Hydrogen Water Measurements

Concrete made with a water-to-cement ratio of w/c = 0.6, white Portland cement and quartz aggregates was cast in 100-mm long and 48-mm diameter cylinders. 

The density weighted images and their absolute quantification demonstrated through concrete drying experiments are very powerful tools for material science. 

This measurement methodology and data analysis is general and can be extended to other porous media. The results from MRI moisture profiles can also be used to measure moisture diffusivity that enable moisture transport models to be developed for a wide range of materials. 

The surface of concrete may be subjected to cycles of wetting and drying during normal service life. This process is a durability concern as harmful ions such as chlorides or sulfates can easily penetrate with the adsorbed water and there is the potential for saturation prior to freezing. Measuring the rate of water penetration into a dry concrete surface is thus important to the quality control of concrete mixes - hopefully yielding a durable product. 

Cano Barrita [27] cast concrete specimens with w/c of 0.6, dried the specimens at 38 °C and 20% relative humidity, then measured the penetration of water in a capillary uptake type of experiment. A 3D centric scan SPRITE measurement was selected, as an image could be acquired in 150 s and the image would therefore be weighted only by the T2 decay. 3D images were acquired at various exposure times and the central 2D image slice was extracted from the data to measure the penetration depth with time. 

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Hydrogen + water. Battino (4) selected 69 solu-bility values from nine papers that reported measurements between temperatures of 273 and 348 K. The mole fraction solubilities at one atmosphere partial pressure of hydrogen at the higher temperatures were estimated from the data of Wiebe and Gaddy (11), Pray, Schweichert, and Minnich (12 ), and Stephan, Hatfield, Peoples and Pray (1 ). The data from Pray, Schweichert and Minnich were combined with Battino s selected data in a linear regression to obtain the tentative four constant equation for the hydrogen solubility in water between 350 and 600 K (Figure 7 and Table V). 

In this respect, the solvatochromic approach developed by Kamlet, Taft and coworkers38 which defines four parameters n. a, ji and <5 (with the addition of others when the need arose), to evaluate the different solvent effects, was highly successful in describing the solvent effects on the rates of reactions, as well as in NMR chemical shifts, IR, UV and fluorescence spectra, sol vent-water partition coefficients etc.38. In addition to the polarity/polarizability of the solvent, measured by the solvatochromic parameter ir, the aptitude to donate a hydrogen atom to form a hydrogen bond, measured by a, or its tendency to provide a pair of electrons to such a bond, /, and the cavity effect (or Hildebrand solubility parameter), S, are integrated in a multi-parametric equation to rationalize the solvent effects. 

Elemental composition Ca 95.41% H 4.79%. A measured amount of the solid is carefully treated with water and the volume of evolved hydrogen is measured using a manometer (Ig liberates 1.16 L H2 at NTP). The solution is then acidified with nitric acid and diluted for the measurement of calcium by AA or ICP spectrophotometry, or by a wet method (see Calcium). The hberat-ed hydrogen gas may be analyzed by GC using a TCD. Many packed and capillary GC columns are commercially available. 

Elemental composition Li 31.85%, B 49.66%, H 18.50%. The compound is dissolved in water cautiously and the evolved hydrogen is measured by GC using a TCD. The aqueous solution is treated with nitric acid and the diluted nitric acid extract is analyzed for lithium by atomic absorption or emission spectroscopy (See Lithium). 

Elemental composition Na 60.77%, B 28.58%, H 10.65%. Sodium and boron content can be measured by AA or ICP measuremeant. The borohydride should be dissolved cautiously in water for the metal analysis. The compound is treated with ethanol and volume of liberated hydrogen is measured to... 

The NADP analyzes the constituents important in precipitation chemistry, including those affecting rainfall acidity and those that may have ecological effects. The Netwoik measures sulfate, nitrate, hydrogen ion (measure of acidity), ammonia, chloride, and base cations (calcium, magnesium. potassium). To ensure comparability of results, laboratory analyses for all samples are conducted by the NADP s Central Analytical Lab at the Illinois State Water Survey, A new subnetwork of the NADP, the Mercury Deposition Network (MDN) measures mercury in precipitation. 

