Ammonia solution

Names
IUPAC name Ammonium hydroxide
Other names Ammonia water
Identifiers
CAS Number	1336-21-6 Y 7664-41-7
3D model (JSmol)	Interactive image
ChEBI	CHEBI:18219 Y
ChemSpider	14218 Y
ECHA InfoCard	100.014.225
EC Number	215-647-6
E number	E527 (acidity regulators, ...)
KEGG	C01358 Y
PubChem CID	14923
RTECS number	BQ9625000
UNII	5138Q19F1X Y
UN number	2672
CompTox Dashboard (EPA)	DTXSID4020080
InChI InChI=1S/H3N.H2O/h1H3;1H2 Y Key: VHUUQVKOLVNVRT-UHFFFAOYSA-N Y InChI=1/H3N.H2O/h1H3;1H2 Key: VHUUQVKOLVNVRT-UHFFFAOYAI
SMILES [OH2].[NH3]
Properties[1]
Chemical formula	NH3(aq)
Molar mass	17.031 g/mol
Appearance	Colourless liquid
Odor	"Fishy", highly pungent
Density	0.91 g/cm3 (25 % w/w) 0.88 g/cm3 (35 % w/w)
Melting point	−57.5 °C (−71.5 °F; 215.7 K) (25 % w/w) −91.5 °C (35% w/w)
Boiling point	37.7 °C (99.9 °F; 310.8 K) (25 % w/w)
Solubility in water	Miscible
Magnetic susceptibility (χ)	−31.5×10−6 cm3/mol
Thermochemistry
Std molar entropy (S⦵298)	111 J/(mol·K)[2]
Std enthalpy of formation (ΔfH⦵298)	−80 kJ/mol[2]
Hazards[4][5]
Occupational safety and health (OHS/OSH):
Main hazards	Moderately toxic
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H302, H314, H335, H410
Precautionary statements	P261, P271, P273, P280, P303+P361+P353, P305+P351+P338
NFPA 704 (fire diamond)	3 1 0 COR
Lethal dose or concentration (LD, LC):
LD50 (median dose)	100 — 200 mg/kg[3]
Safety data sheet (SDS)	ICSC 0215 (10%-35% solution)
Related compounds
Other anions	Ammonium chloride Ammonium cyanide
Other cations	Tetramethylammonium hydroxide
Related compounds	Ammonia Hydroxylamine
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Ammonia solution, also known as ammonia water, ammonium hydroxide, ammoniacal liquor, ammonia liquor, aqua ammonia, aqueous ammonia, or (inaccurately) ammonia, is a solution of ammonia in water. It can be denoted by the symbols NH₃(aq). Although the name ammonium hydroxide suggests an alkali with the composition [NH⁺
₄][OH⁻
], it is actually impossible to isolate samples of NH₄OH. The ions NH⁺
₄ and OH⁻ do not account for a significant fraction of the total amount of ammonia except in extremely dilute solutions.^[6]

Basicity of ammonia in water

In aqueous solution, ammonia deprotonates a small fraction of the water to give ammonium and hydroxide according to the following equilibrium:

NH₃ + H₂O ${\displaystyle {\ce {<<=>))}$ NH⁺
₄ + OH⁻.

In a 1 M ammonia solution, about 0.42% of the ammonia is converted to ammonium, equivalent to pH = 11.63 because [NH⁺
₄] = 0.0042 M, [OH⁻] = 0.0042 M, [NH₃] = 0.9958 M, and pH = 14 + log₁₀[OH⁻] = 11.62. The base ionization constant is

K_b = [NH⁺
₄][OH⁻]/[NH₃] = 1.77×10⁻⁵.

