Ionic Phosphates of Iron, Aluminium and Manganese

There are numerous phosphates of iron, aluminium and manganese, many of which occur as minerals and which are intimately involved in the complexities of soil chemistry [33,34] (Table 12.8 and Chapter 2). These crystaUine compounds form essentially ionic structures in which the cations are coordinated (usually octahedrally) by water molecules and/or oxygen atoms belonging to the PO anions. 

Orthophosphates crystallise not only as tribasic, monohydrogen or dihydrogen add salts, but also as oxide, hydroxide or halide double salts. Calcium salts, for example, include oxyapatite, hydroxy- 

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