The Collaborative International Dictionary
Nitrous \Ni"trous\, a. [L. nitrosus full of natron: cf. F. nitreux. See Niter.]
Of, pertaining to, or containing, niter; of the quality of niter, or resembling it.
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(Chem.) Of, pertaining to, or designating, any one of those compounds in which nitrogen has a relatively lower valence as contrasted with nitric compounds.
Nitrous acid (Chem.), a hypothetical acid of nitrogen HNO2, not known in the free state, but forming a well known series of salts, viz., the nitrites.
Nitrous oxide. See Laughing gas.
Wiktionary
n. (context inorganic compound English) A weak acid, HNO2, known only in solution, or as its salts and esters, the nitrites; it has a linear structure, H-O-N=O
WordNet
n. an unstable inorganic acid known only in solution and as nitrite salts
Wikipedia
Nitrous acid (molecular formula H N O) is a weak and monobasic acid known only in solution and in the form of nitrite salts.
Nitrous acid is used to make diazides from amines; this occurs by nucleophilic attack of the amine onto the nitrite, reprotonation by the surrounding solvent, and double-elimination of water. The diazide can then be liberated to give a carbene or carbenoid.
Usage examples of "nitrous acid".
Monsieur Bertholet, by dissolving silver in the nitrous acid, precipitating it with lime water, and drying the precipitate on ammoniac, has discovered a powder which fulminates most powerfully, on coming into contact with any substance whatever.
Like the Cotton-seed oils, it forms more or less elaidin on treatment with nitrous acid or mercuric nitrate, but does not become wholly solidified.