Calcium complexes hydrates

The more highly complexed hydrates of calcium chloride (CaCl2 nH2 O where n > 2) may also exhibit the characteristics of a Class 2 dryiag agent, because the hydrated species can physically absorb additional water to form a saturated solution. The term absorption is used to describe the phenomenon that occurs when a gas or vapor penetrates the soHd stmcture to produce a saturated solution ... 

Calcium-binding proteins, 6, 564, 572, 596 intestinal, 6, 576 structure, 6, 573 Calcium carbonate calcium deposition as, 6, 597 Calcium complexes acetylacetone, 2, 372 amides, 2,164 amino acids, 3, 33 arsine oxides, 3, 9 biology, 6, 549 bipyridyl, 3, 13 crown ethers, 3, 39 dimethylphthalate, 3, 16 enzyme stabilization, 6, 549 hydrates, 3, 7 ionophores, 3, 66 malonic acid, 2, 444 peptides, 3, 33 phosphines, 3, 9 phthalocyanines, 2,863 porphyrins, 2, 820 proteins, 2, 770 pyridine oxide, 3,9 Schiff bases, 3, 29 urea, 3, 9... 

Addition of dampproofers based on caprylic, capric or stearic acids, stearates or wax emulsions do not have any effect on the setting characteristics of hydration products of Portland cement. However, the unsaturated fatty acid salts, such as oleates, although not affecting the tricalcium silicate hydration, have a marked effect on the ettringite and monosulfate reaction [12] and this is illustrated in the isothermal calorimetry results in Fig. 4.4. It is possible that a calcium oleoaluminate hydrate complex is formed involving the double bond of the oleic acid. 

French town (Montmorillon) where it was first discovered. In the USA, bentonite is principally mined in Wyoming - hence the term Wyoming clay . The type of bentonite, the source, and its purity influence its properties (Marchal et al. 1995). Bentonite is a complex hydrated aluminum silicate with exchangeable cationic components (Al, Fe, Mg) Si40io (0H)2 (Na+, Ca++). The most commonly used bentonite form in enology is the sodium bentonite. Sodium bentonite has enhanced protein binding capabilities over calcium bentonite. 

Calcium complexes amino acids, 33 arsine oxides, 9 bipyridyl, 13 crown ethers, 39 dimethylphthalate, 16 hydrates, 7, ionophores, 66 peptides, 33 phosphines, 9 pyridine oxide, 9 Schiff bases, 29 urea,9 Calixarenes... 

The composition of the liquid phase co-existing with the solid, as it has been mentioned above, is of special importance in the hydration process. This system is far from the equilibrium and at the usual water content on the level 33 % approximately (w/c=0.5), there are the micro-areas of different composition. Simultaneously, the diffusion becomes more and more difficult as the hydrates are formed. The gradients of concentrations appear, as well as the differences of temperature between the particular micro-areas. Therefore the image of the process becomes more sophisticated. To simplify this, we take into account the model, three-component systems CaO-Si02-H20 or Ca0-Al203-H20 which correspond to the calcium silicate or calcium aluminate hydration. However, the processes occurring in these simplified systems are complex, as one could conclude from the aforementioned considerations. 

The reaction of tricalcium silicate with water is a complex heterogeneous process with not fully recognized mechanism. It occurs with the formation of calcium silicate hydrate C-S-H and calcium Itydroxide. The relationship between these two products is given by the schematic equation ... 

Pollmann, H. (1986) Solid solutions of complex calcium aluminate hydrates containing Cr, OH and CO anions, in Proceedings 8th ICCC, Rio de Janeiro, Vol. 3, pp. 300-306. 

Perhaps the most significant finding reported in a series of articles," describing these research results, was that a large positive entropy change was found to accompany the association of calcium with polyphosphates. This positive entropy change was attributed to the release of waters of hydration upon association." The enthalpies of association for calcium complexes of the polyphosphates were found to be small. 

Equations 13.1 to 13.5 are part of the whole hydration reaction of a relatively complex mixture of cement phases. Following are the hydration reactions of p-belite in which several kinds of calcium silicate hydrates (xC-yS-zH) have been found (Babushkin et al. 1985). 

Several complex reactions occur when concrete is exposed to sea water. Compounds such as aragonite, calcium bicarbonate, calcium monosulfate hydrate, ettringite, Ca-Mg silicate hydrates, magnesium silicate, thaumasite, etc., have been identified by the application of thermal analysis in conjunction with other techniques. Thus, the factors leading to the deterioration of concrete can be established. 

Si MAS NMR was used by Cappelletto et al to examine calcium silicate hydrate gel (C-S-H) present in Portland cement and is the complex phase mostly responsible for the binding properties and the mechanical resistance of the material. The effects of different comb-shaped superplasticizers on the silicate structure are investigate. The analysis of Si MAS NMR spectra shows that the additives increase the degree of polymerization and hence the average length of the silicate chains in C-S-H. ... 

Portland cement clinker. In addition to the major dicalcium silicate and tricalcium silicate phases, the structure shows silicate and tricalcium silicate phases, smaller amounts of tricalcium aluminate (3Ca0-Al203), and millerite (4Ca0-Al203-Fe203). On reaction with water, the clinker forms a complex hydrated product. This product is the cementitious material. It is a noncrystalline calcium silicate gel resulting from the tricalcium silicate and dicalcium silicate. The microstructure of set cement is shown in Figure 11.25. 

Calcium Silicate Brick. Sand—lime brick is used ia masonry ia the same way as common clay brick. The bricks, molded from a wet mixture of sand and high calcium hydrated lime, are heated under pressure ia a steam atmosphere. Complex hydrosiUcates are formed that give the bricks high dimensional stabiUty (6). 

Scandium, Sc, which was first isolated in 1937, is a reactive metal it reacts with water about as vigorously as calcium does. It has few uses and is not thought to be essential to life. The small, highly charged Sc3+ ion is strongly hydrated in water (like Al3+), and the resulting Sc(H2())6]3+ complex is about as strong a Bronsted acid as acetic acid. 

Acetylcyclohexanone. Method A. Place a mixture of 24-6 g. of cyclohexanone (regenerated from the bisulphite compound) and 61 g. (47 5 ml.) of A.R. acetic anhydride in a 500 ml. three-necked flask, fitted with an efficient sealed stirrer, a gas inlet tube reaching to within 1-2 cm. of the surface of the liquid combined with a thermometer immersed in the liquid (compare Fig. II, 7, 12, 6), and (in the third neck) a gas outlet tube leading to an alkali or water trap (Fig. II, 8, 1). Immerse the flask in a bath of Dry Ice - acetone, stir the mixture vigorously and pass commercial boron trifluoride (via an empty wash bottle and then through 95 per cent, sulphuric acid) as fast as possible (10-20 minutes) until the mixture, kept at 0-10°, is saturated (copious evolution of white fumes when the outlet tube is disconnected from the trap). Replace the Dry Ice-acetone bath by an ice bath and pass the gas in at a slower rate to ensure maximum absorption. Stir for 3 6 hours whilst allowing the ice bath to attain room temperature slowly. Pour the reaction mixture into a solution of 136 g. of hydrated sodium acetate in 250 ml. of water, reflux for 60 minutes (or until the boron fluoride complexes are hydrolysed), cool in ice and extract with three 50 ml. portions of petroleum ether, b.p. 40-60° (1), wash the combined extracts free of acid with sodium bicarbonate solution, dry over anhydrous calcium sulphate, remove the solvent by... 

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