Ammonium Hydroxide

What is Ammonium Hydroxide?

Ammonium hydroxide is a solution where ammonia is mixed in water. It is denoted by the symbols NH3(aq). The ammonium hydroxide is an alkali with composition of [NH4+] [OH−] ions; it is not possible to isolate samples of NH4OH.

Except in highly dilute solutions, the ions NH4 + and OH− do not account for a significant fraction of the total volume of ammonia.

It is Known by Various Names: ammonia solution, ammonia liquor, aqua ammonia, aqueous ammonia, ammoniacal liquor, ammonia water

Chemical Formula for Ammonium Hydroxide: NH4OH or H5NO

IUPAC Name: Ammonium hydroxide


  • Ammonium hydroxide

  • Ammonia, aqueous solution

  • Ammonium hydroxide solution

  • Ammonia water

  • Ammonia, monohydrate

Appearance: it appears as colorless liquid


The compound structure is formed by one hydroxide anion (OH-) and one ammonium cation NH4+ which share an ionic bond. In the common representations used for organic molecules, its chemical structure can be written as below.

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Preparation of Ammonium Hydroxide

NH3 + H2O \[\rightarrow\] NH4OH

The Ammonium hydroxide is prepared by saturating water with gaseous ammonia.


Physical Properties of Ammonium Hydroxide:

Molar mass 35.04 g/mol

Odour: It has fishy odour and highly pungent

Density: 0.91 g/cm3 (25 % w/w)

Its Melting point is 57.5 °C (−71.5 °F; 215.7 K) (25 % w/w)

Solubility: it is soluble in water.

Chemical Properties:

Basicity of ammonia in water

Ammonium hydroxide is a weak basic compound that does not dissociate completely in water leaving the next equilibrium with ammonium ion and hydroxide ion

NH4OH + H2O ⇌ NH4+ + OH

The equilibrium is used to control the pH in solutions because the ion OH-raises a solution's pOH or basicity level.

Saturated Solutions

Ammonia’s solubility is decreased in solvent liquids as the temperature increases in the solvent increases. 

Ammonia solutions decrease in density as the dissolved ammonia concentration increases. At 15.6 ° C (60.1 ° F), a saturated solution has a density of 0.88 g / ml and contains 35.6 percent ammonia by mass, 308 grams of ammonia per liter of solution, and a molarity of about 18 mol / L.

 The molarity of the saturated solution decreases at higher temperatures, and the density increases. The ammonia gas is released upon heating of saturated solutions.

Ammonium Hydroxide Uses:

  • Diluted ammonia (1–3 percent) is also a component of many cleaning agents, including many formulations for window cleaning.

  • Aqueous ammonia may be used in industry as a precursor to certain alkyl amines, whereas anhydrous ammonia is usually preferred.

  • The vapor absorption process became popular and widely used using the water-ammonia systems.

  • Ammonia is used to make monochloramine, used as a disinfectant.

  • Aquarians use ammonia to establish a new fish tank using ammonia, called fishless cycling. 

  • Ammonia solution is used to treat straw and to produce "ammonia straw" which makes it more edible for cattle.

NH4OH Hazards

Health Hazards:

Inhalation, ingestion, or contact with material from the skin can cause serious injury or death. Contact with the molten material can cause severe skin and eye burns. Remove any touch to the skin. Touch or inhalation results may be adjourned. Fire can create gases which are irritating, corrosive and/or toxic. Runoff from fire or dilution water can be corrosive and/or toxic, leading to pollution.

Fire Hazards:

Non - combustible, material does not burn itself, but can decompose to create corrosive and/or toxic fumes when heated. Some are oxidizing agents and may ignite fuels (wood, paper, gasoline, clothes, etc.). Metal contact can result in flammable hydrogen gas. Containers can explode when dry.

FAQ (Frequently Asked Questions)

1. What is Ammonium Hydroxide Used for?

Ammonium hydroxide is used in many household and commercial cleaners as a purifying agent and sanitizer.   Ammonium hydroxide is also used to make products like fertilizer, cotton, rayon, and rubber. For aluminum alloys, brass, copper alloys and galvanized plates, watery ammonia is corrosive.

2. Is Ammonium Hydroxide an Acid or Base?

Ammonium hydroxide partly dissociated OH-ions in the water, and the molecule NH3 is not soluble in the water. So, ammonium hydroxide is a weak base. NaOH dissociate completely in water to give OH- ion, and Na+ ion is stable in water. So NaOH is a solid base.

3. Is Ammonium Hydroxide Safe for Skin?

Ammonium hydroxide is organic, and is sometimes used in AHA (alpha hydroxy acid) or similar exfoliant products instead of sodium hydroxide. The small amounts that are used in cosmetics are not considered skin sensitizer.

4. Is Ammonium Hydroxide Harmful to Humans?

Ammonium hydroxide is irritating to the skin; contact can cause severe irritation and burns. Ingestion can cause vomiting, nausea, gastric pain, perforation, weakness of the central nervous system, shock, seizures, and pulmonary edema in severe cases.