The metals may be arranged in a series according to their power of displacing one another in salt solutions, thus Cs, Rb, K, Na, Mg, Al, Mn, Zn, Cd, Tl, Fe, Co, Ni, Sn, Pb, (H), Sb, Bi, As, Cu, Hg, Ag, Pd, Pt, Au.
Of minerals containing this element mention may be made of cassiterite or tinstone, Sn02, tin pyrites, Cu 4 SnS 4 + (Fe,Zn) 2 SnS 4; the metal also occurs in some epidotes, and in company with columbium, tantalum and other metals.
Of the heavy metals, copper is the one which exhibits by far the greatest avidity for sulphur, its subsulphide Cu 2 S being the stablest of all heavy metallic sulphides in opposition to dry reactions.
They have also formed in this way certain alloys of definite composition, such as AuCd 3, Cu 2 Cd, and, more interesting still, Cu 3 Sn.
Thus, a number of copper-tin alloys when digested with hydrochloric acid leave the same crystalline residue, which on analysis proves to be the compound Cu 3 Sn.
