Wilke-Chang technique

An older, but still widely used, correlation for D°AB, the Wilke-Chang technique, is, in essence, an empirical modification of the Stokes-Einstein relation (Eq. 4). Several systems were studiedby these investigators, and an average error of about 10% was noted ... 

Thus generally, for liquids D°AB D°BA. Different techniques with which to estimate the infinite dilution diffusion coefficient are described by Reid et al. [31]. Various correlation s (valid for an arbitrary composition of a binary mixture and for electrolytes) are also given. In the Wilke-Chang correlation for D°AB the effect of temperature has been accounted for by assuming D°AB — T. Although this approximation may be valid over small temperature ranges, it is usually preferable to assume that... 

Wilkes et al (22.23) coupled calorimetric, dynamic-mechanical and x-ray diffraction techniques to demonstrate crystallization of the lipids was completely reversible in neonatal rat stratum corneum, and only partially reversible in human stratum corneum. Melting regions near 40°C and from 70 to 90°C corresponded to the thermal transitions noted in the calorimetric studies for both species. The crystalline nature of the lipids did not appear to be dependent on the presence of water. X-ray diffraction and infrared spectroscopy studies (23.28-34) have also shown a to p conformational changes occurred in keratin and stratum corneum protein components with hydration or exposure to increased temperatures. Oertel (28) has reported pretreatment with dimethylsulfox-ide, hexylmethylsulfoxide and decylmethylsulfoxide resulted in the formation of p-sheet protein conformations in vitro in human... 

The technique of simultaneous absorption with fast pseudo-mth-order reaction and physical absorption or desorption concurrently, used by Wilke and Robinson (R14), Linek (L15), and Beenacker and Van Swaaij (Bll), is certainly a promising effort to understand the whole complex problem of transport in gas-liquid reactors, since it provides simultaneous measurement oik fi and a. But still it may leave some doubt as to a value of/cL, which can be changed by the occurrence of chemical reaction. As discussed by Prasher (P13), it will be even more promising to conduct such simultaneous experiments in a regime where both hydrodynamics and reaction have comparable effects. 

Comaish (1968) has applied the technique of multiple internal reflection (MIR) to intact human skin in vivo. Using a germanium reflector plate he obtained spectra (in a Wilks Skin Analyzer ) of normal skin (Fig. 18.7) and various dermatoses (e.g., Fig. 18.8) and found gross changes from the normal in the lesions of psoriasis, eczema, and other disorders. He has also demonstrated abnormalities in the clinically normal skin of psoriatic patients. The technique measures surface changes, so that only the outer layers of stratum corneum, sweat, sebum, and extraneous materials will affect the results obtained. Lactic acid, lactate, and ammonia from sweat probably contribute substantially to the bands at 2935, 1465, 1125, and 1045 cm . After the skin was washed and dried these bands were diminished or disappeared entirely. Any contributions the stratum corneum makes to the infrared spectrum are at 2870, 1650, and 1550 cm . ... 

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