Oxalic Acid: Sugar Oxidised with Nitric Acid, Ure 1839

Sugar heated with dilute nitric acid gives off nitrous fumes and is oxidised to oxalic acid, which crystallizes when the liquid cools; drying the crystals in warm air drives the nitric acid off, and the third crystallization is pure (Ure, 1839). Oxalic acid is a poison. Here it is the start of formic acid and allyl alcohol. The picture: our diagram of the four stages.