Ammonium Sulfate

OVERVIEW

Ammonium sulfate (uh-MOH-ni-um SUL-fate) is an odorless, colorless to white crystalline solid that occurs in nature as the mineral mascagnite. In 2004, 2.6 million metric tons (2.9 million short tons) of the compound were produced in the United States, placing it in 21st place among chemicals made in that year. More than 95 percent of the ammonium sulfate produced is used in the production of fertilizers.

KEY FACTS

OTHER NAMES:

Diammonium sulfate; sulfuric acid, diammonium salt

FORMULA:

(NH₄)₂SO₄

ELEMENTS:

Nitrogen, hydrogen, sulfur, oxygen

COMPOUND TYPE:

Inorganic salt

STATE:

Solid

MOLECULAR WEIGHT:

132.14 g/mol

MELTING POINT:

Not applicable; decomposes above 235°C (455°F)

BOILING POINT:

Not applicable

SOLUBILITY:

Soluble in water; insoluble in alcohol, acetone, and other common organic solvents

HOW IT IS MADE

The primary method of preparation for ammonium sulfate is the direction reaction between ammonia gas (NH₃) and sulfuric acid (H₂SO₄). The ammonium sulfate produced in the reaction is recovered as white crystals after evaporation of the water present in the reaction mixture. Other methods of preparation are also used. For example, gypsum (CaSO₄·2H₂O) can be treated with ammonia (NH₃) and carbon dioxide (CO₂) to generate ammonium sulfate.

COMMON USES AND POTENTIAL HAZARDS

Ammonium sulfate is used as a fertilizer because it supplies nitrogen and sulfur, two nutrients that plants need to grow properly. Lesser quantities of the compound are utilized in water treatment plants where it is used to control the acidity of the water being processed. Among other uses of ammonium sulfate are:

• In the tanning of leather;
• As a fireproofing agent for fabrics and paper;
• In the manufacture of viscose rayon;
• As an additive to cattle feed
• As a nutrient in bacterial cultures;
• In the processing of certain metals, such as chromium and gold; and
• In the manufacture of polymers used in the production of chipboard.

Interesting Facts

The German alchemist Andreas Libau (c.1540–1616), better known by his Latinized name of Libavius, wrote what is widely regarded as the first textbook on chemistry in 1597. In that book, Alchemia, he described a method for making ammonium sulfate, probably the first mention of the compound in modern sources.

Words to Know

ALCHEMY

Ancient field of study from which the modern science of chemistry evolved.

POLYMER

A compound consisting of very large molecules made of one or two small repeated units called monomers.

FOR FURTHER INFORMATION

"Ammonium Sulfate." Hazardous Substances Data Bank. http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@na+Ammonium+Sulfate (accessed on September 20, 2005).

"Ammonium Sulfate Advantage: FAQs." Honeywell. http://www.sulfn.com/main/pages/faqs.asp (accessed on July 22, 2005).

"Ammonium Sulfate Industrial Grade." BASF. http://www.basf.de/en/produkte/chemikalien/anorganika/ammonium/ammoniumsulfat_industrial.htm?id=V00-YYuHV7-Ro7bsf1Gb (accessed on September 20, 2005).

Bariyanga, Joseph. "Fertilizer." Chemistry: Foundations and Applications. Edited by J. J. Lagowski. Vol. 2. New York: Macmillan Reference USA, 2004.

See AlsoAmmonia; Sulfuric Acid