This document discusses acidifying reagents, including dilute hydrochloric acid and ammonium chloride. It provides details on their preparation, properties, tests for identification and purity, assays, storage, and uses. Dilute hydrochloric acid is a clear, colorless liquid prepared by diluting concentrated hydrochloric acid with water. Ammonium chloride is a white, crystalline powder prepared by neutralizing ammonia with hydrochloric acid. Both are used as acidifiers in pharmaceutical preparations and to treat conditions like metabolic alkalosis.