What is ammonium nitrate, the probable cause of the explosion in Beirut

From fertilizer to instant ice. Ammonium nitrate is a very versatile, inexpensive and easily available compound. So much so that it is also used to produce explosives. But what exactly is it?

(photo: Daniel Carde / Getty Images) The victims are over 100, while the injured are over 4 thousand. Numbers that, unfortunately, are destined to increase, in a disaster that perhaps could have been avoided. The huge explosion in the port area of ​​Beirut, Lebanon, in fact, was probably caused, according to the first reconstructions, by the outbreak of a deposit containing over 2,700 tons of ammonium nitrate. Site, therefore, considered dangerous that would have been reported over and over again by customs officials to have the authorization to transfer the material, unfortunately so far never granted. But what exactly is it about?

The ammonium nitrate (the formula is NH 4 NO 3 ) is a chemical compound that has crystals, colourless and odourless, highly soluble in water and is very versatile : it is, for example, the active component of the instant ice pack , used for example by athletes to relieve pain, and is commonly used in agriculture as a fertilizer (source of nitrogen for plants). But also for the production of explosives such as ammonal, and the Anfo (Ammonnium Nitrate Fuel Oil). Due to its easy availability, being economical and safe, in fact, ammonium nitrate has been used both for civilian purposes (quarries and mines), both for military purposes and terrorist, where it is used in mixture with other substances for the manufacture of explosives . Previous accidents, as well as the last of Beirut , they saw as co-responsible for the ammonium nitrate . Recall, for example, the disaster of Texas City, which occurred April 16, 1947 explosion at the port of Tientsion (or Tianjin) in northern China, August 12, 2015 that caused hundreds of victims.

what you are now asking how it can be generated the explosion in Beirut . Ammonium nitrate pure, in fact, is chemically quite stable and can not, therefore, to burn alone. However, in certain conditions (such as closed spaces) and at particularly high temperatures, such as those of an explosion or a fire , the compound may decompose releasing gaseous substances such as nitrogen oxides so quickly to trigger the outbreak. “It is plausible that the ammonium nitrate face a disaster of this kind,” comments on Instagram, the chemist Dario Bressanini . “One of the problems with ammonium nitrate is that it contains the oxygen necessary for decomposition and, therefore, can explode also in closed places” . Perhaps, then, given that the compound is stable, and there were combustible materials that created the fire around the deposit. The ammonium nitrate, then, can melt and leach into environments that are less open to the air: here the nitrous oxide generated by the decomposition system compensates for the lack of oxygen , continuing to supply the combustion indoors, until the gases released, which does not have a vent valve, to generate the burst.