Effect of solvent concentration

The effect of solvent concentration on the activity coefficients of the key components is shown in Fig. 13-72 for the system methanol-acetone with either water or methylisopropylketone (MIPK) as solvent. For an initial-feed mixture of 50 mol % methanol and 50 mol % acetone (no solvent present), the ratio of activity coefficients of methanol and acetone is close to unity. With water as the solvent, the activity coefficient of the similar key (methanol) rises slightly as the solvent concentration increases, while the coefficient of acetone approaches the relatively large infinite-dilution value. With methylisopropylketone as the solvent, acetone is the similar key and its activity coefficient drops toward unity as the solvent concentration increases, while the activity coefficient of the methanol increases. 

FIG. 13-72 Effect of solvent concentration on activity coefficients for acetone-methanol system, (a) water solvent, (h) MIPK solvent. 

From a practical point of view the change in retention with solvent concentration will be greater at the lower concentrations of chloroform where interactions in both phases are being changed. At concentrations above 50%, however, interactions are only changing in the mobile phase and so the effect of solvent concentration on retention will be less significant. 

Figure 13.23. Examples of vapor-liquid equilibria in presence of solvents, (a) Mixture of-octane and toluene in the presence of phenol, (b) Mixtures of chloroform and acetone in the presence of methylisobutylketone. The mole fraction of solvent is indicated, (c) Mixture of ethanol and water (a) without additive (b) with 10gCaCl2 in 100 mL of mix. (d) Mixture of acetone and methanol (a) in 2.3Af CaCl2 ip) salt-free, (e) Effect of solvent concentration on the activity coefficients and relative volatility of an equimolal mixture of acetone and water (Carlson and Stewart, in Weissbergers Technique of Organic Chemistry IV, Distillation, 1965). (f) Relative volatilities in the presence of acetonitrile. Compositions of hydrocarbons in liquid phase on solvent-free basis (1) 0.76 isopentane + 0.24 isoprene (2) 0.24 iC5 + 0.76 IP (3) 0.5 iC5 + 0.5 2-methylbutene-2 (4) 0.25-0.76 2MB2 + 0.75-0.24 IP [Ogorodnikov et al., Zh. Prikl. Kh. 34, 1096-1102 (1961)].

The assay procedure was modified to study the effect of solvent concentration and use of CPO with in situ H202. To produce H202 in situ, 24 pmol of glucose and 20 ig GOx were added in a 3 mL reaction mixture. The disappearance of MCD was monitored spectrophotometrically at 278 nm with an extinction coefficient of 12,200 M 1 cm The various enzymatic reactions are as follows ... 

Solvent Loading. The solvent circulation rate is a function of the reflux ratio in the primary tower and the liquid-phase concentration of the solvent. For a given solvent selectivity, as the solvent concentration rises, the propane-propylene relative volatility increases and hence the required reflux rate falls. The increased relative volatility results in a decreased number of equilibrium stages required for the desired separation. Figure 4 shows the effect of solvent concentration on the number... 

Figure 4. Effect of solvent concentration on the number of equilibrium stages and the solvent-to-feed ratio in primary column...

The Effect of Solvent and Solute Concentration. The effect of solvent concentration on selectivity is qualitatively described by three types (2, 11) shown in Figure 3. 

Chamberlain, E. K. 1999. Rheological properties of acid converted waxy maize starches effect of solvent, concentration and dissolution time. Ph.D. thesis. Cornell University. Ithaca, NY. 

Aj is the plasticization coefficient to account for interaction of the particular permeant and polymer. It represents the magnitude of the effect of solvent concentration on solvent mobility in the membrane. 

A major disadvantage of optical rotation as a measure of stereochemical purity is that interpretation of the single value lacks significance if any impurities are chiral. To insure the validity of an optical rotation specification, it should be supported by specific rotation measurements on any known chiral impurity or degradation product. This is, of course, in addition to the usual studies of the effects of solvent, concentration, and temperature on the specific rotation of the principal analyte. 

In some cases it is desirable to conduct a copolymerization in the presence of a solvent. Table III illustrates the effect of solvent concentration on the copolymerization of styrene and acrylonitrile. Higher concentrations of solvent produced a pronounced lowering of the rate without changing the molecular weight as measured by the solution viscosity of the copolymer. 

Effect of Solvent Concentration on Reaction Rate. In the kinetic modeling of chemical (such as kraTt) pulping, the effect of cooking liquor on delignificatlon rate Is sometimes considered. For example, the alkali concentration [0H ] can be Included In the rate equation (12,13,32). Since the extraction experiments In this study have been conducted under constant solvent flow (1 g/mln) and the solvent ratios In binary fluid extractions have been maintained at a constant, one can combine the solvent concentration factor Into an effective rate constant (keff). Therefore, Equation 13 can be rewritten as ... 

D. Solvent-Free Systems and the Effect of Solvent Concentration. 362... 

While the effect of a third olefinic substrate on the selectivity of hydrogenation of a binary olefinic mixture could be investigated only at comparable concentrations of all three substrates, because the use of a single olefinic substrate in a considerable excess would lead to its preferential hydrogenation, the inert solvent was mainly used in a much higher concentration. An attempt to solve the problem of the effect of solvent concentration on the selectivity of hydrogenation was made (101). The measurements were again carried out in olefin-unsaturated alcohol systems. 

The effect of solvent concentration and type on rupture voltage appears in Table III. At the low solids concentration 2-butoxyethanol gives the poorest results. However, as the solid concentration increases, the rupture voltage also increases dramatically compared with the other solvents examined. 2-(2-Butoxyethoxy) ethanol, is relatively unaffected by concentration. 

The effect of solvent concentration on viscosity is shown in Figure 10. There is little to choose from among the various solvents. Generally higher viscosities were obtained with the 2- (2-butoxy ethoxy) ethanol, but the differences are small. 

The concentration of solvent can critically control both the absolute retention of the enantiomers as well as the chiral selectivity. An example of the effect of solvent concentration on retention and selectivity is demonstrated in the chromatogram showing the separation of the Metroprolol isomers, depicted in figure 8.1. As the concentrations of solvent are relatively low, and the water content high, it is clear that the... 

The Effect of Solvent Concentration on the Retention and Resolution of Metroprolol Enantiomers on CHIRAL-AGP Courtesy of ChromTech Sweden... 

Effects of solvent-concentration, adsorption temperature and pressure.1526... 

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