Water miscibility diagram

Figure 5.2. Miscibility diagram (and solubility gaps) of water and organic-phase liquids. Solvents not connected by a binding line in Figure 5.2 are immiscible solvents of unlimited miscibility are connected by a solid line, those of limited miscibility by a dotted line [16]...

The disadvantage of such a course of action is that water builds up in the residue and will be present in the vapour leaving the still. For an immiscible solvent the distillate will separate into two phases after condensing and because of the shape of the vapour-liquid equilibrium (VLB) diagram (Fig. 5.4) no fractionating column is needed. However, a water-miscible solvent will have to be freed of water by fractionation or some other means. Further, there are only two solvents in this class that do not form azeotropes with water—methanol and acetone. The latter is difficult to separate from water by fractionation below a level of about 1.5% w/w water so that only methanol can be mixed with water without a... 

Fig. 5.4 VLB diagram of methylene dichloride (l)/water (2) at 40 °C. This is typical of the shape of the VLB relationship of aU sparingly water-miscible solvents (e.g. hydrocarbons, chlorinated hydrocarbons).

The VLB diagram for MDC/water is very like that of all hydrocarbons and typifies the appearance that one would observe in the steam distillation of materials very sparingly water miscible. 

Fig. 6. Boiling point (a) and phase diagram (b) for the heterogeneous a2eotropic system, water/ 1-butanol at atmospheric pressure, yi, B and C, D are representative equiUbrium points Z is the a2eotropic point M and N are Hquid miscibility limits.

Ternary-phase equilibrium data can be tabulated as in Table 15-1 and then worked into an electronic spreadsheet as in Table 15-2 to be presented as a right-triangular diagram as shown in Fig. 15-7. The weight-fraction solute is on the horizontal axis and the weight-fraciion extraciion-solvent is on the veriical axis. The tie-lines connect the points that are in equilibrium. For low-solute concentrations the horizontal scale can be expanded. The water-acetic acid-methylisobutylketone ternary is a Type I system where only one of the binary pairs, water-MIBK, is immiscible. In a Type II system two of the binary pairs are immiscible, i.e. the solute is not totally miscible in one of the liquids. 

HF is miscible with water in all proportions and the phase diagram (Fig. 17.4a) shows the presence of three compounds H2O.HF (mp — 35.5°), H2O.2HF (mp-75.5°) and H2O.4HF (mp — 100.4°, i.e. 17° below the mp of pure HF). Recent X-ray studies have confirmed earlier conjectures that these compounds are best formulated as H-bonded oxonium salts [HsOJF, [H30][HF2], and [H30][H3F4] with three very strong H bonds per oxonium ion and average O - - F distances of 246.7, 250.2... 

We have recently shown that the hydrophobic hexafluorophosphate ILs can in fact be made totally miscible with water by addition of alcohols [47, 48] the ternary phase diagram for [BMIM][PF(3]/water/ethanol (left part of Figure 3.3-7) shows the... 

A plant explosion involved a mixture of nitrobenzene, nitric acid and a substantial quantity of water. Detonation occurred with a speed and power comparable to TNT. This was unexpected in view of the presence of water in the mixture [1]. The later reference deals with a detailed practical and theoretical study of this system and determination of the detonability limits and shock-sensitivity. The limits of detonability coincided with the limits of miscibility over a wide portion of the ternary composition diagram. In absence of water, very high sensitivity (similar to that of glyceryl nitrate) occurred between 50 and 80% nitric acid, the stoicheiometric proportion being 73% [2],... 

Most hydrophobic substances have low solubilities in water, and in the case of liquids, water is also sparingly soluble in the pure substance. Some substances such as butanols and chlorophenols display relatively high mutual solubilities. As temperature increases, these mutual solubilities increase until a point of total miscibility is reached at a critical solution temperature. Above this temperature, no mutual solubilities exist. A simple plot of solubility versus temperature thus ends at this critical point. At low temperatures near freezing, the phase diagram also become complex. Example of such systems have been reported for sec-butyl alcohol (2-butanol) by Ochi et al. (1996) and for chlorophenols by Jaoui et al. (1999). 

The temperature also affects the composition of the two phases at equilibrium, but the effect is not equivalent in all systems. In the example shown in Figure 2.6, raising the temperature increases the solubility of the two phases and this is what is usually observed. The diagram shows that by heating the system, more of A dissolves in B and vice versa. However, other solvent pairs become less miscible with raised temperature, for example, water and ethylamine. In the case of these liquid pairs, the temperature-composition diagram is essentially reversed, as shown in Figure 2.7. 

The system polyethylene glycol (PEG)-dextran-water is still the most used and best-studied aqueous polymer two-phase system. A phase diagram for a typical two-phase system is shown in Fig. 10.12 for the PEG-dextran system. Both polymers are separately miscible with water in all proportions. As the polymer concentration increases, phase separation occurs, with the... 

The effect of adding a surfactant, (NaDDS), was also investigated. One such case only is shown in Fig. 6 where BE is replaced by a 5 1 mixture of BE-NaDDS. The main effect of NaDDS is to increase the miscibility range of the oil in water. Various ratios of BE-NaDDS were used and, as a first approximation, the change in the phase diagram is directly proportional to the concentration of NaDDS. The addition of a surfactant probably stabilizes the microstructures which were already present in the ternary system BE-DEC-H O and decreases the quantity of BE needed to solubilize DEC. Therefore the presence of a surfactant is useful but not essential to the stability of microemulsions. 

Figure 13.28. Vapor-liquid equilibria of some azeotropic and partially miscible liquids, (a) Effect of pressure on vapor-liquid equilibria of a typical homogeneous azeotropic mixture, acetone and water, (b) Uncommon behavior of the partially miscible system of methylethylketone and water whose two-phase boundary does not extend byond the y = x line, (c) x-y diagram of a partially miscible system represented by the Margules equation with the given parameters and vapor pressures Pj = 3, = 1 atm the broken line is not physically significant but is...

Besides the l.c. phases, the phase diagram of the p-l.c./water is very similar to the diagram of the m-l.c./water. The broad miscibility gap of the polymer/water system shows a lower critical consolute point, which is shifted to lower concentrations (3.2% of polymer). This is consistent with experiments and theory on the position of miscibility gaps in polymer solutions112). 

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