Saturated solutions

Like other gases, ammonia exhibits decreasing solubility in solvent liquids as the temperature of the solvent increases. Ammonia solutions decrease in density as the concentration of dissolved ammonia increases. At 15.6 °C (60.1 °F), the density of a saturated solution is 0.88 g/ml and contains 35.6% ammonia by mass, 308 grams of ammonia per litre of solution, and has a molarity of approximately 18 mol/L. At higher temperatures, the molarity of the saturated solution decreases and the density increases.^[7] Upon warming of saturated solutions, ammonia gas is released.

Applications

In contrast to anhydrous ammonia, aqueous ammonia finds few non-niche uses outside of cleaning agents.

Household cleaner

Diluted (1–3%) ammonia is also an ingredient of numerous cleaning agents, including many window cleaning formulas.^[8] Because aqueous ammonia is a gas dissolved in water, as the water evaporates from a window, the gas evaporates also, leaving the window streak-free.

In addition to use as an ingredient in cleansers with other cleansing ingredients, ammonia in water is also sold as a cleaning agent by itself, usually labeled as simply "ammonia". It may be sold plain, lemon-scented (and typically colored yellow), or pine-scented (green). Commonly available ammonia with soap added is known as "cloudy ammonia".

Alkyl amine precursor

In industry, aqueous ammonia can be used as a precursor to some alkyl amines, although anhydrous ammonia is usually preferred. Hexamethylenetetramine forms readily from aqueous ammonia and formaldehyde. Ethylenediamine forms from 1,2-dichloroethane and aqueous ammonia.^[9]

Absorption refrigeration

In the early years of the twentieth century, the vapor absorption cycle using water-ammonia systems was popular and widely used, but after the development of the vapor compression cycle it lost much of its importance because of its low coefficient of performance (about one fifth of that of the vapor compression cycle). Both the Electrolux refrigerator^[10] and the Einstein refrigerator are well known examples of this application of the ammonia solution.

Water treatment

Ammonia is used to produce chloramine, which may be utilised as a disinfectant.^[11] In drinking water, chloramine is preferred over direct chlorination for its ability to remain active in stagnant water pipes longer, thereby reducing the risk of waterborne infections.

Ammonia is used by aquarists for the purposes of setting up a new fish tank using an ammonia process called fishless cycling.^[12] This application requires that the ammonia contain no additives.

Food production

Baking ammonia (ammonium carbonate and ammonium bicarbonate) was one of the original chemical leavening agents. It was obtained from deer antlers.^[13] It is useful as a leavening agent, because ammonium carbonate is heat activated. This characteristic allows bakers to avoid both yeast's long proofing time and the quick CO₂ dissipation of baking soda in making breads and cookies rise. It is still used to make ammonia cookies and other crisp baked goods, but its popularity has waned because of ammonia's off-putting smell and concerns over its use as a food ingredient compared to modern-day baking powder formulations. It has been assigned E number E527 for use as a food additive in the European Union.

Aqueous ammonia is used as an acidity regulator to bring down the acid levels in food. It is classified in the United States by the Food and Drug Administration as generally recognized as safe (GRAS) when using the food grade version.^[14] Its pH control abilities make it an effective antimicrobial agent.

Furniture darkening

In furniture-making, ammonia fuming was traditionally used to darken or stain wood containing tannic acid. After being sealed inside a container with the wood, fumes from the ammonia solution react with the tannic acid and iron salts naturally found in wood, creating a rich, dark stained look to the wood. This technique was commonly used during the arts and crafts movement in furniture – a furniture style which was primarily constructed of oak and stained using these methods.^[15]

Treatment of straw for cattle

Ammonia solution is used to treat straw, producing "ammoniated straw" making it more edible for cattle.^[16]

Laboratory use

Aqueous ammonia is used in traditional qualitative inorganic analysis as a complexant and base. Like many amines, it gives a deep blue coloration with copper(II) solutions. Ammonia solution can dissolve silver oxide residues, such as those formed from Tollens' reagent. It is often found in solutions used to clean gold, silver, and platinum jewelry, but may have adverse effects on porous gem stones like opals and pearls.^[17]