Fremy's salt

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Fremy's salt, discovered in 1845 by Edmond Fremy (1814 - 1894), is a chemical compound and a strong oxidizing agent. The formal name is disodium nitrosodisulfonic acid or NO(SO3Na)2 but Fremy's salt refers equally well to the potassium salt potassium nitrosodisulfonate.

Properties and reactions

The nitroso compound is a persistent organic radical like TEMPO. It is especially useful in oxidations of phenols to hydroquinones in the Teuber reaction.


The salt can be prepared from sodium nitrite, sodium bicarbonate and sulfur dioxide to disodium hydroxylaminedisulfonate and carbon dioxide followed by one-electron oxidation by electrolysis in a basic solution.


  • H.-J. Teuber and S. Benz, Chem. Ber., 100, 2918, 1967.