Nitric acid
Nitric acid also known as aqua fortis
Aqua fortis
Aqua fortis, or "strong water," in alchemy, is a solution of nitric acid in water. Being highly corrosive, the solution was used in alchemy for dissolving silver and most other metals with the notable exception of gold, which can only be dissolved using aqua regia...

and spirit of nitre, is a highly corrosive
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...

 and toxic strong acid
Strong acid
A strong acid is an acid that ionizes completely in an aqueous solution by losing one proton, according to the equationFor sulfuric acid which is diprotic, the "strong acid" designation refers only to dissociation of the first protonMore precisely, the acid must be stronger in aqueous solution than...


Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen
Nitrogen oxide
Nitrogen oxide can refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:* Nitric oxide, also known as nitrogen monoxide, , nitrogen oxide* Nitrogen dioxide , nitrogen oxide...

. If the solution contains more than 86% nitric acid, it is referred to as fuming nitric acid. Depending on the amount of nitrogen dioxide
Nitrogen dioxide
Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...

 present, fuming nitric acid is further characterized as white fuming nitric acid
White fuming nitric acid
White fuming nitric acid is a storable liquid oxidizer used with kerosene and hydrazine rocket fuel. It consists of nearly pure nitric acid . WFNA is commonly specified as containing no more than 2% water and less than 0.5% dissolved nitrogen dioxide or dinitrogen tetroxide.WFNA was sometimes...

 or red fuming nitric acid
Red fuming nitric acid
Red fuming nitric acid is a storable oxidizer used as a rocket propellant. It consists mainly of nitric acid , also containing 13% dinitrogen tetroxide and 3% water. The dissolved nitrogen dioxide is very concentrated and can be found at room temperature...

, at concentrations above 95%.