Parental solutions

The obvious drawback of this method is that the parent solute, at least, has to be available or must be synthesized, and its log P value has to be determined experimentally. Nys and Rekker therefore developed a method known as the fragmental constant approach, which is based on the additivity of fragment contributions to the molecular lipophilidty [7] (see Eq. (9), where a( is the inddence of fragment i, fi the lipophilic fragment constant, Ci a corredion factor, and the frequency of Cm). 

Opposing reactions. Use the data on the right side of Table 3-2, concerning the triphenyl methyl radical, to calculate ki. This experiment refers to the concentration-jump method in which the parent solution was diluted with solvent to twice its initial volume. 

As present in parent solution (g/l) Potash Alum (g/l) pH Precipitate of Arsenic (g/l) Removal of Arsenic (%)... 

Fig. 2(a) shows dependencies of KCN content in model solutions on time of plasma treatment. They were prepared by means of dilution of the parent solution, containing 21% KCN and 42% KOH. It was shown that at low concentrations of KCN (0,01 - 0,10 %), complete neutralization of solutions was achieved in 2 -8 min. Under cyanide content of 0,3-U,0 %, this time makes 30 minutes. Solutions with KCN concentration of 1,30 % are not neutralized completely within this time. 

The crossover operation replaces some of the elements in each parent solution with those in the other. For example, in one-point crossover, with parents PI and P2 represented by real-valued vectors, and with the crossover point after the third component, the parents and offspring are as shown here for a five-variable problem ... 

After 1 h on an orbital shaker, pH is recorded and 5 mL aliquots of each thin slurry are filtered for ICP analysis. Over powders, Pt adsorption is complete within minutes [19,23], and 1 h contact is sufficient to ensure equilibration. Samples of the parent solution (before contact) are also filtered and analyzed with ICP, which can be used to determine not only metal uptake, but also dissolution of the support. The metal uptake, in terms of surface density (mol/m2), is calculated by dividing the concentration difference by the SL ... 

Figure 1. The partitioning of Ba2 + into calcite at various Ba 2+/Ca2 + solid solution ratios. Note that kcBa varies from 0.03 to 0.05 independently of the concentration of Ba2 + in the calcite and also, by implication, in the parent solution.

Molecular Weight. The four KL solutions and 50 50 mixtures of the SAM, NASM and LAM with FAM were ultrafiltered at pH 13.8 and 8.5 to explore the effect of the parent solution molecular weight distribution on the association process. The results at pH 13.8 are presented as rejection coefficient distributions in Figure 2. The rejection coefficient distribution was... 

The amount of small molecules in the permeate at low alkalinity increased with the relative concentration of small molecules (Figure 3). If hydrophobic bonding or simple solubility was the dominant mechanism for the association, the solubility of lignin molecules should be solely a function of pH regardless of the MWD of the parent solution. Consequently, the permeate MWD should be approximately the same and not a function of the MWD of the parent solution. Since the experimental permeate MWD varied with the parent MWD, the solubility or hydrophobic interaction mechanism was no longer accepted. 

Figure 3. Molecular weight distributions of permeates obtained from parent solutions of differing molecular weight distributions at pH 8.5. Sephadex G-100/0.10 M NaOH.

Figure 4. The correction for concentration polarization effects. Parent solution was 50 g/L at pH 13.0. Stirrer rates varied from 350 to 510 rpm, transmembrane pressure ranged from 34 to 207 kP0.

The equation of the calibration curve is [signal] = 148 900C + 1.407. We will find that the unknown solution is such that C=1.89xl04. The parent solution has a concentration 25 times greater, being 4.73 x 10 3 mol/1, or 0.19 g/1 in... 

Tekely and co-workers74 75 were the first to reveal that SS 31P NMR spectroscopy yields an unambiguous visualisation of the presence and the nature of singly and/or doubly ionised phosphate groups in lyophilisates prepared from parent solutions at different pH values. Employing O-phospho-L-serine as a model sample, they showed that both isotropic and anisotropic parameters are very sensitive to the change of the ionisation state (Figure 16). 

The crossover operation is the heart of the method. Technically, it is the simple exchange of parts of strings between pairs of solutions, but it has a large impact on the effectiveness of the search, since it allows exploration of regions of the search space not accessible to either of the two parent solutions. Through crossover operations, solutions can cooperate in the sense that favorable features... 

In the experiments which we carried out with Vorob yeva, the change in iron hydroxide sediments in the parent solution (concentration of NaCl 17 -20 g/1) was studied in the course of 8.5 years. 

From these data it follows that when iron is precipitated in acid and neutral environments the first products should be X-ray-amorphous highly dispersed iron hydroxides, which in the course of time acquire the crystal structure of goethite or hematite. The mechanism of this process depends on kinetic factors (rate of oxidation of Fe " ), form of migration of the iron (ionic or colloidal), and acidity of the parent solution. In neutral environments ferrihydrite possibly is formed as an intermediate metastable phase, especially if the iron migrates in colloidal form or in the form of the Fe ion. The products of diagenesis of such a sediment may be both goethite (in the case of low Eh values typical of the Precambrian iron-ore process) and dispersed hematite (in the case of deposition of the oxide facies of BIF). 

Hayward, D.S., Kenley, R.A., Jenke, D.R. (1990) Interactions between polymer containers and parental solutions the correlation of equihbrium constants for polymer-water partitioning with octanol-water partition coefficients. Inti. J. Pharm. 59(3), 245-253. 

The standard solutions are prepared using a parent solution of boron made from boric acid. A range of standard solutions with boron concentration levels encompassing the sample solution concentrations is prepared in plastic volumetric flasks by diluting the parent solution. The standard solutions and the blank have the same acid and aluminium contents as the sample solutions. The emission intensity of boron is measured at 249.77 nm. The quantification limit is 10 ppm in the catalysts. 

It is possible to link this heterogeneity to the synthesis process. This favours the formation of a structure rich in gallium. The parent solution thus becomes depleted in gallium and at the end of the synthesis, when the exterior of the grains is constructed, the structure is less rich in this element. 

The large number of methods used to calculate log P values have been elegantly reviewed by Leo. The method proposed in 1964 by Fujita, Iwasa and Hansch used values for the parent molecule and values for substituents gathered by analysis of thousands of values of log P for homologous and other series. In this method of substituents log P is considered to be an additive-constitutive free-energy-related property, where one can define Ft for substituent X as the difference between the log P values for the parent solute and the compound with the substituent ... 

For crystallisation of Y the optimum composition of solution was 10Na 0.0. 45A1 0. 26Si02.270H2<). Faujasite (zeolite Y) appeared after 12 hours, and the crystals were of rather constant composition, having, over all the experiments, ratios SiO Al O between 5.1 and 5.6. Because these ratios are so much greater in the parent solutions the A1 has been selectively removed from solution and its concentration therein drops much faster than those of Na and Si. 

Up to now several methods have been used to prepare iron molybdates, the most part of them based on coprecipitation techniques. Previous studies [11] have evidenced that the catalytic behavior of Mo-Fe oxides depends on many variables of the coprecipitation procedure starting compounds, concentration of parent solutions, pH and temperature of coprecipitation step, order of addition of parent solutions, ripening etc. In a typical preparation procedure iron molybdate is coprecipitated from solutions of ferric chloride or ferric nitrate and ammonium molybdate [8]. The control of all the above mentioned procedure variables, strongly difficult the preparation of these catalysts and deviations from the preparation recipe can have very adverse effects on the performances of the catalyst from the standpoint of activity, selectivity and stability. 

---