MgCl2 · 6H2O
M.W.: 203.30
Appearance : White to gray white powder
MgCl2 • 6H2O , W/% :  ≥98.0
pH :  5.0 – 6.5  (50g/L in H2O at 25 °C)
Specific Gravity : 1.59 (Water = 1)
Solubility : 1 M in H2O at 20 °C, clear, colorless
Easily soluble in cold water, hot water, methanol ; Insoluble in diethyl ether, n-octanol.

In chemistry and molecular biology applications, Magnesium Chloride is widely used as a source of magnesium ion.
In biological systems, magnesium is a co-factor for many enzymes including deoxyribonuclease (DNase) and various restriction enzymes.
Also plays a role in cell membrane integrity, muscle cell physiology, cardiovascular and muscular activity, and nucleic acid structure.
Magnesium chloride solution is a favorable choice as an elution buffer for antibody affinity column purifications; it is much milder on most antigens than acid elution, allowing reuse of the antigen column.
Also an essential cofactor for the DNA polymerase in polymerase chain reaction (PCR) amplification.