Vs. solvent composition

One can interpret the trends in bH and bS in Figures 1-8 in terms of solvation of the reactants or products. Negative values of bH are a possible indication that the products in the reaction are more strongly solvated in solvent S than they are in water. Negative bH values also might indicate that reactants in the reaction are less strongly solvated in solvent S than in water. Conversely, positive values of bH are a possible indication that products are less solvated in solvent S than in water or that reactants are more solvated in solvent S than in water. Another possible factor in the interpretation of bH vs. solvent composition data is the possibility of large contributions of solvent-solvent interactions. 

Fig. 2 Corticosteroid recovery by SPE extraction as a function of solvent composition. Solvents used in the Wash-2 step were composed of 0.1 % formic acid and the indicated solvent composition. Corticosteroid recovery vs. solvent composition is shown for the following conditions (a) SPE cartridges were washed respectively with a range of 20-65 % methanol and eluted with 100 % methanol (b) SPE cartridges were washed with 5 % methanol and eluted respectively with 60-100 % methanol (Reproduced with permission from American Chemical Society)...

Figure 5. Retention volumes for the peak amounts of ( ), A9-THC and (0), II-hydroxy-A9-THC for reverse-phase HPLC vs. solvent composition. Each point represents the mean peak retention volume for two determinations. The vertical bars represent the ranges of retention volumes that contained approximately 98% of the area under the plot of recovered radioactivity vs. retention volume (15).

AH° and AS0 vs. solvent composition for the ethanol-water solvent systems (see Figures 5 and 6) show a more complex behavior at about 60% ethanol than the corresponding plots for the tert-butanol-water solvent systems (see Figures 6 and 8 at about 60% terf-butanol. The ethanol-water system shows a slight minimum and then a maximum in the 0 to 60% ethanol range, while tert-butanol-water system shows only a maximum in the 0 to 60% terf-butanol range. 

Thermal analysis has been used to identify and characterize polymorphs of chlordiazepoxide hydrochloride, phenobarbital monohydrate, chloramphenicol palmitate, 3 (3-hydroxy-3-methyl-butylamino)-5-methyl-as. triazino ZB,6-b7 indole (SKF 30097), sulfathiazole, and sulfanilamide-d4. Solubility vs. solvent composition diagroms have been useful in the systematic study of pseudopolymorphism in the antibiotics cephaloglycin and cephalexin. This technique is recommended for the detection of solvate farmation when the instability of the compound at elevated temperatures precludes the use of conventional thermal methods, or when poor crystal development limits the use of microscopic methods. 

MEK is an antisolvent for the wax and helps to reduce its solubility. If the MEK content is too high the Basestock may become insoluble and a phase separation will occur. MIBK or Toluene is added to help solubilize the oil. Both of these prosolvents have a higher affinity for wax molecules than MEK. The higher the concentration of prosolvent the more wax stays in solution, and ends up in the filtrate. This raises the pour point of the dewaxed oil and since the manufacturer must meet dewaxed oil pour point specification the manufacturer is forced to reduce the filtration temperature to remove more wax. The reduction in filtration temperature increases the viscosity of the slurry and filtration rates are slower and oil removal from the wax cake becomes more difficult. Thus the objective is to use the maximum amount of MEK without having a phase separation. A plot of the phase separation temperature or miscibility temperatures vs. solvent composition may be used to help set the optimum solvent composition. 

Optimum compositions may be planned with the help of plots of vs solvent composition, where /Cmax increases with increasing amount of the low viscosity component, reaching its maximum at k and then decreases again in accordance with increasing association of the electrolyte [427]. Many examples of this approach exist [15]. 

Figure 11. Plots of graft yield and surface polyAM concentration vs. dielectric constant of reacting solution [AM] = 2.00M, [BP] = 0.20M, irradiation for 90 min. Solvent compositions (1) acetone alone (2) acetone/acetonitrile (8.6/1.4) (3) acetone/acetonitrile(3/l) (4) acetone/Hs0(9/1) (5) acetone/acetonitrile(l/l) (6) acetone/acetonitrile] 1/3) (7) acetonitrile alone.

Plotting ixbase VS. pH gives a sigmoidal curve, whose inflection point reflects the apparent base-pAi, which may be corrected for ionic strength, I, using Equation 6.11 in order to obtain the thermodynamic pATa value in the respective solvent composition. Parameters A and B are Debye-Hiickel parameters, which are functions of temperature (T) and dielectric constant (e) of the solvent medium. For the buffers used, z = 1 for all ions ao expresses the distance of closest approach of the ions, that is, the sum of their effective radii in solution (solvated radii). Examples of the plots are shown in Figure 6.12. 

