Bulk solution, sulfate concentration

Fig. 12. Salt retention by coUoidal particles. The curved dashed and soHd lines represent the surface of a negatively charged siUca particle. Around this there is a layer of counter sodium cations outside there is a layer in which sulfate anions (Q) are more concentrated than in the bulk solution.

At their critical micelle concentrations, surface active agents (such as sodium dodecyl sulfate, Triton X-100, lysolecithin, and bile salts) self-associate into spherical or rod-shaped structures. Because dilution to below the c.m.c. results in rapid disassembly or dissolution of these detergent micelles, micelles are in dynamic equilibrium with other dissolved detergent molecules in the bulk solution. 

Fig. 8 Results of the regression analysis of Eq. 56 for surface potential of the air-water interface with the adsorption of alkali dodecyl sulfate molecules as a function of the surfactant concentration in the bulk solution...

Figure 7.16 Dependence on tlie polysaccharide concentration CDS of (a) tlie second virial coefficient A2 and (b) tlie stmcture-sensitive parameter p of complexes of sodium caseinate + dextran sulfate , complexes prepared in bulk solution a, complexes prepared at tlie interface in a protein-stabilized foam , sodium caseinate alone. Reproduced from Semenova et al. (2009) with permission.

The hydrolysis of concentrated solutions of titanium sulfate (170-230 g Ti02/L) proceeds very sluggishly and incompletely (even if boiled) unless suitable nuclei are added or formed to accelerate hydrolysis. The nuclei are usually produced by two methods. In the Mecklenburg method, colloidal titanium oxide hydrate is precipitated with sodium hydroxide at 100°C 1% of this hydrate is sufficient. In the Blumenfeld method a small part of the sulfate solution is hydrolyzed in boiling water and then added to the bulk solution [2.31]. The particle size of the hydrolysate depends on the number of nuclei. 

The bulk solution becomes impoverished with respect to oxygen. However, the sulfate concentration remains constant as long as the recycling rate of reduced sulfur to sulfate is higher than the sulfate reduction rate (denoted SRR in Figure 6). In the opposite case the sulfate concentration of the bulk solution also decreases, and H2S is slowly enriched (point 6). The requirements for FeS precipitation and subsequent pyrite formation are then fulfilled (point 7). 

A comprehensive study on the sonochemical synthesis of colloidal solutions of noble metals was conducted by Grieser and coworkers [32-34]. The 515 kHz ultrasound-initiated reduction of AuCl4 to Au (0) was examined as a function of the concentration of various surface-active solutes [32]. The amount of AuCU reduced in the presence of ethanol, 1-propanol, and 1-butanol was found to be dependent on the surface excess of the alcohol at the gas/solution interface, i.e., the relative concentration of the alcohol at the gas/solution interface compared to the bulk solution concentration. The efficiency of reduction of AuCl4 in the presence of the surfactants sodium dodecyl sulfate or octaethylene glycol monodecyl ether was found to be related to the monomer concentration of the surfactant in solution. 

The addition of nitrate to the bulk solution led to more significant delays in initiation of crevice corrosion (Fig. 7) of 304 SS compared to sulfate. For example, to produce an initiation time of 75 min required 1.5 mM S04 , but only 23 pM NOs. At low bulk [Cl ] [NO3-] ratios ([N03 ] = 1.7 mM), no initiation of crevice corrosion was observed within 180 min, whereas in solutions in which crevice corrosion did occur the composition of the crevice solution was essentially independent of the initial concentration of nitrate in the bulk solution. However, the relative concentration of Cl compared to NO3 in the crevice was nearly three times... 

If foam is produced by blowing an inert gas through the solution of alkyl sulfate (or any other surfactant), the bulk of hydrophobic impurities will be enriched in the thin films of the foam bubbles. The remaining solution will then become more and more purified. Another method uses the primary adsorption of substances with the strongest surface activity at interfaces. Hence, the hydrophobic impurities will adsorb at the water/air interface and can then be sucked away from the surface. Automatic devices can decrease the surface area of the solution to concentrate the surfactant-containing layer, suck away these layers, expand the surface again for repeated adsorption, and repeat the cycle, etc. After some hundred cycles, the solution will become interfacially pure . 

Under a low evaporation condition, the wet-dry interface can occur in the tip of the pwre solution zone, where the rate of evaporation is fast compared with the rate of solution rise, because solution rises into the bulk at a rate that decreases with height. At the same time the sulfate concentration of pore solution will slowly increase until the complete sample has reached saturation, forming a high concentration pore solution zone, where the efflorescence occurs. Near the solution a liquid film occurs on the surface of the element, where the rate of rise if fast compared with the evapwration and the sulfate concentration is dose to the expwsure solution l o). In this case the deterioration due to salt crystallization is minor (as shown in Fig. 4 (b)). 

For example, let us consider a solution of an ionic surfactant, which is a synunetric 1 1 electrolyte, in the presence of a symmetric, 1 1, inorganic electrolyte (salt). We assume that the counterions due to the surfactant and salt are identical. For example, this can be a solution of sodium dodecyl sulfate (SDS) in the presence of NaCl. We denote by c, , C2 , and the bulk concentrations of the surface-active ions, counterions, and coions, respectively (Figure 4.1). For the special system of SDS with NaCl c, , C2 , and are the bulk concentrations of the DS", Na+ and Cl ions, respectively. The requirement for the bulk solution to be electroneutral implies C2 = c, + The multiplication of the last equation by y yields... 

Figures 12 and 13 show plots of the surface tension of sodium dodecyl ether (1 EO) sulfate and sodium dodecyl sulfate (2 EO) sulfate vs. their bulk concentration in distilled water and in sodium chloride solutions of 0.1 and 0.5 M total ionic strength at 10, 25, and 40°C [125].

Most primary and secondary minerals found in soil systems are barely soluble in the soil solution. The amount of mass from the bulk phase to hydrated ions in soil solution is negligible compared to the total mass of the solid phase. In arid and semi-arid soils, concentrations of most trace metals in soil solution may be controlled by their carbonates and to some extent by their hydroxides. Other than carbonates, trace elements in arid and semi-arid soils may also occur as sulfate, phosphate or siliceous compounds, or as a minor component adsorbed on the surface of various solid phase components. The solubility of carbonates, sulfates and other common minerals of trace elements in arid and semi-arid soils will be discussed in Chapter 5. Badawy et al. (2002) reported that in near neutral and alkaline soils representative of alluvial, desertic and calcareous soils of Egypt, the measured Pb2+ activities were undersaturated with regard to the solubility of... 

This reaction resembles decarboxylation of carboxylates during electrode one-electron oxidation (Kolbe reaction). Kolbe reaction also consists of one-electron oxidation, decarboxylation, and culminates in dimerization of alkyl radicals just after their formation at the electrode surface. When the sulfate radical acts as a one-electron oxidant, the caboradical dimerization is hampered. The radicals can be used in preparative procedures. One typical example is alkylation of heterocyclic nitrogen bases (Minisci et al. 1983). This difference between Kolbe reaction and the reaction with the help of a dissolved electrode (the sulfate radical) deserves some explanation. The concentration of the one-electron oxidation products in the electrode vicinity is significantly higher than that in the bulk of the solution. Therefore, in the case of anode-impelled reactions, the dimerization of radicals produced from carboxylates proceeds easily. Noticeably, 864 secures the single electron nature of oxidation more strictly than an anode. In electrode reactions, radical intermediates can... 

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