Samples, hydrated

A certain hydrate of potassium aluminum sulfate (alum) has foe formula KA1(S04)2 - xH20. When a hydrate sample weighing 5.459 g is heated to remove all foe water, 2.583 g ofKAl(S04)2 remains. What is foe mass percent of water in foe hydrate What is x ... 

The cytoplasmic domains reconstructed from negatively stained [90] and from frozen-hydrated samples [91,177] have similar shapes. Both include the protruding lobe and the bridge region that links the Ca " -ATPase molecules into dimers. The intramembranous peptide domains of the two ATPase molecules which make up a dimer spread apart as they pass through the bilayer toward the luminal side of the membrane, establishing contacts with the Ca -ATPase molecules in the neighboring dimer chains. The lateral association of dimer chains into extended crystal lattice is... 

Figure 8. 29Si MASS and CPMASS NMR spectra of silica gels dried at 50°C, heated to 200 and 600°C, and consolidated at 1100°C. Hydrated samples were exposed to 100% RH at 25°C for 24 hours prior to analysis.

It was also found that the degree of hydration of the complex affected the rate of racemization. Generally, the hydrated complexes reacted faster than anhydrous samples. It was also found that reducing the particle size increased the rate of racemization, but when the iodide compound was heated with water in a sealed tube, the racemization was slower than for the hydrated solid from which the water could escape. The fact that the hydrated samples racemized faster could indicate that an aquation-anation mechanism is involved, but the results obtained in the sealed tube experiments do not agree with that idea. 

Mass of H20= 2.574 g CuS04 x H20 - 1.647 g CuS04 = 0.927 g H20 Next we need to find the number of moles of anhydrous copper(II) sulfate and water that were initially present together in the original hydrate sample. 

The reaction of benzene with Cu(II) and Fe(III)-exchanged hectorites at elevated temperatures produced a variety of organic radical products, depending on the concentration of water in the reaction medium and the reaction time (90). The formation of free radicals was accompanied by a reduction in oxidation state of the metals, a process that had a zero-order dependence on the metal ion concentration. Under anhydrous conditions the free radicals appeared to populate sites in the interlayer region, the activation energies under these conditions being lower than in the hydrated samples. 

Al MAS NMR has been demonstrated to be an invaluable tool for the zeoHte sdentist It provides a simple and direct way to quantify the proportions of A1 in four [Al(4)j, five [Al(5)j and six [Al(6)j coordinations. Quantitative determination of these species is an important issue in catalysis, and major effort is devoted on this topic. As mentioned already, for A1 only the central transition (-i-half to —half selective exdtation ) is detected. The central transition is unaffected by first order quadmpolar interaction, but the presence of second order effects causes broadening and complicates the quantitation of the A1 species. Usually hydrated samples and short radiofrequency pulses are employed for quantitative determination of framework and extra framework aluminum species. It is uncertain whether hydration changes the coordination of A1 species. Certain extra framework A1 can have very large quadmpolar interactions resulting in very broad lines ( NMR invisible ) [155, 202]. Unlike Si NMR, Al has a short relaxation time due to its quadmpolar nature, and the Al NMR spectrum with good signal to noise can be obtained in a relatively short time. 

Risen et al. investigated cation—anion interactions using far IR spectroscopy (50—300 cm ) to study Nafion sulfonate membranes that were neutralized by cations in the series Na+, K+, Rb+, and Cs+ and the series Mg +, Ca +, Sr +, and Ba +, as well as the acid form." The spectra in this region for hydrated samples show a broad but well-defined band below 300 cm that is not present for the acid form. For both the monovalent alkali and divalent alkaline earth series, the band monotonically shifts to lower frequencies, f, such that foe where Mis the... 

Proton conductivity diffusion coefficients for hydrated samples and samples solvated with... 

H. (2003). Dissociation Behavior of Pellet-Shaped Methane-Ethane Mixed Gas Hydrate Samples. Energy and Fuels, 17, 614-618. 

J.-H. Ohga, K. (2006). Dissociation behavior of pellet shaped mixed gas hydrate samples that contain propane as a guest. Energy Convers. Manage., 47 (15-16), 2491-2498. 

