Solubility criterion

Solubility Criteria from Solubility Parameter Comparison of Fullerenes in Fatty Acids and Fatty Acid Esters of Glycerol... 

There are many different solubility criteria available in order to establish the solubility of a certain molecule in a given solvent. Hansen (2007) and Hansen and Smith (2004) have made extensive review of such criteria. For simplicity of the mathematical treatment we prefer to follow the criteria proposed by Van Krevelen (1990) for the solubility of a polymer in a solvent. The first point is that we assume that C60 and C70 are polymeric forms of elemental carbon and treat them on these terms. To predict the solubility according to Van Krevelen (1990), the difference in the solubility parameters between solute and solvent should conform to the following equation ... 

Liquid concentrate medium has emerged recently as an alternative to powdered medium (33,34). For liquid concentrate preparation, medium components are grouped according to solubility criteria. Liquid medium concentrates allow for the preparation of medium in-line, by automated dilution of the concentrates with water of the appropriate quality (35). This would be particularly useful in continuous or perfused processes that require constant preparation of medium. Medium cost and component stability make it a secondary option for batch or fed-batch processes. 

Solubility is a very important criterium for the different uses of polysaccharides in pharmacy. Table 4 lists the solubility criteria of some polysaccharides in water. Solutions containing sugars and alcohol generally depress the solubility of polysaccharides. Polysaccharides containing carboxyl groups, i.e., pectins, alginates, and carboxy-methylcellulose, are insoluble at low pH values. They will be precipitated when the pH is lowered below 3. 

In the food and pharmaceutical industries agglomerates must often conform to specific solubility criteria. The finely divided powders which, in foods, sometimes contain fats tend to lumping, caking, coating, segregation, etc., and... 

Based on their low permeability and low solubility characteristics, it might be expected that dass 4 compounds would hardly be effective drugs. However, a considerable number of class 4 compounds may be misclassified in terms of in vivo characteristics, as solubility in aqueous solutions may not reflect solubility in gut content. For example, the FDA publication [72] and others have suggested that solubility measurements in surfactant-containing solution may be a more appropriate basis for the solubility criteria. Oral bioavailability for true class 4 compounds is already minimal so that any transporter effect could be relevant, as a small increase in bioavailability (e.g., from 2 to 4%) would make a significant difference [61]. 

Rates and Equilibria Based on Spectroscopic and Solubility Criteria... 

Foam Effectiveness in Porous Media. No generally accepted correlations exist between foam characteristics measured outside the porous medium and foam effectiveness as a gas mobility-reducing agent in porous media. The performance of the nine surfactants that passed the solubility criteria was therefore evaluated in porous media under typical reservoir conditions. The results of such an evaluation can be expressed in several ways. One of the simplest measures of foam effectiveness, and arguably the most straightforward one, is the mobility-reduction factor (MRF). The MRF is defined as the ratio of pressure gradients across a... 

Extraction-Purification. Purification of polymeric molecules is often easier than for small molecules. It is relatively easy to separate small (impurities) from large molecules on solubility criteria, gel filtration, or by dialysis. 

More fundamental treatments of polymer solubility go back to the lattice theory developed independently and almost simultaneously by Flory (13) and Huggins (14) in 1942. By imagining the solvent molecules and polymer chain segments to be distributed on a lattice, they statistically evaluated the entropy of solution. The enthalpy of solution was characterized by %, the Flory-Huggins interaction parameter, which is related to solubility parameters by equation 5. For high molecular weight polymers in monomeric solvents, the Flory-Huggins solubility criterion is x A 0.5. 

There are a number of chemical methods that may be used to probe the chiral absolute structures of inorganic complexes. Werner established a diastereomer solubility criterion that he used to relate absolute configurations from complexes to complexes... 

Similar solubility phenomena can also be observed for the resins. The sample for resin separation after removal of asphaltenes is normally applied as a solution in nC5. However, after the removal of the oil, the fractions obtained from the ion exchangers show a marked decline in solubility in the same solvent. Also, if resin separation is done by the SARA method, the tetrahydro-furan fraction is hardly soluble in nC5. This again shows the solubility criterion to be a function of several variables the removal of some of the solubilizing components of the resins renders the remainder insoluble. 

There is, however, still some doubt whether the alleged block copolymers are indeed copolymers and not predominantly a mixture of homopolymers containing some graft and block copolymers. The solubility criterion was mostly relied upon, and it was shown that 40 % of DXL entered the copolymer (60 % was isolated as methanol-soluble low-molecular-weight polyDXL). This criterion may be misleading as we already stressed, because, except for the very low-molecular-weight fraction, polyDXL is insoluble in methanol. Thus, the question whether or not block copolymers are formed in this system and if so, what is the efficiency of this reaction is still unresolved. 

