Compound formation capability metals

Figure 2.22. Compound formation capability in binary systems. The different element combinations are mapped on Mendeleev number coordinates and those systems are indicated in which the formation of intermediate phases has been observed (either from the liquid or in the solid state). Blank boxes indicate systems for which no certain data are available. Notice that the compound-forming alloys are crowded in a region corresponding to a large difference in the Mendeleev numbers of the elements involved (for instance, basic metals with semi-metals).

Phase diagrams of alkali metal alloys. The pattern of the intermetallic reactivity of these metals is shown in Fig. 5.6, where the compound formation capability with the different elements is summarized. 

Figure 5.6. Compound formation capability in the binary alloys of alkali metals. The different elements, the binary combinations of which with Li, Na, K, Rb, Cs are considered, are identified by their positions in the Periodic Table. No rehable data have been found about the stable equilibrium phases in the Na-P and Cs-As systems compound formation is, however, probable.

Figure 5.7. Binary compound formation capability of Ca, Sr, Ba and of Eu and Yb. Those elements are marked for which compounds with the mentioned divalent metals are known.

R-Me andAn-Me alloys. A summary of the alloying behaviour of the 3rd group metals with special attention to the compound formation capability is shown in Fig. 5.14. For the lanthanides two examples are shown La and Gd, the behaviour of which may be considered to give a reasonable first approximation description of the general intermetallic reactivity pattern of the lanthanides. For the actinides the reactivity schemes are shown for Th, U and Pu for the alloys of the other metals of this series, only a few data are available. 

Figure 5.14. Compound formation capability in the binary alloys of Sc, Y, light trivalent lanthanides (as exemplified by La), heavy trivalent lanthanides (exemplified by Gd) and of the actinides (exemplified by Th, U and Pu). The different partners of the 3rd group metals are identified by their position in the Periodic Table. Notice that a sharper subdivision between compound-forming and not forming metals will result from a shifting of Be and Mg from their position in the 2nd group towards the 12th group (see 5.12.3). The behaviour of the divalent lanthanides Eu and Yb is shown in Fig. 5.7 where it is compared with that of the alkaline earth metals.

Figure 5.17. Compound formation capability in the binary alloys of Ti, Zr, Hf. Notice the reactivity pattern similar to that shown by the metals of previous groups. No compound formation with metals of the first groups, except Be, lanthanides included.

Figure 5.25. Compound formation capability in the binary alloys of Fe, Co, Ni and Pt-family metals.

Considering the overall compound formation capability of the various elements of the 13th group we notice a certain number of analogies between them, such as the compound formation with the metals at the left side of the Periodic Table (with the exception of A1 with the alkali metals), including lanthanides and actinides. 

The complexing of chitosan and its basic derivatives with anionic substances is paralleled by compatibility with cationic and nonionic compounds. Similarly, the anionic derivatives of chitosan show complex formation with cationic agents and are compatible with anionic and nonionic compounds. The capability of these chitosan derivatives to complex with certain metal ions, notably those of the transition series, is also important, having possibilities for the removal of metal salts from effluent. The hierarchy in terms of binding capacity is Cr(III) < Cr(II) < Pb(II) < Mn(II) < Cd(II) < Ni(II) < Fe(II) < Co(II). 

It appears to be a stable covalent highly crystalline compound (unlike other metal methanediazoates). Alkanediazoates are easily converted to diazoalkanes, so should be regarded as capable of detonation. (Though named by the author as a methanedia-zoate, it is indexed and registered in CA as a nitrosomethylamide salt) [1], A sample of the freshly synthesised compound was dissolved in dichlorodideuteromethane and sealed into an NMR tube. Four days later, when the tube was being opened for recovery of the sample, the tube exploded. This was attributed to diazomethane formation, possibly from reaction with traces of moisture sealed into the tube [2], See other heavy metal derivatives, n-o compounds... 

Just as an example about the ternary intermetallic reactivity, a few schemes of ternary compound formation for aluminium are given in Fig. 5.41, summarizing the formation capability of (true) ternary compounds. Data are generally available (although partial) about ternary aluminium alloys with selected metals (Fe, Mg, Si, etc.), owing to their relevant applications and commercial interest. With reference to the indicated metal pairs (Al-Fe, Al-Co, Al-Cu, etc.), the preferential formation of compounds with metals is evident. 

It has been shown that R metals and compounds are capable of being used in many of these roles. Moreover, it is an area of application for R metals that is relatively new, and consequently, the reasons why they improve corrosion resistance are not completely understood. Clearly, in most of the areas described during the course of this chapter, considerably more research is required. However, there is one common factor which seems to be central to the whole topic of corrosion prevention and control with R metals and compounds, namely the effective formation/participation of a R oxide or hydroxide film. 

---