The molar solubility (molL−1) of a sparingly soluble salt MX4 is ′S′. The corresponding solubility product is KSP . ′S′ is given in terms of KSP by the relation
S = (KSP/256)1/5
MX4 → M+4X
s 4s
KSP = (4s)4s
KSP = 256s5
S = (KSP256)15