Solubility dependence on temperature

Solutions are mixtures, and therefore do not have definite compositions. For example, in a glass of water it is possible to dissolve 1 teaspoonful of sugar or 2 or 3 or more. However, for most solutions there is a limit to how much solute will dissolve in a given quantity of solvent at a given temperature. The maximum concentration of solute that will dissolve in contact with excess solute is called the solubility of the solute. Solubility depends on temperature. Most solids dissolve in liquids more at higher temperatures than at lower temperatures, while gases dissolve in cold liquids better than in hot liquids. 

In reverse, the surfactant precipitates from solution as a hydrated crystal at temperatures below 7k, rather than forming micelles. For this reason, below about 20 °C, the micelles precipitate from solution and (being less dense than water) accumulate on the surface of the washing bowl. We say the water and micelle phases are immiscible. The oils re-enter solution when the water is re-heated above the Krafft point, causing the oily scum to peptize. The way the micelle s solubility depends on temperature is depicted in Figure 10.14, which shows a graph of [sodium decyl sulphate] in water (as y ) against temperature (as V). 

You know intuitively that solubility depends on temperature. For most ionic compounds, more solute can dissolve in a solvent at higher temperatures. Chemists determine the solubility of an ionic compound by experiment, and then use the solubility data to determine Ksp. Like the equilibrium constant, Ksp is temperature-dependent. Therefore, different experiments must be carried out to determine Ksp at different temperatures. 

Lead azide is insoluble in an aqueous solution of ammonia. Acetic acid causes its decomposition but it is soluble in water and concentrated solutions of sodium nitrate, sodium acetate or ammonium acetate. There are fairly big differences of solubility, depending on temperature. 

Another interesting result of carbon dioxide solubility in water is that it constitutes the basis for the phenomenon of spontaneous and violent liberation of dissolved C02 to the atmosphere in a stratified lake, as in the case of Lake Nyos in Cameroon mentioned above (see Section 6.1.3). When dissolved C02 seeps from a hydrothermal vent into a stratified lake, the pressure and low temperature favor the dissolution and saturation in the lower strata of the lake. Because of its high solubility, more than five volumes of C02 can dissolve in one volume of water. As for any other gas, however, its solubility depends on temperature and pressure, making the... 

Solubility dependence on temperature may be different for different solvent compositions. Therefore, it is important to use a statistical factorial design to study the effect of composition and temperature simultaneously. 

The solubility of so-called insoluble materials is often ignored in surface charging studies, but it must be realized that a certain fraction of the adsorbent undergoes dissolution in the form of various species. In some experiments, this solubility is in fact immaterial, but in a few other experiments, solubility matters. Solubility may be responsible for irreproducibility of experiments and for scatter in the PZCs/IEPs reported in the literature. Solubility depends on temperature, pH, and ionic strength. Solubilities of thermodynamically stable forms are lower than those of less stable forms, and solubilities of small crystals are higher than those of large crystals. Moreover, dissolution is a slow process, and the concentration of dissolved species in solution in many experiments is well below saturation. Thus, thermodynamic (equilibrium) data on solubility are of limited relevance to surface charging experiments with short equilibration times. 

Neutralisation of guaiacol with sodium hydroxide results in a guaiacol-sodium guaiacolate complex of which the solubility depends on temperature and dilution. To carry out the condensation with glyoxylic acid, it is necessary to have an homogeneous mixture. The temperature can be raised, but due to the Cannizzaro reaction of glyoxylic acid, it is economically uninteresting, and productivity decreases with dilution. 

During crystallization any excess material, not accommodated in the amorphous regions, is driven ahead of the spheralite growth front and crystallizes out when the solubility exceeds the relevant threshold." Solubility depends on temperature." ... 

Temperature Temperature exerts a major influence on most chemical equilibria, including solution equilibria. Consequently, solubility depends on temperature. Figure 16.11 indicates that the solubility of most solids increases with rising temperature, but... 

The use of accurate isotope ratio measurement is exemplified here by a method used to determine the temperature of the Mediterranean Sea 10,000 years ago. It is known that the relative solubility of the two isotopic forms of carbon dioxide COj) in sea water depends on temperature... 

Iron, cobalt, and nickel catalyze this reaction. The rate depends on temperature and sodium concentration. At —33.5°C, 0.251 kg sodium is soluble in 1 kg ammonia. Concentrated solutions of sodium in ammonia separate into two Hquid phases when cooled below the consolute temperature of —41.6°C. The compositions of the phases depend on the temperature. At the peak of the conjugate solutions curve, the composition is 4.15 atom % sodium. The density decreases with increasing concentration of sodium. Thus, in the two-phase region the dilute bottom phase, low in sodium concentration, has a deep-blue color the light top phase, high in sodium concentration, has a metallic bronze appearance (9—13). 

The concentration of dissolved ionic substances can be roughly estimated by multiplying the specific conductance by an empirical factor of 0.55—0.9, depending on temperature and soluble components. Since specific conductance is temperature dependent, all samples should be measured at the same temperature. Alternatively, an appropriate temperature-correction factor obtained by comparisons with known concentrations of potassium chloride may be used. Instmments are available that automatically correct conductance measurements for different temperatures. 

Now, we should ask ourselves about the properties of water in this continuum of behavior mapped with temperature and pressure coordinates. First, let us look at temperature influence. The viscosity of the liquid water and its dielectric constant both drop when the temperature is raised (19). The balance between hydrogen bonding and other interactions changes. The diffusion rates increase with temperature. These dependencies on temperature provide uS with an opportunity to tune the solvation properties of the liquid and change the relative solubilities of dissolved solutes without invoking a chemical composition change on the water. 

