Ammonium sulfate (American English and international scientific usage; ammonium sulphate in
British English
British English (BrE, en-GB, or BE) is, according to Lexico, Oxford Dictionaries, "English language, English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the English language in ...
); (NH
4)
2SO
4, is an inorganic
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21%
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
and 24%
sulfur.
Uses
The primary use of ammonium sulfate is as a
fertilizer
A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
for
alkaline soil
Alkali, or Alkaline, soils are clay soils with high pH (greater than 8.5), a poor soil structure and a low infiltration capacity. Often they have a hard calcareous layer at 0.5 to 1 metre depth. Alkali soils owe their unfavorable physico ...
s. In the soil the
ammonium ion is released and forms a small amount of acid, lowering the
pH balance of the
soil
Soil, also commonly referred to as earth or dirt
Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty.
Common types of dirt include:
* Debri ...
, while contributing essential
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
for plant growth. The main disadvantage to the use of ammonium sulfate is its low nitrogen content relative to
ammonium nitrate
Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...
, which elevates transportation costs.
[Karl-Heinz Zapp "Ammonium Compounds" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2012, Wiley-VCH, Weinheim. ]
It is also used as an agricultural spray
adjuvant In pharmacology, an adjuvant is a drug or other substance, or a combination of substances, that is used to increase the efficacy or potency of certain drugs. Specifically, the term can refer to:
* Adjuvant therapy in cancer management
* Analgesi ...
for water-soluble
insecticides,
herbicides, and
fungicides. There, it functions to bind iron and calcium cations that are present in both well water and plant cells. It is particularly effective as an adjuvant for
2,4-D (amine),
glyphosate
Glyphosate (IUPAC name: ''N''-(phosphonomethyl)glycine) is a broad-spectrum systemic herbicide and crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by inhibiting the plant enzyme 5-enolpyruvylshik ...
, and
glufosinate
Glufosinate (also known as phosphinothricin and often sold as an ammonium salt) is a naturally occurring broad-spectrum herbicide produced by several species of ''Streptomyces'' soil bacteria. Glufosinate is a non-selective, contact herbicide, w ...
herbicides.
Laboratory use
Ammonium sulfate precipitation is a common method for
protein purification Protein purification is a series of processes intended to isolate one or a few proteins from a complex mixture, usually cells, tissues or whole organisms. Protein purification is vital for the specification of the function, structure and interact ...
by precipitation. As the
ionic strength of a solution increases, the solubility of proteins in that solution decreases. Ammonium sulfate is extremely soluble in water due to its ionic nature, therefore it can "salt out" proteins by precipitation. Due to the high
dielectric constant of water, the dissociated salt ions being cationic ammonium and anionic sulfate are readily solvated within hydration shells of water molecules. The significance of this substance in the purification of compounds stems from its ability to become more so hydrated compared to relatively more
nonpolar molecules
In chemistry, polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively charged end and a positively charged end.
Polar molecules must contain one or more polar ...
and so the desirable nonpolar molecules coalesce and precipitate out of the solution in a concentrated form. This method is called
salting out
Salting out (also known as salt-induced precipitation, salt fractionation, anti-solvent crystallization, precipitation crystallization, or drowning out) is a purification technique that utilizes the reduced solubility of certain molecules in a s ...
and necessitates the use of high salt concentrations that can reliably dissolve in the aqueous mixture. The percentage of the salt used is in comparison to the maximal concentration of the salt in the mixture can dissolve. As such, although high concentrations are needed for the method to work adding an abundance of the salt, over 100%, can also oversaturate the solution, therefore, contaminating the nonpolar precipitate with salt precipitate. A high salt concentration, which can be achieved by adding or increasing the concentration of ammonium sulfate in a solution, enables protein separation based on a decrease in protein solubility; this separation may be achieved by
centrifugation. Precipitation by ammonium sulfate is a result of a reduction in solubility rather than
protein denaturation
In biochemistry, denaturation is a process in which proteins or nucleic acids lose the quaternary structure, tertiary structure, and secondary structure which is present in their native state, by application of some external stress or comp ...
, thus the precipitated protein can be solubilized through the use of standard
buffers. Ammonium sulfate precipitation provides a convenient and simple means to fractionate complex protein mixtures.
In the analysis of rubber lattices, volatile fatty acids are analyzed by precipitating rubber with a 35% ammonium sulfate solution, which leaves a clear liquid from which volatile fatty acids are regenerated with sulfuric acid and then distilled with steam. Selective precipitation with ammonium sulfate, opposite to the usual precipitation technique which uses acetic acid, does not interfere with the determination of volatile fatty acids.
Food additive
As a food additive, ammonium sulfate is considered
generally recognized as safe (GRAS) by the U.S.
