Magnesium chloride ($\mathrm{MgC}{\mathrm{l}}_2$)

Magnesium chloride is an ionic compound with two chloride anions per magnesium cation. Complete dissolution supplies one divalent magnesium ion and two monovalent chloride ions per formula unit. At analytical salt concentration $C$, these species contribute molar ionic strength $I=\frac{1}{2}(4C+2C)=3C$, provided additional dissolved ions are absent.