NH4OHaq

NH4OHaq, or ammonium hydroxide in water, is an aqueous solution of ammonia (NH3) in water. In solution, ammonia exists in equilibrium with ammonium and hydroxide ions: NH3 + H2O ⇌ NH4+ + OH−. The term NH4OH is commonly used, but no discrete NH4OH molecule is present; the solution is described by its NH3 content and pH. The solution is a weak base, with a high pH that depends on concentration.

Concentrations of commercial ammonium hydroxide vary widely. Household or laboratory products typically contain a few percent NH3 by weight, while industrial solutions may exceed 25–30% NH3. Densities and pH depend on concentration, with concentrated solutions being strongly basic and pungent due to ammonia gas being released. Ammonia in water is fully miscible with water.

Reactivity and uses: NH4OHaq acts as a base, neutralizing acids to form ammonium salts. It is used for cleaning and degreasing, pH adjustment in laboratories and industries, and as a reagent in organic synthesis. It can react with carbon dioxide to form ammonium carbonate/bicarbonate in solution. Concentrated solutions can liberate ammonia gas in air, especially when heated or exposed to acids.

Safety and handling: Ammonium hydroxide is corrosive and irritant to skin, eyes, and the respiratory tract. It can cause burns and inhalation can irritate the lungs. Use in a well-ventilated area or fume hood, wear appropriate gloves and eye protection, and keep containers tightly closed away from acids and oxidizers. Storage is in labeled, compatible containers in a cool, ventilated space.