Magnesium chloride hexahydrate is a colorless salt. The salt is soluble in water and slightly soluble in ethanol, acetone, and pyridine. Chemically, magnesium chloride is a weak Lewis acid.
Magnesium chloride is extracted from naturally occurring brine, for example by solar evaporation of sea water, and purified by solution chemistries.

Magnesium chloride is used as a source of the divalent magnesium ion, often to control zeta potential and ionic strength. Commonly, magnesium chloride is used in water desalination experiments, particularly research investigating nanofiltration membranes. In addition, researchers have used magnesium chloride to alter the stability of colloidal suspensions, for example driving the coagulation of graphene oxide. Magnesium chloride has also been used to control the interlayer spacing of graphene-oxide membranes