Solubility and rate

In the experiments using a i i mixture of nitric and sulphuric acids (table 4.1, eolumn (y)) reaetion oceurred under heterogeneous eonditions, about 50 cm of mixed aromatie eompounds and 25 em of mixed aeids being used. The results are therefore eomplicated by differenees in solubilities and rates of diffusion to the aeid layer. 

Seymour and coworkers (27,28,29,30) actually used these composition gradients to prepare block copolymers by swelling particles containing occluded (i.e., living) macroradicals with a second monomer. Such block copolymers were prepared from occluded vinylacetate, methyl methacrylate, and acrylonitrile macroradicals, and the yield of block copolymers was studied as a function of the solubility and rate of diffusion of the swelling monomer in the particles. 

These opposing tendencies may defeat the purpose of the fractional precipitation process. The fractional precipitation of crystalline polymers such as nitrocellulose, cellulose acetate, high-melting polyamides, and polyvinylidene chloride consequently is notoriously inefficient, unless conditions are so chosen as to avoid the separation of the polymer in semicrystalline form. Intermediate fractions removed in the course of fractional precipitation may even exceed in molecular weight those removed earlier. Separation by fractional extraction should be more appropriate for crystalline polymers inasmuch as both equilibrium solubility and rate of solution favor dissolution of the components of lowest molecular weight remaining in the sample. 

Ferry, J.D., Carritt, D.E. Action of Antifouling Paints. Solubility and Rate of Solution of Cuprous oxide in Seawater. Industrial and Engineering Chemistry, 38 (6) (1946), 612-617... 

One of the main impetuses for using ILs for gas separations and as a solvent for reactions involving permanent gases is that most ILs have extremely low-vapor pressures at normal operating conditions. Thus, one will not lose any of the solvent in the purified gas sfream or in fhe products. Another attractive feature is that ILs are highly tunable by varying the cation, anion, and substituents. Thus, they can be tailored for specific applications to optimize selectivity, capacities, reactant or product solubilities, and rates. 

Whereas the literature frequently suggests the use of ammonium persulfate, this reagent is not very storage stable and consequently a sample of this reagent may not be very active. Potassium persulfate is a useful initiator, but its water solubility and rate of dissolution are not as great as those of its sodium analog. These properties may be significant when solutions of the initiator have to be added to a reaction. 

Muller, R. H., Becker, R., Kruss, B., and Peters, K. (1999) Pharmaceutical nanosuspensions for medicament administration as systems with increased saturation solubility and rate of solution, US Patent 5,858,410. 

Silica Apparent Solubilities and Rates of Dissolution and Precipitation... 

Know the factors that influence solubility and rate of solution. Be familiar with different types of solution. 

A substantial advance in technique was provided by Freudenberg and Jacobi, " who relied not only on solubility differences of the dextrins themselves, but also on the differences of solubilities and rates of crystallization of the dextrin acetates. Although the scheme appears somewhat tedious,... 

It is clear from the DTA curves that Form I is the more stable polymorph in the high-temperature range. However, based upon solubility and rate of dissolution measurements (Tables 3-2 and 3-3 and Fig. 3-4), the reverse situation applies at lower temperatures. Form II is more stable near room temperature. The extrapolation of the solubility and dissolution rate date indicate a transition point at about 165°C for Form II to Form I. This transition is not observed in the DTA curve for Form II, as it should be if the situation were thermodynamically ideal. The lack of transition in the DTA curve corresponds to a case of suspended transformation. Forms I and II of sulindac are enantiotropic polymorphs, with Form II being more stable at room temperature (McCauley 1991). 

The solubility and rate of dissolution of mo.st minerals is strongly pH-dependent. Weathering of carbonate, silicate, and alumino-silicate minerals consumes protons and releases metal cations. (See Chaps. 7 and 9.)... 

Application of subcritical gaseous CO2 to an organic liquid causes the liquid phase to expand noticeably, due to extensive dissolution of the CO2 into the liquid phase (131). This expansion is accompanied by a reduction in the liquid phase viscosity, an increase in the solubility of H2 in the liquid, and an increase in the mass transfer rates from the gas to liquid phase. There is evidence that this can affect the enantioselectivity of reactions in viscous liquids. The enantioselectivity of asymmetric hydrogenation of unsaturated carboxylic acids in a viscous ionic liquid was shown to be strongly affected by CO2 expansion of the liquid, the enantioselectively being improved for one substrate (atropic acid) and decreased for another (tiglic acid). The results were explained in terms of the solubility and rate of transfer of H2 gas into the expanded ionic liquid (23). The same effect was not observed in expanded methanol. 

Water solubility and rate of migration should also influence the choice of biocide. This can be related to the MIC value to give an index of solubility (MIC/solubility in water) (Table 2). 

It is very likely that the solubility and rates of absorption of sulfonylureas influence the contours of their hypoglycemic curves (20, 28). It is also possible that differences in metabolism affect their acute potencies. Nevertheless, it is likely that the known sulfonylureas act via the same mechanism—i.e., via f3 cell stimulation with release of insulin (5). The spectrum of activity of all the current sulfonylureas seems to be virtually identical—i.e., their effectiveness as sole hypoglycemic therapy is limited to the maturity-onset type of diabetic. 

In degraded wood the biopolymers may be altered (4, 5). There may be losses in bound water, losses or increases in side chains, and bonding and depolymerization. With other changes the chemical characteristics may be altered, crystallinity may be lost, solubilities and rates of oxidation and... 

In short, pesticide manufacturers are devising chemical substances with an in-buUt degree of water (and fat) solubility and rate of persistence, so that... 

As far as we know, transformations of steroids, carried out with intact microbial cells, occur within the cell and not in the medium surroundii the cell. To enter the cell the steroid being transformed must dissolve to some extent in the medium so that it can diffuse through the cell wall and into the enzyme-rich interior. The practical implication of this requirement is that solubility and rate of diffusion may become the rate-limiting factors for transformation. Most steroid substrates ordinarily employed have modest, though measurable, solubilities in water and in the aqueous media used for microbial culture. To ensure saturation of the mediiun and to minimize this rate-limiting effect, steroids are often introduced into reactions in micronized form or, more conveniently, in solution in a water-miscible solvent from which precipitation in very fine particles occurs upon dilution with the aqueous medium containing the microorganism. 

Precipitated hydroxyapatites usually have extremely small crystal sizes (hexagonal plates -200 A sides) and large surface areas (50-200 m /g). With very small crystal sizes (<0.1 pm), both the solubility and rate of dissolution can be iuCTeased. This arises from the increased importance of surface effects associated with absorption of ions, hydrolysis, crystal defects, etc. 

Gas Composition and Pressures. Under FT conditions, the catalyst pores are, if not full, at least partly filled with liquid products. Because of the differences in solubility and rates of diffusion of the different gases in the liquid phase, their actual concentrations at the catalyst surface sites should be different from those present in the gas phase. This does, however, not mean that the gas composition outside the catalyst particles cannot be used to manipulate the overall product selectivity. 

Uncertainties associated with the parameter values that are used in Eqs. (6.55) and (6.56) need to be carefully evaluated, and accurate data have to be obtained. For example, relatively little solubility and rate information is currently available for reduced environments. 

Hibbard, R.R., Evans, A., 1968. On the solubilities and rates of solution of gases in liquid methane. NASA-TN-D-4701. 

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