Solubility calculated

As a key first step towards oral absorption, considerable effort has been directed towards the development of computational solubility prediction [26-30]. However, partly due to a lack of large experimental datasets measured under identical conditions, today s methods are not sufficiently robust for reliable predictions [31]. Nonetheless, further fine-tuning of these models can be expected since high-throughput data have become available for their construction. 

It was assumed for a long time that molecules can only cross a membrane in their neutral form. This dogma, based on the pH-partition theory, has been challenged [42, 43]. Using cyclic voltammetry it was demonstrated that compounds in their ionized form pass into organic phases and might well cross membranes in this ionized form [44]. 

The importance of drug ionization using cell-based methods such as Caco-2 in the in vitro prediction of in vivo absorption was discussed [45]. It was observed that when the apical pH used in Caco-2 studies was lowered from 7.4 to 6.0 a better correlation was obtained with in vivo data, demonstrating that careful selection of experimental conditions in vitro is crucial to produce a reUable model. Studies with Caco-2 monolayers also suggested that the ionic species might contribute considerably to overall drug transport [46]. 

Various ways that a charged compound may cross a membrane by a passive mechanism have been described [42]. These include transport as ion (trans- and/or paraceUular), ion-pair or protein-assisted (using the outer surface of a protein spaiming a membrane). 

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For more precise values, computer programs can be used to calculate soluble recoveiy as weh as solution compositions for conditions that are typical of a CCD circuit, with varying underflow concentrations, stage efficiencies, and solution densities in each of the stages. The calculation sequence is easily performed by utihzing material-balance equations around each thickener. 

Figure 5.8. Relationship between A and boiling point for use in calculating solubility parameters.

The following examples illustrate the method of calculating solubility products from solubility data and also the reverse procedure. 

The comparison of calculated solubilities by Equation 13 with the values from experiment (12 months contact time). The values are plotted as a function of the concentration of free hydroxide ion at solubility equilibria (cf. Figure 6). 

The comparison of calculated solubilities by Equation 13 with the values from experiment (12 months contact time). 

Experimental data vs. calculated solubilities for hydrolysis reactions. 325-30 Experimental data vs. Hartree-Fock methods, energy level... 

Calculated Solubility Parameter and Experimental Oil Swell for a Variety of Rubbers... 

FIGURE 13.1 Oil swell in ASTM oil 3 (70 h at 150°C) for a variety of rubbers versus calculated solubility parameter. 

Amount of soluble polymer generated in this reaction (Figure 9) was only 18-19% solids, which was well below the 29% total solids found after reaction completion. Differences between calculated soluble solids and gravimetrically measured total solids were large, but variable, for all three polymerizations studied. Thus, amount of soluble polymer was not proportional to total solids. However, a good correlation between total solids and the sum of refractometer peak areas for both polymer peaks was obtained. Figure 10. This correlation included all three polymerizations and there was little or no batch bias. 

Glomme, A., Marz, J., Dressman, J. B. Comparison of a miniaturized shake-flask solubility method with automated potentiometric acid/base titrations and calculated solubilities. /. Pharm. Set. 2005, 94, 1-15. 

The use of the solubility envelope, together with the volumetric additivity rule for calculating solubility parameters of solvent blend and the solvent evaporation model described previously, allows an approximate assessment whether phase separation will take place or not during solvent evaporation. 

Fig. 17.3. Experimental versus calculated solubility from VolSurf model. Lower left part, poor solubility central part, medium solubility upper right part, high-solubility compounds.

Figure 19 Plot of calculated solubilities versus solubility parameter of solvents.

In most experiments to calculate solubilities the magnesian calcites have been treated as solids of fixed compositions of one component, whereas they are actually a series of at least two-component compounds forming a partial solid solution series. 

Salts for Low Solubility. A different test of these relations involves calculating solubilities of salts of low solubility in mixed solutions at 25°C. Thus a pure solution saturated with Gypsum, namely CaSC I O, has a molality of 0.0156 (7), hence... 

Figure 5 shows only the solubility values from the high temperature experiments (6,9 ) and the lines for Battino s low temperature equation, and the three and four constant equations from all of the data. The three constants are given in Table V for the tentative equation to calculate solubilities in the 350 to 600 K temperature interval. 

Greater emphasis on generalized computer techniques for calculating solubility and vapor-liquid equilibria would be helpful in encouraging greater application of thermodynamics in practice. 

This chapter shows that the solubility of C60 and C70 fullerenes can be predicted from the solubility parameter of these two molecules and the calculated solubility parameters of fatty acids and their esters. Furthermore, the solubility of C60 and C70 fullerenes in a series of vegetable oils and fatty acid esters will be presented and discussed. 

The calculated solubility parameter derived from the Van Krevelen approach has been compared with the experimental solubility parameters of C60 and C70 reported in the literature and derived experimentally. An excellent agreement has been found between the calculated and the experimental <5d values. A comparison with the calculated solubility parameter of the vegetable oils, under certain conditions, permits to show that a good solubility of fullerenes in glycerol esters of fatty acids can be expected. Fulleiene solubility in molten free fatty acids can be predicted on the basis of solubility parameters comparison and it has been verified by dissolving C60 and C70 in molten fatty acids. 

Alkene Solubility at room temperature/ppm Calculated solubility of liquid alkane at 25 °C/ppm... 

Table 4-3 Calculated solubility as a function of crystal size...

Fig. 9. Experimental solubilities as total uranium concentration in solution for experiments on dissolution of uraninite samples from Oklo and Cigar Lake. Solid lines correspond to the calculated solubilities. Calculations performed with PHREEQC geochemical code (Parkhust Appelo 1999) and uranium database taken from Grenthe et al. (1992) and Bruno Puigdomenech (1989).

J. T. Lowitz found the solubility of potassium hydroxide to be such that it dissolved in half its weight of water A. Bineau found water dissolved two-thirds its weight of sodium hydroxide, and its own weight of potassium hydroxide and J. Dalton compiled the first table of the solubility of the last-named compound. H. Schiff, and G. T. Gerlach calculated solubility tables from Dalton s data. The solubility curve27 of lithium hydroxide has a eutectic at —18° with 11 2 per cent, of lithium hydroxide at —59°, the soln. contains 4 31 per cent. LiOH and the solid phase with ice, at the eutectic, is the monohydrateof lithium hydroxide, Li0H.H20, of sp. gr. 1 829 it has a heat of soln. of 0 720 Cal. at 18°. The solubility of the monohydrate is ... 

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