Solubilizing effect

The covalent character of mercury compounds and the corresponding abiUty to complex with various organic compounds explains the unusually wide solubihty characteristics. Mercury compounds are soluble in alcohols, ethyl ether, benzene, and other organic solvents. Moreover, small amounts of chemicals such as amines, ammonia (qv), and ammonium acetate can have a profound solubilizing effect (see COORDINATION COMPOUNDS). The solubihty of mercury and a wide variety of mercury salts and complexes in water and aqueous electrolyte solutions has been well outlined (5). 

LialkylSulfosuccinates. Introduced in 1939 by the American Cyanamid Company under the Aerosol trademark, dialkyl sulfosuccinates have become widely used specialty surfactants (Table 8) (9). Within the limitations in hydrolytic stabiUty imposed by the presence of the ester groups, sulfosuccinates are mild, versatile surfactants used when strong wetting, detergency, rewetting, penetration, and solubilization effectiveness is needed. 

Salts of monovalent metals of alcohol and alcohol ether sulfates are soluble in water, with the solubility dependend on the cation and the chain length. Ammonium salts are more soluble than sodium salts and these are more soluble than potassium salts. On the other hand, sulfates with short hydrophobic chains are more soluble than those with longer chains but the short-chain molecules have a solubilizing effect on the more insoluble longer chain molecules [68], The solubility of sodium salts of different alcohol sulfates is shown in Fig. 2 and the solubility of sodium and potassium salts of dodecyl sulfate is compared. 

Since commercial products are mixtures of homologs they are more soluble than the pure components due to the solubilizing effect of the short-chain homologs as mentioned above. Table 5 shows the solubility in water of calcium salts of alcohol sulfates at 25°C [73]. 

Foam low high Alkali stab Electrolyte stab Acid stab Chlorine stab Surface tension Detergent effect Hydrotropic effect Solubilizing effect Biodegrad- ability... 

The effect of surfactant structures and properties on emulsion polymerization have been investigated by numerous authors [82-89]. Efforts were made to study the effects of surfactants with different molecular weights on the rate of polymerization [82], swelling and solubilization effects [83], effects of alkyl chain length of homologous series on the rate of polymerization, particle size... 

There are different ways in which the nanoparticles prepared by ME-technique can be used in catalysis. The use of ME per se [16,17] implies the addition of extra components to the catalytic reaction mixture (hydrocarbon, water, surfactant, excess of a metal reducing agent). This leads to a considerable increase of the reaction volume, and a catal5fiic reaction may be affected by the presence of ME via the medium and solubilization effects. The complex composition of ME does not allow performing solvent-free reactions. 

In addition to knowing the total MTC solubility, it was important to determine the amount of methanol or other solvent retained by the MTC. This quantity, the incorporation ratio (R, gm incorporated organic material/gm coal-derived organic material), was determined by a carbon balance on the reaction. By assuming that any solvent retained in the dried MTC is pyridine-soluble, and subtracting it from the total dissolved material, the minimum solubility of the coal-derived material may be calculated. This quantity, the corrected solubility, is an indicator of the true solubilizing effect on the coal by the particular run conditions. ... 

Other solubilities relevant to this section include those for LaCl3 in aqueous ammonia (173), lanthanide trifluorides in aqueous hydrofluoric acid (133b, 240b, 281,315), and lanthanide trifluorides in aqueous trifluoroacetic acid (316). Trifluoroacetic acid seems to have a marked solubilizing effect on these trifluorides. 

The situation is further confused by qualitative observations, such as the conflicting views as to the solubilizing effect or otherwise of the CH2OH group in kojates and derived hydroxypyridinonates (238). In relation to Table XVIII, the trend of increasing solubility from water to ethanol followed by a steady decrease to 1-decanol, common to ethylmaltol and its iron complex, resembles that established for Fe(bipy)2(CN)2 and Fe(phen)2(CN)2, though in the case of these... 

