NITRIC ACID

Nitric acid is the very corrosive and strongly oxidizing mineral acid with formula HNO3. It is a major industrial chemical made by oxidizing ammonia to nitrogen oxides, which are absorbed into water.

There are three types of nitric acid.

(1) Lab grade "concentrated nitric acid": 68% HNO3, which is constant-boiling at 120°C and thus cannot be increased further through evaporation. It is a colorless liquid that turns yellow quickly due to decomposition to NO2 gas.

(2) Red fuming nitric acid (RFNA): around 86% HNO3, 13% dissolved nitrogen oxides, and 1% water. It is the most dangerously toxic kind of nitric acid.

(3) White fuming nitric acid (WFNA): at least 95% HNO3 and little nitrogen oxides or water. Pure anhydrous HNO3 has a boiling point of 83°C.

Nitric acid reacts exothermically with almost everything and may ignite organic materials. It dissolves most metals -- a common demonstration is the reaction of concentrated HNO3 with a penny, which produces billows of red NO2 gas and leaves behind a hot green solution of copper nitrate (and no penny).

Of the 50 million tons of nitric acid produced annually, about 80% is converted to the fertilizer ammonium nitrate. Other major products are nitro compounds, such as the explosives nitroglycerin and TNT. The extra-concentrated forms RFNA and WFNA are used as hypergolic rocket propellants.