Wednesday night, ammonium nitrate exploded with deadly results at the West Fertilizer Company plant near Waco, Texas.
Ammonium nitrate is a capricious chemical. Fertilizers made with the chemical provide nitrogen to crops, which helps them grow leaves and maintain their green color. However, ammonium nitrate can also break down rapidly and produce a tremendous amount of heat. In other words, it explodes.
When exposed to an intense shock or high heat, ammonium nitrate decomposes quickly into nitrogen, oxygen and water. This chemical reaction is exothermic, meaning it expels heat.
The heat can trigger a chemical chain reaction in which a large amount of ammonium nitrate decomposes at once and produces the lethal explosion of fertilizer plants or bombs.
During fertilizer production, high-pressure tanks keep ammonium nitrate in a liquid state. If those tanks rupture, the liquid becomes a gas and mixes with oxygen in the air. This combination explodes easily.
The exact circumstances of the fire and explosion at the West Fertilizer Company plant remain to be pieced together from the wreckage.
The recent disaster occurred one day after the 66th anniversary of another ammonium nitrate catastrophe in Texas. On April 16, 1947, nearly 600 people died when approximately 2,300 tons of ammonium nitrate exploded in the port of Texas City, southeast of Houston, Texas.
The United States Department of Homeland Security and other government agencies monitor and regulate the sale and transport of ammonium nitrate, since it can easily be made into an explosive. For example, in 1995 a truck bomb detonated diesel fuel that spurred the explosive chemical reaction of ammonium nitrate and massacred 168 people in the Oklahoma City bombing.
Despite its deadly potential, the chemical serves many purposes in the United States.
A mixture of ammonium nitrate and fuel blasts holes for miners. Ammonium fertilizers feeds plants for farmers. The instant cold packs found in first aid kits use a form of ammonium nitrate. When the chemical is mixed with water, it sucks heat from the environment and makes the cold pack an easily portable stand-in for an ice pack.
Image: A fire burns at a fertilizer plant in West, Texas after an explosion Wednesday April 17, 2013. Credit: Michael Ainsworth/The Dallas Morning News/Corbis