Oxalic acid is an organic substance with the chemical formula of C2H2O4. It is a metabolite of organisms. It is a binary weak
acid, which is widely distributed in plants, animals and plays different functions in different organisms. It is found that more
than 100 kinds of plants are rich in oxalic acid, especially spinach, amaranth, sugar beet, purslane, taro, sweet potato and
rhubarb. Because oxalic acid can reduce the bioavailability of mineral elements, it is easy to form calcium oxalate with calcium
ions in human body, resulting in kidney stones, oxalic acid is often considered as an antagonist for the absorption and
utilization of mineral elements. Its anhydride is carbon trioxide.