Magnesium Peroxide

Hydrogen peroxide precipitates from ammoniacal solutions of magnesium salts a substance with peroxide properties. The dried product from the action of sodium hydroxide on magnesium sulphate in the presence of hydrogen peroxide corresponds roughly with MgO₂.3MgO. Aq. More highly peroxidised products result when magnesium chloride solution is electrolysed in the presence of hydrogen peroxide. The electrolytic cell is divided into two parts by a porous diaphragm, and the cathodic compartment contains the hydrogen peroxide. The anodes are platinum or carbon, and the cathodes platinum or tin. The reaction is represented by the equation

Mg+O₂+2H₂O = Mg(OH)₄.

A substance containing 42 per cent, magnesium peroxide is obtained by treating ignited magnesia with pure hydrogen peroxide.

Commercial magnesium peroxide is a white amorphous powder which is apparently a compound consisting of magnesium peroxide, magnesium hydroxide, and constitutional water. The ordinary product contains 8 per cent, available oxygen, and has a density of 0.615. One part dissolves in 14,550 parts of water at 20° C. It is stable in dry air, even up to 160° C., but is sensitive to the carbon dioxide in moist air.

Compounds with the general formula xMgO.yMgO₂.zH₂O result when ethereal solutions of nearly anhydrous hydrogen peroxide act on magnesium oxide. They are light white powders which decompose violently when heated, and are decomposed by water. The compound 2MgO.2MgO₂.3H₂O, which is stable at 30° C., passes, by gradual heating, into 3MgO.2MgO₂.3H₂O at 50° C. and into 4MgO.2MgO₂.3H₂O at 70° C.

KCl.MgO(OH)₂ results from the action of an ethereal solution of hydrogen peroxide on MgO and KCl, and MgCl₂.2MgO₂.Aq. when the potassium chloride is replaced by magnesium chloride.

Many methods for preparing magnesium peroxide have been patented - the action of sodium peroxide on magnesium salts being often applied. It is used as a bleaching or sterilising agent, and, medicinally, as a wash for wounds.

Weltzien obtained an alkaline solution by acting on magnesium with hydrogen peroxide. A white mass, soluble in water, remained after evaporation. He attributed the formula MgO₂H₂ to it, but Prudhomme, who found that it lost oxygen at about 300° C., formulated it as 3Mg(OH)₂+MgO(OH)₂.