Bulk phase absorption

Due to reasons like scattering of visible light at the droplet-bulk interface (the nature of which is dependent on factors like the droplet size as also difference in refractive index of the droplet and the bulk phase), absorption of light in presence of colored matter etc. emulsions are not always clear to the naked eye, but can be opaque to translucent to transparent according to their nature. Table 1.1 gives a... 

In the classical set-up of bulk liquid membranes, the membrane phase is a well-mixed bulk phase instead of an immobilized phase within a pore or film. The principle comprises enantioselective extraction from the feed phase to the carrier phase, and subsequently the carrier releases the enantiomer into the receiving phase. As formation and dissociation of the chiral complex occur at different locations, suitable conditions for absorption and desorption can be established. In order to allow for effective mass transport between the different liquid phases involved, hollow fiber... 

In addition to the surface physics and chemistry phenomena involved, a further effect may follow the interaction at the hydrogen-metal surface, that is the absorption of hydrogen by the bulk phase of the metal. This absorption leads to the formation of a solid solution within a certain, usually low, range of hydrogen concentrations. However, with several transition metals, exceeding a certain limit of hydrogen concentration results in the formation of a specific crystallographically distinct phase of the... 

Thus making samples not too thick helps in getting sharper spectra and facilitates the quantitative interpretation. Finally, particularly in the Mossbauer spectra of small catalyst particles, one should be aware of the temperature dependence of the absorption area through the recoil-free fraction. If the spectrum contains contributions from surface and bulk phases, the intensity of the former will be greatly underestimated if the spectrum is measured at room temperature. The only way to obtain reliable concentrations of surface and bulk phases is to determine their spectral contributions as a function of temperature and make an extrapolation to zero Kelvin [13]. 

Although by now a large number of electrochemical systems have been examined using both SERS and IRRAS, including some common to both techniques (2b), the conditions employed are usually sufficiently different (e.g. disparate surface state, adsorbate concentrations) so to preclude a quantitative comparison of the spectral responses. One further hindrance to such comparisons is that it usually is difficult to remove entirely the contribution to the infrared spectra from solution-phase species. Two types of approaches are commonly used in IRRAS with this objective in mind. Firstly, modulating the infrared beam between s- and p-polarization can achieve a measure of demarcation between surface and bulk-phase components since considerably greater infrared absorption will occur for the former, but not the latter, species for p- versus s-polarized light (2.81. However, a complication is that the "surface... 

Kb, Sb = the absorption and scattering constants of the vehicle (bulk phase of the coating) ... 

The dimensionality of the lattice depends on the physical nature of the phase. For transitions in linear biopolymers and associative colloids, a one-dimensional lattice is used because these materials become ordered in a onc-dimcnsional manner even though they actually exist in three dimensions. For absorption of gas onto a surface, a two-dimensional lattice is sufficient. For bulk phase changes, however, a three-dimensional lattice must be used. 

Materials that have a nonzero second-order susceptibility will produce light at twice the incident frequency. The magnitude of this effect is small, and has been a practical consideration only since the advent of lasers. If the symmetry of a crystal or other medium is such that it has a center of inversion, no SHG effect will be observed. However, surfaces by their very nature break this inversion symmetry. Hence, an SHG signal may arise at the electrode-solution interface even though both bulk phases may be considered centrosymmetric [66], The magnitude of the SHG signal is sensitive to surface conditions (e.g., electrode potential, ionic or molecular adsorption, etc.). Surface spectroscopy is also feasible since the SHG signal will be enhanced if either the incident frequency (to) or SHG (2co) corresponds to an electronic absorption of a surface species [66]. 

Bulk-Phase Compounds Some of our results in the studies of the bulk-phase compounds have been published (3-7) These studies have shown that oxidation state is preserved for these actinides in either a or fT decay Trivalent einsteinium will transmute to trivalent berkelium which transmutes to trivalent californium It has also been observed that divalent einsteinium yields divalent californium. It is interesting to note in this latter case that it has not yet been possible to synthesize divalent berkelium in the bulk phase Berkelium(II) has not been observed in our aged einsteinium(II) compounds either, but it would be logical to assume it has been produced there. Our inability to observe Bk(II) could be related to weak absorption intensities and/or interference by absorption bands of einsteinium(II) or... 

There is substantial history regarding the application of conventional vibrational spectroscopy methods to study the intact surface of skin, the extracted stratum corneum and the ceramide-cholesterol-fatty acid mixtures that constitute the primary lipid components of the barrier. The complexity of the barrier and the multiple phases formed by the interactions of the barrier components have begun to reveal the role of each of these substances in barrier structure and stability. The use of bulk phase IR to monitor lipid phase behavior and protein secondary structures in the epidermis, as well as in stratum corneum models, is also well established 24-28 In addition, in vivo and ex vivo attenuated total reflectance (ATR) techniques have examined the outer layers of skin to probe hydration levels, drug delivery and percutaneous absorption at a macroscopic level.29-32 Both mid-IR and near-IR spectroscopy have been used to differentiate pathological skin samples.33,34 The above studies, and many others too numerous to mention, lend confidence to the fact that the extension to IR imaging will produce useful results. 

Water solubilized by RMs in hydrocarbon solvents by different surfactants (anionic, cationic and zwitterionic) exhibits two absorption bands in the near infrared spectral region (5200-4700 cm 1) due to water populations (Sunamoto et al., 1980), one assigned to the surfactant polar heads and the other to water dispersed in the bulk phase. Three methods have been proposed to evaluate the acidity in the water pool of soft-core of reverse micelles ... 

A purely numerical approach to the solution of this complex reactive absorption problem has been suggested in Ref. [92]. The liquid film is considered as an additional balance region in which reaction and mass transfer occur simultaneously. Therefore, the reactions are considered both in the differential film balances, Eq. (10), and in the liquid bulk phase, Eq. (3). 

This absorption spectrophotometric technique has also been applied to the study of the chemical consequences of radioactive decay in bulk-phase solid state samples (12, 110-112). It was found that the 249Cf daughters growing into crystalline 249BkBr3 and 249BkCl3 exhibited the same oxidation state and crystal structure as their respective berke-lium parents (12, 112). 

As noted earlier, the term adsorption is universally understood to mean the enrichment of one or more of the components in the region between between two bulk phases (i.e. the interfacial layer). In the present context, one of these phases is necessarily a solid and the other a fluid (i.e. gas or liquid). With certain systems (e.g. some metals exposed to hydrogen, oxygen or water), the adsorption process is accompanied by absorption, i.e. the penetration of the fluid into the solid phase. As already indicated, one may then use the term sorption (and the related terms sorbent, sorptive and sorbate). This is the convention that we shall adopt in the present book. The term sorption is used by some authors to denote the uptake of gas or liquid by a molecular sieve, but we do not favour this practice. 

The first is used for the investigation of EPR signals of VO " -containing bulk phases under reaction conditions (i.e., at elevated temperatures and in the presence of reactants). It is based on calculation of the second and the fourth moment of the EPR absorption signals by using Eq. (3) (24) with n — 2 and n — 4, respectively, where A is the area under the absorption curve, Bj and yj are the resonance field value and amplitude at the /th point of the spectrum, and Bq the resonance field value at the center of the absorption line ... 

---