Salicylaldehyde carbonyl hydrazone (SACH) mr194 18 yellow crystal, soluble in methanol, ethanol, dimethylformamide and methyl isobutyl ketone, slightly soluble in water, chloroform, hexane and benzene. mp(235±1)℃。 The acid dissociation constant of reagent PK1 = 10.5, PK2 = 13.6. It is used for the determination of zinc, scandium, gallium, etc. by fluorescence spectrophotometry.