Magnesium bromide hexahydrate

Magnesium Bromide Hexahydrate which crystallizes from an aqueous solution at temperatures above 0°C, is highly hygroscopic and isomorphous with MgCl2·6H2O. Magnesium Bromide has two different forms - anhydrous and hexahydrate forms. It appears as white hygroscopic crystals in the anhydrous form and as colorless monoclinic crystals in the hexahydrate form.

Magnesium bromide occurs in sea water, surface and subterranean brines, and salt deposits. It is an electrolyte component in certain dry cells. In medicine, it is a sedative and anticonvulsant for treatment of nervous disorder. It also is used in organic synthesis forming several addition compounds.

Magnesium bromide hexahydrate is used as flame retardant. Used as source of magnesium ion and a co-factor for many enzymes including deoxyribonuclease (DNase) and various restriction enzymes.

Magnesium bromide is prepared by treating MgO with hydrobromic acid and then crystallization above 0.0°C in solution. The product is the hexahydrate salt:
MgO＋2HBr→MgBr2＋H2O→MgBr2·6H2O
The anhydrous form may also be prepared by heating the hexahydrate with dry HBr gas. This compound can also be formed directly from the elements:
Mg＋Br2→MgBr2

It is also formed by the reaction of magnesium carbonate and hydrobromic acid. The solubility of magnesium bromide is 101 g/ 100 mL of water at 20 °C; the solubility of the hexahydrate is 160 g/ 100 mL of 95% ethanol at 20 °C.