Nitrosylsulfuric acid

Nitrosylsulfuric acid
Structural formula of nitrosylsulfuric acid
Ball-and-stick model of the nitrosylsulfuric acid molecule
IUPAC name
Nitrosylsulfuric acid
Other names
nitrosonium bisulfate, chamber crystals
7782-78-7 YesY
3D model (Jmol) Interactive image
ChemSpider 74147 YesY
ECHA InfoCard 100.029.058
PubChem 82157
Molar mass 127.08 g/mol
Appearance pale yellow crystals
Density 1.612 g/mL in
40% sulfuric acid soln
Melting point 73.5 °C (164.3 °F; 346.6 K)
Boiling point decomposes
Solubility soluble in H2SO4
Main hazards oxidizer
Related compounds
Other anions
Other cations
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Nitrosylsulfuric acid is the chemical compound with the formula NOHSO4. It is a colourless solid that is used industrially in the production of caprolactam,[1] and was formerly part of the lead chamber process for producing sulfuric acid.

Synthesis and reactions

A typical procedure entails dissolving sodium nitrite in concentrated sulfuric acid in an ice bath:[2][3]


The molecule can also be viewed as the mixed anhydride of sulfuric acid and nitrous acid. Alternatively, it can be prepared by the reaction of nitric acid and sulfur dioxide.[4]

NOHSO4 is useful in organic chemistry to prepare diazonium salts from amines. Related NO-delivery reagents include nitrosonium tetrafluoroborate ([NO]BF4) and nitrosyl chloride.


  1. Ritz, J.; Fuchs, H.; Kieczka, H.; Moran, W. C. (2002). "Caprolactam". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a05_031.
  2. Hodgson, H. H.; Mahadevan, A. P.; Ward, E. R. (1955). "1,4-Dinitronaphthalene". Org. Synth.; Coll. Vol., 3, p. 341 (diazodization followed by treatment with nitrite)
  3. Sandin, R. B.; Cairns, T. L. (1943). "1,2,3-Triiodo-5-nitrobenzene". Org. Synth.; Coll. Vol., 2, p. 604 (diazodization followed by treatment with iodide)
  4. Coleman, G. H.; Lillis, G. A.; Goheen, G. E. (1939). "Nitrosyl Chloride". Inorganic Syntheses. 1: 55–59. doi:10.1002/9780470132326.ch20. This procedure generates the nitrosylsulfuric acid as an intermediate en route to NOCl.

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