The solubility of calcium carbonate in cold water is approximately 15 to 20 ppm, dependent on temperature and other factors, and is rarely present in MU water supplies. Where it is present, there is a phenolph-thalein or P alkalinity. 

Sulfates in surface MU water sources usually are present at lower concentrations (typically 20-60 ppm) but this level may rise to several hundred ppm in subsurface waters. The maximum solubility of calcium sulfate is dependent on temperature but is in the range of 1,800 to 2,000 ppm in cold water. This rate is significantly less in hot BW where boiler deposits occur, the sulfate scale normally is present as anhydrite (CaS04). Sulfate scales are hard and very difficult to remove, so treatment programs employed must be carefully controlled to avoid risks of scaling. 

Following this, elastomers can be swollen by some high-pressure gases (especially CO2) as the densities of these gases approach liquid-like levels, at appropriate temperatures they become supercritical fluids which possess a solubility parameter magnitudes that, however, are highly dependent on temperature and pressure... 

The efficiency of extraction is mainly dependent on temperature as it influences physical properties of the sample and its interaction with the liquid phase. The extraction is influenced by the surface tension of the solvent and its penetration into the sample (i.e. its viscosity) and by the diffusion rate and solubility of the analytes all parameters that are normally improved by a temperature increase. High temperature increases the rate of extraction. Lou et al. [122] studied the kinetics of mass transfer in PFE of polymeric samples considering that the extraction process in PFE consists of three steps ... 

Lead oxide is soluble in molten phenol (45-60°C) at a level of 20 wt%. Evaporation of phenol from such a solution yields lead (II) phenoxide. Reactions between lead oxide and quaternary bromide in phenol depend on temperature ... 

The solubility of a solid in a relevant solvent medium is a crucial characteristic. Solubility is defined as the concentration of the dissolved solid (the solute) in the solvent medium, which becomes the saturated solution and which is in equilibrium with the solid at a defined temperature and pressure. The solubility depends on the physical form of the solid, the nature and composition of the solvent medium, the temperature, and the pressure [1],... 

Methods for the determination of solubility have been thoroughly reviewed [21,22], Solubility is normally highly dependent on temperature, and so the temperature must be recorded for each solubility measurement. Plots of solubility against temperature, as exemplified by Fig. 4 [23,24], are commonly used for characterizing pharmaceutical solids and have been extensively discussed [1,24]. Frequently (especially over a relatively narrow temperature range), a linear relationship may be given either by a van t Hoff plot according to [23]... 

Kent and Eisenberg (5) also correlated solubility data in the system S+CC +alkanoleimines+ O using pseudo-equilibrium constants based on molarity. Instead of using ionic characterization factors, they accepted published values of all but two pseudoequilibrium constants and found these by fitting data for MEA and DEA solutions. They were able to obtain excellent fits by this approach and also discovered that the fitted pseudo-equilibrium constants showed an Arrhenius dependence on temperature. 

Parameters 0 - for interactions between like molecules were evaluated from single solute solubility data in water. These parameters proved to depend on temperature (cf. Appendix III). Parameters for... 

Figure 2.10. Examples of binary systems characterized by complete mutual solubility in the liquid state and, depending on temperature and/or composition, partial solubility in the solid state and presenting (in certain composition ranges) an invariant (three-phase) reaction (eutectic in the Cu-Ag, peritectic in the Ru-Ni and Re-Co and eutectoidal in Ti-W (one) and in Th-Zr (two)).

Let us illustrate this phenomenon with a practical example, the variation of oxygen and of nitrogen equilibrium solubilities with depth in the ocean [1]. For seawater, the density p depends on temperature and salinity, and it could vary from 1.025 to 1.035 g cm. For dissolved oxygen, V2 = 0.97 cm g in seawater at a water temperarnre near 25°C. If d is expressed in meters, then at the lower limit of the water density. Equation (21.17) becomes... 

Bunsen solubility coefficient (a ) The term that relates the concentration of a gas in seawater to its partial pressure in the atmosphere. It is dependent on temperature and salinity. 

Soluble loss of a reagent (extractant, modifier, or diluent) from the solvent phase is an inherent part of the solvent extraction process, since all organic compounds are soluble, to some extent, in water. The conditions prevailing in the system can also promote solubility, which can be a particular problem if the composition and properties of the aqueous phase are inflexible. For example, the solubility of alkylphosphoric acid and carboxylic acid extractants is dependent on temperature, pH, and salt concentration in the aqueous phase. 

Three causes of extractant solubility in the aqueous phase may be distinguished solubility of un-ionized and ionized extractant and metal-extractant species. For extractants such as acids, amines, and chelating reagents, their polar character will always result in some solubility in the aqueous phase over the pH range in which they are useful for metal extraction. Solubility depends on many factors including temperature, pH, and salt concentration in the aqueous phase, as discussed in Chapter 2. 

An increase in temperature at constant pressure, on one hand, leads to a decrease in solvent density, which would lower the solubility. On the other hand, an increase in temperature results in an increase in vapor pressure of naphthalene. At high pressures, the density dependence on temperature is small compared with the effect of vapor pressure, which results in an increased solubility. At lower pressures, the density effect dominates when increasing the temperatures, resulting in a decrease in solubility. 

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