Alkaline earth metals Group defined

The test ensures that the substance to be examined has a total content of alkaline-earth metals, which is below the limit defined in the individual monograph. Originally, calcium, strontium, and barium were called alkaline-earth metals because of their ability to form basic oxides. Earth is an old word for oxides. Nowadays, the term is most often used for the Group II metals in the periodic table. The selectivity of the limit test suggests that the original definition be applied in the present monograph. 

The rare earths may Ik defined as a group of trivalent metals, forming basic oxides, wi<,h oxalates insoluble in dilute mincml acids. Their fluorides are also difficultly soluble, hence they may be separated, in general, from other elements by adding oxalic or hydrofluoric acid to their solution, to which some mineral acid has previously ls m added. Doubtless the most striking fact which characterizes these elements is the remarkable similarity in both the physical and chemical projmrties of their compounds, Their main differences are in the solubilities of their salts and the basicity of their oxides, which varies l e-tween that of the alkaline earths and that of aluminium. 

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