Water evolution

The sample is weighed and placed in the oven where the water is vaporized. Nitrogen carrier gas flows through the molecular sieve dryer into the oven, where it absorbs the water vapor and transports it to the electrolytic cell. 

The electrolytic cell contains a U-shaped tube, with two parallel, helically wound, platinum electrodes. A thin film of P205 is deposited between the electrodes this substance readily absorbs the water from the carrier gas. The absorbed water transforms the P2Os to H3P04, a conductor. A voltage on the platinum electrodes then electrolyzes the absorbed water to H2 and 02. The current required for this electrolysis is integrated, scaled, and displayed on a digital readout device. Water levels as low as 1 ppm or as high as 10,000 ppm can be determined. 

This instrument has been used to determine the water contents of many substances, included among them are polymers (131-137) pharmaceutical products such as penicillin, vitamins (138) effervescent tablets (139). Nuclear fuels, pulping black liquor, minerals (141) and coal (140) have also been studied. 

Another more elaborate pyrolysis—chromatography—apparatus was described by MacLaury and Schroll (146), which permitted heating rates from 5 C/m to 5000°C/S. It consisted of a Chemical Data Systems geological sample and analysis system and a gas chromatograph. This system is a self-contained bench-top instrument that provides a means of trapping volatiles from a DSC 100 Pyroprobe solids pyrolyzer. The Pyroprobe uses a platinum 

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When low boiling ingredients such as ethylene glycol are used, a special provision in the form of a partial condenser is needed to return them to the reactor. Otherwise, not only is the balance of the reactants upset and the raw material cost of the resin increased, but also they become part of the pollutant in the waste water and incur additional water treatment costs. Usually, a vertical reflux condenser or a packed column is used as the partial condenser, which is installed between the reactor and the overhead total condenser, as shown in Figure 3. The temperature in the partial condenser is monitored and maintained to effect a fractionation between water, which is to pass through, and the glycol or other materials, which are to be condensed and returned to the reactor. If the fractionation is poor, and water vapor is also condensed and returned, the reaction is retarded and there is a loss of productivity. As the reaction proceeds toward completion, water evolution slows down, and most of the glycol has combined into the resin stmcture. The temperature in the partial condenser may then be raised to faciUtate the removal of water vapor. 

Makatun and Shchegrov [583] have considered the kinetics of water evolution in terms of retention of vibrational individuality of the H20... 

U02(N03)2 6 H20 showed unusual behaviour [62] in that there was no induction period to dehydration, the generation of specialized nuclei was apparently unnecessary since water evolution occurred by desorption at existing crystal surfaces and no migratory interface was developed. 

Many studies have been made of the rates of water evolution from layer-type silicate minerals which contain structural hydroxyl groups (clays and micas). Variations in composition of mineral specimens from different sources hinders comparison of the results of different workers. Furthermore, the small crystallite sizes and poor crystallinity that are features of clays limit and sometimes prevent the collection of ancillary observations (e.g. microscopic examination and diffraction measurements). 

Dehydroxylation of the clay mineral kaolinite [71,626—629] is predominantly deceleratory and sensitive to PH2o (Table 11). Sharp and co-workers [71,627] conclude that water evolution is diffusion controlled and that an earlier reported obedience to the first-order equation is incorrect. A particularly critical comparison of a—time data is required to distinguish between these possibilities. Anthony and Garn [629] detected a short initial acceleratory stage in the reaction and concluded that at low Ph2o there is random nucelation, which accounts for the reported... 

Figure 4. Water evolution during hydrogen TPR on all samples.

Sulphate. Melamine sulphate eliminates the water of crystallisation on heating between 100 - 230 0 as shown by TG, DTG and water evolution curves of Figure 10 (1st step). The amount of water evolved corresponds to one molecule per molecule of salt (calculated weight loss 7.4% experimental 8%). The IR of the anhydrous salt is shown in Figure 11A in which the typical strong band of sulphate anion group at 1095 cm-1 is evident. 

Limited decomposition of the sulphate and extensive melamine condensation overlap in this second step with condensation of sulphuric acid residues to pyrosulphuric structures. This is shown by water evolution and appearance of typical absorptions of pyrosulphate... 

