nitrous acid

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nitrous acid

a weak monobasic acid known only in solution and in the form of nitrite salts. Formula: HNO2
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Nitrous Acid


(HNO2) a monoprotic, unstable, and quite weak acid; it exists only in dilute cold water solutions. Its structural formula is HO—N=0. Its dissociation constant is 4.5 x 10-4 at 18°C. It forms along with nitric acid when N02 is dissolved in water:

2N02 + H20 = HN02 + HN03

Upon heating and the action of strong acids or oxidizers, nitrous acid dissociates with the formation of nitric oxide:

3HN02 = HNO3 + 2NO + H20

The compounds N20, NO, NH2OH, NH3, and others may be obtained by the reduction of nitrous acid. The salts of nitrous acid (nitrates) are obtained by the reduction of nitrates.

The most important property of nitrous acid is its ability to diazotize aromatic amines. For this reason, sodium nitrate (NaN02) is widely used in the production of azo dyes; free nitrous acid is produced upon the action of acids on this salt:

NaN02 + HCl = NaCl + HN02

Nitrous acid and its salts are poisonous if ingested. Poisoning of professionals is rare. Sodium nitrite is used in medicine in cases of cardiac angina and spasms of the vessels of the cerebrum.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

nitrous acid

[′nī·trəs ′as·əd]
(inorganic chemistry)
HNO2 Aqueous solution of nitrogen trioxide, N2O3.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The nitrosating agent nitrous acid is formed in situ by the action of acetic or mineral acid on sodium nitrite and a further reaction takes place to give the nitrosonium ion N[O.sup.+] (Figure 2).
In view of the over-production of nitrous acid thus highlighted by researchers, this phenomenon might be responsible for the production of half of all hydroxyl radicals.
Bae, "Modeling kinetics of ammonium oxidation and nitrite oxidation under simultaneous inhibition by free ammonia and free nitrous acid," Process Biochemistry, vol.
They speculated that nitrous acid may be attaching itself to elements found in the ground, only to be released later on.
The selected culture was improved after treatment through ethyl methane sulphonate (EMS) soon after followed by nitrous acid (NA) exposure to further enhance its hydrolytic potential for AY-amylase activity (Table I).
Effect of nitrous acid on lung function in asthmatics: a chamber study.
The study by Researchers from the Biogeochemistry Department at the Max Planck Institute for Chemistry in Mainz shows that nitrous acid is formed in fertilized soil and released into the atmosphere, whereby the amount increases with increasing soil acidity.
Congo red dye 0.001mol aqueous solution was stirred well in a 100 ml beaker and diazotized at 0-5degC with nitrous acid generated in situ by addition of HCl 36.5% (2ml) and sodium nitrite (0.002mol).
The research team at Lawrence Berkeley National Laboratory (Berkeley Lab) showed that nicotine in third-hand smoke reacts with the common indoor air pollutant nitrous acid to produce dangerous carcinogens.
In the acidic stomach, the nitrite is rapidly converted to nitrous acid and then to nitric oxide and nitrosating species, which can react with amines and amides to form N-nitroso compounds (NOC), the potential causative agents in the etiology of specific cancers, adverse reproductive outcomes, and diabetes.
The complete inhibition concentrations of free nitrous acid (FNA) for NOB and AOB were 0.02 and 0.40 mg/L, respectively [22-25].