Magnesia is an alkaline oxides, the reaction with water to form insoluble in water, magnesium hydroxide, magnesium salt with acid to generate magnesia refractories used, such as the making brick, crucibles, used as a pigment modulation paints and cosmetics, can also be used as rubber filler, insulation materials, light can be obtained calcined magnesium carbonate, magnesium hydroxide, basic magnesium carbonate can be obtained by firing heavy magnesium oxide. Odorless, tasteless, insoluble in water and ethanol, magnesium oxide is highly fire-resistant insulation properties, high temperature above 1000 ℃ by burning can be converted into a crystal, rose above 1500 ℃ into dead-burned magnesium oxide or sintered magnesia. Normal non-conductive heat, thermal conductivity, relatively poor. Do firebrick.