These are treated also in natural groups, which associate those together having the strongest points of relationship. Thus in regular sequence we have:

Light Metals.

Alkali Metals.

Alkaline Earth Metals.

Earth Metals.

K, Na, Li, (NH4).

Ba, Ca, Sr, (Mg).

Al, and some rare metals. Oxides insoluble.

Oxides, carbonates, and most salts soluble.

Oxides soluble, carbonates insoluble.

Heavy Metals.

Iron Group.

Lead Group.

Arsenic Group.

Fe, Co, Ni, Mn, Cr, U, Zn.

Cd, Pb, Cu, Bi, Ag, Hg.

As, Sb, Sn, Au, Pt, Mo.

Sulphides soluble in dilute acids.

Sulphides insoluble in dilute acids.

Sulphides insoluble in ammonium sulphide.

Sulphides soluble in ammonium sulphide.