# Peroxomonosulfuric acid

Structural formula
General
Surname Peroxomonosulfuric acid
other names
• Peroxosulphuric acid
• Sulfomonoperic acid
• Peroxy monosulfuric acid
• Caro's acid
Molecular formula H 2 SO 5
Brief description

colorless solid

External identifiers / databases
 CAS number 7722-86-3 EC number 231-766-6 ECHA InfoCard 100,028,879 PubChem 2754594 Wikidata Q408929
properties
Molar mass 114.09 g mol −1
Physical state

firmly

Melting point

Decomposition from 45  ° C

safety instructions
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Peroxomonosulfuric acid (also peroxosulfuric acid , peroxy-monosulfuric acid or Caro's acid ) is an oxo acid of sulfur . Their salts are called peroxomonosulfates , e.g. B. Potassium peroxomonosulfate (KHSO 5 ). The colorless aqueous solutions of peroxomonosulphuric acid are also called snack water, piranha acid or piranha solution in the jargon of chemical laboratories . The chemist Heinrich Caro first described it in 1898.

## presentation

A synthesis can be done by reacting chlorosulfonic acid (ClSO 3 H) with hydrogen peroxide :

${\ displaystyle \ mathrm {H_ {2} O_ {2} \ + \ ClSO_ {3} H \ longrightarrow \ H_ {2} SO_ {5} \ + \ HCl}}$

Further reaction with chlorosulfonic acid forms peroxodisulfuric acid (H 2 S 2 O 8 ).

Peroxomonosulphuric acid as an aqueous solution is unstable under normal conditions and is therefore always prepared anew for use. For this purpose, hydrogen peroxide solution is added to concentrated sulfuric acid (caution: heat generation):

${\ displaystyle \ mathrm {H_ {2} SO_ {4} \ + \ H_ {2} O_ {2} \ longrightarrow \ H_ {2} SO_ {5} \ + \ H_ {2} O}}$

In addition to peroxomonosulfuric acid, water is also formed as a reaction product.

## properties

Peroxomonosulfuric acid is a colorless, extremely hygroscopic , finely crystalline solid that smells of ozone . In the pure state it can be kept for several weeks with only a slight loss of active oxygen , in an impure form it is much less stable. It is soluble in ethanol and only slightly soluble in ether . When dissolved in water, hydrogen peroxide (H 2 O 2 ) is released in an equilibrium reaction:

${\ displaystyle \ mathrm {H_ {2} SO_ {5} \ + \ H_ {2} O \ \ rightleftharpoons \ H_ {2} SO_ {4} \ + \ H_ {2} O_ {2}}}$

Peroxomonosulphuric acid has a strong oxidizing effect.

## use

Peroxomonosulfuric acid is used as a cleaning and bleaching agent. It is used by chemists, for example, to clean glass frits . Under no circumstances should organic solvents such as B. Acetone can be added, as this can lead to explosions.

## hazards

Pure peroxomonosulphuric acid is highly explosive. Like all strong oxidizing agents, peroxomonosulphuric acid forms in contact with organic compounds, e.g. B. ethers, ketones or organic solvents very unstable molecules such. B. acetone peroxide .

## Individual evidence

1. a b Safety data sheet Solvay ( Memento of the original from January 26, 2014 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 235 kB)
2. This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
3. ^ Wiberg, Egon., Wiberg, Nils ,: Textbook of Inorganic Chemistry . 102nd, heavily reworked and verb. Ed. De Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .
4. H. Caro: On the knowledge of the oxidation of aromatic amines . In: Journal of Applied Chemistry . Vol. 11, No. 36 , 1898, pp. 845-846 , doi : 10.1002 / anie.18980113602 .
5. G. Brauer (Ed.): Handbook of Preparative Inorganic Chemistry 2nd ed., Vol. 1, Academic Press 1963, pp. 388-389.
6. Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , p. 392.
7. ^ JO Edwards: SAFETY . In: Chem. & Eng. News . Vol. 33, No. 32 , 1955, pp. 3336 , doi : 10.1021 / cen-v033n032.p3336 .