Oxalic acid
Oxalic acid appears to be a white crystalline solid with no odour.
Uses.
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