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
, and in the European Union it is designated by the
E number E517. It is used as an
acidity regulator in flours and breads.
Other uses
In the
treatment of
drinking water
Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, a ...
, ammonium sulfate is used in combination with
chlorine
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
to generate
monochloramine
Monochloramine, often called chloramine, is the chemical compound with the formula NH2Cl. Together with dichloramine (NHCl2) and nitrogen trichloride (NCl3), it is one of the three chloramines of ammonia. It is a colorless liquid at its melting p ...
for disinfection.
Ammonium sulfate is used on a small scale in the preparation of other ammonium salts, especially
ammonium persulfate
Ammonium persulfate (APS) is the inorganic compound with the formula (NH4)2S2O8. It is a colourless (white) salt that is highly soluble in water, much more so than the related potassium salt. It is a strong oxidizing agent that is used as a catalys ...
.
Ammonium sulfate is listed as an ingredient for many United States vaccines per the
Centers for Disease Control
The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
.
A saturated solution of ammonium sulfate in
heavy water (D
2O) is used as an external standard in sulfur (
33S)
NMR spectroscopy
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fie ...
with shift value of 0 ppm.
Ammonium sulfate has also been used in
flame retardant
The term flame retardants subsumes a diverse group of chemicals that are added to manufactured materials, such as plastics and textiles, and surface finishes and coatings. Flame retardants are activated by the presence of an ignition source and ...
compositions acting much like
diammonium phosphate
Diammonium phosphate (DAP; IUPAC name diammonium hydrogen phosphate; chemical formula (NH4)2(HPO4) is one of a series of water-soluble ammonium phosphate salts that can be produced when ammonia reacts with phosphoric acid.
Solid diammonium phosp ...
. As a flame retardant, it increases the combustion temperature of the material, decreases maximum weight loss rates, and causes an increase in the production of residue or char. Its flame retardant efficacy can be enhanced by blending it with
ammonium sulfamate
Ammonium sulfamate (or ammonium sulphamate) is a white crystalline solid, readily soluble in water. It is commonly used as a broad spectrum herbicide, with additional uses as a compost accelerator, flame retardant and in industrial processes.
Man ...
. It has been used in
aerial firefighting
Aerial may refer to:
Music
* ''Aerial'' (album), by Kate Bush
* ''Aerials'' (song), from the album ''Toxicity'' by System of a Down
Bands
*Aerial (Canadian band)
* Aerial (Scottish band)
* Aerial (Swedish band)
Performance art
* Aerial sil ...
.
Ammonium sulfate has been used as a
wood preservative
Wood easily degrades without sufficient preservation. Apart from structural wood preservation measures, there are a number of different chemical preservatives and processes (also known as "timber treatment", "lumber treatment" or "pressure treat ...
, but due to its hygroscopic nature, this use has been largely discontinued because of associated problems with metal fastener corrosion, dimensional instability, and finish failures.
Preparation
Ammonium sulfate is made by treating
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
with
sulfuric acid:
: 2 NH
3 + H
2SO
4 → (NH
4)
2SO
4
A mixture of ammonia gas and water vapor is introduced into a reactor that contains a saturated solution of ammonium sulfate and about 2 to 4% of free sulfuric acid at 60 °C. Concentrated sulfuric acid is added to keep the solution acidic, and to retain its level of free acid. The heat of reaction keeps reactor temperature at 60 °C. Dry, powdered ammonium sulfate may be formed by spraying sulfuric acid into a reaction chamber filled with ammonia gas. The heat of reaction evaporates all
water
Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
present in the system, forming a powdery salt. Approximately 6,000 million tons were produced in 1981.
[
Ammonium sulfate also is manufactured from ]gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywal ...
(CaSO4·2H2O). Finely divided gypsum is added to an ammonium carbonate
Ammonium carbonate is a salt with the chemical formula (NH4)2CO3. Since it readily degrades to gaseous ammonia and carbon dioxide upon heating, it is used as a leavening agent and also as smelling salt. It is also known as baker's ammonia and is ...
solution. Calcium carbonate precipitates as a solid, leaving ammonium sulfate in the solution.
: (NH4)2CO3 + CaSO4 → (NH4)2SO4 + CaCO3
Ammonium sulfate occurs naturally as the rare mineral mascagnite
Mascagnite is a rare ammonium sulfate mineral ( N H4)2 S O4. It crystallizes in the orthorhombic system typically forming as stalactitic masses exhibiting good cleavage. It is soft (not higher than 2.5 on the Mohs Scale) and water-soluble. Opti ...
in volcanic fumarole
A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...
s and due to coal fires on some dumps.
