It forms a well-crystallized hydrazone with phenylhydrazine; and a-nitroso propionic acid with hydroxylamine.
They react with hydroxylamine and phenylhydrazine, with the formation of aldoximes and hydrazones.
The hydrazones are best prepared by mixing the aldehyde with phenylhydrazine in dilute acetic acid solution, in the absence of any free mineral acid.
The remaining oxygen atom is aldehydic or ketonic, for the sugars combine with hydrocyanic acid, hydroxylamine and phenylhydrazine.
On warming the osazone with hydrochloric acid the phenylhydrazine residues are removed and an osone results, which on reduction with zinc and acetic acid gives a ketose.