Nitrosylsulfuric acid

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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
3D model (JSmol)
ECHA InfoCard 100.029.058
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[edit]

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

HNO2 + H2SO4 → NOHSO4 +H2O

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. Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. ISBN 3527306730. 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. Inorganic Syntheses. 1: 55–59. ISBN 9780470132326. doi:10.1002/9780470132326.ch20.  This procedure generates the nitrosylsulfuric acid as an intermediate en route to NOCl.