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| Names | |||
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| IUPAC name Ammonium hydroxide | |||
Other names
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| Identifiers | |||
3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider |
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| ECHA InfoCard | 100.014.225 | ||
| EC Number |
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| E number | E527(acidity regulators, ...) | ||
| KEGG |
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| RTECS number |
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| UNII | |||
| UN number | 2672 | ||
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| Properties[1] | |||
| 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) | ||
| Miscible | |||
| −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 and irritating towards mucous membranes | ||
| GHS labelling: | |||
    | |||
| Danger | |||
| H302,H314,H335,H410 | |||
| P261,P271,P273,P280,P303+P361+P353,P305+P351+P338 | |||
| NFPA 704 (fire diamond) | |||
| 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 | |||
Otheranions | Ammonium chloride Ammonium cyanide | ||
Othercations | Tetramethylammonium hydroxide | ||
Related compounds | Ammonia Hydroxylamine | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Ammonia solution, also known asammonia water,ammonium hydroxide,ammoniacal liquor,ammonia liquor,aqua ammonia,aqueous ammonia, or (inaccurately)ammonia, is a solution ofammonia in water. It can be denoted by the symbols NH3(aq). Although the name ammonium hydroxide suggests asalt with thecomposition[NH+
4][OH−
], it is impossible to isolate samples of NH4OH. The ionsNH+
4 and OH− do not account for a significant fraction of the total amount of ammonia except in extremely dilute solutions.[6]
The concentration of such solutions is measured in units of theBaumé scale (density), with 26 degrees Baumé (about 30% of ammonia by weight at 15.5 °C or 59.9 °F) being the typical high-concentration commercial product.[7]
In aqueous solution, ammoniadeprotonates a small fraction of the water to giveammonium andhydroxide according to the followingequilibrium:
In a 1 Mammonia solution, about 0.42% of the ammonia is converted to ammonium, equivalent to pH = 11.63because [NH+
4] = 0.0042 M, [OH−] = 0.0042 M, [NH3] = 0.9958 M, and pH = 14 + log10[OH−] = 11.62. Thebase ionization constant is
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; it contains 35.6% ammonia by mass, 308 grams of ammonia per litre of solution, and has amolarity of approximately 18 mol/L. At higher temperatures, the molarity of the saturated solution decreases and the density increases.[8] Upon warming of saturated solutions, ammonia gas is released.
In contrast to anhydrous ammonia, aqueous ammonia finds few non-niche uses outside ofcleaning agents.
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Ammonia solutions are used as a cleaning products for many surfaces and applications. Ammonia in water is sold as a cleaning agent by itself, usually labeled as simply "ammonia", as well as in cleaning products combined with other ingredients. 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".
Household ammonia ranges in concentration by weight from 5% to 10% ammonia.[9] Because aqueous ammonia is a gas dissolved in water, as the water evaporates from a surface, the gas evaporates also, leaving the surface streak-free. Its most common uses are to cleanglass,[10]porcelain, andstainless steel. It is good at removing grease and is found in products for cleaning ovens and for soaking items to loosen baked-on grime. Experts also warn not to use ammonia-based cleaners on cartouchscreens, due to the risk of damage to the screen'santi-glare and anti-fingerprint coatings.[11]
More concentrated solutions (higher than 10%) are used for in professional and industrial cleaning products.
US manufacturers of cleaning products are required to provide the product'smaterial safety data sheet that lists the concentration used.[12] Solutions of ammonia can be dangerous. These solutions are irritating to the eyes andmucous membranes (respiratory and digestive tracts), and to a lesser extent the skin. Experts advise that caution be used to ensure the chemical is not mixed into any liquid containingbleach, due to the danger of forming toxic chloramine gas. Mixing withchlorine-containing products or strong oxidants, such as household bleach, can generate toxicchloramine fumes.[13]
In industry, aqueous ammonia can be used as a precursor to somealkyl amines, although anhydrous ammonia is usually preferred.Hexamethylenetetramine forms readily from aqueous ammonia andformaldehyde.Ethylenediamine forms from1,2-dichloroethane and aqueous ammonia.[14]
In the early years of the twentieth century, thevapor 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 lowcoefficient of performance (about one fifth of that of the vapor compression cycle). Both the Electrolux refrigerator[15] and theEinstein refrigerator are well known examples of this application of the ammonia solution.
Ammonia is used to producechloramine, which may be utilised as a disinfectant.[16] In drinking water, chloramine is preferred over directchlorination for its ability to remain active in stagnant water pipes longer, thereby reducing the risk of waterborne infections.
Ammonia is used byaquarists for the purposes of setting up a new fish tank using an ammonia process calledfishless cycling.[17] This application requires that the ammonia contain no additives.
Baking ammonia (ammonium carbonate andammonium bicarbonate) was one of the original chemicalleavening agents. It was obtained from deer antlers.[18] 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 quickCO2 dissipation of baking soda in making breads and cookies rise. It is still used to makeammonia 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 assignedE number E527 for use as a food additive in theEuropean Union.
Aqueous ammonia is used as anacidity regulator to bring down the acid levels in food. It is classified in theUnited States by theFood and Drug Administration asgenerally recognized as safe (GRAS) when using the food grade version.[19] Its pH control abilities make it an effectiveantimicrobial agent.
In furniture-making,ammonia fuming was traditionally used to darken or stain wood containingtannic 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 theArts and Crafts movement in furniture – a furniture style which was primarily constructed of oak and stained using these methods.[20]
Ammonia solution is used to treat straw, producing "ammoniated straw" making it more edible forcattle.[21]
Ammonia solution is not used for the treatment of straw and other stover, Anhydrous Ammonia,or NH3 is used, ammoniating stover raises the protein content, and makes the feed more palatable.
Aqueous ammonia is used in traditionalqualitative 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 fromTollens' 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.[22]
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