As terrorists increasingly use
ammonium nitrate (a commonly used agricultural fertilizer) for their bombs (by
mixing it with fuel oil and setting it off with a detonator), there has been a
lot of research by chemical and fertilizer manufacturers to reformulate
ammonium nitrate so that it will not so easily explod. The Honeywell
corporation found that by adding some ammonium sulfate to the ammonium nitrate,
you actually improve the fertilizing ability of the mix (by making the treated soil
less acidic), and prevent the fertilizer from being used as an explosive.
Actually, you can still use the ammonium sulfate nitrate mix as an explosive,
but it requires some creative chemistry to do so, and serves as a technological
barrier for most terrorist groups.
has long used ammonium nitrate as an explosive in large bombs (usually five
tons or more of ammonium nitrate, fuel oil and powdered aluminum) and would continue to do so. But plain old
ammonium nitrate would be reclassified as "military grade explosives
material" and its sale would be restricted.