refined oxalic acid, that is, adipic acid, the most simple binary acids. Structural Short Form HOOCCOOH. It is usually colorless and transparent crystal, pairs of human health, and make the body's pH out of balance, affect children's development, oxalic acid plays an important role in industry, oxalic acid can be rust. Oxalic acid all over in nature, often in the form of oxalate found in plants such as barberry, sheep hoof grass, wood sorrel and sorrel grass of the cell membrane, almost all of the plants contain calcium oxalate.