MnCl22H2O

Manganese(II) chloride dihydrate, with the formula MnCl2·2H2O, is an inorganic salt of manganese in the +2 oxidation state. It commonly appears as pale pink to colorless crystals that are soluble in water and tend to be hygroscopic. The compound forms as a dihydrate in the presence of water, and upon heating it losses its two water molecules to give the anhydrous salt; further heating can lead to hydrolysis and the formation of basic manganese chlorides.

Preparation and occurrence: MnCl2·2H2O is typically prepared by dissolving manganese compounds such as MnO, MnO2, or MnCO3 in hydrochloric acid, followed by crystallization of the dihydrate from the solution. It is also obtainable commercially as a laboratory reagent. In aqueous solution, Mn2+ ions are present as [Mn(H2O)6]2+.

Properties and reactions: The dihydrate is readily soluble in water. It serves as a convenient source of Mn2+ ions for various chemical syntheses and analyses. In the solid state, MnCl2·2H2O can dehydrate with heat to yield MnCl2, and in moist air it may slowly convert to basic manganese chlorides through hydrolysis.

Applications: In the laboratory, MnCl2·2H2O is used as a manganese(II) source for synthesis and catalysis, as well as in some electrochemical and material science contexts. It also serves as a precursor to other manganese compounds.

Safety: Soluble manganese(II) salts can be irritants to skin, eyes, and the respiratory tract. Inhalation of dust or mist should be avoided; use appropriate protective equipment and work in a ventilated area. Prolonged exposure and high concentrations can be harmful to health and the environment; handle with care and dispose of according to regulations.