Ammonium sulfate

Ammonium sulfate, ((NH4)2SO4), is an inorganic chemical compound commonly used as a fertilizer. It contains 21% nitrogen as ammonium ions and 24% sulfur as sulfate ions.

Properties
Ammonium sulfate is not soluble in alcohol or liquid ammonia. The compound is slightly hygroscopic and absorbs water from the air at relative humidity > 81% (at ca. 20°C).

Synthesis
Ammonium sulfate is prepared commercially by reacting ammonia with sulfuric acid (H2SO4). Ammonium sulfate is prepared commercially from the ammoniacal liquor of gas-works and is purified by recrystallisation. It forms large rhombic prisms, has a somewhat saline taste and is easily soluble in water. The aqueous solution on boiling loses some ammonia and forms an acid sulfate.

Uses
It is used largely as an artificial fertilizer for alkaline soils. In the soil the sulfate ion is released and forms sulfuric acid, 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.

Ammonium sulfate is also listed as an ingredient for many United States vaccines per the Center for Disease Control.

Ammonium sulfate is also a food additive.