Preparative-scale separations are optimized on an analytical scale initially to minimize sample waste, and then scaled-up to a large volume column. A series of screening experiments are employed to identify the most selective solvent system for the separation in which the sample has favorable solubility [6,237,245,247]. The solubility criterion is important for preparative-scale separations, since the sample throughput is limited by the phase in which the sample is least soluble. In addition, the solvent system should provide a suitable range of partition coefficients for the target compounds, and... 

The critical value of %i sufficient for solubility of polymer having large molecular mass is 0.5. Good solvents have a low %i value. %i is a popular practical solubility criterion and comprehensive compilations of these values have been published. ... 

Surfactants are molecules made up of two parts, each of which displays a quite different affinity with respect to the solubility criterion. A simple example is provided by sodium dodecylsulfate, with formula... 

Equation (1.15) is important because it shows that Afxi represents the slope of AGs versus the moles of drug dissolved (both per constant amount of solvent), which is shown in Fig. 1.5. The solubility criterion of A/ii = 0 corresponds to... 

The Flory-Huggins theory can be improved to incorporate new terms. For example, the Prigogine-Flory-Patterson theory introduces an entropic contribution due to free volume effects in order to obtain more realistic results [70]. This contribution does not modify the solubility criterion as stated above. When the Flory interaction parameter (/) is considered to have both an enthalpic component and... 

In the following chapter on results and discussion, first solute solubility, is used to describe the two particle generation models developed. Second, the role of the mixing behavior of solvents and supercritical carbon dioxide in the SAS process to produce solid dispersions is defined. The crystallization and the time-scale models are then presented in terms of the solute solubility criterion. A final and more... 

To illustrate the criterion for parameter estimation, let 1, 2, and 3 represent the three components in a mixture. Components 1 and 2 are only partially miscible components 1 and 3, as well as components 2 and 3 are totally miscible. The two binary parameters for the 1-2 binary are determined from mutual-solubility data and remain fixed. Initial estimates of the four binary parameters for the two completely miscible binaries, 1-3 and 2-3, are determined from sets of binary vapor-liquid equilibrium (VLE) data. The final values of these parameters are then obtained by fitting both sets of binary vapor-liquid equilibrium data simultaneously with the limited ternary tie-line data. 

The first criterion was associated with improved secondary and tertiary petroleum recovery processes. This is the justification for the patent appHcations issued to the Dow (50) and Exxon (51) corporations. The additional costs of production and the increased adsorption of such modified water-soluble polymers are detrimental to the commercial appHcation of such polymers and even the academic studies in this area have decreased in recent years. 

Free ionic silver readily forms soluble complexes or insoluble materials with dissolved and suspended material present in natural waters, such as sediments and sulfide ions (44). The hardness of water is sometimes used as an indicator of its complex-forming capacity. Because of the direct relationship between the availabiUty of free silver ions and adverse environmental effects, the 1980 ambient freshwater criterion for the protection of aquatic life is expressed as a function of the hardness of the water in question. The maximum recommended concentration of total recoverable silver, in fresh water is thus given by the following expression (45) in Fg/L. 

The way to obtain the membranes as well their composition has been optimized. The main operational criterion for the membranes is the solubility of applicable ionic pairs. The solubility should be quite low - else the substance will be outwashed from the membrane. At the same time, the ionic pairs which have very low solubility are not suitable too because of the complicated obtaining homogeneous membranes. 

Lohse et al. have summarized the results of recent work in this area [21]. The focus of the work is obtaining the interaction parameter x of the Hory-Huggins-Stavermann equation for the free energy of mixing per unit volume for a polymer blend. For two polymers to be miscible, the interaction parameter has to be very small, of the order of 0.01. The interaction density coefficient X = ( y/y)R7 , a more relevant term, is directly measured by SANS using random phase approximation study. It may be related to the square of the Hildebrand solubility parameter (d) difference which is an established criterion for polymer-polymer miscibility ... 

The general criterion for solubility is the rule that like dissolves like . In other words polar solvents dissolve polar and ionic solutes, non-polar solvents dissolve non-polar solutes. In the case of water, this means that ionic compounds such as sodium chloride and polar compounds such as sucrose are soluble, but non-polar compounds such as paraffin wax are not. 

A micro mixer-tube reactor set-up, in which pulses of substrates and catalysts were injected (Figure 4.64), fulfilled that criterion [111]. By this means, a ranking of substrate reactivity was possible. It was shown that the different reactivities of the 10 substrates found were due to their varying solubility in the aqueous phase where the catalyst is provided. 

Having introduced matters pertaining to the electrochemical series earlier, it is only relevant that an appraisal is given on some of its applications. The coverage hereunder describes different examples which include aspects of spontaneity of a galvanic cell reaction, feasibility of different species for reaction, criterion of choice of electrodes to form galvanic cells, sacrificial protection, cementation, concentration and tempera lure effects on emf of electrochemical cells, clues on chemical reaction, caution notes on the use of electrochemical series, and finally determination of equilibrium constants and solubility products. 

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