Solids sublimation behavior

Zirconium tetrachloride is a white crystalline solid with specific gravity 2.803.4 The solid sublimes under atmospheric pressure at 331° [log pBin. = — (26,000/4.57T) + 12.30] but melts at 437° under its own pressure, which is about 25 atm. at this temperature.18 The vapor density shows normal behavior up to 500°, at which point dissociation is suspected.16 Electron-diffraction results show tetrahedral symmetry with the Zr-Cl distance 2.33 A.17 Todd18 has recently determined the heat capacity of zirconium tetrachloride at low temperatures (extrapolated below —222°) and calculated the usual thermodynamic constants for the compound. The melting point of hafnium tetrachloride has been estimated as 432° under its own pressure, but the solid sublimes under atmospheric pressure at 317°.12 Both metal chlorides are extremely hygroscopic. They are easily soluble in water, although extensively hydrolyzed. All high-purity samples should be desiccated as well as possible. [Pg.125]

Actually, the temperature does not change as heat is added to change the solid to gas at the equilibrium sublimation temperature. Hence, the heat capacity becomes infinite at this temperature, and the dotted line shown in Figure 8.12 should extend vertically to infinity. The compressibility and coefficient of expansion would show a similar behavior. [Pg.404]

Its inert behavior towards numerous chemical compounds and its adsorbent properties (responsible for the retention of volatile or sublimable organic compounds), make graphite the choice support for thermal reactions. Among its impurities, magnetite was revealed to be an active catalyst, and some reactions can be performed without any added catalyst. Two processes are then possible, the graphite-supported reaction ( dry process), and the reaction in the presence of a small amount of graphite (solid-liquid medium). [Pg.247]

A 40-cu ft tank is filled with air at 14.7 psia and 80°F. The tank also contains a 15-lb block of dry ice (solid C02, specific gravity of 1.53 based on water). After the dry ice sublimes, the temperature is 30°F. What is the pressure Assume ideal gas behavior. [Pg.124]

As described in Figure 4b the phase behavior of a type II binary system is depicted by the vapor pressure (L-V boundary) curves for the pure components, sublimation (S-V boundary) and melting (S-L boundary) curves for the solid component, and especially the S-L-V line on the P-T space. For an organic solid drug solute, the triple-point temperature is sufficiently higher than the critical temperature of the SCF solvent. The (L = V) critical locus has two branches and is intersected by two S-L-V lines at LfCEP and LCEP, respectively, in the presence of the solid phase. The S-L-V line indicates that the melting of the solid is lowered in the presence of the SCF solvent component as it is dissolved in the molten (liquid) phase. The S-L-V line... [Pg.36]

The volume of a material is a function of both the temperature T and the pressure p, as described by its pressure-volume-temperature (PVT) relationships. These relationships incorporate a description of the complete phase behavior of a material, such as the significant changes which take place when the material undergoes a phase transition (for example when a solid melts or sublimes, or when a liquid boils). The preceding discussion focused on the dependence of the volumetric properties on the temperature only, at atmospheric pressure, since there are no simple and general quantitative stmcture-property relationships to describe the full PVT behavior. This topic is of great importance, however, and will now be reviewed. [Pg.126]

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