Diffusion, xiii

The cleaning process proceeds by one of three primary mechanisms solubilization, emulsification, and roll-up [229]. In solubilization the oily phase partitions into surfactant micelles that desorb from the solid surface and diffuse into the bulk. As mentioned above, there is a body of theoretical work on solubilization [146, 147] and numerous experimental studies by a variety of spectroscopic techniques [143-145,230]. Emulsification involves the formation and removal of an emulsion at the oil-water interface the removal step may involve hydrodynamic as well as surface chemical forces. Emulsion formation is covered in Chapter XIV. In roll-up the surfactant reduces the contact angle of the liquid soil or the surface free energy of a solid particle aiding its detachment and subsequent removal by hydrodynamic forces. Adam and Stevenson s beautiful photographs illustrate roll-up of lanoline on wood fibers [231]. In order to achieve roll-up, one requires the surface free energies for soil detachment illustrated in Fig. XIII-14 to obey... 

The Primary Processes. The energetics of the dissociation are given in Table XIII. Herzberg and Ramsay found the absorption bands of NH2 in the region from 5700 to 6900 A. when they carried out the flash photolysis of ammonia in the diffuse-banded region.98 The detailed analysis of these bands was later made by Dressier and Ramsay.97 These absorption bands coincided with the ammonia a bands in emission. They found no absorption by NH. 

Zwietering, P., I. Overeem, and D. W. van Krevelen Chemical Structure and Properties of Coal. XIII — Activated Diffusion of Gases in Coal. Fuel 35, 66/70 (1956). 

William T. Carnall 37, p. xiii diketonates, see beta-diketonates diffusion in metals 1, ch. 12, p. 847 divalent samarium in organic... 

J. Chem. Soc., 1851, iii, 60- Researches, 1876, 544-51. Some interesting remarks on liquid diffusion were made by Berthollet, Statique Chimique, 1803, i, 412, 428 Wroblewski, Ann. Phys.y 1881, xiii, 606. Rumford (1807) measured the rise of a drop of oil of cloves floating in... 

Fig. 14. Current versus l//t at 370 C for cell XIII, The slopes are linear indicating a diffusion process. See Eqs. (51) and (52), The voltages at infinite time given by the intercepts are due to the residual steady state electron hole leakage. After Goldman (36),...

Hallervorden, j. Die familiare infantile diffuse Himsclerose, Typus Krabbe. In Die degenerative diffuse Sklerose (Pelizaeus-Merzbachersche Krankheit, Leukodystrophie Typus Scholz, diffuse Sklerose Typus Krabbe). In Handbuch der spez. path. Anat., Bd. XIII/1, S. 716. Berlin-Gottingen-Heidelberg Springer 1957. 

The results for the persulfate-initiated polymerizations were used to calculate the kinetic parameters of the benzoyl peroxide-initiated pol3mierizations. Table XIII shows that the values of z were all smaller than one, i.e., the rates of emulsion polymerization are smaller than for the corresponding persulfate-initiated solution polymerization. Moreover, the values of n were in the range 0.006-0.2, in accord with Smith-Ewart case 1 kinetics (n l). Since benzoyl peroxide is soluble in o-xylene and virtually insoluble in water, the radicals which initiate polymerization apparently arise from the decomposition of that benzoyl peroxide dissolved in the aqueous phase the presence of monomer may increase the solubility of benzoyl peroxide in the aqueous phase and the layer of Span 60 adsorbed at the particle interface may form a barrier to the diffusion of the hydrophobic radicals from the o-xylene phase to the aqueous phase. 

Equation 10.13 is the classical rate expression for a homogeneous, free-radical polymerization. It has been an extremely useful approximation over the years, particularly in fairly dilute solutions, but deviations from it are sometimes observed. It is now evident that many deviations are due to the fact that the termination reaction is diffusion controlled, so k, is not really a constant. In certain cases of practical interest, these deviations can be of major significance. They are discussed in Chapter XIII on polymerization practice. 

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