Solubilities temperature

Fig. 5. Solubility—temperature curves for boric acid, borax, sodium pentaborate, and sodium metaborate (71).

Atmospheric Reaeration. Interfacial properties and phenomena that govern oxygen concentrations in river systems include 1) oxygen solubility (temperature, partial pressure and surface dependency), 2) rate of dissolution of oxygen (saturation level, temperature and surface thin film dependency, i.e., ice, wind), and 3) transport of oxygen via mixing and molecular diffusion. A number of field and empirically derived mathematical relationships have been developed to describe these processes and phenomena, the most common of which is (32) ... 

The derivation of the quantitative relationship between this equilibrium temperature and the composition of the liquid phase may be carried out according to the well-known thermodynamic procedures for treating the depression of the melting point and for deriving solubility-temperature relations. The condition of equilibrium between crystalline polymer and the polymer unit in the solution may be restated as follows ... 

It is known [37,38] that conformational and phase transitions of water-soluble temperature-responsive polymers significantly influence the molecular dynamics of water molecules. Therefore, the studies of temperature dependence of the parameters capable of reflecting such mobility are of signifi-... 

Henry s law constant can be regarded as a ratio of vapor pressure to solubility, thus it is subject to the same effects that electrolytes have on solubility. Temperature affects both properties. Some methods are as follows ... 

Solubility-temperature relationship(s) sodium with other elements, 22 763 for surfactants, 24 125-126... 

Smith et al. [64] prepared a series of PET/PTT copolyesters, and found that addition of the other component suppressed the melting point of the respective homopolymer. Between 37 and 60 % PTT content, the copolymers became amorphous and did not show any melting endotherms in the differential thermal analyzer scans. A similar behavior was observed by Balakrishnan and coworkers [102] in PET/PTT copolyesters prepared by the transesterification of PET with PDO, and by the copolymerization of EG and PDO with DMT [103, 104], The non-crystallizing behavior of copolymers with intermediate contents of the respective component is similar to that of a eutectic mixture, indicating formation of random copolyesters. The 7 g and solubility temperature of the copolyesters were, however, continuous and went through minima with increasing PTT content [64],... 

The rate of chemical hydrolysis is highly dependent upon the compound s solubility, temperature and pH. Since other environmental factors such as photolysis, adsorption, volatility (i.e., Hemy s law constants) and adsorption can affect the rate of hydrolysis, these factors are virtually eliminated by... 

Mills AC, Biggar JW (1969) Solubility-temperature effect on the adsorption of gamma and beta—BHC from aqueous and hexane solutions by soils materials. Soil Sci Am Soc Am Proc 33 210-216... 

Poly(N-isopropylacrylamide) (polyNIPAAM), formed by a free radical polymerization of N-isopropylacrylamide, is a water soluble, temperature sensitive polymer. In aqueous solution, it exhibits a lower critical solution temperature (LCST) in the range of 30-35 C depending on the concentration and the chain length of the polymer. Thus, as the solution temperature is raised above the LCST, the polymer undergoes a reversible phase transition characterized by the separation of a solid phase which redissolves when the solution temperature is lowered below the LCST. Its physicochemical properties have been investigated by several laboratories (1-3). 

Due to the neighbourhood of secondary alcohol groups and remaining hydro-phobic acetyl groups in a not fully hydrolysed polymer, a balanced situation results that dictates the overall water solubility. Temperature plays an important role in that interplay between the intermolecular attracting forces and the polymer water interaction. An optimum in cold water solubility can be observed with a DH of 87-89 mol% for molecular weights between 25,000 and 100,000 Da (degree of polymerisation, DP, 600-2,400). 

The solubility—temperature curves for the Aa () 1)0 11 () system are given in Figure 5 (Table 9). The solubility curves of the penta- and... 

H2 (aq.). The heat of solution is computed from the solubility-temperature data of Turnofejen1 and Winkler.9... 

Studies on non-ionic surfactants as effective drag-reducing additives have been submitted by Zakin (1972). He studied various effects on three non-ionic surfactants formed from straight-chain alcohols and ethyleneoxide. These surfactants have an upper and a lower temperature limit for solubility in water and prove effective drag reducers near their upper critical solubility temperature or clouding point. The clouding point is the point at which a solution of a non-ionic agent in water becomes turbid as the temperature is raised. 

Temperature Effect. Near the boiling point of water, the solubility—temperature relationship undeigoes an abmpt inversion. Over a narrow temperature range, solutions become cloudy and the polymer precipitates the polymer cannot dissolve in water above this precipitation temperature. In Figure 4, this limit or cloud point is shown as a function of polymer concentration for poly(ethylene oxide) of 2 x 106 molecular weight. 

Mole fraction water solubilities, Xk, are conveniently used in solubility-temperature and in multicomponent representations of solubility information. The mole fraction, Xk, of a component k in a system of m components is defined as... 

C2H2 (aq.). Villard7 reported the heat of solution of acetylene in water to be 5.3. The solubility-temperature data of Winkler5 yield 4.0. 

FIGURE 19.5 Solubility/temperature plots for enantiotropic (E) and monotropic (M) polymorphs at a xed pressure. 

Enantiotropic polymorphs exhibit this transition temperature below their melting temperature (Figure 19.5), which means that the stable modiLcation depends on the temperature of reference This temperature represents the point of equal solubility for the two polymorphs, and one will have greater solubility above this temperature, and one below it. These transitions are often reversible, but may be kinetically limited or outside the temperature range studied. Haleblian and McCrone (1969) have cautioned that an enantiotropic relationship cannot be discounted because of the lack of an observed transition point. The transition can be examined microscopically if the crystal habits differ, or by solubility-temperature curves if the metastable form solubility can be measured before transformation. 

A poly(propylenamine) dendrimer (11, Fig. 6.37) functionalised with poly-(N-isopropylacrylamide) (PIPAAm) (see Section 4.1.2) was used as dendritic host for anionic cobalt(II)-phthalocyanine complexes (a, b) as guests, which are held together by supramolecular (electrostatic and hydrophobic) interactions [57]. These dendritic complexes were investigated as catalysts in the above-mentioned oxidation of thiols, where they show a remarkable temperature dependence the reaction rate suddenly increases above 34°C. One attempted explanation assumes that the dendritic arms undergo phase separation and contraction above the Lower Critical Solubility Temperature (LCST). At this temperature the phthalocyanine complex site is more readily accessible for substrates and the reaction rate is therefore higher. 

Mixing. Because the solubility-temperature curves are concave from above (Fig. 4.1), mixing of waters equilibrated at different temperatures will produce apparent supersaturation relative to the temperature of the mix. The effect will be greatest for the heavier gases but will be minimal for He and Ne, and in the normally encountered range it is greater at lower temperatures. 

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