## Nitric acid

**Formula**

$HNO3$

**Pyrotechnics use**

Synthesis of nitrate compounds

**Synonyms**
 
TBD

**Description**

Nitric acid is not used in pyrotechnic compositions but it can be used to prepare a variety of useful nitrates from carbonates, hydroxides, oxides or free elements. It is used in the explosives industry in the preparation of a lot of commonly used explosives (eg TNT, RDX, PETN, nitrocellulose). Most high explosives have no use in fireworks, though nitrocellulose is used in some fireworks compositions as an acetone soluble binder.

**Sources** 

It is possible to prepare nitric acid in several ways. It can also be bought at some drug stores. It is sold at professional gardening suppliers and at welding shops (it is used to passivate stainless steel after welding). One way to prepare it is by distilling a mixture of sulfuric acid and sodium nitrate. This process is dangerous and requires some equipment. This method is probably too dangerous for the average amateur pyro. Another possible method is by precipitating barium sulfate from a barium nitrate solution by adding sulfuric acid. What remains is a nitric acid solution. It should be possible to prepare quite concentrated solutions by using concentrated sulfuric acid and a saturated (not hot!) barium nitrate solution. It is important that the sulfuric acid is added to the barium nitrate solution and not the other way around. The mixing of the liquids will produce heat and if the barium nitrate solution is added to the sulfuric acid it could cause sudden boiling and splatting. Therefore, add the sulfuric acid slowly to the barium nitrate while constantly stirring. Allow the mixture to cool from time to time if it gets too hot. A white precipitate of barium sulfate should form. The mixture is then filtered through a sintered glass filter to obtain clear solution of nitric acid. Another method would consist of equal amounts of sulfuric acid and potassium nitrate heated a retort. The retort is heated until the solution starts bubbling, and the nitric acid evaporates. The acid then condenses in the neck of the retort, and drips out the end into a separate flask that is submerged in chilled water. After the reaction is complete, the resulting nitric acid is around 80-95% pure. This process yields red fuming nitric acid, which you'll see fumes coming out of the flask when the lid is removed. A byproduct of this reaction is potassium hydrogen sulfate (KHSO4), which appears as a white crystalline mass at the bottom of the retort.

**Hazards**
 
Nitric acid is corrosive. The fumes are dangerous to the lungs, eyes and skin. Skin will be stained yellow upon contact. Avoid all contact with both liquid and fumes. Wear eye and skin protection (lab apron, gloves, safety glasses, etc). In some reactions (especially those with metals) a brown gas will develop: nitrogen dioxide. It is very toxic, corrosive and will attack your lungs badly. Only work with nitric acid with adequate ventilation and proper protective clothing. Don't use any solutions more concentrated than 60%. Don't try to prepare high explosives at home and don't allow any organic material to contact nitric acid accidentially because that may result in the formation of dangerously explosive and/or sensitive materials.