Temperature dehydrated

The most common form of calcium thiosulfate is the hexahydrate [10035-02-6] CaS202 6H20, which has triclinic crystals and a density of 1.872 g/cm at 16°C (84). Heating, however, does not give the anhydrous salt because of decomposition at 80°C. At lower temperatures, dehydration stops at the monohydrate [15091-91-5]. The solubiUty of calcium thiosulfates in water is as follows ... 

Anhydrite. In addition to ketde calcination (Fig. 1), soluble anhydrite is commercially manufactured in a variety of forms, from fine powders to granules 4.76 mm (4 mesh) in size, by low temperature dehydration of gypsum. 

The wood pyrolysis is attractive because forest and industrial wood residues can be readily converted into liqtrid products. These liqtrids, as erode bio-oil or slurry of charcoal of water or oil, have advantages in transport, storage, combustion, retrofitting and flexibility in production and marketing (Demirbas, 2007). In the first step of pyrolysis of carbohydrates dehydration occtrrs and at low temperatures dehydration predominates. Dehydration is also known as a char-forming reaction. Between 550 and 675 K volatile products, tar, and char are formed. The volatile products are CO, CO, H O, acetals, furfural, aldehydes and ketones. Levoglucosan is the principle component in tar. 

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). 

Boric Acid Boric oxide, [CAS 1303-86-21, B2O3, is acidic, It exists in two forms, a glassy form obtained by high temperature dehydration of boric acid, and crystalline form obtained by slow heating of metabolic acid. 

Despite the high reactivity and the low cost of the reagents, the use of sulfuric acid is however connected with some disadvantages. First of all, because it captures all the water liberated, it cannot be recycled directly without a high temperature dehydrating step (sulfuric concentration SC). If no SC is operated, the outcoming aqueous sulfuric acid has to be neutralized and produces highly salty effluents, non desirable for the environment. Furthermore, dilute sulfuric acid can produce severe corrosion problems of the reaction vessels. 

In neither process is it commercially feasible to produce a dehydrated juice without the addition of a drying aid, although 100% orange juice has been produced with the continuous vacuum belt dehydrator (42,A3). This product is extremely hygroscopic and very temperature sensitive. As a result, the product "cakes" or hardens if exposed to moist air or to temperatures much above 24°C. The product is also subject to browning if not stored at refrigerated temperatures. Dehydrated citrus juices are produced on a vacuum belt dryer at Crystals International, Plant City, Florida, and are items of commerce. 

Roozeboom et al106 in an investigation of both unsupported V2 Os and a number of supported catalysts observed that at low temperatures dehydration of methanol to dimethyl ether is a side-reaction on some catalysts and at higher temperatures consecutive oxidation of dimethyl ether and/or formaldehyde to CO. Selectivity to formaldehyde increased with decreasing reducibility of the catalyst, which itself was a function of the catalyst-support interaction. 

Shafizadeh and Lai (48) have summarized the degradation of oligosaccharides as arising by three types of thermal transformations. At low temperatures, dehydration and melting... 

Normal anhydrous BeC03 may not exist at ambient temperatures. Dehydration of the hydrate at elevated temperatures probably forms basic carbonates.10 The values of AHf° for BeC03 are calculated from a measured value of AH for the reaction BeO + C02 = BeC0310 and the current value for BeO. The known thermodynamic values are summarized in Table 2.10. 

The sorption capacity and x-ray pattern were essentially the same as for a similar sample dehydrated under milder conditions at 400°C. For the larger crystals the diffusivity was also essentially independent of the dehydration conditions but for the small (high temperature dehydration to within an order to magnitude of the previously reported sorption data for small Linde 5A crystals(29,39). Furthermore the reduction in diffusivity was accompanied by an increase in activation energy from 1.3 kcal/mole to 2.8 kcal/mole, very close to the value of 3.0 kcal/mole for the Linde crystals(39). 

Four TES ethers were cleaved in the final step of an approach to N1999-A2, a member of the highly unstable enediynes.20 After low temperature dehydration of 17.1 via its triflate [Scheme 4.17], deprotection was implemented by treatment with trifluoroacetic acid in aqueous THE at 0 °C to give the target epoxy-dienediyne 17.2 in 45% yield for the two steps. rtrf-Butyldimethytsilyl ethers could not be removed without total destruction of the molecule. 

Several classes of lipids common for the biomembranes can form inverted nonlamellar phases under physiologic conditions (4). The principle ones are phosphatidylethanolamines and monogalactosyldiglycerides. Also, cardiolipins and phos-phatidic acids can form inverted phases in the presence of divalent cations, and phosphatidylserines and phosphatidic acids both form inverted phases at low pH. Moreover, biomembrane lipid extracts and membrane-mimicking lipid compositions form nonlamellar phases if heated above physiologic temperatures, dehydrated, or treated with divalent cations (5-7). 

Final temperature DEHYDRATOR OPERATIHG SCHBHJLE Continuous . or, if intermittent TYPE OF OPERATION... 

Only one monocarboxylic acid anhydride is encountered very often however, this one, acetic anhydride, is immensely important. It is prepared by the reaction of acetic acid with ketene, CH2==C- O, which itself is prepared by high-temperature dehydration of acetic acid. 

Cyclic anhydrides with five- or six-membered rings are obtained by high-temperature dehydration of the diacids. 

The r-time curves for the decomposition of anhydrous cobalt oxalate (570 to 590 K) were [59] sigmoid, following an initial deceleratory process to a about 0.02. The kinetic behaviour was, however, influenced by the temperature of dehydration. For salt pretreated at 420 K, the exponential acceleratory process extended to flr= 0.5 and was followed by an approximately constant reaction rate to a = 0.92, the slope of which was almost independent of temperature. In contrast, the decomposition of salt previously dehydrated at 470 K was best described by the Prout-Tompkins equation (0.24 < a< 0.97) with 7 = 165 kJ mol . This difference in behaviour was attributed to differences in reactant texture. Decomposition of the highly porous material obtained from low temperature dehydration was believed to proceed outwards from internal pores, and inwards from external surfaces in a region of highly strained lattice. This geometry results in zero-order kinetic behaviour. Dehydration at 470 K, however, yielded non-porous material in which the strain had been relieved and the decomposition behaviour was broadly comparable with that of the nickel salt. Kadlec and Danes [55] also obtained sigmoid ar-time curves which fitted the Avrami-Erofeev equation with n = 2.4 and = 184 kJ mol" . The kinetic behaviour of cobalt oxalate [60] may be influenced by the disposition of the sample in the reaction vessel. 

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