Elements, chemical, 14 origin

Basic chemical element The original and still present meaning of element or principle in chemistry is the basic sub-stance behind chemical stuffs, only implicitly defined through a conservation law in chemical reactions. 

The case studies cover key applications in chemical process industries, from petrochemistry to polymers and biofuels. The selection of processes was confronted with the problem of availability of sufficient design and technology data. The development of the flowsheet and its integration is based on employing a systems viewpoint and systematic process synthesis techniques, amply explained over three chapters. In consequence, the solution contains elements of originality, but in each case this is compared to schemes and economic indices reported in the literature. 

A coordination chemist might prefer a formula like B and consider the X—Y metal fragment. However, someone engaged in the chemistry of either element X or Y might look at it in a different way. Formula B stresses the chemical origin of most of these compounds, which are usually obtained by addition of X—Y to a coordina-tively unsaturated metal fragment [Eq. (1)]. 

Compositional contrast refers to the variation in gray levels in an SEM image that correspond to variation in chemical composition in a specimen. An image formed by BSEs exhibits very useful compositional contrast if the specimen consists of more than one chemical element. The origin of compositional contrast arises because the capability of BSEs to escape from the specimen depends on the atomic numbers of the specimen atoms. The backscatter coefficient (rj) characterizes such capability. 

The chemical composition of groundwaters depends on many causes rainwaters have a notable chemical charge, especially in marine salts (M. Schoeller, 1962) and in elements which originate from atmospheric dusts (silts, clays, pollen and bacteria) or from urban and industrial activity (Crozat, 1978 Dessfevre Delepoule, 1978). 

Sen Gupta J.G. Abundances of the six platinum metals in some iron and stony meteorites Relationships to the theories of evolution of parent bodies of meteorites and the origin of these elements. Chemical Geology 1968 3 293-305. 

This chapter will examine the ways in which major element data axe used in geochemistry. The discussion will be restricted to the ten elements traditionally listed as oxides in a major element chemical analysis — Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K and P. Geochemists make use of major element data in three principal ways — in rock classification, in the construction of variation diagrams and as a means of comparison with experimentally determined rock compositions, whose conditions of formation are known. Each of these uses will be discussed in a separate section of this chapter. In addition, major elements are used, often together with trace elements, in the identification of the original tectonic setting of igneous and some sedimentary rocks. This topic will be discussed in Chapter 5. 

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