Phase crystalline salt

The third example involves growth of a crystalline salt phase from the saturated solution. The thermodynamic description again is inadequate for describing the detailed states of the solid. The relatively anhydrous chloride ion readily deposits into the surface lattice but the sodium ion must be dehydrated to form NaCl. This means that water must be diffused away from the surface during solidification. The white cast of salt, termed veiling, involves solution incorporation during growth with a subsequent diffusion of the solvent out of the crystal. 

The samples thus contain crystalline salt phases and including PEO-salt complex. We conclude that the high conductivity is due to the presence of since a decreases with decreasing MAg4l5 content and... 

Then, 1-(3-acetylthio-2-methylpropanoyl)-L-proline is produced. The 1-(3-acetylthio-3-methyl-propanoyl)-L-proline tert-butyl ester (7.8 g) is dissolved in a mixture of anisole (55 ml) and trifluoroacetic acid (110 ml). After one hour storage at room temperature the solvent Is removed in vacuo and the residue is precipitated several times from ether-hexane. The residue (6.8 g) is dissolved in acetonitrile (40 ml) and dicyclohexylamine (4.5 ml) is added. The crystalline salt is boiled with fresh acetonitrile (100 ml), chilled to room temperature and filtered, yield 3 g, MP 187°C to 188°C. This material is recrystallized from isopropanol [ttlo -67° (C 1.4, EtOH). The crystalline dicyclohexylamine salt is suspended in a mixture of 5% aqueous potassium bisulfate and ethyl acetate. The organic phase is washed with water and concentrated to dryness. The residue is crystallized from ethyl acetate-hexane to yield the 1-(3-acetylthio-2-D-methylpropanoyl-L-proline, MP83°Cto 85°C. 

Crystalline salts of many organic acids and bases often have a maximum solubility in a mixture of water and water-miscible solvents. The ionic part of snch a molecule requires a strongly polar solvent, snch as water, to initiate dissociation. A mixture of water-miscible solvents hydrates and dissociates the ionic fraction of pollutants at a higher concentration than wonld either solvent alone. Therefore, from a practical point of view, the deliberate nse of a water-soluble solvent as a cosolvent in the formnlation of toxic organic chemicals can lead to an increased solnbility of hydrophobic organic contaminants in the aqueous phase and, conse-qnently, to a potential increase in their transport from land surface to groundwater. 

Some of the unusual properties of a solid propellant results from its basic composition. The two general categories of double-base and composite rubber binder propellants have many subcategories, but no exhaustive compilation will be attempted here. Most modem propellants consist of a deformable binder phase and a crystalline salt filler, such as ammonium perchlorate and usually a powdered metallic fuel such as aluminum. Table I gives some typical compositions for both composite rubber-based and composite double-base systems. 

According to the standard electrochemical potentials (Table 1), with Cu/Cu2+ and Ru/Ru3+ couples, the amount of ruthenium deposited on metallic copper will be small, whereas the redox reaction carried out in presence of platinum or gold salts will occur to a large extent. On the other hand, for electrodes of first type (metal immersed in a solution of a salt of that metal), the standard electrochemical potentials as defined by thermodynamics are calculated with regard to a poly-crystalline metallic phase of infinite size. However, in the case of small metallic particles, characterized by metallic atoms of different coordination numbers, the notion of a local potential can be introduced. That no-... 

Salts such as sodium, calcium, and magnesium chloride are generally contained in water suspended in the oil phase of hydrocarbon feedstocks.9 Other impurities are also present in crude oils as mechanical suspensions of silt (dirt), iron oxides, sand, and crystalline salt.14 These contaminants must be removed before processing the crude oil feeds thus, the best method is mixing the crude oil with water and creating an emulsion.12... 

As mentioned above, polymorphs may also be related by order-disorder transitions, e.g. the onset of free rotation of a group of atoms, or local tumbling in semi-plastic or plastic phases. This may be due to random orientation of the molecules or ions, but is also diagnostic of the onset of a reorientational motion. Roughly spherical molecules and ions are likely to show order-disorder phase transitions to a plastic state. In the cases of co-crystals or of crystalline salts this process may affect only one of the components, leading to semi-plastic crystals (an example will be discussed below). Order-disorder phase transitions have often... 

FIGURE 1.14 Neutron diffraction patterns of n-butylammonium vermiculite close to the crystalline-gel phase transition at T = 14°C and an external salt concentration of c — 0.1 M. (a) low-angle region, (b) wide-angle region... 

The most common definition of a microemulsion characterises it as a thermodynamically stable, transparent, optically isotropic, freely flowing surfactant mixture, often containing co-surfactants (e.g. alcohol) and added salts [37]. We restrict the definition further to non-crystalline (disordered) aggregates, since crystalline isotropic phases are better considered as liquid crystalline mesophases. Indeed, the most succinct description of a microemulsion would involve its microstructure. However, this has proven to be a very equivocal issue. So much so that until very recently it was widely believed that microemulsions were devoid of microstructure hence the thermod)mamic definition. 

The acid sodium phosphate NaH2P04 can be dehydrated quantitatively to the corresponding crystalline diphosphate. Sodimn trimetaphosphate, a crystalline salt with a ring structure anion, is also stable and complicates the polymerization of NaH2P04 on dehydration. Thilo and Grunze (52) have shown that under equilibrium conditions according to the phase rule five different temperature regions can be delineated. Three different quadrupel points are possible ... 

In the potassium Kurrol s salt phase system the crystalline analogues to Ca2P60i7 or CaP O i were not found by a literature search. (22) The amorphous potassium ultraphosphate systems have been studied. (23) Amorphous condensed phosphates are seldom, if ever, single compounds, but are a random mixtures of compounds and can be large and very complex. If the ultraphosphates were embedded between crystals of pure potassium phosphate fibers they would be very difficult to detect. 

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