In dehydration

Fig. 6. Adsorption capacity of various dessicants vs years of service in dehydrating high pressure natural gas (39). a, Alumin a H-151, gas 27° C and 123 kPa, from oil and water separators b, siUca gel, gas 38° C and 145 kPa, from oil absorption plant c, sorbead, 136-kPa gas from absorption plant ...

Drying is an operation in which volatile Hquids are separated by vaporization from soHds, slurries, and solutions to yield soHd products. In dehydration, vegetable and animal materials are dried to less than their natural moisture contents, or water of crystallization is removed from hydrates. In freeze drying (lyophilization), wet material is cooled to freeze the Hquid vaporization occurs by sublimation. Gas drying is the separation of condensable vapors from noncondensable gases by cooling, adsorption (qv), or absorption (qv) (see also Adsorption, gas separation). Evaporation (qv) differs from drying in that feed and product are both pumpable fluids. 

A regenerative absorbent consisting of the amorphous silica manufactured by the action of MCI on sodium silicate. Hard, glossy, quartz-like in appearance. Used in dehydrating and in drying and as a catalyst carrier. 

Hydrolysis is slow at room temperature and the corresponding reaction with anhydrous HNO3 results in dehydration to the parent N2O5 ... 

It was claimed3 that heating the oxime 2-[2-(hydroxyimino)propanyl]benzoic acid above its melting point resulted in dehydration to give 4-methyl-2,3-benzoxazepin-l(5//)-one (2, R = Me), as orange-red needles,4 but the color of the compound indicates that it has a different structure. 

An application of this instrument is illustrated in the study of color change in dehydrated carrots with storage at different temperatures. Typical results are given in Table IY. The measurements were made on the dry material packed level in a tray designed to fit at a specific level in the instrument. The instrument is mounted so that the tray rests horizontally and no cover glass is then necessary to hold the sample in place. 

Direct or indirect methods may be used to determine moisture in dehydrated foods. Indirect methods must be calibrated in terms of direct methods—the most common of which are the oven, distillation, and Fischer methods. Accuracy of the direct methods is difficult to evaluate except by comparison with a chosen reference method. Several reference methods are reviewed, but none can be given an unqualified recommendation as most practical and suitable for all foods. An indirect measure of moisture is the equilibrium vapor pressure of water, which can be measured easily and accurately. Arguments are presented to show that vapor pressure may be a better index of the stability of dehydrated foods than the moisture content, which has been frequently used for this purpose. 

General Considerations in Determination of Moisture in Dehydrated Foods... 

The methods used for the determination of moisture in dehydrated foods have been divided into two classes, the direct and the indirect. The indirect methods, such as the electrical ones, must be calibrated in terms of the direct methods. 

Fig. 12. Schematic representation of variations in dehydration rates (ft) with prevailing water vapour pressure (Ph2o) These examples include Smith—Topley behaviour and indicate correlations with phase stability diagrams. (After Bertrand et al. [596], reproduced with permission, from Journal of Inorganic and Nuclear Clemistry.)...

In a discussion of these results, Bertrand et al. [596,1258] point out that S—T behaviour is not a specific feature of any restricted group of hydrates and is not determined by the nature of the residual phase, since it occurs in dehydrations which yield products that are amorphous or crystalline and anhydrous or lower hydrates. Reactions may be controlled by interface or diffusion processes. The magnitudes of S—T effects observed in different systems are not markedly different, which indicates that the controlling factor is relatively insensitive to the chemical properties of the reactant. From these observations, it is concluded that S—T behaviour is determined by heat and gas diffusion at the microdomain level, the highly localized departures from equilibrium are not, however, readily investigated experimentally. 

Potassium amide ip conversion of o-acetoacetochloroanilide to 3-acetyk)xindole, 40, 1 Potassium ierf-butoxide, 41, 101 in dehydration of formamides to isocyanides, 41, 101... 

Zhang, J. Davies, W.J. (1989). Abscisic acid produced in dehydrating roots may enable the plant to measure the water status of the soil. Plant, Cell and Environment, 12, 73-81. 

The coacervation of tropoelastin plays a crucial role in the assembly into elastic fibers. This coacervation is based on the LCST behavior of tropoelastin, which causes tropoelastins structure to become ordered upon raising the temperature. The loss of entropy of the biopolymer is compensated by the release of water from its chain [2, 18, 19]. This release of water results in dehydration of the hydrophobic side chains, and this is the onset of the self-assembly leading to the alignment of tropoelastin molecules. 

Falconer, M.E. et ah. Carotene oxidation and off-flavor development in dehydrated carrot, J. Sci. Food Agric., 15, 857, 1964. 

Maharaj, V. and Sankat, C.K., Quality changes in dehydrated dasheen leaves effects of blanching pre-treatments and drying conditions. Food Res. bit., 29, 563, 1996. 

The quantification of the extra-framework titanium species in titanium silicalites of MFI structure, TS-1, was performed using either XANES at the Ti K-edge or XPS Ti (2p) photolines. In addition, two different framework sites, [Ti(OH)(OSi)3] and [Ti(OSi)4], were characterized in dehydrated samples using Diffuse Reflectance UV-visible, multiple scattering analysis of EXAFS, H and Si NMR spectroscopies. 

Table Al. Partition coefficients used in dehydration and melting models...

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