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Ammonium Nitrate
ammonium hydroxide
nitric acid
water litmus
APPARATUS
beaker
500-mL Erlenmeyer flask
litmus paper
Ammonium nitrate is used as a fertilizer and is supposed to be available from agricultural supply stores or perhaps well stocked garden shops. It may be increasingly hard to find due to its ease of use as an explosive, and especially from the Oklahoma City bombing. The government wants to make it less dangerous by coating the fertilizer pellets with a special chemical. It took me five minutes of research to devise a way of thwarting that method. The proposed anti-explosive would use a similar compound, I think it is ammonium sulfate, mixed in with the ammonium nitrate. Ammonium nitrate is very hygroscopic, or water absorbing, so it completely dissolves in water, but the new stuff is only partially soluble in water. It should not be too difficult to crush up all the nitrate/sulfate nitrate mix, dissolve it in water, and skim off what does not dissolve after a few minutes. Of course it's not all that difficult to make your own. Ammonium hydroxide, the main ingredient, can be obtained in dilute solution as a laundry substance or as a window cleaner, it is ammonia. It is important to get a brand that does not have any fragrance, color, or soap additives in it as it may affect the reaction. More information about ammonium hydroxide is in the chemical synthesis section. The other chemical is nitric acid, that will be far more difficult to obtain and far to precious for most people to make simple ammonium nitrate with.
The 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! I have never actually seen ammonium nitrate for sale in an agricultural supply store, I have also never been in an agricultural supply store, so that may be why. This chemical is so insensitive to detonation that you could store it under your bed and have more worries about your pillow blowing up than the ammonium nitrate. When mixed with a sensitizer like diesel oil, kerosene, gasoline, nitromethane, hydrazine and the like it becomes quite sensitive.