Solubility product temperature dependence

This relationship varies slightly because of the vertical fluctuation in the phosphorus content in the sea. For saline water systems, data on the solubility product of a calcium phosphate is difficult to obtain inasmuch as — aside from temperature and hydrostatic pressure — the solubility product is dependent on the type and amount of solutes present. The apparent dissociation constants of H3P04 are defined by the equations129,130 ... 

The shape of the equilibrium line, or solubility curve, is important in determining the mode of crystallization to be employed in order to crystallize a particular substance. If the curve is steep, i.e. the substance exhibits a strong temperature dependence of solubility (e.g. many salts and organic substances), then a cooling crystallization might be suitable. But if the metastable zone is wide (e.g. sucrose solutions), addition of seed crystal might be necessary. This can be desirable, particularly if a uniformly sized product is required. If on the other hand, the equilibrium line is relatively flat (e.g. for aqueous common salt... 

Temperature-dependent phase behavior was first applied to separate products from an ionic liquid/catalyst solution by de Souza and Dupont in the telomerization of butadiene and water [34]. This concept is especially attractive if one of the substrates shows limited solubility in the ionic liquid solvent. 

The product P, termed the (real or thermodynamic) solubility product, is a constant dependent only on the temperature. The analogous (apparent)... 

Photolytic. Acher et al. (1981) studied the dye-sensitized photolysis of terbacil in aerated aqueous solutions over a wide pH range. After a 2-h exposure to sunlight, terbacil in aqueous solution (pH range 3.0-9.2) in the presence of methylene blue (3 ppm) or riboflavin (10 ppm) decomposed to 3-ter/-5-butyl-5-acetyl-5-hydroxyhydantoin. Deacylation was observed under alkaline conditions (pH 8.0 or 9.2) affording 3-/er/-5-hydroxyhydantoin. In neutral or acidic conditions (pH 6.8 or 3.0) containing riboflavin, a mono-Wdealkylated terbacil dimer and an unidentified water-soluble product formed. Product formation, the relative amounts of products formed, and the rate of photolysis were all dependent upon pH, sensitizer, temperature, and time (Acher et ah, 1981). 

Cellulose is readily hydrolyzed in water at >170° at a rate that depends on the hydrogen-ion concentration, even in the range between pH 5 and 8. Because acids from the degradation of D-glucose are produced when cellulose is exposed to high temperature, the pH of the aqueous mixture drops in the absence of buffers. Earlier work had indicated that ether-soluble products could be obtained by heating cellulose in... 

The ion product of water depends on the ionic strength of the system and on its temperature. At 25 °C and in low ionic strength solution, log = -13.99, whereas in 3 M NaC104 (the ionic medium used by Schindler et al., 1963 for solubility product determination), log = -14.22 + 0.1 the value chosen must correspond to the ionic strength of the system involved. 

The OH concentration increases (decreases) by one order of magnitude for every unit increase (decrease) in pH. This means that the formation of a metal hydroxide (whether as a colloid or as a precipitate) in aqueous solution will be strongly dependent on temperature when the product of the free metal ions and OH ions is close to the hydroxide solubility product, although increase in Ksp with temperature may partially offset this effect. 

Hagenmaier (10) demonstrated that pH had little effect on water absorption of oilseed protein products, but solubility was pH dependent. He suggested that the differing degree of dependence on pH indicates that water absorption and protein solubility are not correlated. Contrastingly, Wolf and Cowan (28) reported the pH-water retention curve of soy proteins to follow the pH-solubility curve. Both solubility and water retention were minimal at the isoelectric point (4.5) and increased as the pH diverged from this point. Hutton and Campbell (20) reported that the effects of pH and temperature on water absorption of soy products paralleled those of solubility for the most part. 

As discussed in section 2.2.5, the solubility of lactose is temperature dependent and solutions are capable of being highly supersaturated before spontaneous crystallization occurs and even then, crystallization may be slow. In general, supersolubility at any temperature equals the saturation (solubility) value at a temperature 30°C higher. The insolubility of lactose, coupled with its capacity to form supersaturated solutions, is of considerable practical importance in the manufacture of concentrated milk products. 

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