If anhydrous oxalic acid (COOH) is available then dissolve 4.5 g of the acid in one litre of distilled water to get 0.1 N oxalic acid solution. Add 13.16 g of NaOH (95% NaOH) in one litre distilled water and shake well.
Oxalic acid has many roles as a bleach, metal polish, stain remover, and mordant. It is used as a Bleaching agent for Straw hats, Leather, and Wood. Oxalic acid acts as a reducing agent for metal oxides to remove tarnish as well as rust or ink stains.
Oxalic acid started to be accumulated just after 700 s, which corresponds to the time when the maleic acid was being decomposed.