Carbon silicate structures

Proton-promoted dissolution reactions are exemplified for carbonates, silicates, and metal oxyhydroxides by Eqs. 3.15, 3.18-3.20, 3.25, 3.39, 3.46, 3.53, 3.56, and 3.59c. The typical response of the rate of dissolution to varying pH is illustrated in Fig. 3.2, and this response is often hypothesized to be a result of the proton adsorption-bond-weakening structural detachment sequence described in connection with Eq. 3.60.36 This sequence can be represented by the following generic reaction scheme ... 

Most analytical measurements are performed on solutions (usually aqueous) of the analyte. While some samples dissolve readily in water or aqueous solutions of the common acids or bases, others require powerful reagents and rigorous treatment. For example, when sulfur or halogens are to be determined in an organic compound, the sample must be subjected to high temperatures and potent reagents to rupture the strong bonds between these elements and carbon. Similarly, drastic conditions are usually required to destroy the silicate structure of a siliceous mineral and to free the ions for analysis. 

A critical provision needs to be emphasized in this discussion on stability of lignin-silicate structures, however. The discussion on alkoxide-silicate bond stability was pie ced by "in isolation", meaning a single bond in solution or a swollen gel. If the alkoxide-siUcate bond is formed in a sample which ultimately loses all water, the sensitivity ofthe carbon-oxygen-silicon bond to hydrolysis, while it still exists, is irrelevant because no water will everreach that bond to lyse and separate it Once a collapsed, hydrophobic aggregate of silicate and lignin-silicate bonds forms, the capacity of... 

The structural roles of phosphate, arsenate and vanadate ions are similar to each other in the crystal structures of rare earth minerals. Like the carbonate ion, these anions almost always exist as isolated anions in the crystal structures, and do not form infinite anionic groups such as chains. A few silicates structurally related to the phosphates are also included in this section. 

The most common fillers used in rubber base formulations will be briefly described. On the basis of their chemical structure, these fillers may be classified in five broad groups silicates, silicas, metal oxides, calcium carbonate, and carbon blacks. 

In the previous paragraph, it has been stated that minerals have the same structure but different compositions (phenomenon of isomorphism of minerals) while some minerals have the same composition but different structures (phenomenon of polymorphism of minerals). Mineral composition and structure are both important in studying and classifying minerals. The major class of minerals - based on composition and structure - include elements, sulfides, halides, carbonates, sulfates, oxides, phosphates, and silicates. The silicate class is especially important, because silicon makes up 95% of the minerals, by volume, in the Earth s crust. Mineral classes are divided into families on the basis of the chemicals in each mineral. Families, in turn, are made of groups of minerals that have a similar structure. Groups are further divided into species. 

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