Critical value, viii

In some cases under the conditions similar to those corresponding to the formation of lyophilic colloidal systems, a spontaneous formation of emulsions, the so-called self-emulsification, may take place. This is possible e.g. when two substances, each of which is soluble in one of the contacting phases, react at the interface to form a highly surface active compound. The adsorption of the formed substance under such highly non-equilibrium conditions may lead to a sharp decrease in the surface tension and spontaneous dispersion (see, Chapter III, 3), as was shown by A.A. Zhukhovitsky [42,43], After the surface active substance has formed, its adsorption decreases as the system reaches equilibrium conditions. The surface tension may then again rise above the critical value, acr. Similar process of emulsification, which is an effective method for preparation of stable emulsions, may take place if a surfactant soluble in both dispersion medium and dispersed liquid is present. If solution of such a surfactant in the dispersion medium is intensively mixed with pure dispersion medium, the transfer of surfactant across the low surface tension interface occurs (Fig. VIII-10). This causes turbulization of interface... 

In the case of electrolytes that are capable of causing the reversal of surface charge of dispersed particles, coagulation occurs only at electrolyte concentrations corresponding to rather small values of the -potential. As electrolyte concentration becomes higher, the C, -potential decreases coagulation starts as soon as the C, -potential drops below the critical value. This corresponds to the first critical coagulation concentration, C.C.C. -1, (c, point in the curves shown in Fig. VIII-19). Further increase in electrolyte... 

Table VIII. Critical SD Values for Mix-Separate Model...

After their leading publication on the osmium-catalyzed dihydroxylation of olefins in the presence of dioxygen [208], Beller et al. [209] recently reported that alcohol oxidations could also be performed using the same conditions. The reactions were carried out in a buffered two-phase system with a constant pH of 10.4. Under these conditions a remarkable catalyst productivity (TON up to 16 600 for acetophenone) was observed. The pH value is critical in order to ensure the reoxidation of Os(VI) to Os(VIII). The scope of this system seems to be limited to benzylic and secondary alcohols. 

The k standard deviation data and R.A.A.D. values listed in Table VIII for the data of the present investigation and certain data from previous studies (3,4) demonstrate clearly that Equation 1 can satisfactorily correlate the salt effects of the inorganic salts tested at fixed-liquid composition in ethanol-water, at all salt concentrations up to saturation. The R.A.A.D. yields a critical evaluation of the applicability... 

Tables of values of 4 for various substances are given by Partington, Kistiakowsky,7 Jellinek, and Landolt-Bdrnstein. A short selection of values, additional to those in Louginine s table ( l.VIII L) is given below in g.cal./mol (i.e. Le=M4). The b.p. abs. (T ), sp. vol. of liquid vi ml./g. at the b.p.) and the critical constants, are also given. (For LJ l) and L 2) see 4.VIII L.)...

For meaningful model simulations, it is important that the thermochemical data base is accurate and internally consistent. The data base contained in PHREEQE is the same as the data base developed for WATEQ2 (30). This data base has been critically reviewed (31) and compared with WATEQFC (32). The values of Log K for solids included in this simulation, along with appropriate reactions from which they were determined, are listed in Table VIII. 

Analogously, for any other fluctuating value, the average square fluctuation equals the ratio of kT to the second derivative of work (free energy) of fluctuations with respect to the fluctuating parameter. We will utilize this approach in describing the optical properties of disperse systems (further down in this chapter), the electric properties of aerosols (see Chapter VIII), and the conditions of the formation of critical emulsions (see Chapter VI,2). 

Scheme VIII has been suggested (3) to explain negative values of dEajdT in the hydrolysis of r-butyl chloride, a possible intermediate being an ion pair. [See, however. Section V for a criticism of this explanation (149).] The impossibility of distinguishing kinetically between the case of E> B and that of E a Ex has been stated. Furthermore, a qualitative graph of Ea versus T has been given, which closely resembles Figs. 1 to 3, with reversed sign.

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