Croal LR, Johnson CM, Beard BL, Newman DK (2004) Iron isotope fractionation by anoxygenic Fe(II)-phototrophic bacteria. Geochim Cosmochim Acta 68 1227-1242 Curtis CD, Coleman ML, Love LG (1986) Pore water evolution during sediment burial from isotopic and mineral chemistry of calcite, dolomite and siderite concretions. Geochim Cosmochim Acta 50 2321-2334... 

Manke, Ch. Hartnig, M. Grunerbel, et al. Investigation of water evolution and transport in fuel cells with high resolution synchrotron x-ray radiography. Applied Physics Letters 90 (2007) 174105-1-174105-3. 

First, 400 kg of finely divided salt with a water content of about 8 % by mass is to be dried in the shortest possible time (about 1 h) until the water content is less than 1 % by mass. The expected water evolution amounts to about 28 kg. The salt in the chamber is continuously agitated during the drying process and heated to about 80 °C. The vacuum system is schematically drawn in Fig. 2.78. 

Reactivity of Functional Groups. The reactivity of the functional groups of liquid prepolymers significantly affects the processing, cure behavior, and the ultimate mechanical properties of the cured binder and propellant. The reactivity of carboxyl groups of CTPB can be determined by the rate of reaction with n-butyl alcohol. The rate of esterification is measured from the rate of water evolution from the alcohol—carboxylic acid reaction, and a plot of water evolved vs. time then permits the calculation of the corresponding rate constants. 

Interpretation of the mechanisms of the hydrocarbon desorption reactions mentioned above was considered (31,291) with due regard for the possible role of clay dehydration. While this water evolution process is not regarded as a heterogeneous catalytic reaction, it is at least possible that water loss occurs at an interface (293) so that estimations of preexponential factors per unit area can be made. On this assumption, Arrhenius parameters (in the units used throughout the present review) were calculated from the available observations in the literature and it was found (Fig. 9, Table V, S) that compensation trends were present in the kinetic data for the dehydration reactions of illite (+) (294), kaolinite ( ) (293,295 298), montmorillonite (x) (294) and muscovite (O) (299). If these surface reactions are at least partially reversible,... 

From the discussion presented in the previous paragraphs, we identify the kinetic characteristics of the hydrocarbon evolution reactions (31,291,292) and the clay dehydration processes with the common mechanistic features reversibility and similar characteristic temperatures of onset of the water evolution step. The compensation effects observed for the two groups of related reactions (Table V, R and S) were not identical, however, since the species participating in the equilibria on the surfaces (believed to be represented by the kinetic characteristics described in Appendix I) are different. Undoubtedly, the interaction of hydroxyl groups to yield water was common to both types of reaction (surface desorption and lattice dehydration) and the properties and reactivities of these species probably determine the temperature at which significant surface activity and product evolution becomes apparent. This surface reaction is... 

Figure 2. pK for equilibrium between Ca-beidellite and kaolinite plotted as a function of Na content of Sierra Nevada spring waters. Arrow ABC is the path of water evolution calculated for the reaction from Na0 62Ca038 plagioclase to kaolinite in a closed system with an initial dissolved C02 of 0.0006 moles per liter. Arrow ABD is the expected path if evolution is also controlled by the two-phase equilibrium kaolinite-montmorillonite... 

Upon completion of a measurement, the raw data were plotted as volts vs. time. The rate of water evolution or the cumulative water evolved was plotted as a function of temperature. The data were normalized by subtracting the corresponding blank measurement, and dividing by the weight of the sample. The quantities of water obtained by integrating under each desorption peak were tabulated as micrograms of water per gram of sample, and as molecules of water per square nanometer of surface. 

It is apparent from Fig. 1 that the water evolution profile is qualitatively similar for water-sized and silane-treated glass fibers. Table 4 shows, however, that the desorption volume of physically adsorbed water (peak 1) is significantly larger for water-sized glass than for silane-treated specimens. This result is in qualitative accord with evidence from wetting experiments demonstrating that silane deposition diminishes the non-dispersive component of the work of adhesion with water [2-5], When bare and silane-treated fibers were equilibrated with water for 6 months, as opposed to several hours in this study, the desorption volumes of... 

