Solid temperature stability

Dust entrained in the exit-gas stream is customarily removed in cyclone cohectors. This dust may be discharged back into the process or separately cohected. For expensive materials or extremely fine particles, bag collectors may follow a cyclone collector, provided fabric temperature stability is not hmiting. When toxic gases or solids are present, the exit gas is at a high temperature, the gas is close to saturation as from a steam-tube diyer, or gas recirculation in a sealed system is involved, wet scrubbers may be used independently or following a cyclone. Cyclones and bag collec tors in diying applications frequently require insulation and steam tracing. The exhaust fan should be located downstream from the cohection system. 

Fig. 4.3.1 Effect of pH on the total light emission of phialidin (A), and the temperature stability profiles of phialidin (minute open circles) and aequorin (solid line) (B). In A, each buffer contained 0.1 M CaCl2 plus 0.1 M Tris, glycine or sodium acetate, the pH being adjusted with NaOH or HC1. In B, the photoprotein samples in 10 mM Tris-EDTA buffer solution, pH 8.0, were maintained at a test temperature for 10 min, and immediately cooled in an ice water bath. Then total luminescence activity was measured by injecting 1ml of 0.1 M CaCl2/Tris-HCl, pH 7.0, to 10 pd of the test solution. From Levine and Ward (1982), with permission from Elsevier.

The phase transition boundaries (phase envelope) of adamantane need to be investigated and constmcted. Predictable and diverse geometries are important features for molecular self-assembly and pharmacophore-based dmg design. Incorporation of higher diamondoids in solid-state systems and polymers should provide high-temperature stability, a property already found in polymers synthesized from lower diamondoids. 

The presence of a solvent, especially water, and/or other additives or impurities, often in nonstoichiometric proportions, may modify the physical properties of a solid, often through impurity defects, through changes in crystal habit (shape) or by lowering the glass transition temperature of an amorphous solid. The effects of water on the solid-state stability of proteins and peptides and the removal of water by lyophilization to produce materials of certain crystallinity are of great practical importance although still imperfectly understood. 

Negative deviation from ideal behaviour in the solid state stabilizes the solid solution. 2so1 = -10 kJ mol-1, combined with an ideal liquid or a liquid which shows positive deviation from ideality, gives rise to a maximum in the liquidus temperature for intermediate compositions see Figures 4.10(h) and (i). Finally, negative and close to equal deviations from ideality in the liquid and solid states produces a phase diagram with a shallow minimum or maximum for the liquidus temperature, as shown in Figure 4.10(g). 

Aspartame is relatively unstable in solution, undergoing cyclisation by intramolecular self-aminolysis at pH values in excess of 2.0 [91]. This follows nucleophilic attack of the free base N-terminal amino group on the phenylalanine carboxyl group resulting in the formation of 3-methylenecarboxyl-6-benzyl-2, 5-diketopiperazine (DKP). The DKP further hydrolyses to L-aspartyl-L-phenyl-alanine and to L-phenylalanine-L-aspartate [92]. Grant and co-workers [93] have extensively investigated the solid-state stability of aspartame. At elevated temperatures, dehydration followed by loss of methanol and the resultant cyclisation to DKP were observed. The solid-state reaction mechanism was described as Prout-Tompkins kinetics (via nucleation control mechanism). 

Selected experimental agents were subjected to an accelerated low-temperature stability test to determine the sensitivity of each sample to form solids. Samples that... 

Applications. Polymers with small alkyl substituents are ideal candidates for elastomer formulation because of quite low temperature flexibility, hydrolytic and chemical stability, and high temperature stability. In light of the biocompatibilily of polysiloxanes and P-O- and P-N-suhslituted ptilyphosphazenes. polytalkyl/arylphosphazenes) are also likely lo he hiocompatible polymers. A third potential application is in the area of solid-state batteries. 

Applications. Polymers with small alkyl substituents, particularly (13), are ideal candidates for elastomer formulation because of quite low temperature flexibility, hydrolytic and chemical stability, and high temperature stability. The ability to readily incorporate other substituents (in addition to methyl), particularly vinyl groups, should provide for conventional cure sites. In light of the biocompatibility of polysiloxanes and P—O- and P—N-substituted polyphosphazenes, poly(alkyl/arylphosphazenes) are also likely to be biocompatible polymers. Therefore, biomedical applications can also be envisaged for (3). A third potential application is in the area of solid-state batteries. The first steps toward ionic conductivity have been observed with polymers (13) and (15) using lithium and silver salts (78). 

Matsuda, Y. and S. Kawaguchi. 1986. Physicochemical characterization of oxyphenbutazone and solid-state stability of its amorphous form under various temperature and humidity condEtlrota. 

Minimally, one should have a brief foreknowledge of the thermal and thermal/humidity solid-state stability of the API prior to initiation of excipient compatibility studies. These protocols should include investigation of stability at various temperature and humidity conditions and should always include information about both chemical stability and physical-form integrity of the API. Thermal and thermal moisture-induced solid-state chemical reactions are well known (5), with hydrolysis and oxidation being the most prevalent mechanisms of decay. Changes in physical form with thermal and... 

The essential requirements for hydrogen storage in solids are that it be (a) high H-mass density (b) high H-volume density (c) appropriate pressure, temperature stability (d) reversible absorption/desorption. The results of research in the field of hydrogen solubility in the metal-hydrogen systems and carbon nanostructures are presented in this paper. 

Mandal, H., Thompson, D.P., Liu, Q., Gao, L. (1997), High temperature stability of a-SiAlON ceramics containing glass additions , Eur. J. Solid. State. Inorg. Chem., 34, 179. 

A great variety of formulas for this phase can be found, e.g. 48 s°). Some of these data are dubious, others are only correct in respect of the temperature-dependent solid solution range of the Y-phase. However, the Y-phase should be described as a compound with a Fe Mo ratio of 1 4, as this represents the only formula valid for the temperature stability range from slightly below 800 °C up to its melting point. The Y-phase can only be synthesized above 535 15 °C46 it is quench-able and probably remains metastable at room temperature. 

Fig. 19. Schematic T-Xi -X2 diagram of the Cu-Mo-S system. Temperature stability and solid solution widths of the X-phase ( CuMo2S3) in the Cu-Mo-S system are displayed. To simplify the perspective drawing a few isotherms are indicated with a projection onto the base, demonstrating the whole compositional X-phase solid solution...

The above considerations were a starting point in the formulation of the problems in the series of investigations discussed in this chapter.14-24 The motive for elucidating the mechanochemical aspect of the radiation cryochemistry of solids was the discovery14 of the effect of excitation of a reaction in the irradiated, low-temperature-stabilized samples of reactants in response to a local fracture. 

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