Classification of hydrates

A second classification of hydrates is obtained through consideration of the guest molecules. Such a classification is a function of two factors (1) the chemical nature of the guest molecule and (2) the size and shape (particularly in sH) of the guest. The size of the guest molecule is directly related to the hydration number and, in most cases, to its nonstoichiometric value. 

Structural analysis of protein-DNA complex classification of hydration water... 

The term alumina hydrates or hydrated aluminas is used in industry and commerce to designate aluminum hydroxides. These compounds are tme hydroxides and do not contain water of hydration. Several forms are known a general classification is shown in Figure 1. The most weU-defined crystalline forms ate the trihydroxides, Al(OH) gibbsite [14762-49-3], bayerite [20257-20-9], and nordstrandite [13840-05-6], In addition, two aluminum oxide—hydroxides, AIO(OH), boelimite [1318-23-6] and diaspote [14457-84-2], have been clearly defined. The existence of several other forms of aluminum hydroxides have been claimed. However, there is controversy as to whether they ate truly new phases or stmctures having distorted lattices containing adsorbed or intedameUar water and impurities. 

It is possible to indicate by thermodynamic considerations 24,25,27>, by spectroscopic methods (IR28), Raman29 , NMR30,31 ), by dielectric 32> and viscosimetric measurements 26), that the mobility of water molecules in the hydration shell differs from the mobility in pure water, so justifying the classification of solutes in the water structure breaker and maker, as mentioned above. 

Classification of water molecules in crystalline hydrates on the basis of co-ordination environment... 

See also Iron entries hydration, 5 477-478 in Portland cement, 5 467 in Portland cement clinker, 5 473t classification of, 11 55-58 crystal chemistry of, 11 59-71 defined, 11 55 energy losses in, 11 64-66 physical properties of, 11 59-71 processing of, 11 71-75 properties of spinel and M-type,... 

In 1893 Werner founded his new constitutional formula for inorganic compounds, applied the theory to the systematic classification of the chromi-ammines, and found that all the chromi-ammines which had been investigated could be fitted in to his system of classification. Since then the chemistry of the chromi-ammines has been further developed hv Werner, Pfeiffer, and many others relationships have been traced between chromi-ammines, complex salts, and chromic salt hydrates, and numerous cases of isomerism have been discovered in this series of ammines. 

As to the first of these, I have elsewhere [10] discussed the classification of the ionic hydrates, which can best be taken on a geometrical basis according to the way the water molecules are grouped, In the first group the water molecules occur singly or in clusters they may be... 

Ionization, hydrate and coordination isomerism are classifications of constitutional isomerism that originated with Werner.27,28 Ionization and hydrate isomerism (equation 1) apply to cases in which there is a ligand exchange between primary and outer coordination spheres, whereas coordination isomerism (equation 2) arises in systems containing at least two metal ions, so that alternative primary coordination spheres are available. 

In Figure 1.2, the intersection of the above three phase lines defines both a lower hydrate quadruple point Qi (I-Lw-H-V) and an upper quadruple point Q2 (Lw-H-V-Lhc)- These quadruple points are unique for each hydrate former, providing a quantitative classification for hydrate components of natural gas. 

Table I lists many of the known hydrated borate structures, except for those containing silicon. The compounds are arranged according to structural similarity under the classification of Christ and Clark (80)...

Figure 40. Time scales of two hydration dynamics component % (top) and t2 (bottom) of 16 mutants in native (right) and MG (left) states. In each panel, above the bars are the classification of mutation sites, which are divided according to their secondary structure (solid black bars), charge distribution (empty bars), and probe location (solid light gray bars). The beads correspond to the data below them. The insets in the lower two panels show the correlation between the two dynamics.

Ionic potential — Function defined by = zjr, where z and r are the valence and radius of an ion, respectively. This function was introduced by G.H. Cartledge [i,ii], who used it as a quantitative basis of the periodic classification of elements. The ionic potential is directly connected with the heat of hydration of ions (see - Born equation), and thus related to the heat of solution of salts, acidic properties of ions, and others. It is also known that the ionic potential is correlated with electrochemical redox potentials (e.g., for solid metal hexacyanomet-allates [iii]). 

Three classifications of food are proteins, fats, and carbohydrates. Many carbohydrates have the empirical formula CH2O. This empirical formula looks like a hydrate of carbon, hence the name "carbohydrate."... 

In 1970, Heller suggested a classification of borates based on the number of boron atoms in the fundamental building block . In 1971, J. R. Clark added, in an article on crystal chemistry of borates , a further principle as the fifth rule, namely that "the boric acid group, B(OH)3, may exist in isolated form in the presence of more complex polyanions, or such insular groups may themselves polymerize and attach to side-chains of more complex polyanions , as first observed in the crystal structures of veatchite and paraveatchite. In 1977, Christ and Clark reviewed the various principles and classifications in their article on a crystal-chemical classification of borate structures with emphasis on hydrated borates . In addition to a sixth rule. 

Christ, C. L., and J. R. Clark (1977). A crystal-chemical classification of borate structures with emphasis on hydrated borates. Phys. Chem. Minerals 2, 59-88. 

The classification of lipids is largely arbitrary. It can be based on water solubility (hydration) or swelling of a lipid system at the air-water interface, for example. Here, we approach lipids in terms of increasing complexity and focus on those lipids that are found mostly in cells, see Fig. 1. A more thorough discussion of the topic is given by Hauser and Poupart (1) and Larson (4). 

A preliminary classification of the weak forces which hold together well-separated units such as the individual molecules in ice or napthalene has already been made (p. 82). The strongest of these are often termed electrostatic, signifying that the forces can be attributed to an interaction of the unmodified, static charge distributions of the separate systems. Examples are the ion-dipole bonds which occur in hydrates and ammoniates. These are usually weaker than ordinary covalent bonds and relatively easily break on heating. The binding force arises (Fig. 62) from the attraction between the... 

Table 1. Classification of water molecules in solid hydrates with respect to their lone-pair coordination (after Chidambaram et al. ) (see Fig. 1)...

Many modern dermatological formulations are washable oil-in-water systems. Simple aqueous lotions are also used as they have a cooling effect on the skin. Ointments are used for the application of insoluble or oil-soluble medicaments and leave a greasy film on the skin, inhibiting loss of moisture and encouraging the hydration of the keratin layer. Aqueous creams combine the characteristics of the lotions and ointments. A classification of semisolid bases is given in Fig. 9.24. 

The classification adopted here is not, without undue elaboration, applicable to hydrates in which there are different degrees of hydration of some of the cations. For example, in ZnCl2. H20 two-thirds of the Zn atoms are tetrahedrally... 

The most suitable basis for the classification [5] of the structures of hydrates is by grouping together substances in which water molecules are in similar environments. One group of hydrates has water arranged in a three-dimensional lattice framework... 

The identification of similarities and of differences of behaviour of reactant hydrates may provide insights into not only the mechanisms of dehydration, but also a wider range of crystolysis reactions. Inconsistencies of behaviour may be recognized and directions for future research identified. The progress achieved towards a general classification of solid state decompositions is discussed in Chapter 18,... 

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