When ferns appeared on earth, oxygen was introduced into the atmosphere. This brought about a dramatic change in the composition of the atmosphere. Oxygen changed methane to carbon dioxide and water and ammonia to nitrogen and water. Evolution of plants and animals helped to stabilize the atmosphere. The composition of the atmosphere has remained more or less the same for the last 2 billion years. 

C. Hartnig, I. Manke, R. Kuhn, S. Kleinau, J. Goebbels, J. Banhart, High-resolution in-plane investigation of the water evolution and transport in PEM fuel cells. J. Power Sources 188, 468-474 (2009)... 

Thermogravimetric analysis of nickel(II) chloride hexa-hydrate shows that water evolution occurs from ambient temperatures (25°) to 66.6°. The resulting dihydrate is stable up to 133.3°, beyond which temperature further water loss occurs. Differential thermal analysis shows an endotherm at 53.9° related to the first dehydration step, and a second, strong endotherm at 118.9°, not accompanied by any weight loss, indicates the transformation of an octahedrally coordinated to a close-packed cubic structure. 

Thermogravimetric analysis of a sample of the 5 hydrate shows that water evolution occurs between 34.1° and 89.6°, at which latter temperature a dihydrate has formed. This is stable up to 107°, beyond which temperature the remaining two water molecules are slowly lost. Differential thermal analysis shows two dehydration endotherms at 36.4 and 132.8° and a structure transformation (octahedrally coordinated to close-packed hexagonal) endotherm at 151.8°. 

Examination of the data on C02 and pyrolytic water evolution may provide some insight into the thermal decomposition behavior of specific organic and inorganic structures in the parent coals. Some C02 may arise from the decomposition of inorganic matter within the coal. It also has been suggested (16) that decomposition of carboxyl groups in the... 

Another possible correlation between coal structure and pyrolysis behavior is indicated by the temperature dependence of the evolution of pyrolytic water being strikingly different for the two coals. Figure 5 shows pyrolytic water evolution data for experiments in which the sample was heated at 1000°C/sec to the peak temperature indicated on the abscissa and then immediately allowed to cool at around 200°C/sec. The smooth curves are based on a single reaction, first-order decomposition model (7,8) and on the stated temperature-time history. Parameters used for the lignite have been published (8) while for the bituminous coal the Arrhenius frequency factor and activation energy were taken as 1013 sec"1 and 35 kcal/mol, respectively, with the yield of pyrolytic water ultimately attainable estimated from experimental measurements as 4.6 wt % of the coal (as-received). 

Banner J. L., Musgrove M., and Capo R. C. (1994) Tracing ground-water evolution in a limestone aquifer using Sr isotopes effects of multiple sources of dissolved ions and mineral-solution reactions. Geology 22, 687—690. 

Woods T. L., Fullagar P. D., Spruill R. K., and Sutton-Lynn C. (2000) Strontium isotopes and major elements as tracers of ground water evolution example from the upper Castle... 

Cookenboo H. O. and Bustin R. M. (1999) Pore water evolution in sandstones of the Groundhog Coalfield, northern Bowser Basin, British Columbia. Sedim. Geol. 123, 129-146. 

Moisture content saccharin sodium 76% contains 14.5% w/w water saccharin sodium 84% contains 5.5% w/w water. During drying, water evolution occurs in two distinct phases. The 76% material dries under ambient conditions to approximately 5.5% moisture (84% saccharin sodium) the remaining moisture is then removed only by heating. Solubility see Table III. 

It was established that complete decarbonylation occurs at 675 K and that treatment at this temperature is sufficient to obtain Mo-loaded samples with the lowest oxidation number possible. A low oxidation number of the Mo species is essential during nhridation with NH3 because water evolution due to reduction inhibits the... 

G. Capodaglio, C. Turetta, G. Toscano, A. Gambaro, G. Scarponi, P. Cescon. Cadmium, Lead and Copper Complexation in Antarctic Coastal sea water. Evolution During the Austral summer. Int. J. Environ. Anal. Chem., 71 (1998), 195-226. 

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