Figure 1. Rate of change of the standard chemical potential of n-Bu NBr with solvent composition vs. water mole fraction at 298.15°K...

Binary systems. A typical plot of the log of partition ratios (k ) vs. % modifier is presented in Figure 2. Like solvent strength, chromatographic retention is a nonlinear function of mobile phase composition. However, plots of log k vs solvent strength (i.e., Ej ) are linear, for at least some solutes, as shown for phenols... 

Our decision also obviates consideration of the additional structural ambiguity arising from the temperature, phase and solvent dependence of the keto vs enol composition of the tautomeric mixture. 

A value of 5.2A for the ion-size parameter a yielded straight-line plots of E0 vs. m at each temperature and solvent composition. The intercepts were obtained by standard linear regression techniques. A graphical representation of the data for each of the H20/NMA solvent mixtures at 25°C is shown in Figure 1. The calculations were performed with the aid of a PDP-11 computer with a teletype output. The intercepts (E°) and the standard deviations of the intercepts are summarized in Table III. 

Equation 3 was obtained by combining the Nemst equation for the emf of Cell I with the equilibrium constant of the acidic dissociation of glycine. In Equations 2 and 3, E° is the standard emf of the cell in the respective solvent composition and these values were obtained from an earlier work (20). In Equation 4, /3 is the linear slope parameter for the plot of pK/ vs. I, a0 is the ion-size parameter, A and B are the Debye-Huckel constants on the molal scale (20) for the respective mixed solvent systems, and I is the ionic strength given by mi. 

The values of E, log y , Mxy> A, and B from Equations 5-10 substituted into Equation 4, make it possible to calculate Em0 at known molalities of hydrobromic acid, solvent compositions, and temperatures. By plotting values of Em° at a given solvent composition and temperature vs. molality, one can find the standard electrode potential E° of the Ag-AgBr electrode at that solvent composition and temperature from the value of Em° extrapolated to infinite dilution. This method has been used successfully in water and in organic solvent-water mixtures of higher dielectric constants, but if the mixed solvents have low dielectric constants, ca. 50 or below, the curvatures of the Em0f vs. m plots are sufficient to prevent accurate determinations of Em0 and hence of E°. 

Films of the three block copolymers were cast from chloroform, a mutual solvent for PS and PEO,( ) and the measured and 0. core level spectra are shown in Figure 2. The spectra show the characteristic peak of PEO, the shake-up satellite of PS, and an easily deconvoluted doublet for the core levels in PS and PEO. It is apparent from the spectra that he PS concentration at the copolymer surface increases as the PS in the copolymer increases. More importantly, however, an analysis of the spectral data clearly shows that the surface compositions are significantly richer in PS than would be predicted based on a knowledge of the bulk compositions of the block copolymers. In Figure 3 is shown a plot of the surface-vs-bulk compositions for the diblock copolymers. ... 

More complicated behavior was observed in the m-cresol-dioxane system. The twisting power vs. the solvent composition curve shows both the maximum and... 

A wider expansion of the available potential window down to -3.3 V vs Fc/Fc is reported in this communication. This was accomplished by the use of a mixed solvent system and low temperature. On the basis of supporting electrolyte and fullerene solubility considerations, the optimal solvent composition was between 15 and 20% by volume of acetonitrile in toluene. These new conditions have allowed the first observation of the sixth... 

Figure 2. Mass spectral response vs nebulizer setting as a function of solvent composition. ( B ), 100 acetonitrile ( B ). 80 acetonitrile ( B ), 60 acetonitrile ( B), 40 acetonitrile ( D ), 20 acetonitrile.

The monomer charge vs. copolymer composition data for a series of isobutylene and 0-pinene copolymerizations using EtAlCl2 in EtCl solvent between —50° and —130° are shown in Fig. 7. Evidently from —50° to —100°, 0-pinene is more reactive than isobutylene, and the copolymer is relatively richer in 0-pinene than the monomer charge. However, in the range from —110° to —130° the two monomers exhibit equal reactivities and the copolymer composition is equal to that of the monomer charge. Table 4 shows the reactivity ratios obtained together with the calculation methods employed. 

---