Reverse solubility

Campion and Morgan developed the technique of reverse solubility parameter spectroscopy (RSPS)" to determine the 8 value for a liquid (e.g., an oU), from a series of swelling measurements using a range of elastomers of known 8. In this way, 8 for cmde Brent oU from the North Sea has been found to be 8.2 (cal cm ). ... 

Table 1. Reversible solubility of various fluorinated compounds in C02-expanded liquids at 25°C. PFPE = poly(hexafluoropropyleneoxide) Fl-Wilkinson s Catalyst RhCKPR,), with R = C6H4-P-CH2CH2C6F13 (D-...

While the reverse solubility curve of calcium sulfate is often the main reason for scale deposition in fresh water boilers and in brackish water distillation, when the sea water is not chemically treated the cause is chemical rather than physical. Sea water contains bicarbonate ion. On heating, the bicarbonate ion reacts with water to form carbonate ion plus carbon dioxide, which tends to be evolved as a gas as shown in the equations... 

The initial step was to study systems with reverse solubility curves to learn the general pattern of the onset of scaling which would be of value for understanding the sea water system. Calcium sulfate, lithium carbonate, sodium sulfate, and calcium hydroxide have reverse solubility curves in water, are readily available, and are soluble to an extent that neither visual observation of scale nor chemical analysis would be a problem. 

Table 8.3 lists the properties of the azeotropes that 2-ethylhexanol and lauric acid form with water, both heterogeneous. It is remarkable that the solubility of water in acid and alcohol is large, while the reverse solubility, organic components in water, is extremely low, particularly for the acid. Pressure has little effect No information about water/fatty ester azeotrope is available, but this should not affect the analysis. 

Fig. 15.12 (a) Schematic illustration of covalent functionahzation of MWCNTs with hydroxyl-terminated ILs, X=C1, Br, NO3, SO4, CH3CO2, BF, PF, CIO, and (CF3S02)2N, and (b) reversible solubility of IL-functionalized MWCNTs in aqueous and organic solvents by anion exchange... 

A revised, updated suinmary of equilibrium constants and reaction enthalpies for aqueous ion association reactions and mineral solubilities has been compiled from the literature for common equilibria occurring in natural waters at 0-100 C and 1 bar pressure. The species have been limited to those containing the elements Na, K, Li, Ca, Mg, Ba, Sr, Ra, Fe(II/III), Al, Mn(II,III,IV), Si, C, Cl, S(VI) and F. The necessary criteria for obtaining reliable and consistent thermodynamic data for water chemistry modeling is outlined and limitations on the application of equilibrium computations is described. An important limitation is that minerals that do not show reversible solubility behavior should not be assumed to attain chemical equilibrium in natural aquatic systems. 

It may also be argued that the simulation of water-rock interactions should allow for solubility equilibria involving feldspars, micas, etc. For such studies the choice of solublity product constants and free energies must and should be made by the investigators. We cannot propose such values here when an enormous range of values and properties (solid-solutions, interlayering, defects, surface areas, etc.) is known to exist for these minerals and reversible solubility behavior has not been demonstrated. 

Figure 11.2-4 shows typical solubility diagrams for solutions of various salts in water. The curve for salt (NaCI) is nearly vertical, which indicates little effect of temperature ou solubility. The sodium sulfate curve shows reverse solubility as temperature increases thus, sodium solfate has a tendency to coat heat-exchanger surfaces where heat is added to saturated solutions of this system. 

The major challenge in using (20.11) is that the gas- and aqueous-phase concentrations Cg(z, t) and Caq(z, t) for a horizontally uniform atmosphere are a function of time and altitude. Therefore one needs to estimate the evolution of both variables in the general case. We shall consider two cases, the simplified one of an irreversibly soluble gas and then the more general case of a reversibly soluble one. 

For a reversibly soluble gas, one needs to retain both the flux from the gas to the aqueous phase and the inverse flux. The mass balance of (20.15) is still valid, so combining it with (20.11), we get... 

II Stable < transition Transition reversible Solubility I higher < transition Solubility I lower > transition... 

Chauthaiwale J, Rao M (1994) Production and purification of extracellular D-xylose isomerase from an alkaliphilic, thermophilic Bacillus sp. Appl Environ Microbiol 60(12) 4495-4499 Chen JP, Chen YC (1996) Improvement of cell lysis activity of immobilized lysozyme with reversibly soluble-insoluble polymer as carrier. Biotechnol Tech 10(10) 749-754 Chen R (2001) Enzyme engineering rational design versus directed evolution. TIBTECH 19(1) 13-14... 

The reversible solubility changes of thermo-responsive polymers are due to small temperature alterations. The aqueous solutions of these polymers exhibit a critical solution temperature at which the solubility phase of the polymer is changed. Thermo-responsive polymers that are soluble in water above a certain temperature and insoluble below it exhibit upper critical solution temperature behaviour. On the... 

Chen, J.P. and Chen, Y.C., Preparations of immohilized lysozyme with reversibly soluble polymer for hydrolysis of microbial cells, Bioresour. Technol., 60, 231,1997. 

Methyl cellulose and its alkylene oxide derivatives are nonionic polymers soluble in cold but not hot water. This phenomenon is commonly referred to as reverse solubility. 

Chen, S.-H., Yen, Y.-H., Wang, C.-L., and Wang, S.-L. 2003. Reversible immobilization of lysozyme via con-pling to reversibly soluble polymer. Enzyme Microb Technol. 33 643-649. 

The designer of brine pipelines must consider the possibility of deposition of solids. Solids may arise by settling from a slurry or suspension, by precipitation of salt as the brine cools, or by deposition of hardness compoimds (with their reverse solubility characteristics) as the brine is heated. 

Magnesium exhibits reverse solubility at very high temperatures and may precipitate in the PAL autoclave as kieserite [24]. A tolerable level seems to be around 20 g/L in flash discharge, although this may be conservative. 

For the preparation of the LiCl-KCl eutectic, reasonable purity anhydrous LiCl is readily available, although in the United States, the fully purified eutectic can be obtained. Otherwise, treatment with dry HCl followed by dry CI2 prior to preelectrolysis at 2.7 V, and, finally, filtration, is recommended. Similar procedures, with suitable modifications to the gas purges and electrolysis voltages, may be adopted for MgCl2-KCl, NaCl-KCl, CaC -KCl, ZnC -KCl, and for the bromides and iodides. Advantageously, vitreous carbon crucibles can be used for halide melts they are reusable and can form the counterelectrode. Purity of these systems may again be assessed voltammetri-cally. Surprisingly, water is reversibly soluble at low partial pressures, but hydrolysis occurs at a 18 mm ... 

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