable change in the optical properties. In particular, at least one of the compound s oxidation states (both or either of the reduced and oxidized forms) exhibits optical absorption. We first assume that the reflectance at the modified electrode is a linear (first-order) function of the superficial fraction of a chromophore in a given oxidation state. Note that this assumption does not necessarily have a strict rationale in optical theory. We will later return to this point and reconsider it. 

Several studies indicate that the inhibitor blends are effective in solutions whereas pure solvents as dimethylethanolamine are not [1]. A commercial migrating inhibitor blend could be fractionated into a volatile (dimethylethanolamine) and a non-volatile (benzoate) component (9). For complete prevention of corrosion initiation in saturated Ca(OH)2 solution with 1 M NaCl added, the presence of both components at the steel surface in a concentration ratio of inhibitor/chloride of about one was necessary (Figure 13.3). Modern surface analytical techniques such as XPS have confirmed that for the formation of a significantly thicker and protective organic film on iron in aUcahne solutions, both components of the commercial inhibitor blend have to be present (10). Experiments with inhibitor added to mortar showed similar results the inhibitor blend admixed in the recommended dosage could delay the average time to corrosion initiation of passive steel in mor-... 

Fig. 2 Summary of N2O5 uptake suppression for coated particles and films. The ratio of the reactive uptake coefficient, YN205. with and without an organic surface coating, as a function of aerosol organic mass fraction top panel) and liactional surface coverage bottom panel)...

Latexes of synthetic resins are identified by ir spectrometry. Selective extraction with organic solvents is used to obtain purified fractions of the polymers for spectrometric identification. Polymeric films can be identified by the multiple internal reflectance ir technique, if the film is smooth enough to permit intimate contact with the reflectance plate. TAPPI and ASTM procedures have not been written for these instmmental methods, because the interpretation of spectra is not amenable to standardization. 

Porous membranes with selective permeabiUty to organic solvents have been prepared by the extraction of latex films prepared with moderate ratios of PVA—PVAc graft copolymer fractions. The extracted films are made up of a composite of spherical cells of PVA, PVAc microgel, and PVA—PVAc graft copolymers (113). 

The usual range of film coefficient values is 40-50 for organic solvents and light petroleum fractions such as hexanes 25 for heavier materials such as aniline, straw oil, etc. and 0.5-3 for low temperature (10-40°F) subcooling of heavier organics and inorganics such as chlorine. 

Thin self-supporting clay films (appropriate for IR measurement) readily take up organic amines such as cyclohexylamine with displacement of the major fraction of the intercalated water. For the Ua -exchanged sample the majority of the amine is present in the unprotonated form - there being insufficient Bronsted acidity generated by the interlayer cation. When Al + is the exchangeable cation, however, a major fraction of the intercalated amine becomes protonated (see Figure 2). 

The most widely studied deformable systems are emulsions. These can come in many forms, with oil in water (O/W) and water in oil (W/O) the most commonly encountered. However, there are multiple emulsions where oil or water droplets become trapped inside another drop such that they are W/O/W or O/W/O. Silicone oils can become incompatible at certain molecular weights and with different chemical substitutions and this can lead to oil in oil emulsions O/O. At high concentrations, typical of some pharmaceutical creams, cosmetics and foodstuffs the droplets are in contact and deform. Volume fractions in excess of 0.90 can be achieved. The drops are separated by thin surfactant films. Selfbodied systems are multicomponent systems in which the dispersion is a mixture of droplets and precipitated organic species such as a long chain alcohol. The solids can form part of the stabilising layer - these are called Pickering emulsions. 

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