In other words, since for solvents with H-bonding ability (methanol and water) the aN of the nitroxide radical is shifted to higher values because of the influence of one or more hydrogen bonds between the solute and the solvent, it becomes necessary to build a model in which nonspecific effects are described in terms of continuum polarizable medium with a dielectric constant typical of the protic solvent under study, whereas specific effects are taken into account through an explicit hydrogen-bonded complex between the radical and some solvent molecules. Figure 2.6 reports the aN values for the complexes formed by TEMPO with phenol, methanol, and water measured experimentally at room temperature, and computed in the gas phase and in solution. The values computed in solution fit the experimental data quite well. 

Practically all the hydrogen in the lunar fines was implanted by the solar wind, as the indigenous water content of the lunar surface samples is extremely low. We can thus investigate solar hydrogen directly. Measurements indicated that the solar hydrogen was depleted in deuterium by a factor of at least SO54. Deuterium may even be completely absent in solar hydrogen since the amount present in the lunar fines could have been formed by spallation reactions. 

We tried to make use of this dihydrate-trick for reaching molecular structures of DISPIRO 3 and DISPIRO 4. Unfortunately, we have failed so far in obtaining suitable single crystals of such DISPIRO dihydrate from solutions in wet methanol in every case, single crystals of the genuine chemicals are obtained which break down under X-ray exposure. The fact that DISPIRO compounds are not able to take up water from wet methanol may be related to the lower acidic character of NH hydrogens as measured by IR spectroscopy 65). 

The activities of several enzymes have been studied in partially hydrated powders as a funcuon of water activity or water content. Experiments of this type are not difficult to perform. Solutions of substrate and enzyme are mixed quickly, and the mixture is immediately frozen and lyophilized, which stops the reaction and gives a stable dry powder. If appropriately high concentrations of enzyme and substrate are mixed, the powder is of the enzyme-substrate complex. The sample is rehydrated under a controlled atmosphere to give the desired final hydration level. Conditions, particularly the pH of the sample, are set such that the hydration equilibrium is substantially complete (within several hours) before appreciable enzyme reaction has taken place. The problem of defining pH in partially hydrated powders was discussed in Section II,D in connection with hydrogen-exchange measurements. The pH of a powder appears to equal the nominal pH (that of the solution from which the powder was lyophilized) above about 0.15 A. 

Acetic acid in this system may be considered as slightly basic since it combines with hydrogen ions. Salts such as sodium acetate become strong bases. Acids may vary from their corresponding strengths in aqueous solutions in a manner dependent upon the relative tendencies of water and acetic acid to take up hydrogen ions. Measurements have... 

Myelin P2 was the first protein in the iLBP family whose structure was determined (Jones et al., 1988). The crystals contain three copies of the molecule in the asymmetric unit and the structure has now been refined at 2.7 A (Cowan et al., 1993). Because the crystals do not diffract beyond 2.7 A, the precision of the model is not as high as in the other studies and this factor could affect precise hydrogen bonding measurements. In an attempt to overcome this problem, the three molecules were restrained to be similar during the refinement. Only well-determined water molecules were included in the final model. No fatty acid was added to the sample, but later mass spectroscopy measurements indicated that the predominant ligand was oleic acid, which also agreed with the shape of the electron density. This density could not be accounted for by the protein model. 

If 5.00 L of hydrogen gas, measured at 20.0°C and 80.1 kPa is burned in excess oxygen to form water, what mass of oxygen (measured at the same temper-atme and pressme) will be consumed ... 

Those that are incorporated interstitially on a molecular scale in CaC03 (e.g. P04, Na and F in calcite). Typically these components are preferentially incorporated at growth defects and so tend to be more abundant where crystals have more defects, related to either rate or style of growth. Hydrogen, as measured by ion probe (Fairchild et al., 2001), probably reflects either molecular water or fluid nano-inclusions. 

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