Investigators have determined that ammonium nitrate was the cause of the explosion at a West

Investigators have determined that ammonium nitrate was the cause of the explosion at a West,  fertiliser plant last month that left 14 people dead and some 200 injured, a spokeswoman for the Texas state fire marshal's office said on Tuesday.

"The investigators have been able to narrow down the origin to the fertilizer and seed building on site, and we also know that what caused the explosion was the ammonium nitrate," said Rachel Moreno, a spokeswoman for the Texas state fire marshal's office. "What we don't know is exactly why."

The fire marshal's office has been leading the investigation of the April 17 blast, along with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).

Ammonium nitrate is a dry fertiliser mixed with other fertilisers such as phosphate and applied to crops to promote growth. It can be combustible under certain conditions, and was used as an ingredient in the Oklahoma City bombing in 1995 that left 168 people dead.

Ammonium nitrate - research history and main purposes

Ammonium nitrate - research history

Ammonium nitrate in 1659, German J.R. Gelaobeier first obtained ammonium nitrate. The end of the nineteenth Century, the Europeans with ammonium sulfate and nitrate by double decomposition reaction of ammonium nitrate production. Due to the large-scale development of synthetic ammonia industry, ammonium nitrate production was rich in raw materials, in the middle of twentieth Century has obtained the rapid development, the Second World War, some countries established the ammonium nitrate plant, used in the manufacture of explosives. In 60, the ammonium nitrate was the leading varieties of nitrogen fertilizer. China has established a number of ammonium nitrate plant in the 50's..

In 40, in order to prevent hygroscopicity and caking of ammonium nitrate, were coated with paraffin wax and other organic matter, because it had detonated explosion in shipping. Therefore, some countries have established the relevant agricultural ammonium nitrate production, storage and transportation management regulations, some countries have even banned ammonium nitrate transport and fertilizer use, are only allowed to use it with calcium ammonium nitrate and calcium carbonate mixture. At the beginning, calcium ammonium nitrate containing N20.5%, equivalent to about 60% containing ammonium nitrate. Now content increased to N26%, the equivalent of 75% containing ammonium nitrate.

Because later mastered the use of ammonium nitrate, some countries such as France, the Soviet Union, Romania, the United States of America and Britain, allowing the ammonium nitrate directly used as fertilizer, but for the safe use of the product standards. For example: the United States of America fertilizer association rules of solid ammonium nitrate for agricultural use of pH shall not be less than 4 (10% of ammonium nitrate in aqueous solution containing C PH); shall not exceed 0.2%; S shall not exceed 0.01%; Cl- containing not more than 0.15%.

Ammonium nitrate - main purposes

Agriculture as a cotton, flax, hemp, tobacco and vegetable crops such as fertilizer, the effect is very good; also used in compound fertilizer manufacturing potassium, phosphorus, calcium and so on. Explosive industry for manufacturing perchlorate explosive, ammonium nitrate fuel oil and slurry explosives and other raw materials. Making a two oxidation nitrogen, nitrous oxide used in pharmaceutical industry (anesthetic), vitamin B. Manufacturing alkali-free glass used in glass industry. In addition, the refrigerant, can also be used to manufacture micro bacteria agent, fireworks, music bug agent, catalyst. [1]

Used as an oxidizing agent, refrigerant, fireworks and explosive materials.