Lattice water

Fibrous or finely divided refractory materials, asbestos, glass wool, sand, or tungsten carbide, may ignite with the liquid and continue to burn in the gas [1]. The presence of adsorbed or lattice water seems necessary for attack on the siliceous materials to occur [2],... 

Zelentsov et al. also observed that the high spin fraction in virtually all samples increased to varying extents after the samples were heated [105]. The origin of this effect is not clear since the complexes were mostly unsolvated and thus loss of solvate molecules, the most common cause of such a change, was not applicable. Nevertheless, the importance of the inclusion of lattice water molecules in co-determining the spin crossover properties is evident in the different magnetic properties of Li[Fe(5-Br-thsa)2] [105] and Li[Fe(5-Br-thsa)2]-H20 [111]. For the unsolvated compound neg= 1.93 B.M. 

The Fe(III) complexes of the dianion of pyruvic acid thiosemicarbazone (thpu2- Fig. 7), (cation+)[Fe(thpu)2]-nH20, are very similar to those of the salicylaldehyde derivatives (Fig. 6) discussed above. The spin state properties are quite sensitive to changes in the counter-cation (typically an alkali-metal cation or a protonated nitrogenous base) and the lattice water content of the material. The parent compound, NH4[Fe(thpu)2], is low spin at room temperature [113]. Li[Fe(thpu)2]-3H20 is also low spin but K[Fe(thpu)2] 2-H20 shows almost complete spin crossover between 80 and 300 K [108]. 

Many LFe "(/u-0)(//-02CR)2Fe" L complexes have terdentate, triazamacrocyclic, or triazatri-podal ligands L. Examples include species with L = HB(pz)3, R = Me with L = tacn, R = Me with L = bis(2-benzimidazolylmethyl)amine, R = Me, Ph with L = A, A -bis(2-ethyl-5-methylimidazol-4-ylmethyl)aminopropane (213X R = Ph with L= Af-alkyl-Af,Af-bis(2-pyridyl-methyl)amine, alkyl = Me, Bz, adamantyl for R = Ph, also several other R for alkyl = Me and with L = bis((l-methylimidazol-2-yl)methyl)amine (214), R = Ph. In this last case hydrogen-bonding between lattice water and -oxo in the hydrated form results in a significant decrease in... 

The compounds have been characterized by elemental analyses, spectroscopy [electronic absorption, IR, Raman (or resonance Raman for the blue compounds with Ae = 1064 nm)], redox titration [for the determination of the (formal) number of Mo centers], thermal gravimetric analyses (TGA), and single-crystal X-ray structure analyses (see Refs. 2, 5 and literature cited therein). Mainly the crystals of the compounds that contain discrete wheel-shaped anions lose lattice water rapidly on removal from the mother liquor even at room temperature, a... 

As noted earlier, metal ions in polar solvents will form complexes with the solvent molecules. X-Ray diffraction, EXAFS, and visible absorption spectroscopy show that nickel(II) ion in dilute aqueous solution is present as the green hexaaqua complex Ni(H20)62+, just as in solids such as NiS04-7H20, which is actually [Ni(H20)e]S04-H20. In the crystal, the extra water molecule is loosely associated with the sulfate ion independently of the nickel-aqua complex it is sometimes referred to as lattice water, as distinct from complexed water. 

The word lattice is one that suffers terrible abuse at the hands of chemists (and other scientists) writing about crystals. A lattice is not-a physical thing it is simply an abstraction, a collection of points whereon real objects may be placed. A term like lattice water is as absurd as it is common. 

DTA is used in this study to understand the endothermic and exothermic phenomena resulting from desorption, decomposition and combustion of water and surfactant molecules occluded in the framework of samples A and B. Both samples have these common DTA features (Figure 3) an endothermic peak below 100 °C (apparently due to the evaporation of physically adsorbed water), an endothermic peak below 300 °C (attributed to the removal of lattice water and the decomposition of surfactant molecules), and a strong exothermic peak at around 335 °C (attributed to the combustion of surfactant molecules in air). The DTA results distinctly show that the surfactant molecules are occluded in almost identical positions within silica framework of samples A and B. 

Most solid-state photoreactions that have been reported involve photoredox, although examples of photoisomerization and photoaquation involving lattice water have also appeared. For example,... 

Photoaquation involving lattice water has been observed for trani-[Cr(en)2X2]X H20 (where X- = Cl- or Br-). The quantum efficiency is very similar to that for the aquation in water solution, and the photoaquation apparently obeys the same photostereochemical selection rules that apply in solution.102... 

The degree of hydration of the products from these preparations and the water content given by analytical procedures depends upon the heat treatment (method and history) of the product. A sample subjected to TGA (thermal gravimetric analysis) looses water almost continually from room temperature until it becomes the completely anhydrous heteropolytungstate salt at about 400°C. On the other hand, these crystals lose some lattice water rapidly upon removal from the mother liquor and exposure to air even at room temperature. 

The term lattice water" is commonly applied to cases in which the water molecules are occupying definite positions in the crystal lattice but arc apparently not coordinated with either cations ur anions. Again, clear-cut cases are those in which the compound is so highly hydrated that both lattice water and "ion water" arc present... 

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