Magnesium oxide is a basic oxide that exhibits the general characteristics of basic oxides and is classified as a cementing material. It appears as a white or off-white powder that is odorless, tasteless, and non-toxic; it is a typical alkaline earth metal oxide with the chemical formula MgO. It has a melting point of 2852°C, a boiling point of 3600°C, and a density of 3.58 g/cm³ (at 25°C). It is soluble in acids and ammonium salt solutions but insoluble in alcohol. Its solubility in water is 0.00062 g/100 mL at 0°C and 0.0086 g/100 mL at 30°C. When exposed to air, it readily absorbs moisture and carbon dioxide, gradually converting into basic magnesium carbonate-a process that occurs more rapidly with the "light" grade than the "heavy" grade. It reacts with water under certain conditions to form magnesium hydroxide, exhibiting a slightly alkaline reaction; the pH of a saturated aqueous solution is 10.3. It is soluble in acids and ammonium salts but sparingly soluble in water, yielding an alkaline solution. It is insoluble in ethanol and exhibits strong refraction in the visible and near-ultraviolet ranges. Magnesite (MgCO₃), dolomite (MgCO₃·CaCO₃), and seawater are the primary raw materials for producing magnesium oxide. Magnesium oxide is obtained through the thermal decomposition of magnesite or dolomite.
Alternatively, treating seawater with slaked lime yields a magnesium hydroxide precipitate, which is then calcined to produce magnesium oxide. Other production methods utilize magnesium chloride brine blocks (obtained from comprehensive seawater utilization) or debrominated brine as raw materials; adding sodium hydroxide or sodium carbonate precipitates magnesium hydroxide or basic magnesium carbonate, which is subsequently calcined to yield magnesium oxide. In China, production primarily relies on magnesite, dolomite, brine, or brine blocks as raw materials.