At concentrations well above the CMC, these effects are complicated by solubilization, but while it seems clear that protein solubilizing effectiveness and membrane activity correlate well, the structural basis for protein solubilization has not yet been clarified either. 

Let us compare the methods applied by Pedersen for establishing the complex formation with a modern approach. Today tedious solubility studies are carried out almost exclusively with practical applications in mind, but they are not performed to prove the complex formation. For instance, one ofthe main reasons for the use of cyclodextrin complexes in the pharmaceutical industry is their solubilizing effect on drugs [8]. There, and almost only there, solubility studies are a must. As concerns spectroscopic methods, at present the NMR technique is one ofthe main tools enabling one to prove the formation of inclusion complex, carry out structural studies (for instance, making use of the NOE effect [9a]), determine the complex stability [9b, c] and mobility of its constituent parts [9d]. However, at the time when Pedersen performed his work, the NMR method was in the early stage of development, and thus inaccurate, and its results proved inconclusive. UV spectra retained their significance in supramolecular chemistry, whilst at present the IR method is used to prove the complex formation only in very special cases. 

Synthetic methods in dendrimer chemistry have developed in recent year to such an extent that one can obtain dendrimers with hydrophilic surface and hydrophobic inside. In such a way dendrimers can exhibit solubilizing effect analogous to that shown by micelles. Similarly to cyclodextrins 278 in the pharmaceutical industry discussed in Sect. 6.3.3, dendrimers can be used as drug... 

Hermansson et al. (36) used pepsin and papain to solubilize rapeseed protein concentrate. Papain had a lower solubilizing effect than did pepsin. However, the fact that pepsin has an optimum pH for activity at about 1.6, far below the pH range of most foods, made it possible to study the effects of controlled hydrolysis. At pH 7.0, all hydrolysates were more soluble than the original rapeseed protein concentrate. 

Despite all the attractive advantages of complexation, there are several disadvantages. First, the compound has to be able to form complexes with a selected ligand. For compounds with very limited solubility to start with, the solubility enhancement can be very limited. Second limitation is that for the complexes oAp type, dilution of a system may still result in precipitation. This is also true for solubilization through combined techniques such as complexation with pH adjustment. Third, the potential toxicity issue, regulatory, and quality control issues related to the presence of the ligand may add to complication and cost of the development process. Finally, the complexation efLciency is often rather low, thus relatively large amount of CDs are typically required to achieve desirable solubilization effect (Loftsson et al., 1999). 

Delmau et al. (129) studied the self-association of fluorinated alcohols used as diluent modifiers for the selective extraction of cesium from caustic media by calixarene-crown ethers. They found that the salt distribution ratio is enhanced by the modifiers and explained this by a solubilization effect of the modifier due to its amphiphilic properties. 

In previous studies, the solubilization of hydrophobic organic contaminants using surfactants has been shown to increase the rate of contaminant desorption from soil to water (Deitsch and Smith 1995 Yeom et al. 1995 Tiehm et al. 1997). A 3,000 mg/L solution of Triton X-100 (CMC = 140 mg/L) increased the rate of desorption of laboratory-contaminated TCE from a peat soil (Deitsch and Smith 1995). However, the solubilization effect was secondary compared to the surfactant s effect on the desorption rate coefficient. Yeom et al (1995) developed a model that satisfactorily predicted the extent of polycyclic aromatic hydrocarbon solubilization from a coal tar-contaminated soil. Only at high surfactant dosages did the model fail to accurately predict the ability of different surfactants to solubilize polycyclic aromatic hydrocarbons. It was hypothesized that mass-transfer limitations encountered by the polycyclic aromatic hydrocarbons in the soil caused the observed differences between the data and the model simulations. In another study (Tiehm et al. 1997), two nonionic surfactants, Arkopal N-300 and Saogenat T-300, increased the rate of polycyclic aromatic hydrocarbon desorption from a field-contaminated soil. The primary mechanism for the enhanced desorption of polycyclic aromatic hydrocarbons was attributed to surfactant solubilization of the polycyclic aromatic hydrocarbons. 

---