(Light Magnesia; Calcined Magnesia.)

Origin. - Prepared by subjecting magnesium carbonate to a low red heat in a Cornish or Hessian crucible closed loosely by a lid.

Description and Properties. - A white, very light, and very fine powder, without odor, and having an earthy, but not a saline, taste. On exposure to the air it slowly absorbs moisture and carbon dioxide. Almost insoluble in water and insoluble in alcohol, but soluble in diluted acids. Magnesia should be kept in well-closed vessels.

Dose. - As an antacid, 10-15 grains (0.6-1.0 Gm.) [30 grains (2 Gm.), U. S. P.],