magnesia : Idioms & Phrases
Magnesia alba
L. (Med. Chem.) , a bulky white amorphous substance, consisting of a hydrous basic carbonate of magnesium, and used as a mild cathartic.
Webster 1913
milk of magnesia
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noun purgative consisting of a milky white liquid suspension of magnesium hydroxide; used as a laxative and (in smaller doses) as an antacid