Properties
Ammonium sulfate becomes ferroelectric
Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are also piezoelectric and pyroelectric, with the ad ...
at temperatures below –49.5 °C. At room temperature it crystallises in the orthorhombic system, with cell sizes of ''a'' = 7.729 Å, ''b'' = 10.560 Å, ''c'' = 5.951 Å. When chilled into the ferrorelectric state, the symmetry of the crystal changes to space group
In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...
Pna21.
Reactions
Ammonium sulfate decomposes upon heating above , first forming ammonium bisulfate
Ammonium bisulfate, also known as ammonium hydrogen sulfate, is a white, crystalline solid with the chemical formula, formula (NH4)HSO4. This salt is the product of the half-neutralization of sulfuric acid by ammonia.
Production
It is commonly co ...
. Heating at higher temperatures results in decomposition into ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
, nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
, sulfur dioxide, and water.
As a salt of a strong acid (H2SO4) and weak base (NH3), its solution is acidic; pH of 0.1 M solution is 5.5. In aqueous solution the reactions are those of NH4+ and SO4−2 ions. For example, addition of barium chloride
Barium chloride is an inorganic compound with the formula Ba Cl2. It is one of the most common water-soluble salts of barium. Like most other water-soluble barium salts, it is white, highly toxic, and imparts a yellow-green coloration to a flame. ...
, precipitates out barium sulfate. The filtrate on evaporation yields ammonium chloride.
Ammonium sulfate forms many double salt
A double salt is a salt that contains two or more different cations or anions. Examples of double salts include alums (with the general formula ) and Tutton's salts (with the general formula ). Other examples include potassium sodium tartrate, a ...
s (ammonium metal sulfates) when its solution is mixed with equimolar solutions of metal sulfates and the solution is slowly evaporated. With trivalent metal ions, alums such as ferric ammonium sulfate are formed. Double metal sulfates include ammonium cobaltous sulfate, ferrous diammonium sulfate, ammonium nickel sulfate which are known as Tutton's salts
Tutton's salts are a family of salts with the formula M2M'(SO4)2(H2O)6 (sulfates) or M2M'(SeO4)2(H2O)6 (selenates). These materials are double salts, which means that they contain two different cations, M+ and M'2+ crystallized in the same regular ...
and ammonium ceric sulfate.[ Anhydrous double sulfates of ammonium also occur in the ]Langbeinites
Langbeinites are a family of crystalline substances based on the structure of langbeinite with general formula , where M is a large univalent cation (such as potassium, rubidium, caesium, or ammonium), and M' is a small divalent cation (for examp ...
family. The ammonia produced has a pungent smell and is toxic.
Airborne particles of evaporated ammonium sulfate comprise approximately 30% of fine particulate pollution worldwide.
Legislation and control
In November 2009, a ban on ammonium sulfate, ammonium nitrate
Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...
and calcium ammonium nitrate fertilizers was imposed in the former Malakand Division
Malakand Division is an administrative division of the Khyber Pakhtunkhwa of Pakistan. It contains the following districts:
Districts
* Bajaur District
* Buner District
* Upper Chitral District
* Lower Chitral District
* Lower Dir Distric ...
—comprising the Upper Dir
Upper Dir District ( ps, بر دير ولسوالۍ, ur, ) is a district in Malakand Division of Khyber Pakhtunkhwa province in Pakistan. The city of Dir is the district headquarters. Badogai Pass connects it to Utror.
At the time of indepen ...
, Lower Dir
Lower Dir District ( ps, لر / کوز دير ولسوالۍ, ur, ) is a district of Khyber Pakhtunkhwa province in Pakistan. Timergara city is the district headquarter and largest city. The district was formed in 1996, when Dir District was d ...
, Swat, Chitral and Malakand districts of the North West Frontier Province
The North-West Frontier Province (NWFP; ps, شمال لویدیځ سرحدي ولایت, ) was a Chief Commissioner's Province of British India, established on 9 November 1901 from the north-western districts of the Punjab Province. Followin ...
(NWFP) of Pakistan
Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's fifth-most populous country, with a population of almost 243 million people, and has the world's second-lar ...
, by the NWFP government, following reports that they were used by militants to make explosives. In January 2010, these substances were also banned in Afghanistan
Afghanistan, officially the Islamic Emirate of Afghanistan,; prs, امارت اسلامی افغانستان is a landlocked country located at the crossroads of Central Asia and South Asia. Referred to as the Heart of Asia, it is bordere ...
for the same reason.
See also
* Ammonium sulfate precipitation
References
Further reading
* Properties: UNIDO and International Fertilizer Development Center (1998), ''Fertilizer Manual'', Kluwer Academic Publishers, .
External links
*
*Calculators
surface tensions
an
densities, molarities and molalities
of aqueous ammonium sulfate
{{Authority control
Ammonium compounds
Sulfates
Fire suppression agents
Inorganic fertilizers
Food additives
Food stabilizers
E-number additives