nitrous acidn.
/ˌnʌɪtrəs ˈasɪd/, U.S. /ˌnaɪtrəs ˈæsəd/ Chemistry.
†(a) Any of various acidic compounds derived from nitre or containing nitrogen, esp. (in later use) fuming nitric acid (see quot. 1867). Obsolete. (b) spec. An unstable, moderately weak acid, HNO2, existing only in solution and in the gas phase, and made by the action of acids on nitrites.
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nitrous acid1682
1682 N. Grew Exper. Luctation ii. ii. §8 in Anat. Plants 243 Upon its solution by a Nitrous Acid.
1755 Philos. Trans. 1754 (Royal Soc.) 48 649 (heading) Experiment 3. Platina with the nitrous acid.
1780 Philos. Trans. 1779 (Royal Soc.) 69 396 Nitre is composed of two different ingredients, viz. an acid, called..the nitrous acid, and the vegetable alkali.
1804 J. Abernethy Surg. Observ. 139 The administration of nitrous acid, opium, and other remedies.
1849 D. Campbell Pract. Text-bk. Inorg. Chem. 24 Nitrous acid pure is a colourless liquid at a low temperature, but becomes green on a slight elevation of heat.
1867 C. L. Bloxam Chemistry 134 The so-called nitrous acid of commerce is really nitric acid holding in solution a large proportion of nitric peroxide.
1876 J. Tyndall Fragm. Sci. (ed. 5) i. iv. 96 The brown fumes of nitrous acid were also seen.
1903 W. H. Lang Strasburger's Text-bk. Bot. (ed. 2) 197 The necessary energy is here obtained..from the oxidation of ammonia into nitrous acid, and this into nitric acid (chemosynthesis).
1991 D. T. Sawyer Oxygen Chem. i. 8 Priestley..noted that nitric oxide reacts with O2 to produce NO2 and N2O4, which react with water to form HON(O) and HON(O)2 (nitrous acid and nitric acid).
This entry has been updated (OED Third Edition, December 2003; most recently modified version published online March 2022).
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