Oxalic acid has several common uses in different fields, some of which include:

1. Rust removal: Oxalic acid is an effective rust remover and is commonly used to clean rust stains from metal surfaces.
2. Wood bleaching: It is used in wood bleaching to remove stains, discolorations, and watermarks from wood.
3. Cleaning: Oxalic acid is used as a cleaning agent in many applications, such as cleaning concrete, tiles, and other surfaces.
4. Removing mineral deposits: It can dissolve mineral deposits, such as calcium and iron, from toilets, sinks, and other plumbing fixtures.
5. Metal cleaning: Oxalic acid is used to clean metals, such as brass and bronze, and to remove tarnish from silver.
6. Medical applications: It is used in medical applications as a chelating agent to remove excess iron from the body.
7. Synthesis of chemicals: Oxalic acid is used as a raw material for the synthesis of various chemicals, such as formic acid, glyoxylic acid, and oxamide.