Water/methanol phase diagram

Figure 11 -42. Water-methanol system phase diagram. From Nielsen and Bucklin (1983)...

The use of dissociable diastereomers for enantiomer resolution may be illustrated by the case where racemic mandelic acid is resolved using en-antiomerically pure a-methylbenzylamine. The n and p salts of a-methylbenzyl-amine mandelate have aqueous solubilities of 49.1 and 180 g/L, respectively, at 25°C [153], A more recent example, which focuses on the crystallographic origin of the solubility differences, is provided by the resolution of ( )-mandelic acid with (-)-ephedrine in water or methanol solution [154], In general, the relative solubilities of the n and p salt pairs are strongly influenced by the choice of solvent medium and temperature, which provide considerable flexiblity in optimizing the crystallization conditions and the efficiency of resolution. This process may be facilitated by the development of a full solubility phase diagram. 

Figure 3.4 shows the water-methanol mobile phase example of a mixture problem. A three-component mixture that must add up to 100% can be represented on a triangular graph, also called a ternary or trilinear diagram (see figure 3.5). When a system is optimized, it is important to be alert for... 

Figure 7.18 A phase diagram showing the three common hydrate dissociation techniques, relative to the initial sample condition (intersection of horizontal and vertical arrows). Depressurization is shown as AT = 0 thermal stimulation as AP = 0 inhibitor injection is represented by displacing the solid hydrate formation curve to the dashed curve, via injection of 10 wt% methanol in the free water phase.

A Quadruple Point Figure 14.20 shows phase diagrams for (water + acetonitrile) at five different pressures.16 The diagram in (a) at / = 0.1 MPa for this system is very similar to the (cyclohexane + methanol) diagram shown in Figure 14.19a that we described earlier, with a (liquid-I-liquid) equilibrium region present above the (solid + liquid) equilibrium curve for water. 

Fig. 11.12. Schematic diagram of a column-switching HPLC system. V-l, V-2, and V-3 switching valves. The position of °—c means position 1, and ° ° is position 2. P-1 and P-2 pumping system at 0.2 mL min-1 flow rate. Detector electrochemical detector with diamond electrodes. Column-1 and Column-2 Inertsil ODS-3. Loop 500 pL. A Mobile phase of 60% methanol-water containing 0.5% phosphoric acid.

Fig. 8.1. Original diagrams of the first COSMO-RS phase-diagram calculations by Iven Clausen [96] for four alcohol-water mixtures (methanol at 60 C, ethanol at 55 °C, 1-propanol at 60 °C and 1-butanol...

Otto and Wegscheider [562, 563] applied the window diagram method for the simultaneous optimization of the (binary methanol-water) mobile phase composition, the ionic strength and the pH for the separation of ionic solutes in RPLC. They fitted the experimental data to a semi-empirical 13-parameter equation based on eqn.(3.45) for the composition effect, eqn.(3.71) for the effect of the ionic strength and eqn.(3.70) for the... 

Figure 3.7 Phase diagram for methanol-acetonitrile tetrahydrofuran-water solvents systems in reversed-phase liquid chromatography, showing the isoelutropic plane, A-B-C, and the positions of the isoelutropic mobile phases D and E described in Table 3.5.

Of particular interest to those in the natural gas industry is the phase diagram of hydrate systems in the presence of inhibitors. Fig. 3 shows the phase diagram for methane hydrates in the presence of methanol and a NaCl and KCl mixture. The solid line is the three-phase equilibrium curve for methane in pure water. As seen from Fig. 3, forming hydrates in the presence of either an alcohol or salt increases the pressure required for gas hydrate formation, at a given temperature. 

Ethylene-o-dichlorobenzene system, 39 Ethylene glycol, 181,182, 327 Ethylene-methanol system, 183 Ethylene-naphthalene system, 69 Ethylene-polyethylene system, 319 Ethylene-n-propanol system, 39 Ethylene-water-organic solvent phase diagrams, 71 Explosives, 347 Extractibility, 367... 

Figure 1.19 draws a comparison between the predictions of the RISM/KH approach and the simulation data for the liquid-vapor coexistence envelopes of SPC water [107] and OPLS-UA methanol [108]. The theory qualitatively reproduces the phase diagrams. Remarkable is a good fit for their vapor branches. The predicted critical temperature of water,... 

Figure 9.13 gives a ternary diagram for the isopentane-methanol-TAME system at 4 bar. The phase equilibrium of this system is complex because of the existence of azeotropes. The UNIFAC physical property package in Aspen Plus is used to model the VLB in all units except the methanol/water column where the van Laar equations are used because of their ability to accurately match the experimental data. 

In Pxy- and T%y-diagrams, the law of the opposite lever arms can be applied to determine the amount of vapor and liquid in the two-phase region. This is demonstrated in the Txy-diagram of the system methanol-water at 101.3 kPa (see Figure 5.5). 

Fig. 7 Schematic LCST phase diagram of PNIPAM [0.1 wt%] as a function of the composition of the methanol-water solvent mixture. Adapted from Soft Matter , 2010, 1176-1184, figure 1, [125] with permission of The Royal Society of Chemistry...

We used tie lines with liquid-vapor phase diagrams to calculate the compositions and flow rates of the two phases that separated. Tie lines can also be used to analyze the mixing of two miscible liquids. The composition of two miscible liquids, such as water and methanol, can be represented by a linear scale. 

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