Ammonium sulfate

Ammonium sulfate
IUPAC name
Ammonium sulfate
Other names
ammonium sulfate (2:1)
diammonium sulfate
sulfuric acid diammonium salt
mascagnite
Actamaster
Dolamin
Identifiers
CAS number 7783-20-2 YesY
ChemSpider 22944
Properties
Molecular formula (NH4)2SO4
Molar mass 132.14 g/mol
Appearance Fine white hygroscopic granules or crystals.
Density 1.769 g/cm3 (20 °C)
Melting point

235-280 °C, 508-553 K, 455-536 °F (decomposes)
Solubility in water 70.6 g/100 mL (0 °C)

74.4 g/100 mL (20 °C)
103.8 g/100 mL (100 °C)[1]
Solubility insoluble in acetone, alcohol and ether
Critical relative humidity 79.2% (30 °C)
Hazards
EU Index Not listed
NFPA 704
NFPA 704.svg
1
2
0
Flash point Non-flammable
LD50 2840 mg/kg, rat (oral)
Related compounds
Other anions Ammonium thiosulfate
Ammonium sulfite
Ammonium bisulfate
Ammonium persulfate
Other cations Sodium sulfate
Potassium sulfate
Related compounds Ammonium iron(II) sulfate
 YesY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Ammonium sulfate (IUPAC-recommended spelling; also ammonium sulphate in British English), (NH4)2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen as ammonium cations, and 24% sulfur as sulfate anions. In fertilizer the purpose of the sulfate is to reduce the soil pH.

Contents

Uses

It is used largely as an artificial fertilizer for alkaline soils. In the soil the sulfate ion is released and forms bisulfate, lowering the pH balance of the soil (as do other sulfate compounds such as aluminium sulfate), while contributing essential nitrogen for plant growth.

It is also used as an agricultural spray adjuvant 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, and glufosinate herbicides.

It is also used in the preparation of other ammonium salts.

In biochemistry, ammonium sulfate precipitation is a common method for purifying proteins by precipitation. As such, ammonium sulfate is also listed as an ingredient for many United States vaccines per the Center for Disease Control.[2]

Ammonium sulfate is also a food additive.[3][4]

A saturated solution of ammonium sulfate in heavy water (D2O) is used as an external standard in sulfur (33S) NMR spectroscopy with shift value of 0 ppm.

It has also been used in flame retardant compositions acting much like Diammonium phosphate. As a flame retardant, it lowers the combustion temperature of the material, decreases maximum weight loss rates, and causes an increase in the production of residue or char.[5]

In November 2009, a ban on ammonium sulfate, ammonium nitrate and calcium ammonium nitrate fertilizers was imposed in the Malakand Division - comprising the Dir, Swat, Chitral and Malakand districts of the North West Frontier Province (NWFP) of Pakistan, by the NWFP government, following reports that those chemicals were used by militants to make explosives. In January 2010, these substances were also banned in Afghanistan for the same reason.

Preparation

Ammonium sulfate is made by reacting synthetic ammonia (or by-product ammonia from coke-ovens) with sulfuric acid:[6]

2 NH3 + H2SO4 → (NH4)2SO4

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 present in the system, forming a powdery salt.

Ammonium sulfate also is manufactured from gypsum (CaSO4·2H2O). Finely divided gypsum is added to an ammonium carbonate solution. Calcium carbonate precipitates out, leaving ammonium sulfate in the solution.

(NH4)2CO3 + CaSO4 → (NH4)2SO4 + CaCO3

Ammonium sulfate occurs naturally as the rare mineral mascagnite in volcanic fumaroles and due to coal fires on some dumps.[7]

Reactions

Ammonium sulfate decomposes upon heating at 100 °C in an open system, forming ammonium bisulfate. As a salt of a strong acid (i.e. H2SO4) and weak base (i.e. NH3), its solution is acidic; pH of 0.1M solution is 5.5.

In aqueous solution the reactions are those of NH4+ and SO4−2 ions. For example, addition of barium chloride, precipitates out barium sulfate. The filtrate on evaporation yields ammonium chloride.

Ammonium sulfate forms many double salts (ammonium metal sulfates) when its solution is mixed with equimolar solutions of metal sulfates and the solution is slowly evaporated. Such double metal sulfates include ammonium cobaltous sulfate, ferric ammonium sulfate, ammonium nickel sulfate and ammonium cerous sulfate. [6]

References

  1. ↑ Handbook of Chemistry and Physics
  2. ↑ Pink Book | Appendix B: Vaccine Excipient & Media Summary, Part 2
  3. ↑ Panera Bread › Menu & Nutrition › Nutrition Information Profile
  4. ↑ Official Subway Restaurants U.S. Products Ingredients Guide
  5. ↑ George, C.W.; Susott, R.A. (April 1971), "Effects of Ammonium Phosphate and Sulfate on the Pyrolysis and Combustion of Cellulose", Research Paper INT-90 (Intermountain Forest and Range Experiment Station: USDA Forest Service), http://openlibrary.org/b/OL16022833M/Effects_of_ammonium_phosphate_and_sulfate_on_the_pyrolysis_and_combustion_of_cellulose 
  6. ↑ 6.0 6.1 Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
  7. ↑ http://www.mindat.org/min-2584.html/ Mindat data

Further reading