Ammonium hydroxide, also known as ammonia water or aqua ammonia, is an aqueous solution of ammonia gas dissolved in water. It is an alkaline solution with widespread uses in both household and industrial settings.
Understanding the Chemical Formula
The chemical formula for ammonium hydroxide is NH₄OH. This formula indicates that the solution contains an ammonium ion (NH₄⁺) and a hydroxide ion (OH⁻).
While NH₄OH is the accepted formula, ammonium hydroxide does not exist as a stable, isolable compound. Instead, it represents the equilibrium that occurs when ammonia gas (NH₃) dissolves in water (H₂O). In this equilibrium, most of the ammonia remains as dissolved NH₃ molecules and water, with only a small fraction reacting to form ammonium ions and hydroxide ions. The presence of these hydroxide ions is what gives the solution its alkaline properties.
Key Characteristics
Ammonium hydroxide typically appears as a colorless liquid. It possesses a strong, pungent ammonia odor. This odor is due to the volatility of ammonium hydroxide, meaning it readily releases ammonia gas into the air.
The solution is highly alkaline, acting as a weak base. A 1M solution of ammonium hydroxide generally has a pH ranging from 11.3 to 11.63, reflecting its basic nature. Ammonium hydroxide is also highly soluble in water, forming a homogeneous mixture. The density of a 25% w/w solution is approximately 0.91 grams per cubic centimeter, and it has a melting point around -57.5 °C and a boiling point near 37.7 °C.
Everyday Applications
Ammonium hydroxide finds extensive use in various everyday applications, often due to its alkaline nature and ability to dissolve certain substances. It is a common ingredient in household cleaning products, such as window cleaners, floor cleaners, and general surface cleaners. Its cleaning efficacy stems from its ability to break down grease and stains, and its rapid evaporation helps prevent streaking. Household ammonia solutions typically contain between 5% and 10% ammonium hydroxide.
Beyond household use, ammonium hydroxide plays a role in industrial processes. It serves as a nitrogen source in the production of fertilizers. In water treatment, it is used for pH adjustment. The chemical is also employed in the manufacturing of plastics, rubber, and textiles. Additionally, ammonium hydroxide is utilized in food processing as an acidity regulator, a leavening agent in baked goods, and even as an antimicrobial in some food products.
Handling and Safety
Handling ammonium hydroxide requires careful attention due to its potential hazards. The substance is corrosive to skin and eyes, capable of causing severe burns and eye damage, which can lead to permanent vision impairment. Inhaling its vapors can irritate the respiratory tract, leading to symptoms such as coughing, throat irritation, and difficulty breathing, with prolonged exposure potentially causing fluid buildup in the lungs. If ingested, ammonium hydroxide can cause internal burns and other severe health issues.
To minimize risks, it is important to work with ammonium hydroxide in well-ventilated areas, ideally under a fume hood, to prevent vapor inhalation. Personal protective equipment should always be worn, including chemical-resistant gloves, safety goggles, and a face shield to protect the eyes and skin from splashes.
First aid measures for ammonium hydroxide exposure include:
- If skin contact occurs, the affected area should be rinsed immediately with copious amounts of water for at least 15 to 20 minutes, and contaminated clothing should be removed.
- For eye contact, flushing with water for at least 15 minutes while lifting the eyelids is recommended, followed by immediate medical attention.
- If vapors are inhaled, moving to fresh air is important, and medical assistance should be sought if symptoms persist.
- In cases of ingestion, rinsing the mouth and drinking water or milk is advised, but vomiting should not be induced; immediate medical attention is necessary.
Proper storage is also important; ammonium hydroxide should be kept in tightly closed, corrosion-resistant containers in a cool, dry, and well-ventilated area, away from heat, direct sunlight, and incompatible chemicals such as acids or heavy metals. Spills should be contained using absorbent materials and neutralized with a weak acid, such as citric acid or vinegar, before disposal according to local regulations. Ammonium hydroxide is considered very toxic to aquatic life, so direct discharge into drains or waterways should be avoided.