Synthesis of ammonium nitrate
Ammonium nitrate is primarily used as a fertilizer, and it used to be available from agricultural supply stores and well stocked garden shops. It has become very hard to find due to its prevalence as an improvised explosive, particularly after the Oklahoma City bombing, which used a mixture of ammonium nitrate and diesel fuel called ANFO. The government has proposed many schemes to make ammonium nitrate less dangerous, but it seems they have settled on a universal ban at the retail level and tight restrictions on any farmers who dare use it. Ammonium nitrate is easy to prepare from a simple acid-base reaction, if you want to waste the precious nitric acid.
- ammonium (I) nitrate
- AN
- Emulite
- EXP 200
- German saltpeter
- nitric acid, ammonium salt
- nitric acid ammonium salt (1:1)
- Norge saltpeter
- Norway saltpeter
- Norwegian saltpeter
- Plenco 12203
- Varioform
- Varioform I
- ZhVK
Ammonium nitrate is formed by a simple double displacement reaction when the ammonium ion, NH4+, replaces the H+ ion from the nitric acid and bonds to the remaining nitrate ion, NO3, then the H+ ion forms water from the hydroxide ion, OH-, left by the ammonium ion. The equation is NH4OH + HNO3 = NH4NO3 + H2O
Into a 500-mL Erlenmeyer flask , add 100 mL of water then add 100 mL of concentrated nitric acid. Always add acid to water, not the reverse, because the acid will splash when water is added. Slowly add ammonium hydroxide from a beaker to the Erlenmeyer flask while stirring by swirling the flask occasionally until the mixture is alkaline to litmus paper. Keep the flask in a salt-ice bath to keep it cool, and add the ammonium hydroxide in small portions so it may cool a bit. If the reaction gets too hot it will instantly come to a boil and splatter acid all over the place (the first time that happened to me I dropped the whole damned beaker of ammonium hydroxide when I jumped back quite startled, the second time I lost most of my product when it splattered out of the flask). Remember that red litmus turns blue in the presence of base and blue turns red in the presence of acid. Gently boil the mixture until only a crust remains. Let the remaining water evaporate or heat gently to drive out the remaining moisture, you can use an oven for this. Ammonium nitrate will draw moisture from the air so keep it tightly sealed right after you are done heating it. If strongly heated the ammonium nitrate will decompose to form nitrous oxide, which is laughing gas, and then will begin to emit white fumes. If you see white fumes stop heating because that's one step from detonation, don't get too worried though the detonation temperature is several hundred degrees above the fumes stage.
It seems wasteful to use all that nitric acid just to make this particular substance, but knowledge is power! You have to use nitric acid in some way, so why not to make ammonium nitrate? I have actually seen ammonium nitrate for sale in an agricultural supply store once, just one lonely bag, but they no longer carry it. The government publishes a terrorist propaganda pamphlet instructing store owners to get the names, phone numbers, addresses, and license plates of anyone asking about ammonium nitrate. The pamphlet says for the clerk to pump you for all of your personal details, and if you act suspicious, like you are not going to be fertilizing parsnips anytime soon, to follow you to your car, get the license plate, and report you immediately to an FBI hotline. If you really have the urge to ask, park around the corner, unless you want some stormtroopers hauling you to gitmo in the middle of the night.
Ammonium nitrate is so insensitive to detonation that you could store it under your bed and have more worries about your pillow blowing up than the substance itself. When mixed with a sensitizer like diesel oil, kerosene, gasoline, nitromethane, hydrazine and the like it becomes quite sensitive.
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