Hydration at low temperatures

About half the propane produced annually in the U.S. is used as a domestic and industrial fuel. When it is used as a fuel, propane is not separated from the related compounds, butane, ethane, and propylene. Butane, with boiling point -0.5 °C (31.1 °F), however, reduces somewhat the rate of evaporation of the liquid mixture. Propane forms a solid hydrate at low temperatures, and this causes great inconvenience when a blockage occurs in a natural-gas line. Propane is used also as so-called bottled gas, as a motor fuel, as a refrigerant, as a low-temperature solvent, and as a source of propylene and ethylene. 

Yoon, J.-H. Kawamura, T. Ohtake, M. Takeya, S. Komai, T. Yamamoto, Y. Emi, H. Kohara, M. Tanaka, S. Takano, O. Uchida, K. (2006). Highly selective encaging of carbon dioxide molecules in the mixed carbon dioxide and nitrogen hydrate at low temperatures. J. Phys. Chem. B, 110 (35), 17595-17599. 

The increased hydration at low temperature is due to lower protein content in the pellet owing to dissociation of protein from the micelle (mainly beta-casein), and corresponds to data from the literature42. 

In addition to the aforementioned examples of a cultured system that uses a thermoresponsive PNIPAAm, Morra and Cassinelli [123] reported coating a polystyrene surface via covalent bonds using UV radiation. Rollason et al. [124] reported on work that explored increasing hydro-phobicity and handling a culture by copolymerizing PNIPAAm with N-t-butylacrylamide and by lowering LCST. Morra and Cassinelli reexamined and confirmed the work done by Okano et al. [112, 114]. They reported that the thickness of the surfece gel layer and its hydration at low temperature strongly influence desorption. 

Results of the calculated thermal conductivity for ice Ih, S-I methane hydrate and empty hydrate are depicted in Figure 14. The thermal conductivity of ice Ih has improved, but the absolute value is still slightly smaller than the experiment. The calculations reproduced previous observation that the thermal conductivity of the hydrate is lower than ice Ih and the empty hydrate. Even though the empty hydrate has a lower thermal conductivity than ice Ih, the crystalline temperature profile is similar. A surprising finding is the reversal in the thermal conductivity of methane hydrate at low temperature. From 250 to 100 K, the thermal conductivity decreases slightly. When the hydrate is cooled below 100 K, the conductivity increases and follows the trend as a crystal. This unusual temperature profile has indeed been observed in methane and xenon hydrates,details of which will be deferred to a later part of this chapter. To unravel the thermal transport mechanism, various correlation functions were computed and the relaxation times analyzed.The HCACF can be fitted to... 

These are acids which can be regarded, in respect of their formulae (but not their properties) as hydrates of the hypothetical diiodine heptoxide, liO-j. The acid commonly called periodic acid , I2O7. 5H2O, is written HglO (since the acid is pentabasic) and should strictly be called hexaoxoiodic(VII) acid. It is a weak acid and its salts are hydrolysed in solution. It can be prepared by electrolytic oxidation of iodic(V) acid at low temperatures ... 

Iron(III) fluoride ttihydrate [15469-38-2] FeF3-3H2 0, crystallizes from 40% HF solution ia two possible crystalline forms. At low temperature the a-form, which is isostmctural with a-AlF 3H2O, is favored. High temperatures favor P-FeF 3H2O, the stmcture of which consists of fluoride-bridged octahedra with one water of hydration per unit cell. 

Physical Properties. Sodium metabisulfite (sodium pyrosulfite, sodium bisulfite (a misnomer)), Na2S20, is a white granular or powdered salt (specific gravity 1.48) and is storable when kept dry and protected from air. In the presence of traces of water it develops an odor of sulfur dioxide and in moist air it decomposes with loss of part of its SO2 content and by oxidation to sodium sulfate. Dry sodium metabisulfite is more stable to oxidation than dry sodium sulfite. At low temperatures, sodium metabisulfite forms hydrates with 6 and 7 moles of water. The solubiHty of sodium metabisulfite in water is 39.5 wt % at 20°C, 41.6 wt % at 40°C, and 44.6 wt % at 60°C (340). Sodium metabisulfite is fairly soluble in glycerol and slightly soluble in alcohol. 

