1. Osazone are a class of carbohydrate derivatives found in organic chemistry formed when reducing sugars are reacted with excess of phenylhydrazine at boiling temperatures. == Formation == Osazone formation was developed by Emil Fischer, who used the reaction as a test to identify monosaccharides. The formation of a pair of hydrazone functionalities involves both oxidation and condensation reactions. Since the reaction requires a free carbonyl group, only "reducing sugars" participate. Sucrose, which is nonreducing, does not form an osazone. == Appearance == Osazones are highly coloured and crystalline compounds. Osazones are readily distinguished. Maltosazone (from maltose) forms petal-shaped crystals. Lactosazone (from lactose) forms powder puff-shaped crystals. Galactosazone (from galactose) forms rhombic-plate shaped crystals. Glucosazone (from glucose, fructose or mannose) forms broomstick or needle-shaped crystals. == Historic references == Fischer, Emil (1908). "Schmelzpunkt des... from wikipedia.org