To obtain more detailed information on the ultrastructure of lipid dispersions and the morphology of the particles, electron microscopy is usually performed on replicas of freeze fractured or on frozen hydrated samples. These techniques aim to preserve the liquid-like state of the sample and the organization of the dispersed structures during preparation. By using special devices, the sample is frozen so quickly that all liquid structures, including the dispersion medium, solidify in an amorphous state. 

The optimization of CHEMFIX reagents on the hydrated samples was then conducted. Four samples of SSM were treated with varying ratios of reagents. The soil sample and reagents were thoroughly mixed and consolidated into one large lump artd allowed to cure for 48 hours. 

The properties of zeolitic water and the behavior of the exchangeable cations can be studied simultaneously by dielectric measurements (5, 6). In X-type zeolites Schirmer et al. (7) interpreted the dielectric relaxation as a jump of cations from sites II to III or from sites II to II. Jansen and Schoonheydt found only relaxations of cations on sites III in the dehydrated zeolites (8) as well as in the hydrated samples (9). Matron et al. (10) found three relaxations, a, (, and 7, in partially hydrated and hydrated NaX. They ascribed them respectively to cations on sites I and II, on sites III, and to water molecules. 

The hydrophobicity of the trimethylsilylated Ti-MCM-41 was estimated from the weight loss of the hydrated samples at 150°C, since this weight loss is generally attributed to physisorbed water on the surface of the mesoporous solids. It was found that there is a nearly linear correlation between amount of water adsorbed on the fully hydrated trimethylsilylated catalysts and the amount of trimethylsilyl groups bounded to the surface as it is shown in figure 5. 

Bosa5ek et al. (168) used wide-line 27A1 NMR measurements of stationary samples to measure the EFG at the nuclear site in decationated zeolites. In zeolite Na-Y they measured a line half-width of Sv1/2 = 61 kHz (for vL = 16 MHz) which led, via theoretical considerations (173) to vD = 840 kHz the calculated field gradient was 2.9 V/A2. In hydrated samples this gradient was partially averaged by random reorientation of water molecules, giving <5v,/2 = 5.7 kHz and vQ = 256 kHz. 

West (231) observed no 23Na resonance in dehydrated synthetic faujasites, suggesting that the EFG at the cationic site is larger than in hydrated samples because of the displacement of the cations away from their high-symmetry positions. The signal appeared when seven H20 molecules per cage were present. Fully hydrated Na-X and Na-Y had Tf of 100 and 140 fj.sec, respectively, while in dehydrated samples much faster transverse relaxation was observed. 

The Indian National Gas Hydrate Program (NGHP) expedition of ocean hydrates was performed in 2006. During this expedition, over 494 cores were recovered at depths ranging from 952 to 2674 mbsf. The cores were distributed to a number of research laboratories (including USGS, GFZ, CSM, NRC) for meso-and molecular-level analysis on the hydrate samples (T. Collett and R. Boswell, Personal Communication, August 31, 2006). 

FIGURE 3.36 Average rates for methane hydrate samples reaching 50% dissociation at 0.1 MPa, following destabilization by rapid release of P. The anomalous preservation regime is between 242 and 271 K. Square symbols experiments in which P is maintained at 2 MPa, Diamonds 0.1 MPa rapid depressurization tests on sll methane-ethane hydrate, showing no comparable preservation behavior at 268 K. (Reproduced from Stern, L.A., Circone, S., Kirby, S.H., Durhan, W., Can. J. Phys., 81, 271 (2003). With permission from the National Research Council.)... 

Using this instrument in Figure 6.5, Handa (1986b) measured the heat input to a hydrate sample in the sample container S, relative to helium at ambient temperature and 5 kPa in reference cell R. The hydrate was externally prepared from ice in a rolling-rod mill, before a 4 g sample was loaded into the calorimeter at liquid nitrogen temperatures. For heat capacity measurements, a pressure greater than the hydrate dissociation pressure was maintained in the sample cell. By cycling... 

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