Overview

What is Nitric Acid

Nitric acid (HNO3), also known as aqua fortis (Latin for “strong water”) and spirit of niter, is a highly corrosive mineral acid. The pure compound is colorless, but older samples tend to acquire a yellow cast due to decomposition into oxides of nitrogen and water. Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% HNO3, it is referred to as fuming nitric acid. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as white fuming nitric acid at concentrations above 95%, or red fuming nitric acid at concentrations above 86%. Nitric acid is the primary reagent used for nitration – the addition of a nitro group, typically to an organic molecule. While some resulting nitro compounds are shock- and thermally-sensitive explosives, a few are stable enough to be used in munitions and demolition, while others are still more stable and used as pigments in inks and dyes. Nitric acid is also commonly used as a strong oxidizing agent.

Structure

The structure of nitric acid is planar, meaning the chemical structure is flat. There are two major resonance forms of nitric acid. Resonance form occurs when there are multiple ways of drawing the Lewis structure of a compound. A Lewis structure is a diagram that shows how atoms are bonded together and illustrates the presence of non-bonded pairs of electrons in a compound. The double-headed arrow drawn between the two resonance structures is there to show that there is more than one way to draw the structure.