Salting point

Most of the work on chiral recognition has been carried out with amino-acid ester salts. The limited number of available data of similar experiments with amino-acid salts point to an increased enantiomeric differentiation (Table 69 Peacock and Cram, 1976). The reason might be the higher -acidity of the carboxyl group (vide ir fra). In solid-liquid chromatography (see Table 68) the difference between amino-acid salts and amino-acid ester salts is not consistent and not always in favour of the amino-acid salts. However, it should be... 

Mussels. Mytilus californianus were usually collected at low tide in the rocky, intertidal zone of Schoolhouse Beach near Bodega Bay (Sonoma Co.) on the central California coast. Other sites have included Salt Point, Bodega Head, and Fort Bragg. Animals were used on the coast or transported to Davis where they were maintained in aerated aquaria containing Instant 0ceanR Synthetic Sea Salt (1.025 specific gravity, 11°C, 12/12 L/D). Except as noted, mussels were used within 2 weeks. 

Figure 16.5. Supersaturation behavior, (a) Schematic plot of the Gibbs energy of a solid solute and solvent mixture at a fixed temperature. The true equilibrium compositions are given by points b and e, the limits of metastability by the inflection points c and d. For a salt-water system, point d virtually coincides with the 100% salt point e, with water contents of the order of 10-6 mol fraction with common salts, (b) Effects of supersaturation and temperature on the linear growth rate of sucrose crystals [data of Smythe (1967) analyzed by Ohara and Reid, 1973],...

Haloaluminates have special properties from the molten salt point of view. These salts form low melting liquids with good thermal stability, and they have a wide range of acid-base properties as a function of composition. Likewise, recent studies have shown the existence of some unusual dissolved species, and this represents a vast potential field for the use of molten haloaluminates as solvents. 

This diagram explains very clearly the phenomenon of the decomposition of a double salt at the transition point. As is evident, this decomposition will occur when the solution which is saturated at the temperature of the transition point, with respect to the two single salts (point C), does not contain these salts in the same ratio in which they are present in the double salt. If point C lay on the dotted line bisecting the right angle, then the pure saturated solution of the double salt would not be supersaturated with respect to either of the single salts, and the double salt would, therefore, not be decomposed by water. As has already been mentioned, this behaviour is found in the case of optically active isomerides, the solubilities of which are identical. 

In connection with the isothermal represented in Fig. 123, it should be noted that at this particular temperature a solution saturated with respect to the pure double salt is no longer supersaturated for one of the single salts (point D) so that at the temperature of this isothermal the double salt is not decomposed by water. At this temperature, further, the boundary curve consists of three branches—AD, DF, and FB—which give the composition of the solutions in equilibrium with pure A, double salt, and pure B respectively while the points D and F represent solutions saturated for double salt plus A and double salt plus B. 

Potassium Chloride—Potassium Sulphate— Water.— The ease with which separation of mixtures of potassium chloride and sodium chloride into the pure salts can be effected is due to the fact that the solubility of potassium chloride varies considerably, whereas the solubility of sodium chloride varies but little with the temperature. That is, the ratio of KCl NaCl in the solution saturated for the two salts (points c and c in Fig. 138) varies markedly with the temperature. Such conditions, however, do not exist in the case of, say, potassium sulphate and potassium chloride. 

TABLE 11.3 - Melting Temperature of Four 1-B (bmim ) Salts Point and Decomposition utyl-3-methyl imidazolium ... 

PO Box 110, Salt Point Rd.. Watkins Glen, NY, 14891. USA (Tel 888-USA-SALT E-mail customerservice ussallllc.com Internet www.ussaltllc.com)... 

Cases are encountered in ternary systems where the two dissolved solutes combine in fixed proportions to form a definite double compound. Figure 4.24 shows two possible cases for a hypothetical aqueous solution of two salts A and B. Point C on the AB side of each triangle represents the composition of the double salt points L and O show the solubilities of salts A and B in water at the given temperature. Curves LM and NO denote ternary solutions saturated... 

In order to simplify the interpretation of the phase equilibria in reciprocal salt pair systems, the water content may be excluded. The curves of the space model can then be projected on to the square base to give a two-dimensional graph, called a Janecke diagram as described in section 4.7.1. A typical projection is shown in Figure 4.31a the lettering is that used in Figure 4.30. The enclosed areas, which represent saturation surfaces, indicate solutions in equilibrium with one salt, the curves solutions in equilibrium with two salts, points P and Q solutions in equilibrium with three salts. 

After the class has completed the exercise, hold a plenary session where you explore the decisions students made and their reasoning (especially in any cases where groups did not agree). There is clearly room for some disagreement about what counts as being similar enough not to be considered a mixture (this can be used to reinforce the point about scientists using models and useful simplifications). If students have not noticed that the peanuts in one jar are salted, point this out, and ask if it makes a difference to their classification. 

KCI in a NaCI-saturated solution that still increases with temperature, NaCI shows retrograde solubility in KCI-saturated solutions (lines 3 and 4). This particular solubility behavior is used in the so-called hot leaching process to separate KCI and NaCI from sylvinite crude salts. It is obvious from the solubility curves that cooling a solution saturated with both salts (point of intersection of lines 3 and 4 at about 100 "C) leads to selective crystallization of KCI as target compound. (Reproduced with permission from Ref [8].)... 

Formation of double salt with 1 1 desired and undesired salts can occur. Figures 56.4a and 56.4b display phase diagrams of congruent and incongruent2 salts, respectively. No separation or enrichment can be achieved when a congruent salt is formed. Separation can be achieved, however, in the case of incongruent salt formation, and the separation efficiency is e = 2 (RO/DO) = (l — 2xo)/(l — Xo)- Because the double salt has solubility lower than the undesired salt (point O is generally closer to R), the separation is typically low in these systems. 

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