Use
semicarbazones: Organic compoundscontaining the unsaturatedgroup =C:N·NH·CO·NH2. They areformed when aldehydes or ketonesreact with a semicarbazide(H2N·NH·CO·NH2). Semicarbazonesare crystalline compounds with relativelyhigh melting points. They areused to identify aldehydes and ketonesin quantitative analysis: thesemicarbazone derivative is madeand identified by its melting point.Semicarbazones are also used in separating ketones from reaction mixtures:the derivative is crystallizedout and hydrolysed to give the ketone.