PHOSPHORIC ACID

A term applied to any of three oxygen acids of phosphorus known respectively as ordinary or orthophosphoric, pyrophosphoric, and metaphosphoric acids. The most common form, orthophosphoric acid, or simply phosphoric acid, H3PO4, is a syrup-like compound and an important ingredient in fertilizers. However, to be available for use by plants, the phosphates must be soluble in water or plant juices. Insoluble normal phosphates, as mineral phosphates, are therefore often converted into soluble acid salts by treatment with sulfuric acid. Phosphoric acid, when used as a fertilizer ingredient, is often blamed for excessive algae growth and oxygen losses in rivers and is frequently a leading toxin to aquatic life.