Crystal chemical relationships

GROUP-SUBGROUP RELATIONS BETWEEN SPACE GROUPS FOR THE REPRESENTATION OF CRYSTAL-CHEMICAL RELATIONSHIPS... 

BALGORD (W.D.) and ROY (R.), 1970. Crystal chemical relationships in the analcite family. Amer. Chem. Soc. 2nd Int. Zeolite Conf. 321-27. 

Crystal Chemical Relationships in the Analcite Family II. Influence of Temperature and PH2Q on Structure... 

The Al203 Si02 ratio influences the dehydration characteristics of analcite only to a limited extent. Both high and low alumina Na-analcites dehydrate in a continuous fashion. However, the high alumina form undergoes water loss beginning at lower temperatures and is more nearly reversible. The overall crystal chemical relationships are summarized in Table II. 

Only a numeric code notation is useful for the derivation of the symmetry of an intergrowth structure (see 3.3.). The other notation with the formula of the parent structures offers the possibility to study the crystal chemical relationships of the intergrowth structure with structures of compounds in chemically analogous systems. 

The various members of the feldspar group show many characteristics in common. Crystallizing in the monoclime and irieiinie systems, they show similarity of crystal habit, cleavage and other physical properties as well as similar chemical relationships,... 

The crystal chemical reason for polytypism is that adjacent layers (two-dimensionally-periodic units) can be linked to each other in many translationally nonequivalent ways. However, the nearest-neighbor relationships remain preserved. Translated into the language of symmetry, this means that the pairs of adjacent layers remain geometrically equivalent in all polytypes of the same family. 

Moore PB (1970) Crystal chemistry of the basic iron phosphates. Am Mineral 55 135-169 Moore PB (1971a) The Fe3 (H20)n(P04)2 homologous series Ciystal-chemical relationships and oxidized equivalents. Am Mineral 56 1-16... 

In the present study, it has been highlighted that SIMS data in association with high-quality structural data and information derived from other complementary techniques allows the crystal chemical properties of difficult mineral phases to be successfully established. Moreover, a SIMS study of inhomogeneous samples at the micrometer scale can provide insightful relationships between their crystal chemistry and the volcanological processes to which they have partaken. 

Knowing the coordination numbers, one can solve a number of crystal chemical problems. Thus, 80 years ago Goldschmidt discovered the dependence of the chemical bond length on the coordination number of a cation [245], At the same time Pauling introduced the concept of bond strength [246], according to which the valence of an atom i, which is linked to atoms j, obeys the relationship... 

Scheme 13.9. On the left, a representation of the work of Fischer, E. Raske, K. Chem. Ber., 1907, 40, 3717) demonstrating the chemical relationship between (S)-(-)-serme and (S)-(+)-alanine. On the right, a representation of the X-ray crystal structure of ferrichrome A from the information presented by Zalkin, A. Forrester, J. D. Templeton, D. Yi.J.Am. Chem. Soc., 1966,88,1810.

Figure 18-82 illustrates the relationship between solids concentration, iuterparticle cohesiveuess, and the type of sedimentation that may exist. Totally discrete particles include many mineral particles (usually greater in diameter than 20 Im), salt crystals, and similar substances that have httle tendency to cohere. Floccnleut particles generally will include those smaller than 20 [Lm (unless present in a dispersed state owing to surface charges), metal hydroxides, many chemical precipitates, and most organic substances other than true colloids. 

In addition to chemical reactions, the isokinetic relationship can be applied to various physical processes accompanied by enthalpy change. Correlations of this kind were found between enthalpies and entropies of solution (20, 83-92), vaporization (86, 91), sublimation (93, 94), desorption (95), and diffusion (96, 97) and between the two parameters characterizing the temperature dependence of thermochromic transitions (98). A kind of isokinetic relationship was claimed even for enthalpy and entropy of pure substances when relative values referred to those at 298° K are used (99). Enthalpies and entropies of intermolecular interaction were correlated for solutions, pure liquids, and crystals (6). Quite generally, for any temperature-dependent physical quantity, the activation parameters can be computed in a formal way, and correlations between them have been observed for dielectric absorption (100) and resistance of semiconductors (101-105) or fluidity (40, 106). On the other hand, the isokinetic relationship seems to hold in reactions of widely different kinds, starting from elementary processes in the gas phase (107) and including recombination reactions in the solid phase (108), polymerization reactions (109), and inorganic complex formation (110-112), up to such biochemical reactions as denaturation of proteins (113) and even such biological processes as hemolysis of erythrocytes (114). 

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