Nital

Nital is a solution of alcohol and nitric acid commonly used for routine etching of metals. It is especially suitable for revealing the microstructure of steels. The alcohol can be methanol, ethanol or methylated spirits.

Mixtures of ethanol and nitric acid are potentially explosive. This commonly occurs by gas evolution, although ethyl nitrate can also be formed. Methanol is not liable to explosion but it is toxic.

An solution of ethanol and nitric acid will become explosive if the concentation reaches over 10% (by weight). Solutions above 5% should not be stored in closed bottles. This is a consequence of the fact that nitric acid, unlike other oxidants, still functions as such when cold and dilute, and oxidation is always accompanied by gas evolution, sometimes very slow but progressive. It is also able to form explosive ethyl nitrate by slow acid catalyzed esterification.