Temperature solid solubility

One such a situation is the room-temperature solid solubility of hydrogen in Sc (Azarkh and Funin 1965), Y, Gd, Er, Tm and Lu (Beaudry and Spedding 1975), which are plotted in fig. 22 as a function of the metallic radius. It is immediately seen that the amount of hydrogen dissolved in the rare earth elements with no unpaired 4f electrons is enormously higher than in those lanthanides with unpaired electrons. If the 4f electrons were truly localized and not involved in the chemical bonding one... 

Jehn, H., Olzi, E. (1972). High temperature solid solubility limit and phase studies in the system tantalum-oxygen. Journal of the Less Common Metals, 27(3), 297-309. doi 10.1016/0022-5088(72)90062-8. 

When an element has more than one oxidation state the lower halides tend to be ionic whilst the higher ones are covalent—the anhydrous chlorides of lead are a good example, for whilst leadfll) chloride, PbCl2, is a white non-volatile solid, soluble in water without hydrolysis, leadflV) chloride, PbC, is a liquid at room temperature (p. 200) and is immediately hydrolysed. This change of bonding with oxidation state follows from the rules given on p.49... 

Phase Separation. Microporous polymer systems consisting of essentially spherical, intercoimected voids, with a narrow range of pore and ceU-size distribution have been produced from a variety of thermoplastic resins by the phase-separation technique (127). If a polyolefin or polystyrene is insoluble in a solvent at low temperature but soluble at high temperatures, the solvent can be used to prepare a microporous polymer. When the solutions, containing 10—70% polymer, are cooled to ambient temperatures, the polymer separates as a second phase. The remaining nonsolvent can then be extracted from the solid material with common organic solvents. These microporous polymers may be useful in microfiltrations or as controlled-release carriers for a variety of chemicals. 

As you can see from the tables in Chapter 1, few metals are used in their pure state -they nearly always have other elements added to them which turn them into alloys and give them better mechanical properties. The alloying elements will always dissolve in the basic metal to form solid solutions, although the solubility can vary between <0.01% and 100% depending on the combinations of elements we choose. As examples, the iron in a carbon steel can only dissolve 0.007% carbon at room temperature the copper in brass can dissolve more than 30% zinc and the copper-nickel system - the basis of the monels and the cupronickels - has complete solid solubility. 

When the phase diagram for an alloy has the shape shown in Fig. 10.3 (a solid solubility that decreases markedly as the temperature falls), then the potential for age (or precipitation) hardening exists. The classic example is the Duralumins, or 2000 series aluminium alloys, which contain about 4% copper. 

Undersaturated The same quantities of solute and solvent are mixed, as for the above ease, but the system is then heated for about 20 min above the required temperature (if solubility inereases with temperature) so that most, but not all, of the solid is dissolved. The solution is then eooled and agitated at a given temperature for a long period, to allow the exeess solid to deposit and an apparent equilibrium to be reaehed. 

An application of Eq. (11) is shown in Fig. 2, which gives the solubility of solid carbon dioxide in compressed air at a low temperature. The solubility is calculated from the equation of equilibrium... 

The equilibrium pressure when (solid + vapor) equilibrium occurs is known as the sublimation pressure, (The sublimation temperature is the temperature at which the vapor pressure of the solid equals the pressure of the atmosphere.) A norma) sublimation temperature is the temperature at which the sublimation pressure equals one atmosphere (0.101325 MPa). Two solid phases can be in equilibrium at a transition temperature (solid + solid) equilibrium, and (liquid + liquid) equilibrium occurs when two liquids are mixed that are not miscible and separate into two phases. Again, "normal" refers to the condition of one atmosphere (0.101325 MPa) pressure. Thus, the normal transition temperature is the transition temperature when the pressure is one atmosphere (0.101325 MPa) and at the normal (liquid + liquid) solubility condition, the composition of the liquid phases are those that are in equilibrium at an external pressure of one atmosphere (0.101325 MPa). 

E8.12 The melting point of 1,4-dichlorobenzene is 326.4 K and that of naphthalene is 353.4 K. The eutectic point occurs at a temperature of 303.4 K and a mole fraction of naphthalene in the liquid phase of 0.394. Assume ideal liquid solutions, no solid solubility, and ArusCp.m = 0 and calculate AfusHm for 1,4-dichlorobenzene. 

Unlike solids for which solubility in a liquid generally increases with increasing temperature, the solubility of a gas in a liquid usually decreases as the temperature increases. Knowing this, explain why you should never heat a can containing a carbonated soft drink. 

Oxygen and carbon have substantial solid solubilities in niobium at the temperatures normally required for reduction. As the activity coefficients of both carbon and oxygen in niobium are low, their retention in the niobium metal produced by the carbothermic reduction of niobium oxide is expected. It is, however, possible (as explained later) to remove these residual impurities by extending the pyrovacuum treatment to still higher temperatures and lower pressures. 

A sample in the primary crystallization field of phase C will behave differently during crystallization. Here phase C precipitates with composition identical to C (no solid solubility) during cooling keeping the A B ratio in the melt constant until the melt hits the intersection of the two primary crystallization fields. At this temperature a will start to precipitate together with further C and from this point on the cooling process corresponds to that observed for the sample with overall composition P after this sample reaches the same stage of the crystallization path. 

Some substances will dissolve in a particular solvent and others will not. There is a general rule in chemistry that states like dissolves like. Polar substances (such as alcohols) will dissolve in polar solvents like water. Nonpolar solutes (such as iodine) will dissolve in nonpolar solvents such as carbon tetrachloride. The mass of solute per 100 mL of solvent (g/100 mL) is a common alternative to expressing the solubility as molarity. It is necessary to specify the temperature because the solubility of a substance will vary with the temperature. The solubility of a solid dissolving in a liquid normally increases with increasing temperature. The reverse is true for a gas dissolving in a liquid. 

Recrystallization is a purification technique for a solid, usually organic. The separation is based on the solid s solubility in a liquid solvent. The solid must be sparingly soluble in this solvent at room temperature, but highly soluble at higher temperatures. Both soluble and insoluble impurities are considered to be present, and the procedure removes both if the concentrations are not too large. 

Thermodynamic calculations based on the compositional dependence of the equilibrium constant are applied to solubility data in the KCl-KBr-H20 system at 25°C. The experimental distribution coefficient and activity ratio of Br /Cl in solution is within a factor of two of the calculated equilibrium values for compositions containing 19 to 73 mole percent KBr, but based on an assessment of uncertainties in the data, the solid solution system is clearly not at equilibrium after 3-4 weeks of recrystallization. Solid solutions containing less than 19 and more than 73 mole percent KBr are significantly farther from equilibrium. As the highly soluble salts are expected to reach equilibrium most easily, considerable caution should be exercised before reaching the conclusion that equilibrium is established in other low-temperature solid solution-aqueous solution systems. 

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