Ammonium Hydroxide NH4OH is formed when ammonia (NH3) is dissolved in water. Ammonia deprotonates a small portion of water molecules leaving the free hydroxide ion [OH]- to form a slightly basic solution. The resulting solution is clear colorless with a pungent odor and vapors that may irritate the eyes. Ammonium Hydroxide is a weak base mainly used to prepare other ammonium compounds like urea, ammonium carbonate and ammonium sulfate. Lab Alley high-quality Ammonium Hydroxide ACS Reagent Grade 28-30% has been certified as an ACS Grade reagent by the American Chemical Society (ACS). The reagent grade is generally equivalent to the ACS grade and is acceptable for use in analytical applications and research laboratories.