Cooling decomposition, stabilization

The primary phases all contain impurities. In fact these impurities stabilize the stmctures formed at high temperatures so that decomposition or transformations do not occur during cooling, as occurs with the pure compounds. For example, pure C S exists in at least six polymorphic forms each having a sharply defined temperature range of stability, whereas alite exists in three stabilized forms at room temperature depending on the impurities. Some properties of the more common phases in Portland clinkers are given in Table 2. 

Dichloroethylene is usually shipped ia 208-L (55 gal) and 112-L (30 gal) steel dmms. Because of the corrosive products of decomposition, inhibitors are required for storage. The stabilized grades of the isomers can be used or stored ia contact with most common constmction materials, such as steel or black iron. Contact with copper or its alloys and with hot alkaline solutions should be avoided to preclude possible formation of explosive monochloroacetylene. The isomers do have explosive limits ia air (Table 1). However, the Hquid, even hot, bums with a very cool flame which self-extiaguishes unless the temperature is well above the flash poiat. A red label is required for shipping 1,2-dichloroethylene. 

Chemical Reactivity - Reactivity with Water No reaction unless in the presence of acids and caustics Reactivity with Common Materials Slow decomposition occurs, but generally the reactions are not hazardous Stability During Transport Stable if cool Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Violent, exothermic polymerization occurs at about 225 of. Acid fumes will also cause polymerization at ordinary temperatures Inhibitor of Polymerization None reported. 

The thermal stability of NOx adsorbed species and their reactivity in the presence of gaseous reductant molecules was addressed by thermal decomposition in He (TPD) or by heating in flowing H2/He mixtures [temperature-programmed surface reaction (TPSR)], respectively. In these cases, after NOx adsorption and He purge at the adsorption temperature (300 100oC), the samples were cooled to RT under flowing He. Then the samples were heated at 15°C/min up to 500-600°C in He (TPD) or in He + H2 (2000 ppm) (H2-TPSR). 

Because propellants are constantly subjected to abnormally high temperatures in various parts of the propulsion system during operation, high thermal stability is desirable. Decomposition of the propellant at temperatures experienced in the combustion chamber cooling jacket, the injector, and/or the gas film on the combustion chamber wall, can cause undesirable product deposition (resulting in local "hot spots and burnout), explosion in the cooling jacket and/or injector, undesired reaction chains in the combustion chamber, etc. 

Cyanohydrins should be stabilized with acid to pH 3-4 to prevent decomposition 10 hydrogen cyanide and carbonyl compound. When cyanohydrins are shipped, steel drums, carboys, tank cars, and barges are used. In general, cyanohydrins are combustible liquids and many decompose upon heating. They should be stored in a cool, dry place, preferably outside and separated from other storage. Containers should be protected against physical damage. 

Chloro-2-[3-(bromomethyl)-5-methyl-4H-l,2,4-triazol-4-yl]-benzophenone A solution of 5-chloro-2-[3-(hydroxymethyl)-5-methyl-4H-l,2,4-triazol-4-yl]-benzophenone (328 mg, 0.001 mol) in dry, hydrocarbon-stabilized chloroform (5 ml) was cooled in an ice-bath and treated with phosphorus tribromide (0.1 ml). The colorless solution was kept in the ice-bath for 55 minutes, at ambient temperature (22-24°C), for 5 hours. The resulting yellow solution was poured into a mixture of ice and dilute sodium bicarbonate. This mixture was extracted with chloroform. The extract was washed with brine, dried over anhydrous magnesium sulfate and concentrated. The residue was crystallized from methylene chloride-ethyl acetate to give 0.285 g of melting point 200-240°C (decomposition) and 0.030 g of melting point 200-220°C (decomposition) of 5-chloro-2-[3-(bromomethyl)-5-methyl-4H-l,2,4-triazol-4-yl]benzophenone. The analytical sample had a melting point of 200-240°C. 

Summary Potassium perchlorate is readily prepared by fusing potassium chlorate in the presence of potassium chloride. The potassium chloride is used to decrease decomposition of the perchlorate and provide a stabilized uniform mixture. After the initial reaction, the potassium perchlorate is easily collected by thoroughly mixing the cooled mixture in water to dissolve the potassium chloride and any unreacted chlorate, followed by filtration to recover the insoluble perchlorate. 

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