Subject elemental halogens

In addition to the major salt constituents discussed up to this point, the elements listed in Table 1.3 have been detected in normal bovine milk by spectroscopic and chemical analyses. They include a large number of metals, the metalloids As, B, and Si, and the halogens F, Br, and I. The subject of trace elements in milk has been reviewed comprehensively (Archibald 1958 Murthy 1974 Underwood 1977). Their significance for human nutrition is discussed in Chapter 7. 

Reduction of the carbon-halogen bond is an important synthetic reaction in organic chemistry. The importance of the reduction has been enhanced in recent years by the application of a wide range of newly available reductants. However, in the case of fluorine, the reduction is of less importance than for the other halogens. Reviews on the reduction of fluorine bonds have appeared mainly in the more specialized literature,1 4 though some aspects of the subject have formed parts of reviews of the broader topic of hydrogenation, reduction, or substitution.5,6 This section does not include patent literature and all literature data. It is thus selective, not exhaustive, and includes representative examples of the most commonly used procedures for the reduction of C-F and element-fluorine bonds. 

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. 

---