CHARACTERIZATION OF ANTACID COMPOUNDS CONTAINING BOTH ALUMINUM AND MAGNESIUM .1. CRYSTALLINE POWDERS

The composition and antacid properties of 10 samples of crystalline an tacids containing both aluminum and magnesium were determined. The com position was found to vary significantly, even within the same type of antacid. For example, three of four hydrotalcite samples exhibit evid ence of the presence of a minor phase of amorphous aluminum hydroxide. Almagate and almagcit, which are claimed to be unique compounds, were found to be composed of hydrotalcite, magnesium hydroxycarbonate, and /or magnesium carbonate and amorphous aluminum hydroxide. All three ma galdrate samples examined contained a minor phase of amorphous aluminu m hydroxide. All 10 samples passed the preliminary antacid test and ha d high acid neutralizing capacities. However, the rate of acid neutral ization varied between samples. In some cases the rate of acid neutral ization at a dose of 400 mg was too slow to raise the pH to 3.0 as req uired by the Rossett-Rice test.