Magnesium oxide is commonly used as an antacid to relieve heartburn, indigestion and stomach upset. Oral supplements that contain magnesium oxide may also be taken as a short-term laxative. It is also used to improve symptoms of indigestion. The most common side effects of magnesium oxide are cramping and nausea. The long-term usage of magnesium oxide supplements in therapeutic dosage can also result in obstruction of the bowels. Magnesium is an essential element in nutrition and magnesium oxide is commonly used in dietary supplements as a source of magnesium.
Magnesium oxide has a high tolerance for heat, making it useful in heating elements. It's frequently used in crushed form to fill any gaps around the heating element to insulate surrounding materials from the heat. Magnesium oxide is also a basic material in crucibles that hold molten metal. Magnesium oxide's low conductivity to electricity makes it a good insulator for electrical cables.
Magnesium oxide is also a desirable building material due its strength and resistance to moisture. It's is used in general construction as a fireproofing material, especially in wall boards. Portland cement frequently contains magnesium oxide to make concrete with a higher resistance to moisture.
Libraries frequently use magnesium oxide as a desiccant in their book storage areas to preserve older books. Athletes such as gymnasts, rock climbers and weight lifters apply to their hands and holds to reduce moisture and sweat.
Magnesium oxide has optical properties that make it useful in analytical chemistry. Spectrometers use it as a reference material for establishing a white color. Magnesium also diffuses and reflects light effectively. It's transparent to light with wavelengths between 7 micrometers (µm) and 300 nm and has a refractive index of 1.72.
Some materials have a strong tendency to change their electrical resistance when subjected to a magnetic field. This property is known as a magnetoresistance effect and magnesium chloride is a good insulator of magnetoresistance. Magnesium chloride is used in leathermaking where it serves as a base to neutralize the acid in chrome tanning. It's also used to surround radioactive waste in order to prevent radionuclides from dissolving.