Anhydrous a-dextrose is manufactured by dissolving dextrose monohydrate in water and crysta11i2ing at 60—65°C in a vacuum pan. Evaporative crysta11i2ation is necessary to avoid color formation at high temperatures and hydrate formation at low temperatures. The product is separated by centrifugation, washed, dried to a moisture level of ca 0.1%, and marketed as a very pure grade of sugar for special appHcations. 

Many other metal thiosulfates, eg, magnesium thiosulfate [10124-53-5] and its hexahydrate [13446-30-5] have been prepared on a laboratory scale, but with the exception of the calcium, barium [35112-53-9] and lead compounds, these are of Httle commercial or technical interest. Although thaHous [13453-46-8] silver, lead, and barium thiosulfates are only slightly soluble, other metal thiosulfates are usually soluble in water. The lead and silver salts are anhydrous the others usually form more than one hydrate. Aqueous solutions are stable at low temperatures and in the absence of air. The chemical properties are those of thiosulfates and the respective cation. 

The Dravo hydrate addition at low temperature process involves a two-step injection of water and dry sorbent in a rectangular 19.8-m duct having a cross section of 2 m. In one step water is injected through atomization nozzles to cool the flue gas from 150°C to approximately a 15°C approach to adiabatic saturation. The other step involves the dry injection of hydrated lime, either downstream or upstream of the humidifica tion nozzles. Typical SO2 removals were 50—60% at a Ca S ratio of 2. 

Low-temperature exchange (LTX) units use the high flowing temperature of the well stream to melt the hydrates after they are formed. Since they operate at low temperatures, they also stabilize the condensate and recover more of the intermediate hydrocarbon components than would be recovered in a straight multistage flash separation process. 

The equilibrium constant at room temperature corresponds to pKi, = 4.74 and implies that a 1 molar aqueous solution of NH3 contains only 4.25 mmol 1 of NH4+ (or OH ). Such solutions do not contain the undissociated molecule NH4OH, though weakly bonded hydrates have been isolated at low temperature ... 

The chemistry of such solutions has been alluded to on p. 678. At low temperatures a hydrate H28.5IH2O crystallizes. In acid solution H28 is also a mild reducing agent e.g. even on standing in air solutions slowly precipitate sulfur. The gas bums with a bluish flame in air to give H2O and 8O2 (or H2O and 8 if the air supply is restricted). For adducts, see p. 673. 

CIO2 dissolves exothermically in water and the dark-green solutions, containing up to 8g/l, decompose only very slowly in the dark. At low temperatures crystalline clathrate hydrates, C102.nH20, separate (n 6-10). Illumination of neutral aqueous solutions initiates rapid photodecomposition to a mixture of chloric and hydrochloric acids ... 

Borated starch compositions are useful for controlling the rate of cross-linking of hydratable polymers in aqueous media for use in fracturing fluids. The borated starch compositions are prepared by reacting, in an aqueous medium, starch and a borate source to form a borated starch complex. This complex provides a source of borate ions, which cause crosslinking of hydratable polymers in aqueous media [1552]. Delayed crosslinking takes place at low temperatures. 

The 15N spectral peaks of fully hydrated [15N]Gly-bR, obtained via cross-polarization, are suppressed at 293 K due to interference with the proton decoupling frequency, and also because of short values of T2 in the loops.208 The motion of the TM a-helices in bR is strongly affected by the freezing of excess water at low temperatures. It is shown that motions in the 10-j-is correlation regime may be functionally important for the photocycle of bR, and protein-lipid interactions are motionally coupled in this dynamic regime. 

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