notam sulfatul unui metal monovalent = M2SO4
M.M2SO4 = 2Am+96 g/mol, unde Am = masa atomica a metalului M
100% sulfat ................................ 32,39% M
2Am+96 .................................. 2Am
=> Am = 96/4,175 = 23 u.a.m.
=> M = Na, sulfatul = Na2SO4