HAN

     HAN, an acronym for hydroxylamine nitrate, is a reactive oxidizer salt commonly used as a rocket propellant. Other names for HAN include hydroxylamine mononitrate; and hydroxylammonium nitrate. While HAN is an explosive salt, its explosive properties are rather inferior. As a rocket propellant, though, HAN is a valuable commodity. HAN also has a number of other uses in the chemical industry. Its primary government use is as a plutonium recovery agent from waste plutonium/uranium scrap. In an organic solvent HAN reduces Pu(IV) to Pu(III) rendering it water soluble, whereas U(VI), also present in the organic phase, is not water soluble. A few aqueous washes later and all of the Pu can be removed. The US Army mixes HAN with TEAN (triethanolammonium nitrate) to make gun propellants. One such propellant is XM46, a mixture of 60% HAN, 20% TEAN, and 20% water by weight. HAN can react explosively over time if contaminated with nitric acid or iron compounds.

CHEMICALS	APPARATUS
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     While is may seem like here is nothing complex or sophisticated about making HAN, there are some facts to consider. It is basically formed by a simple neutralization reaction between nitric acid and hydroxylamine. Because the presence of unreacted nitric acid and ammonium nitrate in HAN can be dangerous for long term storage getting the reaction just right is important. One should err on the side of using excess hydroxylamine. Prepare a solution of 34 g of hydroxylamine in 65 g of methyl alcohol. The alcohol does not need to be anhydrous. Cool this solution to below 20 C in an ice bath. Slowly add with rapid stirring enough nitric acid to completely neutralize the hydroxylamine, or leave a little excess hydroxylamine. This would be about 63 g worth of nitric acid, but the acid should be from 60% to 90% by weight (in water). The acid should be chilled to below 20 C as well. Always add the acid to the hydroxylamine. If you add it the other way around the hydroxylamine will decompose to ammonia and you will end up with ammonium nitrate as a contaminant. This is also why the acid addition should be slow, with rapid stirring, and cold. The higher the temperature the more likely the hydroxylamine will decompose. The HAN can be isolated by distilling off the alcohol and most of the water. HAN is quite hygroscopic, so getting rid of that last bit of water can be tricky. You do not want to distill to dryness of course! In most cases it is OK to store HAN wet, and it can be detonated wet. To completely dry HAN it will have to be stored in a vacuum desiccator. Synth 2 HAN can also be prepared by displacement of nitrate salts with hydroxylamine salts. A hydroxylammonium salt such as hydroxylammonium sulfate, hydroxylammonium chloride, or hydroxylammonium acid sulfate is acid to a solution of either sodium nitrate, potassium nitrate, or calcium nitrate in water. A non water miscible solvent is added like n-butyl alcohol or diethyl ether and stirred. The reaction happens in the organic solvent in which HAN is soluble, but the other reactants are not. After some time the stirring is stopped and the organic layer is allowed to separate. The water layer is removed in a separatory funnel and the alcohol layer is dried by adding activated alumina or another suitable dehydrating agent. The alcohol will dissolve a small amount of water that contains some nitrate or sulfate salts. When dried these salts precipitate from the alcohol and can be removed by filtration. The dried alcohol is vacuum distilled to isolate HAN as pure crystals.

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