Solids pressure effects

Solid-state pressure effects on stereochemically nonrigid structures. J. R. Ferraro and G. J. Long, Acc, Chem. Res., 1975,8, 171-179 (57). 

Gas production and subsequent pressure-time histories can be investigated successfully only in pressure vessels such as the VSP. If the gaseous product dissolves partly in the reaction mixture (i.e., the vapor-liquid equilibrium is changed), careful investigations of the pressure effect within the possible variations of the operating conditions are necessary. Pressurized vessels are also useful to investigate any mass transfer improvement for gas-liquid or gas-dissolved (suspended) solid reactions. 

Pressure effects on stopping cross sections have been recently addressed within the OLPA-FSGO scheme for molecular targets [25] and preliminary calculations have been reported for stopping and total path ranges of He and Li ions in compressed solid water and methane [68], where total path ranges were found to he predominantly decreased in comparison with those at normal pressure. 

It is well know that melting occurs more rapidly if there is a positive pressure at the end of the transition zone. If Film B is considered to be large and if the pressure in the melt Film C is essentially zero at the trailing flight, a first order approximation of this pressure effect can be achieved by adding a pressure dissipation term to the rate of material loss in the y direction of the solid surface adjacent to the Film C ... 

Akamatsu T, Kumazawa M., Aikawa N., and Takei H. (1993). Pressure effect on the divalent cation distribution in nonideal solid solution of forsterite and fayalite. Phys. Chem. Minerals, 19 431-444. 

Detonation pressure might be taken to mean (1) the pressure in the shock zone ahead of the reaction zone, (2) pressure in the front of the reaction zone or (3) the pressure effect on the first layer of the solid confining medium... 

Recently Lee et al (Ref 3) re-examined the behavior of PETN under 10 to 50 kbars of external pressure. They also find a reduction in decomposition rate with increasing applied pressure. HMX behaves similarly to PETN. TNT whose explosion products contain a high proportion of solid carbon, as expected from LeChatelier s Principle, shows little pressure effect on its thermal decomposition. Nitro-methane, however, appears to decompose more rapidly under an external pressure of 50 kbars than 10 kbars. This effect is not completely understood but Lee et al suggest that high pressure may favor the formation of the thermally less stable aci form of Nitromethane ... 

The LaPlace Equation. The concept of surface energy allows us to describe a number of naturally occurring phenomena involving liquids and solids. One such situation that plays an important role in the processing and application of both liquids and solids is the pressure difference that arises due to a curved surface, such as a bubble or spherical particle. For the most part, we have ignored pressure effects, but for the isolated surfaces under consideration here, we must take pressure into account. 

The dark conductivity of a number of organic solids increases reversibly with increasing pressure details are given in 10>. Because these changes range over several orders of magnitude, the possibility of using them to measure pressure should be tested. For the pressure effect in Cu-phthalocyanine and polymeric phthalocyanines, see 8,141,142). 

Pressure effects on equilibria in liquids or solids are generally less spectacular than temperature effects, at least at the pressures normally encountered in chemical engineering (a few tens of megapascals) or in the environment (hydrostatic pressures in the ocean trenches exceed 100 MPa, but about 40 MPa would be more typical of the ocean floors). Higher lithostatic pressures are, of course, found beneath the Earth s surface, reaching 370 GPa (0.37... 

At low pressures, the liquefaction temperature of PEG in the presence of CO2 increases slightly compared to the melting point of the pure PEG. This increase might be caused by a pressure effect or by a solid-transition of PEG induced by increasing pressure. Then a sharp reduction is observed. The liquefaction temperature passes through a minimum and increases again. 

Hie majority of tetrazoles are crystn solids. There is considerable variation in thermal stability, viz. derivatives which melt above 150° do so with decompn, while 5-guanylaminotetrazole (Vol 7, G366-L) does not melt at -300°. In general, most of the tetrazoles are acids and often yield expl salts. The tetrazoles, in the main, can be looked upon as gas generators, useful where instantaneous or progressive pressure effects are required. They possess moderate brisance. However, their salts, which may detonate with extreme brisance, can be used as primary expls, as can 1- and 2-Methyl-5-Nitro Tetrazoles, which are delineated in this article History of Use ... 

Temperature and pressure effects become important in chemical systems of geological interest. Also, the chemical nature of the system is often not well characterized. Nonstoichiometric compounds and solid solutions are often present, with complex silicates frequently playing an important part. 

Type IV isotherms (e.g. benzene on iron(III) oxide gel at 320 K) level off near the saturation vapour pressure and are considered to reflect capillary condensation in porous solids, the effective pore... 

Mehta (34) has carried out a reactor network optimization study to find improved designs for the production of acrylonitrile in a collaboration between UMIST and one of its industrial partners. Most industrial installations employ fluidized-bed reactors (BP/Sohio process) with a well-mixed reaction zone. Previous process improvements have mainly resulted from better catalysts, which have produced an increase in yield from 58% to around 80%. The reaction model employed in the optimization study is taken from Ref. 81 and considers seven reactions and eight components. Air, pure oxygen, and propylene are available as raw material streams. The optimization study assumes negligible pressure drop along the reaction sections, isothermal and isobaric operation, and negligible mass gas-solid transfer effects. 

The correct answer is (B). Gases are most soluble in liquids at low temperature. This is unlike most solids, which become less soluble at lower temperatures. In addition, high external pressures increase the solubility of gases in liquids. For solids, pressure has a negligible effect. 

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