Magmas are thick, bulky suspensions in water of insoluble substances.

Prepare the official Magma Magnesiae ("Milk of Magnesia") as follows: Smoothly mix 12.5 Gm. magnesium carbonate (in fine powder) with 50 mils distilled water. To this, with constant stirring, add a solution of 8 Gm. sodium hydroxide in 40 mils distilled water; agitate the mixture frequently for 15 minutes. Using 200 mils distilled water each time, wash the Magma by decantation, until 1 drop dil. H2SO4 will discharge the color of 3 drops phenolthalein T. S. when added to a 50-mil sample of the washing. Allow the precipitate to subside until it measures 100 mils; then decant the supernatant liquid, bottle, and tightly stopper.

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A small amount of any flavoring oil may be added if desired. Milk of magnesia is sometimes used as an antacid. Dose, 10 mils.

The other official Magma is Magma Bismuthi ("Milk of Bismuth"), which is a convenient form for the administration of this substance. Dose, 4. mils.